Aftershocks, Earthquake Effects, and the Location ... - GeoScienceWorld

Bulletin of the Seismological Society of America, Vol. 108, No. 1, pp. 66–83, February 2018, doi: 10.1785/0120170224

Aftershocks, Earthquake Effects, and the Location of the Large 14 December 1872 Earthquake near Entiat, Central Washington by Thomas M. Brocher, Margaret G. Hopper,* S. T. Ted Algermissen,† David M. Perkins,* Stanley R. Brockman,‡ and Edouard P. Arnold§

Abstract

Reported aftershock durations, earthquake effects, and other observations from the large 14 December 1872 earthquake in central Washington are consistent with an epicenter near Entiat, Washington. Aftershocks were reported for more than 3 months only near Entiat. Modal intensity data described in this article are consistent with an Entiat area epicenter, where the largest modified Mercalli intensities, VIII, were assigned between Lake Chelan and Wenatchee. Although ground failures and water effects were widespread, there is a concentration of these features along the Columbia River and its tributaries in the Entiat area. Assuming linear ray paths, misfits from 23 reports of the directions of horizontal shaking have a local minima at Entiat, assuming the reports are describing surface waves, but the region having comparable misfit is large. Broadband seismograms recorded for comparable ray paths provide insight into the reasons why possible S–P times estimated from felt reports at two locations are several seconds too small to be consistent with an Entiat area epicenter.

Introduction of 7.8 for the 1906 earthquake, Malone and Bor’s calculated magnitude for the 1872 earthquake would likely have been closer to current magnitude estimates. Bakun et al. (2002), using the modal seismic intensity data described in this article, estimated an M range between 6.5 and 7.0 for the 1872 earthquake assuming a crustal depth, consistent with the following strong aftershock sequence (Spence, 1989), and determined an intensity center near Winesap (Entiat), central Washington (Fig. 2). Sherrod et al. (2015) and B. L. Sherrod et al. (unpublished manuscript, 2017; see Data and Resources) concluded from paleoseismic investigations that a topographic scarp, previously identified using light detection and ranging (lidar) data, is formed as a result of primary surface rupture along the fault plane during a late 1800s earthquake. Dendrochronology of the oldest trees growing on proximal landslides in Spencer Canyon suggests the landslides formed by the mid 1880s (Sherrod et al., 2015; B. L. Sherrod et al., unpublished manuscript, 2017; see Data and Resources). This scarp, the Spencer Canyon scarp, located several kilometers southwest (SW) of Entiat, may resolve the location of the 1872 fault rupture and may indicate that its depth was sufficiently shallow to rupture to the surface. Brocher et al. (2017) investigated the spatial and temporal relationships between the 1872 earthquake and the ongoing Entiat seismicity cluster. They showed that the two share a common footprint and that aftershock forecast

The 14 December 1872 (9:40 p.m. local time, 15 December 1872 UTC) earthquake is the largest historical earthquake in Washington State east of the crest of the Cascade Range (Fig. 1). The earthquake’s location and size is important for disaster planning and for the design of critical facilities and lifelines; for these reasons, a number of researchers have studied this earthquake. Milne (1956) used limited seismic intensity data, only from newspapers in British Columbia, to suggest a very uncertain epicenter in southern British Columbia. Extensive efforts were made by Woodward-Clyde Consultants (1976) to identify the location of the 1872 earthquake: these included the operation of a temporary seismic network around Lake Chelan, a review of intensity data, and development of an isoseismal map. Malone and Bor (1979) used intensity data to infer an epicenter in the north Cascades, with a magnitude of 7.4, assuming an earthquake depth between 40 and 60 km. As Malone and Bor (1979) noted, using the equations and coefficients of Evernden (1975), they calibrated the observed 1872 intensities to the magnitude of the 1906 San Francisco earthquake, which in 1975 had a generally accepted M s of 8.3. Had Evernden (1975) used the currently accepted moment magnitude (M) *Retired. † Deceased (14 September 2006). ‡ Deceased (17 June 2005). § Deceased (15 July 2006).

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Aftershocks, Earthquake Effects, and the Location of the Large 14 December 1872 Earthquake near Entiat

67

found in the files of Margaret Hopper and dating to 1993, is the same paper, beO MO 0 100 200 km UN cause the intensities cited by Bakun et al. TA IN S (2002) and attributed to the M. G. Hopper et al. (unpublished manuscript, 2003; see 52˚N ALBERTA Data and Resources) paper are the same as BRITISH COLUMBIA those in the 1993 manuscript. The authors of the M. G. Hopper et al. (unpublished manuscript, 2003; see Data and Resources) paper are now either retired or deceased. The present article C A N A D A was written entirely by the first author incorporating earlier data and ideas that UNITED STATES Lake these coauthors contributed via earlier unChelan Spok 48˚N ane Olympic . published reports. Figures 1–3, 6, and 7, R R. ri Mountains ou iss M Tables 1–3 and 5, as well as the AfterColumbia WASHINGTON MONTANA Plateau shock Reports, Montana Earthquakes, Columbia R. R. Snake Modal Intensity Assignments for the 1872 Earthquake sections, and Appendix B Columbia R. are largely or entirely based on sections in unpublished reports by the coauthors. The OREGON IDAHO authors of these unpublished reports are listed as coauthors to reflect their substan44˚N tial contributions to this article, but with the exception of David Perkins, who reSnake viewed the present article, they had no WYO R. involvement with the writing or review of this article. 120˚W 116˚W 112˚W 124˚W In the following, we will show that, in addition to the proximity of the Spencer Figure 1. Map of the Pacific Northwest showing locations of physical features mentioned in the text. The suggested epicenter plotted for the 1872 earthquake (star) repCanyon scarp and the Entiat seismicity resents the middle of the Entiat seismicity cluster (Brocher et al., 2017). cluster, an Entiat location for the 1872 earthquake epicenter is consistent with at least four other types of observations, including the observed durations of reported aftershocks, models for an 1872 M 6.5–7 earthquake are compatible with the reported directions of shaking, seismic intensity observathe ongoing seismicity in the cluster. Based on their conclutions, and the distribution of observed ground failures and sion that the ongoing seismicity likely represents aftershocks water effects. Finally, we document the methodology folof the 1872 earthquake, we suggest a location for the 1872 lowed to determine the seismic intensities used by Bakun earthquake at the center of the Entiat seismicity cluster et al. (2002) to constrain the magnitude and location of (47.69° N, 120.19° W). A long-lived aftershock sequence the earthquake. resulting from the 1872 earthquake is consistent with a rateand-state model for mainshocks having recurrence intervals Location of the 1872 Earthquake of a few to several thousand years (Dieterich, 1994), as well as with paleoseismic evidence for two ruptures along the Aftershock Reports Spencer Canyon scarp postdating the deposition of the Mazama ash about 7700 yrs ago (Zdanowicz et al., 1999; The aftershock distribution helps constrain the epicenB. L. Sherrod, written comm., 2017). tral region (Table 1 and Fig. 2). Aftershocks were reported This article is based in large part on an unpublished felt during the first 24 hrs following the mainshock throughpaper by Hopper et al. (2003) that was described as out a wide area including all of Washington, northern Idaho, “in press” by Bakun et al. (2002), but which was never pubwestern Montana, and southern British Columbia. Over time, lished. Bakun et al. (2002) cited that unpublished paper as the area where aftershocks could be felt shrank. After three M. G. Hopper et al. (unpublished manuscript, 2003; see Data months, aftershocks were reported only from the region and Resources). The first author of the present article has along the Columbia River from Wenatchee to Colville. After concluded that a version of the M. G. Hopper et al. (unpubmore than a year, aftershocks continued to be reported only lished manuscript, 2003; see Data and Resources) paper, at Wenatchee, Entiat (Winesap), and Lake Chelan (Fig. 2). CA

RI

BO

er R Fras

CASCADE

Mt. Adams

Mt. St. Helens

ETTE

VALLEY

PORTLAND

WILLAM

OCEAN

OLYMPIA

PACIFIC

MOUNTAINS

OUN D

PUG ET S

SEATTLE

Mt. Hood

Three Sisters

Methow R.

.

Mt. Baker

VICTORIA

Suggested 1872 epicenter

68

T. M. Brocher, M. G. Hopper, S. T. T. Algermissen, D. M. Perkins, S. R. Brockman, and E. P. Arnold

400 km

200

0 Henry House

H

52˚N

1. 3:00 a.m.—felt at Olympia, Steilacoom, Walla Walla, and Portland (2:30 a.m.); 2. 5:00 a.m.—felt at Olympia and Fort Lapwai (about 4:30 a.m.); and 3. 6:30 a.m.—felt at Olympia and Walla Walla (7:00 a.m.).

Hour ?

BRITISH COLUMBIA

H

Day Month Hope

2 H

Matsqui

Oyama

ALBERTA

Two Months

? ? ? Colville

Victoria

48˚N

Port Blakely

D

1 Stuck Valley H 1 Puyallup Steilacoom Olympia

OCEAN

3

WASHINGTON Three

Y H

Wenatchee

1

Fort Simcoe

D

Klickitat

Portland

H

H D The Dalles Hour

H

H

Hour

Colfax

H

Texas Ferry Wallula

Pine Grove

Month

Kittitas Valley

H PACIFIC

MONTANA

? ? ?

Months Lake Port Townsend Chelan Port Madison 3 White Stone Winesap Y Y Year 2 Seattle Snoqualmie 2

2 D

3

Lewiston HH Walla Walla

Fort Lapwei

H

Deer Lodge

OREGON IDAHO

WYO

44˚N 124˚W

120˚W

British Columbia (Fig. 2). Three of these aftershocks seem to have been reported at widely distributed points:

116˚W

112˚W

Figure 2. Map showing the duration of the aftershock sequence as perceived at different localities following the 1872 earthquake. Large aftershocks within the hour after the mainshock were reported as felt over a wide area. Smaller shocks continuing for over a year were reported felt only in the Entiat area from Lake Chelan to Wenatchee. The triangle indicates the intensity center and the dashed line encircles the region having a 95% confidence level for the location of the 1872 earthquake based on intensity data (Bakun et al., 2002). Durations: H, hour; D, day; 1, one month; 2, two months; 3, three months; Y, year.

