(Basin and Range Province) Earthquake - University of Arizona

Contemporary Studies of the 3 May 1887 Mw 7.5 Sonora, Mexico (Basin and Range Province) Earthquake Max Suter

Max Suter

Instituto de Geología, Universidad Nacional Autónoma de México

INTRODUCTION The purpose of this paper is to highlight the outstanding studies George Emory Goodfellow (1855–1910) and José Guadalupe Aguilera Serrano (1857–1941) made of the devastating 3 May 1887 Mw 7.5 Sonora earthquake (Figure 1). Goodfellow’s observational study, based on his fieldwork in 1887 and partly published in Science in 1887 and 1888 (Goodfellow, 1887a, 1887b, 1888), includes the first surface rupture map of an earthquake in North America and photographs of the rupture scarp by Camillus Sidney Fly (1849–1901). Aguilera’s 1888 publication (in Spanish), which is based on his expedition to the epicentral region of this earthquake in the summer of 1887, includes the first geologic map of northeastern Sonora, a detailed surface rupture map, and the earliest isoseismal map, source parameters, and seismic velocities of an earthquake in North America. An abridged translated version of Aguilera’s 1888 article was published without figures in the Bulletin of