Although aftershock reports suggest an 1872 epicenter in the Wenatchee–Lake Chelan region, we note three caveats. First, due to the sparse population at the time of the earthquake, there are few felt reports of aftershocks to the north and northeast (NE) of the Entiat area. We drew the contours close to the areas actually reporting felt aftershocks, but these areas could be expanded toward the north and NE, as indicated by the queried lines there. Second, the contours extend toward the southeast (SE), likely reflecting lower intensity attenuation in that area (Phillips and Stead, 2008). Thus, small aftershocks in the epicentral region continued to be felt to the SE although they were too small to be noticed elsewhere, for example, they were not reported felt in the Columbia River gorge to the south. Third, the durations shown on the map are minima. If we have a report of a felt shock two months after the earthquake, perhaps shocks were felt three months after the earthquake, but we have no record of them. Aftershocks in the 9 hrs immediately after the earthquake (i.e., until 7:00 a.m. Sunday morning following the mainshock at about 10 p.m. Saturday night) were felt over all of Washington and parts of Oregon, Idaho, Montana, Alberta, and

These reported times vary by as much as half an hour. Some of them may refer to different shocks, but the differences are within the precision typical of time observations in the late nineteenth century. Most localities seem to have been on approximate local sun time, so most eastern reports are later than western reports. The times reported for the mainshock increase from west to east by about half an hour but are too inconsistent to firmly associate the times of the aftershocks (Table 2 and Fig. 3). Montana Earthquakes

Some confusion arises in the 1872 reports because of a series of western Montana earthquakes beginning on 10 December (Table 3). Dates and times of many of the reports are ambiguous, but careful reading of the reports suggests that the Washington earthquake on the 14th was in fact felt in Montana: “The series of earthquakes recorded last week was succeeded by another this [week], the first of which, quite strong, occurred at 10:35 p.m. Saturday” (The New Northwest, Deer Lodge, Montana, 21 December 1872). S–P Times for the 1872 Earthquake

At two locations, felt reports of sudden changes in shaking intensity have been interpreted to yield S–P times for the 1872 earthquake (Coombs et al., 1976). Coombs et al. (1976), however, noted that the inferred S–P times are inconsistent with an Entiat area epicenter (Fig. 4). Here, we use broadband seismograms recorded along similar ray paths to investigate why the inferred S–P times underestimate the observed S–P times by several seconds for an Entiat epicenter. One S–P time is estimated from a report made in Olympia, Washington (Fig. 4), by Captain James S. Lawson, published in the Pacific Tribune (Rockwood, 1873; Plummer, 1896; Townley and Allen, 1939). Captain Lawson’s account is notable because he was a surveyor and maintained an accurate chronometer (Pacific Northwest Seismic Network,


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Table 1 Aftershock Reports, Times Are Given in Local Time (Locations Are Shown in Fig. 2) Location

Colfax, Washington Colville, Washington

Deer Lodge, Montana Fort Lapwai, Idaho

Fort Simcoe, Washington Henry House, Alberta Hope, British Columbia Kittitas Valley, Washington Klickitat, Washington Lake Chelan, Washington

Lewiston, Idaho Matsqui, British Columbia Oyama (O'Hamet), British Columbia Olympia, Washington

Perry Creek, British Columbia Pine Grove, Washington Port Blakely, Washington Portland, Oregon Port Madison, Washington Port Townsend, Washington Puyallup, Washington

Reed’s Ferry, Idaho Seattle, Washington

Snoqualmie, Washington

Aftershock Report

1872/12/28 10:30, Saturday. 1872/12/29 10:00, Sunday. Several lighter shocks in the next 5 hrs. Continued at brief intervals for 10 days. Shocks almost every day (as of 12 January 1873). 1873/06/07. A severe shock and has continued to shake and tremble for short intervals ever since the big shake last fall. 1872/12/15 ~10:00, Sunday. Two sharp shocks separated by a very slight interval. 1872/12/14 20:00, Saturday (Foreshock? Mainshock reported at 22:00 here.) 1872/12/15 04:30, Sunday. Almost every hour until 5 a.m. Another not so heavy, half an hour after the mainshock with little or no rumbling. 1873/02/27 09:15, Thursday. Two more, lighter and shorter than the first. Second and third shocks of shorter duration. Daily repetition of slight shocks (as of October 1873). In 1873, from about mid-February throughout most of the rest of the year, the whole mountain range between Lake Wenatchee and Lake Chelan was shaken by continuing tremors that scarcely missed a day. Series of shocks, second lighter, 10 min after the first. Two distinct shocks, second less severe and shorter. Two distinct shocks, second lighter and of shorter duration. First shock followed at intervals of a few minutes by others, less violent. Later, slight trembling, hardly perceptible, several times. Continued all night. Ten distinct shocks during the night. Second shock (after mainshock) heavy; in 6 min another, and then two others 1 min apart. After 23:30 there were five others. First shock followed by seven others during the night. 1872/12/14 22:12:40, Saturday. 1872/12/15 00:00, Sunday. 1872/12/15 01:00, Sunday. 1872/12/15 03:00, Sunday. 1872/12/15 05:00, Sunday. 1872/12/15 06:30 or 06:40, Sunday. 1872/12/15 18:37:30, Sunday. 1872/12/16 09:17, Monday. 1872/12/17 13:45, Tuesday (or 1872/12/18). 1872/12/17 23:20, Tuesday. 1872/12/29 10:00, Sunday. 1872/12/29 later (after 10:00), Sunday. 1873/01/16 14:33, Thursday. 1873/01/22 12:00, Wednesday. 1873/03/(16?), Monday. Two other shocks were felt prior to 14 February 1873. 1872/12/29 10:00, Sunday. Occasional shocks continue (as of 17 January 1873). 1873/02/27 09:00, Thursday. 1872/12/15 02:30, Sunday. 1873/02/27 09:15, Thursday. 1872/12/20, Friday. 1873/01/16 14:33, Thursday. 1873/01/17, Friday. 1873/01/18 ~14:00, Saturday. 1873/01/19, Sunday. 1873/01/22 12:00–12:09, Wednesday. Two others of less duration and violence. Three series of shocks in 12 min, the others soon after the first but of shorter duration. 1872/12/17 23:00, Tuesday. 1872/12/18 01:00, Wednesday. 1872/12/19 14:30, Thursday. 1873/02/27 09:15, Thursday. Thirteen more shocks before daylight, one as heavy as the first. Since then (morning after mainshock) 10 shocks (until 17 December 1872). (continued)

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Table 1 (Continued) Location

Steilacoom, Washington Stuck Valley, Washington Texas Ferry, Washington The Dalles, Oregon

Walla Walla, Washington

Wallula, Washington Wenatchee, Washington Whitestone, Washington

Winesap (Entiat), Washington

Aftershock Report

Two distinct shocks accompanied by several minor shivers. 1872/12/15 03:00, Sunday. 1873/01/16 14:30, Thursday. 1873/01/22 12:00, Wednesday. Ten to twelve more shocks during the night, none as severe as the first. Four or five shocks. 1872/12/15 09:00, Sunday. 1872/12/18 09:00, Wednesday. Since 14 December, light shocks almost daily here and elsewhere (4 January 1873), another shock 10 min after the first, much lighter. Others during night. 1872/12/15 03:00, Sunday. 1872/12/15 07:00, Sunday. Mainshock followed by five lighter shocks at 15 min intervals. Continued at irregular intervals until 4 a.m. Lasted until 05:00 Sunday morning (15 December 1872), 64 shocks in all, 8 severe. Six distinct shocks. The earth is still trembling and there is an occasional shake (as of 27 December 1873). One hundred and forty-two distinct shocks at irregular intervals for 42 days (until 24 January 1873). On the upper Columbia, it has continued to shake at short intervals ever since 14 December (until 14 June 1873). 1873/06/07, Saturday. At Winesap, there were many shakes throughout the entire winter, these earthquakes, when they came, were in intervals of half an hour or longer. Continued to shake 4 or 5 yrs. Lighter shocks forming many small fissures for several years in the surrounding mountains.

Information is from Coombs et al. (1976). “O'Hamet” listed by Coombs et al. (1976) was determined to be Oyama by Dave Tillson (personal comm., to Margaret Hopper, 1977).

1999; see Data and Resources). Captain Lawson reported that the mainshock, at 9:40:30 p.m. local, “commenced with a light movement, gradually increasing for 18 or 20 seconds. Then came the heavy shock, lasting four or five seconds” (Rockwood, 1873, p. 41). Inferring that Captain Lawson’s reported first “light” movement was the P-wave arrival, and his “heavy shock” was the S-wave arrival, Coombs et al. (1976) estimated an S–P time of 18–20 s. However, if the Pn arrival from the 1872 earthquake was as emergent as that observed along a comparable ray path (Fig. 5a), Captain Lawson may have missed the beginning of arrival and thus

underestimated the interval between the P- and S-wave arrivals by several seconds. The second S–P time, from Soda Creek, British Columbia (Fig. 4), was estimated from a newspaper account published at Victoria, British Columbia (Victoria Daily Standard, p. 3, 16 December 1872). According to this account, “Two distinct shocks of earthquake were felt here last night. The first, which occurred about 10:15, was of considerable violence, and lasted about 25 seconds. After an interval of twenty-two seconds, a shock of less violence was felt.” Unlike the observation at Olympia, Washington,

Table 2 Reported (Local) Times for the Mainshock, Saturday, 14 December 1872 Location

Time (hh:mm)*

Location

Time (hh:mm)*

Location

Time (hh:mm)*

Astoria, Oregon Canyon City, Oregon Chilliwack, British Columbia Clinton, British Columbia Deer Lodge, Montana Fort Lapwai, Idaho Fort Simcoe, Washington Kittitas, Washington La Conner, Washington La Grande, Oregon Lewiston, Idaho Lytton, British Columbia New Dungeness, Washington Nicola Valley, British Columbia

21:31 22:00 21:25 21:30 22:35 22:20 21:40 22:20 22:00 22:00 22:20 21:45 22:22 21:45

Olympia, Washington Olympia, Washington Oregon City, Oregon Okanagan Lake Osoyoos Lakes, British Columbia Philipsburg, Montana Pine Grove, Washington Portland, Oregon Portland, Oregon Ribbon Cliff, Washington Seattle, Washington Seattle, Washington Snoqualmie, Washington Soda Creek, British Columbia

22:40 22:40:30 22:00

Spokane Bridge, Washington Steilacoom, Washington Texas Ferry, Washington Union, Oregon Victoria, British Columbia Victoria, British Columbia Virginia City, Montana Walla Walla, Washington Walla Walla, Washington Wallula, Washington Yakima, Washington Yale, British Columbia

22:00 21:50 21:55 22:15 21:37 21:30 22:00 22:00 22:03 21:20 22:00 21:43

*Arrival times are from Coombs et al. (1976).

22:00 22:27 21:50 21:35 21:40 23:00 21:40 21:34 22:00 22:15


Reported local time of mainshock (p.m.)

11:00

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Table 3 Montana Earthquakes, 10–14 December 1872, Given in Local Time Date

MST

Tuesday, 10 December 1872

4:35 p.m.

Wednesday, 11 December 1872 Wednesday, 11 December 1872 Wednesday, 11 December 1872

2:30 a.m.

Wednesday, 11 December 1872 Saturday, 14 December 1872

8:20 a.m.

10:00

9:20 -124

-120

-116

-112

Longitude ( o W)

Figure 3. Reported local times of the mainshock generally increase to the east, as expected if local times were solar times, but the inconsistencies of these times are sufficiently large to confidently preclude mutual association of times that were reported in different communities for some aftershocks. The solid trend line increases about 2.7 min/degree longitude but has a low R2 value of 0.11. The dashed line indicates the trend of sun time of 4 min/degree longitude.

we have no knowledge of the quality of the clock used to estimate the time durations at Soda Creek. Coombs et al. (1976) interpreted this account as indicating an S–P time of 47 s. This interpretation, however, seems unusual for this distance range because one would expect the shear-wave arrivals to have higher amplitude than the P-wave arrival. S-wave arrivals are significantly larger than P-wave arrivals on seismograms recorded along ray paths similar to those from the proposed 1872 epicenter at Soda Creek. This observation holds both for recordings made at station LLLB, at a distance of 350 km from a 2017 event, and at station UBRB, at a distance of 612 km from a 2013 event (Fig. 5b,c). These observations directly contradict the felt account at Soda Creek that the second arrival was not felt as strongly as the first. It is thus possible, perhaps even likely, that the first arrival felt at Soda Creek was actually the S-wave and/or surface-wavetrain produced by the mainshock, which has a duration of 20–25 s in the broadband seismograms (Fig. 5b,c). Our preferred interpretation of the Soda Creek account is that the second arrival was either a local earthquake, possibly triggered by the mainshock, or an aftershock, and therefore the times cannot be used to estimate the S–P time there. Calculations suggest that increasing the focal depth would not sufficiently reduce the S–P times to fit the estimated S–P times determined by Coombs et al. (1976). Relative to a surface focus, a focal depth at 35 km would decrease S–P times by about 2 s. This decrease is too small

6:35 a.m. 6:55 a.m.

~11:30 a.m.

Locations Reported at

Beartown, Blackfoot, Deer Lodge, Helena, Henderson, McClellan Gulch, Missoula, Mouth of Bear, Philipsburg, Warm Springs, and West Chicago. Reported not felt at Silver Bow, and Virginia City Blackfoot, Deer Lodge, Helena, and Philipsburg Blackfoot and Deer Lodge Deer Lodge, Helena, Philipsburg, and West Chicago McClellan Gulch Missoula, Montana, and River Station, Washington

Information is from Coombs et al. (1976). MST, mountain standard time.

to match the estimated S–P times, which are several seconds early. Furthermore, as noted by Spence (1989), a crustal mainshock is suggested by the vigorous aftershock sequence (Brocher et al., 2017), making a lower crustal/upper mantle earthquake unlikely. Observations of the Directions of Horizontal Shaking Unambiguous directions of horizontal shaking produced by the 1872 earthquake were reported from 23 locations (Pacific Northwest Seismic Network, 2002; see Data and Resources) having a fairly uniform azimuthal distribution around Entiat (Fig. 4). The shaking directions, reported at distances from Entiat ranging up to 690 km, were reported in 45° increments as simply north–south (N-S), east–west (E-W), northeast–southwest (NE-SW), or northwest–southeast (NW-SE) (Fig. 4 and Table 4). We assume that many towns and communities of the day would have been platted along north- or east-trending streets and that the buildings and residences built there would have oriented parallel or perpendicular to these streets. Thus, we believe that it would have been possible for observers to determine the direction of shaking that they observed to the accuracy that they reported. Both radial and transverse motions, consistent with Love or Rayleigh surface-wave arrivals, respectively, were observed. Both motions were reported along nearly identical azimuths at different epicentral distances (Fig. 4). The median misfits between the reported and calculated directions of shaking have a local minima at the Entiat area epicenter, where it is 20° (Table 4). These calculations

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Quesnellmouth UBRB

Modal Intensity Assignments for the 1872 Earthquake Henry House

BRITISH COLUMBIA

In their analysis of the location and magnitude of the 1872 earthquake, Bakun 52˚N et al. (2002) used modified Mercalli intensity (MMI) assignments (Wood and Neumann, 1931) for the earthquake that were developed by M. G. Hopper et al. LLLB Lytton (unpublished manuscript, 2003; see Data ALBERTA Oyama Kootenay and Resources) as discussed in the IntroYale duction. Because this report was never Matsqui published, here, we document the methVictoria odology followed to make their modal MONTANA intensity assignments for the 1872 earth48˚N Suggested 1872 epicenter Seattle quake. One major difference between GNW Skokomish these modal intensity values and previous WASHINGTON Olympia Kittitas intensity assignments is that modal intenValley Deer Lodge sities were assigned only for sites having Walla Walla Fort Simcoe intensities that were not based solely on LaGrande The Dalles ground failure or water effects. NewsVirginia City Union Salem IDAHO paper accounts used for the assignments Baker City of MMI III and higher are summarized Canyon City 44˚N in Appendix A. OREGON Ten sets of MMI assignments to the intensity data were used in the M. G. Hop400 km 200 0 per et al. (unpublished manuscript, 2003; see Data and Resources) study—one set 124˚W 120˚W 116˚W 112˚W by each of the five authors of the unpublished report (and an extra one using a difFigure 4. Map summarizing macroseismic observations of azimuths of horizontal ferent method by one author) and four shaking and time intervals from the perceived beginning of shaking and the onset of others assigned by other research teams shaking of a much different character for the 1872 earthquake (star). Shaded arcs show (Coombs et al., 1976; Scott, 1976; Weston ranges consistent with the estimated S–P times of 18–20 s at Olympia, Washington, and Geophysical Research, Inc., 1976; Wood44–47 s at Soda Creek, British Columbia, for the IASP91 model. Bars indicate reported directions of shaking: dashed lines show assumed linear ray paths. The dashed ellipse ward-Clyde Consultants, 1976). This outlines area minimizing misfit to reported directions of shaking. Locations of a June procedure treated each of the intensity 2013 ML 4.3 and a July 2017 M L 3.3 earthquake near the suggested epicenter and broadassignments as if they were equal and band stations GNW (Green Mountain, Washington), LLLB (Lillooet, British Columbia), independent. These assumptions may be and UBRB (Upper Baezaeko River, British Columbia) are also shown. questioned because the Coombs et al. (1976) report was commissioned as an independent panel of experts to settle serious assumed a linear ray path from the source to the locations discrepancies between previous reports by various consulwhere shaking directions were reported. Misfits calculated tants (e.g., Scott, 1976; Weston Geophysical Research, Inc., for different epicentral locations define a broad minima 1976; Woodward-Clyde Consultants, 1976). Coombs et al. (having comparable median misfits between 20° and 25°) (1976) reviewed all previous reports as well as the raw in which the dimension of the N-S uncertainty in epicentral felt data to draw their own conclusions about the intensities. location is about 50% greater than the dimension of the E-W Thus, the Coombs et al. (1976) assignments are neither uncertainty (Fig. 4). Outside of the broad minima, the misfits equal to nor independent of at least three of the other increase rapidly from 28° to as much as 31°, indicating that assignments. the observed shaking directions do provide resolution on the The 10 intensity assignments agreed completely at only epicentral location and that the Entiat area does represent a three sites: two places where the earthquake was reported not local minima in the misfit. Nonetheless, the large area of the felt and Olympia where the assignment of MMI VI was unanimisfit minima indicates that although the observed directions mous (Table 5). Elsewhere, the 10 agreed substantially for of shaking are most consistent with an Entiat epicenter, they about one-third of the sites (i.e., at least 9 of the 10 assigned only loosely constrain the epicentral location in an N-S one of two consecutive MMIs to the site) and disagreed substantially for about half of the sites (i.e., their MMI assigndirection. Soda Creek

M4.3 2013 earthquake

M3.3 2017 earthquake


(a)

Arbitrary units of amplitude

GNW

BHE Pn

Sn

10

30

50

BHN

Inferred S–P time

(b)

BHZ


LLLB

HHE

Pn

60

120

Sn

HHN

HHZ

(c)


UBRB

HHE

Pn

HHN

Sn

HHZ 120

160

200

240

280

Time, s

Figure 5.

Three-component broadband seismograms from 2013 M L 4.3 and 2017 ML 3.3 Entiat area earthquakes recorded along ray paths similar to those of observations of the 1872 earthquake made at Olympia, Washington, and Soda Creek, British Columbia. Locations of the earthquakes and stations GNW, LLLB, and UBRB are shown in Figure 4. Seismograms recorded at (a) station GNW and at (b) station LLLB for the 2017 event, as well as that recorded at (c) station UBRB for the 2013 event, show emergent Pn arrivals and more prominent Sn arrivals. The thick gray line in (a) indicates inferred S–P time at Olympia, Washington. All vertical-component (Z) seismograms as well as the horizontal components (E, N) in (c) were filtered with a 1-Hz high-pass filter. The gray shading for (a) and (b) indicates that the horizontal components were unfiltered.

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ments span four to six different MMIs). The resulting assignments (detailed further in Table 5) did not, therefore, reflect the views of any single person. Because the MMIs assigned to locations that reported solely ground effects in the 10 different lists varied so widely, and because experience with strong earthquakes in the decades since the introduction of the MMI scale has shown that the intensities inferred solely from ground effects tend to correlate poorly with intensities inferred from other macroseismic effects, no such sites were assigned intensities (in Table 5 they are assigned a G instead of an MMI). This omission substantially reduced disagreements among the various MMI assignments. The modal intensities lie generally within one unit of intensity with those reported by Coombs et al. (1976) (see Bakun et al., 2002). Several other intensity assignments, not shown in Table 5, were added to Figure 6 to provide better definition of the felt limit of the earthquake. The earthquake was not reported at either Roseburg, Oregon, or at Edmonton, Alberta, suggesting that the earthquake was not felt there (Weston Geophysical Research, Inc., 1976). Similarly, the Idaho World (Idaho City, Idaho, 26 December 1872) did not report that the earthquake was felt locally even though it reprinted an account of the earthquake as it was felt at nearby Baker City and La Grande, Oregon (Fig. 6). Because the newspaper editor at Idaho City knew that an earthquake had occurred, we interpret their nonreport as indicating that it was not felt there. We include an MMI III–IV for Missoula, Montana, based on the description that it was felt by at least several if not many and that its block of stone buildings rattled severely (Coombs et al., 1976). Although the account from Jacksonville, southern Oregon, is ambiguous, stating that “other parts of Northern and Eastern Oregon, and Washington Territory were also slightly shocked but without damage” (Democratic Times, 21 December 1872, p. 2, Jacksonville, Oregon), we interpret the word “also” to indicate that it was felt (MMI II) at Jacksonville: Coombs et al. (1976) interpreted this report as that it was not felt. The location for the MMI IV for O'Damet or O'Hamet, British Columbia, could not

74


Table 4 Directions of Horizontal Shaking Reported for the 1872 Earthquake Location

Direction of Reported Shaking*

Azimuth to Earthquake (°)

Difference (°)

Orientation

Possible Phase

Baker City, Oregon Canyon City, Oregon Deer Lodge, Montana Fort Simcoe, Washington Henry House, Alberta Kittitas Valley, Washington Kootenay, British Columbia La Grande, Oregon Lytton, British Columbia Matsqui, British Columbia Olympia, Washington Oyama, British Columbia Quesnellmouth, British Columbia Salem, Oregon Seattle, Washington Skokomish, Washington Soda Creek, British Columbia The Dalles, Oregon Union, Oregon Victoria, British Columbia Virginia City, Montana Walla Walla, Washington Yale, British Columbia

NW-SE N-S A little south of west N-S E-W E-W N-S N-S N-S N-S E-W NE-SW E-W NE-SW S-N NW-SE NE-SW E-W NE-SW E-W E-W NE-SW NE-SW

152 166 107 196 15 192 49 149 340 314 250 13 344 215 266 259 343 217 148 289 116 143 336

17 14 32 16 15 12 41 31 20 44 20 32 16 10 4 34 28 37 13 19 26 8 21

Radial Radial Radial Radial Transverse Transverse Radial Radial Radial Radial Radial Radial Transverse Radial Transverse Radial Radial Transverse Transverse Radial Radial Transverse Transverse

Rayleigh Rayleigh Rayleigh Rayleigh Love Love Rayleigh Rayleigh Rayleigh Rayleigh Rayleigh Rayleigh Love Rayleigh Love Rayleigh Rayleigh Love Love Rayleigh Rayleigh Love Love

*Directions of reported shaking are from newspaper accounts available at Pacific Northwest Seismic Network (2002, see Data and Resources). NW, northwest; SE, southeast; N, north; S, south; E, east; W, west; NE, northeast; SW, southwest.

be located by Coombs et al. (1976). O'Damet has since been identified as Oyama, near Okanagan Lake (Fig. 6). Finally, we differ from Coombs et al. (1976) in including the MMI IV at Oysterville, Washington, even though it was for an earthquake at 10:30 p.m. on 10 December, four days before the 1872 earthquake. Although the given date is not that expected, the reported time is consistent with other reported times, and we accordingly believe the notation probably referred to the 14 December earthquake. Unfortunately, the survival of a precariously balanced rock, Omak Rock, about 90 km NE of Entiat (Fig. 6), does not appear to provide strong constraints on the 1872 epicenter. Although Coombs et al. (1976) suggested that the rock’s survival indicated that the earthquake must have occurred at least 50 20 km from the rock, consistent with but not requiring an Entiat area location, Weichert (1994) argued that the rock could survive much larger ground motions than estimated by Coombs et al. (1976). Thus, the 1872 earthquake may have been much closer to Omak Rock than suggested by Coombs et al. (1976), further weakening the constraints imposed by the rock on the location of the epicenter.

Ground Failures and Water Effects Accounts of ground failures, including landslides and ground cracks (Coombs et al., 1976), were limited to a 270 km radius around Entiat (Fig. 6). Because of the many

factors that cause ground failures, it has been long known that such effects can occur at large epicentral distances in areas where the intensity implied by other macroseismic effects may be as low as MMI VI (Richter, 1958). However, contemporary accounts document important ground failures within 20 km of Entiat, including at Ribbon Canyon, Chelan, and Wenatchee (Fig. 7; Appendix B). The northwesterly dip of the fault scarp inferred by Sherrod et al. (2015) and B. L. Sherrod et al. (unpublished manuscript, 2017; see Data and Resources) would imply that many of these failures likely occurred in the hanging wall of the earthquake above the inferred fault rupture. The area encompassing the Entiat seismicity cluster, 680 km2 , encompasses most of the more spectacular ground failures (Fig. 7). This area would be consistent with an M 6.8 (Hanks and Bakun, 2002, 2008), which is the preferred moment magnitude for the 1872 earthquake determined by Bakun et al. (2002) from the modal intensity data. Coombs et al. (1976) noted that water effects such as aquifer changes, liquefaction, and seiches were also reported over a wide area (Fig. 6), providing little resolution of the epicenter. In contrast, a 20–30-ft (6–7 m) high artesian fountain created at Chelan Station (near Lake Chelan), located about 22 km from the nominal epicenter suggested in the Introduction, presumably resulting from liquefaction and high water pressure, may be more indicative of proximity to the epicentral region (Fig. 7; Appendix B). Empirical relationships determined by Kuribayashi and Tatsuoka (1975)


75

Table 5 Modal Intensity Assignments and an Explanation of How They Were Assigned Location

MMI

Method*

Location

MMI

Method*

Astoria, Oregon Aurora, Oregon Baker City, Oregon Camas Prairie, Idaho Canyon City, Oregon Cascades, Washington Chilliwack, British Columbia Clinton, British Columbia Colfax, Washington Columbia City, Washington Colville, Washington Corvallis, Oregon Deer Lodge, Montana Elk City, Idaho Eugene City, Oregon Fort Lapwai, Idaho Fort Shepherd, British Columbia Fort Simcoe, Washington Helena, Montana Henry House, Alberta Jefferson, Oregon Kalama, Washington Kittitas Valley, Washington Klickitat, Washington Kootenay, British Columbia La Conner, Washington La Grande, Oregon Lake Chelan, Washington Lewis River, Washington Lewiston, Idaho Lytton, British Columbia Matsqui, British Columbia New Dungeness, Washington New Westminster, British Columbia Nicola Valley, British Columbia Okanagan Lake, British Columbia Olympia, Washington Oregon City, Oregon Orodell, Oregon Osoyoos Lake, British Columbia Paradise Valley, Idaho Penawawa, Washington Pendleton, Oregon Perry Creek, British Columbia Philipsburg, Montana Pine Grove, Washington

V II† V II† IV II† VII VI II† II† VI Not felt IV III II† IV G‡ IV V III II† III VII V V V V G‡ V V V V VI II† VI G‡ VI III V VII V V V II† II† VI

Mode Felt Mode Felt Mode Felt Higher Mode Felt Felt Mode§ Mode Higher Higher Felt Mode — Mode

Port Gamble, Washington Portland, Oregon Port Madison, Washington Port Townsend, Washington Puyallup, Washington Quesnellmouth, British Columbia Race Rocks, British Columbia Rainier, Oregon Reed’s Ferry, Idaho Ribbon Cliff, Washington Rock Island, Washington Saint Helens, Oregon Salem, Oregon San Juan Camp, Washington Seattle, Washington Shuswap Prairie, British Columbia Skokomish, Washington Snoqualmie, Washington Snoqualmie Pass, Washington Soda Creek, British Columbia Spokane Bridge, Washington Spokane County, Washington Steilacoom, Washington Tenino, Washington Texas Ferry, Washington The Dalles, Oregon Tieton Basin, Washington Touchet, Washington Tukanon, Washington Tumwater, Washington Umatilla, Oregon Union, Oregon Vancouver, Washington Victoria, British Columbia Virginia City, Montana Walla Walla, Washington Wallula, Washington Wenatchee, Washington Weston, Oregon White Bluffs, Washington White Stone, Washington Willow Creek, Oregon Willow Forks, Oregon Winesap, Washington (Entiat) Yakima, Washington Yale, British Columbia

VI V VI VI VI IV V II† III G‡ G‡ II† IV II† VI VI V V VII V V G‡ V Not felt VI IV G‡ IV V VI V V VI VI III VI VI VIII G‡ G‡ G‡ V V VIII V VI

Mode Mode Mode|| Mode|| Mode Mode Higher Felt Higher — — Felt Mode Felt Mode Mode Mode Higher Mode Mode§ Higher — Mode Mode Mode§ Higher — Mode Mode Mode Mode Mode§ Mode Mode Mode Mode Mode Mode§ — — — Mode Higher Mode Mode Mode

Mode Felt Mode Mode Mode Mode Mode Mode§ — Mode Mode Higher Mode Mode Felt Mode — Mode Mode|| Mode Mode Mode Mode Higher Felt Felt Mode

*Histograms of 10 intensity assignments by nine researchers or research teams (Algermissen, Arnold, Brockman, Coombs et al., 1976, Hopper, Perkins, Scott, 1976, Weston Geophysical Research, Inc., 1976, and Woodward-Clyde Consultants, 1976) were consulted in the final decision for each modified Mercalli intensity (MMI) value. The mode of the distribution was usually chosen. However, if four MMI assignments were higher than the mode, then the next intensity above the mode was chosen. These two types of choices are denoted in the listed above by Mode and Higher. † MMI II was assigned to reports that said little more than, “The earthquake was felt here.” ‡ Locations reporting only ground failures were assigned a G rather than an MMI. §In the case of an even split of the 10 intensity assignments, the higher intensity was chosen. || Excluding Felts.

suggest that for an M 6.8 earthquake, liquefaction would be expected to maximum epicentral distances of 26–43 km. Although the reported 20- to 30-ft high waterspout at Chelan Station during the 1872 earthquake might seem

fanciful, there are several observations of spouts this high. Youd and Hoose (1978) provide accounts of spouting during the large 1906 San Francisco earthquake, at Milpitas, Newark, Salinas, and Union City, California. At these four

76


Edmonton (Not reported)

Quesnellmouth

Henry House

2

6

4

MMI

Soda Creek

65

0k

52˚N

m

Clinton

Shuswap Prairie Calgary

BRITISH COLUMBIA Nicola Valley

8

[USGS], 2017, Data and Resources). Finally, a 1-m high waterspout was reported at an epicentral distance of about 12 km from the 2001 M 7.7 Bhuj, India, earthquake (Tuttle et al., 2002); elsewhere water flowed from fissures for at least three weeks following the earthquake (Rajendran et al., 2001).

ALBERTA

Lytton Oyama Okanagan Lake

27

0k

m

Kootenay

Yale New Westminster

Discussion

Perry Creek Chilliwack

Fort Shepherd

Osoyoos Lake

Matsqui

Entiat’s proximity to the locations of many of the observations from the 1872 48˚N earthquake, and to the ongoing Entiat seisSuggested 1872 micity cluster, is highlighted in Figure 7. epicenter The location of the Spencer Canyon scarp, interpreted as a fault scarp resulting from coseismic slip during the 1872 earthquake, lies within several kilometers of Entiat (Sherrod et al., 2015; B. L. Sherrod et al., IDAHO unpublished manuscript, 2017; see Data OREGON 44˚N and Resources). The center of a prolific ongoing seismicity cluster, consisting of shallow earthquakes between 3 and 8 km 400 km 200 0 depth, lies just NE of Entiat (Brocher et al., 2017). Aftershock forecast models indi124˚W 120˚W 116˚W 112˚W cate that the earthquakes in this cluster could represent ongoing aftershocks of an Figure 6. Modal modified Mercalli intensities (MMI) for the 1872 earthquake (Table 5). Intensities for several additional locations are discussed in the Modal Intensity 1872 earthquake near Entiat with M 6.5 Assignments for the 1872 Earthquake section. Intensities are plotted as colored dots (Brocher et al., 2017). The inferred afterusing the ShakeMap and “Did You Feel It?” color palette (U.S. Geological Survey shock sequence underlies Spencer Canyon [USGS], 2016; see Data and Resources). Unfilled circles show locations that reported scarp, Wapato John’s (also known as John that the earthquake was either not felt or not reported. Filled squares show locations that reported ground or water effects only. Locations for Calgary, Alberta, and Boise, Wapato) damaged log cabin at Winesap Idaho, are plotted to provide geographic reference. The triangle indicates the intensity (assigned as MMI VIII), and the Ribbon center and the dark dashed line encircles the region having a 95% confidence level for Cliff landslide, as well as being proximal the epicenter of the 1872 earthquake (Bakun et al., 2002). Larger circle of 650 km to the artesian fountain reported near Lake radius encloses all but two felt observations. Smaller circle of 270 km radius encloses reported ground failures and water effects (Coombs et al., 1976). Black lines near Chelan and the intensity center determined Winesap (Entiat) show possible fault inferred from aeromagnetic anomaly data by Bakun et al. (2002; Fig. 7). (Brocher et al., 2017). Other observations described here are also most consistent with an Entiat area epicenter for the 1872 earthquake. The highest modal MMI for the earthquake, locations, waterspouts ranging from 10 to 20 ft high for fault VIII, was assigned only to Winesap and rupture distances between 21 and 26 km were reported. Wenatchee (Table 5). Aftershocks were perceived for more Newspaper reports indicate a 30-ft high waterspout near than three months only at Lake Chelan, Winesap, and WeDenman Island, British Columbia, during the 1946 M 7.2 natchee (Fig. 2). Indeed, an Entiat resident, Peter Wapato Vancouver Island earthquake (Rogers, 1980). Waterspouts (also known as Wapato Peter), reported shocks continuing as high as 30–40 ft were reported on tidal flats in Alaska for 4 or 5 yrs (Table 1). Many of the ground effects shown during the great 1964 Alaska earthquake (Reimnitz and Marin Figure 7 lie within the Entiat seismicity cluster, which shall, 1965). Waterspouts of 15–20 ft height were reported at given the NW dip of the fault plane responsible for the Chilly Buttes, Idaho, about 11 km from the epicenter of the Spencer Canyon scarp, is consistent with the interpretation 1983 M 6.9 Borah Peak earthquake, and spewed water for that many of these effects occurred within the hanging-wall several minutes with lesser flows lasting for several hours block of the rupture. (Youd et al., 1985; Stover, 1987; U.S. Geological Survey Colville

Victoria

WASHINGTON

La Conner

Race Rocks

Port Townsend

Lake Chelan

New Dungeness

Port Gamble Port Madison Snoqualmie

Winesap

Spokane County

White Stone

Spokane Bridge

Wenatchee

Seattle

Skokomish

MONTANA

Omak Rock

Pine Grove

Rock Island

Snoqualmie Pass

Puyallup Steilacoom

Olympia Tumwater

Tenino (not felt)

Texas Ferry

White Bluffs

OCEAN

Astoria

Tukanon

Saint Helens

Fort Simcoe

Klickitat

Cascades

Aurora

Salem

Wallula

Walla Walla

Willow Forks

Umatilla

Willow Creek

Helena

Fort Lapwei

Deer Lodge

Reed’s Ferry

Camas Prairie

Virginia City

Orodell

Union

La Grande

Baker City

Jefferson

Corvallis (not felt)

Canyon City

Eugene City

Idaho City (Not reported)

Boise

Roseburg (Not reported)

Jacksonville (Felt?)

Phillipsburg

Elk City

Pendleton

The Dalles

Paradise Valley

Lewiston

Touchet

Weston

Vancouver

Portland

Oregon City

PACIFIC

Pen-awawa

Yakima

Rainier Kalama Lewis River Columbia City

Missoula

Colfax

Kittitas Valley

Tieton Basin

Oysterville


77

tions of the aftershock sequence as perceived at different communities, modal intensity data, locations of ground failures and water effects, and the directions of shaking. Only in the Entiat area between Lake Chelan and Wenatchee were aftershocks reported felt for over a year. The analysis by Bakun et al. (2002) of the modal intensity assignments for the 1872 earthquake is consistent with an epicenter near Entiat and a magnitude of about M 6.8. Large well-documented ground failures and an artesian fountain lie within or proximal to the ongoing Entiat seismicity cluster. If the observed directions of horizontal shaking at 23 locations are assumed to describe surface waves, then they are consistent with an epicenter near Entiat.

Data and Resources Figures 1, 2, 4, and 6 were prepared using the Generic Mapping Tool (Wessel and Smith, 1991; Wessel et al., 2013). Newspaper reports for intensity observations from the 1872 earthquake can be accessed online at Pacific Northwest Seismic Network (PNSN, 2002, https://assets. pnsn.org/legacy_news/PRESS_RELEASES/ northcascades.html, last accessed July 2017). Other data are available in the unpublished manuscripts by M. G. Hopper, S. T. Algermissen, D. M. Perkins, S. R. Figure 7. Map of the Entiat area showing locations for the reported shaking effects, Brockman, and E. P. Arnold (2003), “The ground failures, and water effects (see Appendices A and B for more detailed descriptions). The approximate location of the Spencer Canyon scarp, believed to represent December 14, 1872, earthquake in the surface offset formed along the fault plane during the 1872 earthquake (Sherrod et al., Pacific Northwest,” and in B. L. Sherrod, 2015; B. L. Sherrod et al., unpublished manuscript, 2017; see Data and Resources), is R. J. Blakely, and C. S. Weaver (2017), also shown. The dashed rectangle outlines the area of Entiat seismicity cluster (Brocher 2 “LiDAR and paleoseismology solve et al., 2017). The 680 km area of the cluster approximates the rupture area for an M 6.8 140-yr old earthquake mystery in the earthquake (Hanks and Bakun, 2002, 2008), which corresponds with the magnitude inferred for the 1872 earthquake from intensity data (Bakun et al., 2002). The suggested Pacific Northwest U.S.A.” Information 1872 epicenter (star) represents the middle of the Entiat seismicity cluster. The triangle on the June 2013 M L 4.3 and July 2017 indicates intensity center determined by Bakun et al. (2002). Locations of MMI VIII for ML 3.3 events used to interpret Winesap and Wenatchee from Table 5 are also shown. S–P times for the 1872 earthquake can be found at U.S. Geological Survey (USGS, 2017, https://earthquake.usgs .gov/earthquakes/eventpage/uw60546146#executive, last Conclusions accessed September 2017; and https://earthquake.usgs.gov/ The discovery of the Spencer Canyon fault scarp and the earthquakes/eventpage/uw61284707#executive, last accessed ongoing activity in a seismicity cluster near Entiat, WashingSeptember 2017), respectively. Some information was obtained ton, suggest an epicenter near Entiat for the 1872 earthquake from comments on PNSN (1999, https://assets.pnsn.org/HIST_ (Sherrod et al., 2015; Brocher et al., 2017; B. L. Sherrod CAT/1872/aftershock_comments.html, last accessed August et al., unpublished manuscript, 2017; see Data and Resour2017). The color palette used in Figure 6 is available at ces). Our review suggests that almost all other available geoUSGS (2016, https://usgs.github.io/shakemap/manual3_5/ logical and seismological evidence are compatible with an tg_intensity.html#color-palette-for-the-shakemap-instrumentalepicenter near Entiat. These observations include the duraintensity-scale, last accessed November 2017). Magnitudes

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for the 1983 M 6.9 Borah Peak earthquake can be found at USGS (2017, https://earthquake.usgs.gov/earthquakes/eventpage/ usp0001zbv#scientific, last accessed September 2017).

Acknowledgments This work was funded by the U.S. Geological Survey (USGS) Earthquake Hazard Program. Conversations with Tom Holzer about waterspouting during earthquakes helped improve the article. Reviews by Jim Dewey, Garry Rogers, Patricia McCrory, Ivan Wong, Tom Pratt, and an anonymous reviewer greatly strengthened the article. Jim Dewey showed the authors the location of the paper copies of manuscripts prepared by Margaret Hopper and her colleagues and also supplied the figures for stations GNW and LLLB used in Figure 5. Allison Bent kindly plotted the data for station UBRB used in Figure 5.

References Bakun, W. H., R. A. Haugerud, M. G. Hopper, and R. S. Ludwin (2002). The December 1872 Washington state earthquake, Bull. Seismol. Soc. Am. 92, 3239–3258. Brocher, T. M., R. J. Blakely, and B. L. Sherrod (2017). Evaluating spatial and temporal relations between an earthquake cluster near Entiat, central Washington, and the large December 1872 Entiat earthquake, Bull. Seismol. Soc. Am. 107, no. 5, 2380–2393, doi: 10.1785/0120170113. Bushby, A. T. (1872). Diary entry in a journal written from Dec. 10, 1872 to Sept. 10, 1874 (written while in Yale on trip from New Westminster to Cariboo, British Columbia), transcribed by Judith Zach, 84, typescript, The Archives of British Columbia. Coombs, H. A., W. G. Milne, O. W. Nuttli, and D. B. Slemmons (1976). Report of the review panel on the December 14, 1872 earthquake in Washington Public Power Supply System Nuclear Projects Nos. 1 and 4, preliminary site analysis report, Amendment 23, Vol. 2A, Subappendix 2R-A, 30 p., Appendix B, Reports related to the December 14, 1872 earthquake, 247 p., Report to the U.S. Nuclear Regulatory Commission, Washington, D.C. Dieterich, J. H. (1994). A constitutive law for rate of earthquake production and its application to earthquake clustering, J. Geophys. Res. 99, 2601–2618. Evernden, J. F. (1975). Seismic intensities, “size” of earthquakes and related parameters, Bull. Seismol. Soc. Am. 65, 1287–1313. Hanks, T. C., and W. H. Bakun (2002). A bilinear source-scaling model for M–log A observations of continental earthquakes, Bull. Seismol. Soc. Am. 92, 1841–1846. Hanks, T. C., and W. H. Bakun (2008). M–log A observations for recent large earthquakes, Bull. Seismol. Soc. Am. 98, 490–494. Kuribayashi, E., and F. Tatsuoka (1975). Brief review of liquefaction during earthquakes in Japan, Soil Found. 15, 81–92. Madole, R. F., R. L. Schuster, and A. M. Sarna-Wojcicki (1995). Ribbon Cliff landslide, Washington, and the earthquake of 14 December 1872, Bull. Seismol. Soc. Am. 85, 986–1002. Malone, S. D., and S. S. Bor (1979). Attenuation patterns in the Pacific Northwest based on intensity data and the location of the 1872 north Cascades earthquake, Bull. Seismol. Soc. Am. 69, 531–546. Milne, W. G. (1956). Seismic Activity in Canada West of the 113th Meridian, 1841–1951, Vol. 18, Canada Dominion Observatory (Ottawa) Publ., Ottawa, Canada, 126–127. Phillips, W. S., and R. J. Stead (2008). Attenuation of Lg in the western U.S. using the USArray, Geophys. Res. Lett. 35, L07307, doi: 10.1029/ 2007GL032926. Plummer, F. G. (1896). Reported earthquakes on the Pacific Coast, Publ. Astron. Soc. Pac. 8, 78. Rajendran, K., C. P. Rajendran, M. Thakkar, and M. P. Tuttle (2001). The 2001 Kutch (Bhuj) earthquake: Coseismic surface features and their significance, Curr. Res. 80, 1397–1405.

Reimnitz, E., and N. F. Marshall (1965). Effects of the Alaska earthquake and tsunami on recent deltaic sediments, J. Geophys. Res. 70, 2363– 2376. Richter, C. F. (1958). Elementary Seismology, W. H. Freeman and Company, San Francisco, California. Rockwood, C. G., Jr. (1873). Notices of recent earthquakes, Am. J. Sci. Series 3 6, no. 31, 40–43. Rogers, G. (1980). A documentation of soil failure during the British Columbia earthquake of 23 June, 1946, Can. Geotech. J. 17, 122–127. Rylatt, R. M. (1872). Leaves from my diary, two years with the Canadian Pacific Railroad Survey, Rock Mountain Division, typescript, Provincial Archives, 258 pp. Scott, N. H. (1976). Evaluation of the Epicenter and Intensity of the Pacific Northwest Earthquake of December 1872, Prepared for Bechtel, Inc., September 1976, 24 p. Sherrod, B. L., R. J. Blakely, and C. S. Weaver (2015). LiDAR helps identify source of 1872 earthquake near Chelan, Eos Trans. AGU 97, Abstract T31A–2826. Spence, W. (1989). Stress origins and earthquake potentials in Cascadia, J. Geophys. Res. 94, 3076–3088. Stover, C. W. (1987). United States Earthquakes, 1983, Washington, D.C., U.S. Geol. Surv. Bull. 1698, 196 p. Townley, S. D., and M. W. Allen (1939). Descriptive catalog of earthquakes of the Pacific Coast of the United States 1769 to 1928, Bull. Seismol. Soc. Am. 29, no. 1, 1–297. Tuttle, M. P., J. Hengesh, K. B. Tucker, W. Lettis, S. L. Deaton, and J. D. Frost (2002). Observations and comparisons of liquefaction features and related effects induced by the Bhuj earthquake, Earthq. Spectra 18, Supplement A, 79–100. Weichert, D. (1994). Omak Rock and the 1872 Pacific Northwest earthquake, Bull. Seismol. Soc. Am. 84, no. 2, 444–450. Wessel, P., and W. H. F. Smith (1991). Free software helps map and display data, Eos Trans. AGU 72, 441. Wessel, P., W. H. F. Smith, R. Scharroo, J. F. Luis, and F. Wobbe (2013). Generic Mapping Tools: Improved version released, Eos Trans. AGU 94, 409–410. Weston Geophysical Research, Inc. (1976). The 1872 Earthquake, Significant Data and Conclusions, Prepared for United Engineers & Constructors, Inc., pages unnumbered, 4 plates. Wood, H. O., and F. Neumann (1931). Modified Mercalli intensity scale of 1931, Bull. Seismol. Soc. Am. 21, 277–283. Woodward-Clyde Consultants (1976). Review of the Pacific Northwest Earthquake of December 14, 1872, Richland, Washington, Washington Public Power Supply System, San Francisco, California, Woodward-Clyde Consultants, 51 p. and 1 plate. (Although undated, a 1976 publication date is assumed because the last references in the reference are from 1976 and because four researchers quoted in this report published their isoseismal maps for the 1872 earthquake in 1975 and 1976.) Youd, T. L., and S. N. Hoose (1978). Historic ground failures in northern California triggered by earthquakes, U.S. Geol. Surv. Profess. Pap. 993, Vol. iv, 177 p., 5 plates. Youd, T. L., E. L. Harp, D. K. Keefer, and R. C. Wilson (1985). The Borah Peak, Idaho, earthquake of October 28, 1983—Liquefaction, Earthq. Spectra 2, 71–89. Zdanowicz, C. M., G. A. Zielinski, and M. S. Germani (1999). Mount Mazama eruption: Calendrical age verified and atmospheric impact assessed, Geology 27, no. 7, 621–624, doi: 10.1130/0091-7613(1999) 0272.3.CO;2.

Appendix A Summary of Newspaper and Other Accounts of the 1872 Earthquake Newspaper and other historical accounts used to assign modified Mercalli intensities (MMIs) were compiled by

Aftershocks, Earthquake Effects, and the Location of the Large 14 December 1872 Earthquake near Entiat Coombs et al. (1976), and are available online at Pacific Northwest Seismic Network (2002; see Data and Resources). To further enhance their availability in the literature, we summarize accounts that were assigned modal intensities of III and higher.

Intensity III Elk City, Idaho—“To the east of here, as far as Elk City, it was felt very plainly” (Idaho Signal, Lewiston, Idaho, 21 December 1872, p. 3). Henry House, Alberta—“quite a severe shock of earthquake was felt. The oscillation made us quite dizzy; and at first, each man looked at the other, thinking a feeling of dizziness had come over himself, but a low mumbling sound, not very distinct, nor very near apparently, and the sight of the several pairs of new boots hanging from the walls overhead, and gently swinging to and fro convinced us of the fact” (Rylatt, 1872, p. 147). Kalama, Washington—“In the vicinity of Kalama it was hardly noticed” (Kalama Beacon, Kalama, Washington, 21 December 1872, p. 1). Oregon City, Oregon—“A great many people” felt it, but not the newspaper editor, and “it did no damage” (Oregon City Enterprise, Oregon City, Oregon, 20 December 1872, p. 3). Reed’s Ferry, Idaho—“It was felt very plainly,–at Camas Prairie more particularly than elsewhere except at Reed’s Ferry, northeast of the latter place” (Idaho Signal, Lewiston, Idaho, 21 December 1872, p. 3). Virginia City, Montana—“Several of our citizens speak of having recognized a slight shake” and “a suspended lamp vibrating back and forth as a pendulum of a clock” (Weekly Montanian, Virginia City, Montana, 19 December 1872, p. 5).

Intensity IV Canyon City, Oregon—The earthquake caused the “clink of glass and earthen ware, with the simultaneous movement of hanging lamps, tin ware, harness and other pendulous articles.” Lamps swung “and everybody soon agreed that it was a real, genuine earthquake in a mild form” (The Weekly Mountaineer, The Dalles, Oregon, 28 December 1872). Deer Lodge, Montana—“A noiseless, smooth wave from a little south of west that gave lamps with five feet suspension an oscillation of 12 to 14 inches” but caused “no particular damage” (The New Northwest, Deer Lodge, Montana, 21 December 1872). Fort Lapwai, Idaho—“A gentleman was rudely awakened, and in a moment after heard a terrific uproar in his chicken-coop. He jumped out of bed, and with a lighted candle in one hand and an ax in the other he went for the [imagined] intruder with dire intent” (Idaho Signal, Lewiston, Idaho, 21 December 1872, p. 3). Fort Simcoe, Washington—“The buildings here shook like leaves in a heavy wind. The doors, windows, and every-

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thing that was not a positive fixture, rattled, and seemed for a few moments to indicate that we were to have a general crash” (Pacific Christian Advocate, Portland, Oregon, 26 December 1872, p. 2). Quesnellmouth, British Columbia—“A slight shock of earthquake was felt here yesterday evening about 10 o’clock. The motion … resembled the action of a wave and lasted about half a minute. No damage done” (Cariboo Sentinel, Barkerville, British Columbia, 21 December 1872). Salem, Oregon—“A slight earthquake shock was sensibly felt by a number of people in this city” (Willamette Farmer, Salem, Oregon, 21 December 1872). The Dalles, Oregon—The earthquake “did little or no damage. The vibrations lasted probably thirty seconds, and seemed to be from the east to the west. … Animals, especially cows, dogs, and swine, seemed to experience the disturbance if we judge from the commotion they made at that time” (The Weekly Mountaineer, The Dalles, Oregon, 21 December 1872, p. 2). Touchet, Washington—“On the first rumbling of the earthquake, [a man] concluded that robbers were about to make a raid on his house, and, seizing a revolver, rushed to the door” (Walla Walla Weekly Statesman, Saturday, 21 December 1872).

Intensity V Astoria, Oregon—The shock caused “some to jump out of the bed and rush into the street. The clock attached to the U.S. Coast Survey Tidal Observatory was stopped at thirtyone minutes past nine o’clock P.M.” (Plaindealer, Roseburg, Oregon, 27 December 1872, p. 3). Baker City, Oregon—The shock commenced quite severe, causing “the houses to vibrate in all directions, causing the doors to fly open, stoves and dishes, and other movable things to rattle” (Bedrock Democrat, Baker, Oregon, 18 December 1872, p. 2). Several clocks stopped (Scott, 1976). Helena, Montana—“A big piece of plaster fell down” (Weekly Montanian, Virginia City, Montana, 19 December 1872, p. 5). Klickitat, Washington—“A severe shock of earthquake was felt throughout the Klickitat valley, the first shock lasting say one minute” (Pacific Christian Advocate, Portland, Oregon, December 1872, p. 5). Kootenay, British Columbia—“Every one was excited. The Indians were the worst frightened; their lodge poles danced and swayed, the dogs howled” (Walla Walla Statesman, 29 March 1873). La Conner, Washington—“It was so violent that people vacated their houses, which shook like cradles, very quickly” (Daily British Colonist, Victoria, British Columbia, 15 December 1872, p. 3). No damage was reported. La Grande, Oregon—People were awoken by the earthquake; vibrations were gentle, not violent; frightened quite a number; bed moved in various directions; some were made

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dizzy, “thought their senses were leaving them”; no damage (Scott, 1976, p. 12). Lewis River, Washington—“The vibrations were so violent as to shake the chickens from the roost, and to unnerve the confidence of the strongest” (Daily Oregonian, Portland, Oregon, 17 December 1872). Lewiston, Idaho—“Persons who were up at the time ran into the streets, while those who had retired supposed that a fierce and sudden gust of wind caused their buildings to sway and rock. Clocks were stopped and crockery and glassware caused to jingle. Frightened chickens flew about as though possessed by the devil. Dogs howled, cattle lowed, and all nature, animate and inanimate, was much disturbed” (Idaho Signal, Idaho City, Idaho, 21 December 1872, p. 3). Lytton, British Columbia—“Quite a heavy shock of earthquake was felt here last night at 9:45 o’clock. The vibration … lasted about twenty-five seconds. A noise like the rumbling of a carriage preceded the shock about one minute” (Victoria Daily Standard, Victoria, British Columbia, 16 December 1872, p. 3). Matsqui, British Columbia—“The first [shock], … was very severe, causing the houses to shake violently, and lasted for about 30 seconds” (Daily British Colonist, Victoria, British Columbia, 15 December 1872, p. 3). Orodell, Oregon—“People were awakened from sound sleep and frightened by the rattling of furniture and dishes” (The Mountain Sentinel, Union, Oregon, 21 December 1872). Paradise Valley, Idaho—“The shock was so severe as to make everything fairly dance” (Idaho Signal, Lewiston, Idaho, 21 December 1872, p. 3). Penawawa, Washington—“The force was so great as to throw dishes from the shelves, and generally disarrange domestic, utensils. One man, who was resting on the ground, said that it lifted him two feet in the air, and, at the moment, confessed to being badly freight-ened” (Walla Walla Statesman, 21 December 1872). The same report states that a wood pile swayed. Pendleton, Oregon—“The shock lasted a minute. In this county no damage was done, no clocks stopped, nor no crockery smashed…. At Pendleton in Umatilla county the shock was about the same as [at Union]” (The Mountain Sentinel, Union, Oregon, 21 December 1872). Portland, Oregon—“Chandeliers verberated and clocks were stopped. At the Clarendon Hotel guests rushed from their rooms to the street” (Daily British Colonist, 17 December 1872, p. 3). Distinctly felt in East Portland (Scott, 1976). Race Rocks, British Columbia—“The Light keeper reports that the [lighthouse] tower and lantern at Race Rocks were severely shaken by the earthquake…. Things rattled away at a lively rate for some seconds, but no damage was done” (Daily British Colonist, Victoria, British Columbia, 19 December 1872, p. 3). Skokomish, Washington—“Water was spilled from a barrel ….that was not full by six inches. Chickens were thrown from the roost, clocks stopped, etc. The clothing

hanging in [a] room vibrated almost two or three inches” (The Weekly Echo, Olympia, Washington, 2 January 1873). Snoqualmie, Washington—“The first [shock] was about 10 o’clock on Saturday night, lasting a minute and a half, and was very heavy” (Weekly Pacific Tribune, Olympia, Washington, 28 December 1872). Soda Creek, British Columbia—“The first [shock], … was of considerable violence, and lasted about twenty-five seconds. After an interval of twenty-two seconds, a shock of less-violence–was felt” (Victoria Daily Standard, 10 January 1872, p. 1) Spokane Bridge, Washington—“The first one was very severe, lasting about thirty seconds” (Walla Walla Statesman, 17 December 1872). Steilacoom, Washington—“Some of the people had retired to rest, but were aroused by the [earthquake]….chickens were knocked from their perches, windows cracked, and pendant lamps vibrated describing an arc of 90 degrees. We judge the shocks were most severely felt by the Masonic fraternity (who were communing at the time on the third floor…) by the manner in which the members came down stairs and hurried out on the street” (Puget Sound Express, 19 December 1872, p. 2). Tukanon, Washington—“people were rolled out of their beds” (Idaho Signal, Lewiston, Idaho, 21 December 1872, p. 3). Umatilla, Oregon—Heavy shock (Scott, 1976) but no damage (Weekly Corvallis Gazette, 21 December 1872, p. 3). Union, Oregon—“In this county no damage was done, no clocks stopped, nor no crockery smashed.…cracks or openings, of very limited extent however, were left in the earth, unlike those made by the frost” (The Mountain Sentinel, Union, Oregon, 21 December 1872). Willow Creek, Oregon—A witness there stated that “the late earthquake shock was so severe …, that he was nearly thrown out of his bed, and that articles suspended on the walls oscillated like a clock pendulum. The animals, cattle and horses, seemed to be greatly terrified” (Willamette Farmer, Salem, Oregon, 28 December 1872, p. 4). Willow Forks, Oregon—People “were very much disturbed on the night of the earthquake. A few got mad …, as they thought some were playing tricks on them by rattling their windows and doors, and otherwise disturbing their peace” (Willamette Farmer, Salem, Oregon, 3 January 1873, p. 4). Yakima, Washington—The earthquake “was quite severe… people rushed out of doors in a great state of alarm with clubs, revolvers and shot guns, thinking the Indians had made a general attack and were tearing up things generally” (The Oregonian, Portland, Oregon, 30 December 1872). Buildings and a flagpole swayed (Scott, 1976).

Intensity VI Clinton, British Columbia—“The shock was so heavy as to waken persons who were asleep and persons who were

Aftershocks, Earthquake Effects, and the Location of the Large 14 December 1872 Earthquake near Entiat standing were staggered almost off their feet…. At the lower end of town the ground is cracked for some distance. It occasioned considerable excitement and some alarm” (Victoria Daily Sentinel, 16 December 1872, p. 3). No building damage was reported (Scott, 1976). Colville, Washington—“The earthquake … shook down bottles and crockery from the shelves, stopped the clocks and frightened people generally” (Puget Sound Daily Courier, Olympia, Washington, 3 January 1873). New Dungeness, Washington—“It commenced vibrating at 22 minutes past 10 P.M., gradually increasing to such violence that the [lighthouse] tower rocked to and fro, most alarmingly. The tower and dwelling were very badly cracked” (The Olympia Transcript, 1 February 1873, p. 3). Nicola Valley, British Columbia—Report dated 15 December. “Last night about a quarter to ten o’clock we experienced quite a severe shock of earthquake which lasted about twelve minutes; the trees vibrated to and fro, as under the influence of a strong wind” (Daily British Colonist, Victoria, British Columbia, 29 December 1872, p. 3). Olympia, Washington—“All the clocks with pendulums moving east and west had stopped….Chimneys were cracked, milk thrown from pitchers on shelves, animals startled, everything pendent set to swing, doors rattled, and every animate and inanimate object was agitated more or less. People moving on the streets at the time did not experience any motion, but witnessed the swaying of street poles, etc., in every part of the town” (Daily Pacific Tribune, Olympia, Washington, 16 December 1872, p. 3). Pine Grove, Washington—“A terrible shock of earthquake was felt…. It threw chickens from their roosts, and caused large log houses to oscillate like a ship in a storm on the ocean. The shock was so terrific, that it knocked most of my goods off my shelving, breaking crockery ware, etc., in consequence of which I am considerably out and injured” (Walla Walla Union, 21 December 1872). Port Gamble, Washington—“Things were pretty well shaken up. The Teekalet Hotel was so jarred and tilted from side to side as to terrify the inmates, who rushed out of doors fearing the building would fall and crush them. The people were generally alarmed afraid to sleep in their own houses, and many thinking it safer, went down to the ships and steamers at the wharves to spend the remainder of the night on board” (Daily Pacific Tribune, Seattle, Washington, 16 December 1872, p. 2). Port Madison, Washington—“Our citizens were surprised and startled by an earthquake that shook the buildings until everything rattled and creaked and strained like a ship in a cyclone” (The Weekly Echo, Olympia, Washington, 19 December 1872). Puyallup, Washington—“The late earthquake was very severe; shaking fowls from their perches, prostrating large trees and startling people generally” (The Olympia Transcript, 4 January 1873, p. 3). Seattle, Washington—“Several clocks were stopped, swinging lamps put in motion, doors jarred, restless people

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waked up, timid people kept awake, everybody set to talking, some to trembling, others to laughing …. No one nor anything was hurt, and people sighed with relief at its cessation” (Daily Pacific Tribune, Seattle, Washington, 18 December 1872, p. 3). Water sloshed from water tanks and considerable quantities of crockery and glassware were broken in stores (Scott, 1976). Shuswap Prairie, British Columbia—“The earthquake made the houses and trees and everything rattle fearfully, so much so that the people up there (sic) thought the world was coming to an end; it lasted about minutes, and the ground heaved terribly” (Victoria Daily Standard, Victoria, British Columbia, 3 February 1872, p. 3). Texas Ferry, Washington—“It was so severe that it shook the chickens from their roosts. Every person in the house leaped from their beds, and ran out of the house for safety, when it began to subside” (Walla Walla Statesman, 21 December 1872). No damage was reported (Scott, 1976). Tumwater, Washington—“Felt as severely as in Olympia” (Daily Pacific Tribune, 16 December 1872, p. 2). Vancouver, Washington—Felt (Scott, 1976). Victoria, British Columbia—“A sharp shock of an earthquake which rocked houses violently and drove several families into the streets for safety. In some instances doorbells were rung, and crockery knocked from the shelves” (Daily British Colonist, Victoria, British Columbia, 15 December 1872, p. 3). The brick front wall of a building was reportedly cracked from cellar to garret and some plaster ceilings were badly cracked (Scott, 1976). Walla Walla, Washington—“Next the houses, trees and everything began to rock from southwest to northeast. Those who closely observed thought that in the height of a common door the top moved from side to side from four to six inches. The chandeliers in the stores and saloons swung from one to two feet, and kept it up for about three minutes, showing that although you could not feel it, still the earth was being disturbed. Almost all the pendulum clocks were stopped, and Straight’s big chronometer marked 3 minutes past IV. In just three seconds after the first distinct motion was felt, Main Street was filled by hundreds of men” (Walla Walla Union, 21 December 1872, p. 3). Another report stated that a brick wall of a hotel was cracked (Scott, 1976). Wallula, Washington—“Although the first shock was violent enough to shake buildings, and their contents up pretty lively, yet no damage or injury was sustained by any one, that I am aware of” (Willamette Farmer, Salem, Oregon, 21 December 1872). Yale, British Columbia—“an earthquake presented itself in rather an alarming manner by rattling doors, ringing bells, and causing the floors of dwellings to warp like the deck of a vessel in a heavy sea….that all fled in consternation to the street, where they freely discussed the strange phenomenon; fortunately more alarmed than injured” (Victoria Daily Standard, Victoria, British Columbia, 16 December 1872, p. 3).

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“All rushed out of the house-never so much alarmed in my life-dreadful sensation” (Bushby, 1872, p. 2).

building. Inside this cabin, sacks of flour stacked 4 feet deep were tossed about (Bakun et al., 2002).

Appendix B Intensity VII Chilliwack, British Columbia—“The first shock at 9:25 was very heavy; the houses vibrated and shook so that people started from their beds and fled to the open air, regardless of the piercing cold. The earth rolled like waves, and the water in the river much agitated. The fowls left their houses and rushed cackling to and from perfectly stupid” (Mainland Guardian, New Westminster, British Columbia, 19 December 1872, p. 5). “The houses commenced to oscillate; the earth rose like waves of the sea; the rivers splashed their banks; horses neighed and cattle lowed. No loss has been sustained save the displacing of some fencing” (Daily British Colonist, Victoria, British Columbia, 17 December 1872, p. 3). Pleasant Grove, Kittitas Valley, Washington—The earthquake threw “all the poultry from their roosts, frightening dogs, cats, horses, and cattle, stopping clocks, and jarring chimneys from their foundation. During the first shock, a low, rushing sound was heard as if a hurricane–was raging– also a strong sulphur odor prevailed” (Olympia Transcript, Olympic, Washington, 4 January 1873, p. 2). Osoyoos Lake, British Columbia—Felt severely (Scott, 1976). “The ground was cracked in several places, and a chimney of the house of Mr. T. Kruger was shaken down. The family were in the house at the time, and, although much frightened, escaped unhurt” (Daily British Colonist, Victoria, British Columbia, 17 December 1872, p. 3). Snoqualmie, Washington—From a report made from near the foot of the mountains dated 17 December 1872: “This valley has been pretty well shook up during the past three days with earthquakes. The first was about 10 o’clock on Saturday night, lasting a minute and a half, and was very heavy” (Weekly Pacific Tribune, Olympia, 28 December 1872).

Intensity VIII Entiat, Washington—A newspaper article published some 50 years after the 1872 earthquake stated that at John Wapato’s cabin 2 miles upstream of Ribbon Cliff (now Winesap) (Fig. 7), “the quake was so great that all the dirt on their log cabin was shaken down and the logs from one side caved in. The members of the family were afraid to go under the cabin any more, so they spent that night out in the open, although there was a light snow on the ground” (Wenatchee Daily World, Wenatchee, Washington, 8 August 1925). Wenatchee, Washington—A contemporary account was published in the Washington Standard, published in Olympia, Washington, on 11 January 1873, p. 2. The account states that at the Miller–Freer Brothers cabin at Wenatchee (Fig. 7), the two upper logs of the cabin wall and the roof were shifted, and the kitchen was separated from the main

Summary of Ground Failures and Water Effects near Entiat, Washington Ground Failures Ribbon Canyon landslide, Washington (Fig. 7)—The Spencer Canyon scarp is located about 10 km south of the large Ribbon Cliff landslide, along the Columbia River, one of the largest known or suspected ground failures resulting from the 1872 earthquake (Madole et al., 1995). Tephra and dendrochronology are consistent with the formation of the landslide during the 1872 earthquake (Madole et al., 1995). The northwest dip of the scarp (Sherrod et al., 2015) suggests that the Ribbon Cliff landslide lies within the hanging wall of the 1872 earthquake rupture (Fig. 7). Lake Chelan, Washington (Fig. 7)—“Along the banks of the Columbia river large masses of rocks have become detached from the banks and tumbled into the river, causing it to cut new channels” (Walla Walla Union, Walla Walla, Washington, 4 October 1873). A Rufus Woods interview 50 yrs after the earthquake quotes John Baptist Wapato (Chief John Wapato’s grandson): “The earthquake opened a seam in the earth at Chelan about a quarter of a mile from where the Campbell hotel now is. This seam opened up right in the middle of an Indian camp and soaked their provisions with foul smelling water” (Wenatchee Daily World, Wenatchee, Washington, 8 August 1925). Wenatchee, Washington (Fig. 7)—“Trees were crushed to pieces and the river became very muddy, raising three feet inside of ten minutes. Great masses of earth, as if from a tremendous land-slide, rushed down the mountain side, mixed with stone and wood, and the gulches lost their identity by being filled with debris” (Washington Standard, Olympia, Washington, 11 January 1873, p. 2). At nearby Rock Island (Fig. 6), a rock slide killed three people (The Oregonian, Portland, Oregon, 30 December 1872).

Water Effects Lake Chelan, Washington (Fig. 7)—Peter Wapato said, “At what is now Chelan Station a great hole opened in the earth and a veritable geyser was thrown into the air to a height of twenty or thirty feet. For weeks the Indians from all parts of the country came to see the strange phenomenon. The geyser continued all winter but got weaker and as time went on it subsided. Springs in this locality still remain to show the place where there occurred this remarkable water spout. The water being used to irrigate the Beebe orchards comes from this same point and comes through some sub-

Aftershocks, Earthquake Effects, and the Location of the Large 14 December 1872 Earthquake near Entiat terranean channel from Lake Chelan” (Wenatchee Daily World, Wenatchee, Washington, 15 June 1922, p. 5). North and South Beebe Springs emerge from a hillside just north of Chelan Station just above the Columbia River, about 300 feet below Lake Chelan (Fig. 7). Also at Lake Chelan, a natural lake, an unidentified correspondent 10 months after the earthquake wrote: “Some places the earth has sunk, other places lakes have formed where there was no sign formerly of water…. The Indians say… there was an issue of salt water from a fissure in the earth, that covered the ground knee deep, which, too, was charged with a most horrid smell” (Walla Walla Union, Walla Walla, Washington, 4 October 1873). Wenatchee, Washington—An account suggestive of a sand blow caused by liquefaction, or another change in the aquifer (Fig. 7): “There was an outburst of the pent up gasses on the east side of the Columbia that scattered the sand and dust far and wide, and from the fissures there is now flowing three living springs of fresh cold water, all adjacent to each

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other” (Walla Walla Union, Walla Walla, Washington, 27 December 1873, p. 3).

Earthquake Science Center U.S. Geological Survey 345 Middlefield Road, MS 977 Menlo Park, California 94025 [email protected] (T.M.B.)

U.S. Geological Survey Branch of Earthquake and Landslide Hazards Mail Stop 966, Box 25046 Denver Federal Center Denver, Colorado 80225 (M.G.H., S.T.T.A., D.M.P., S.R.B., E.P.A.)

Manuscript received 7 August 2017; Published Online 19 December 2017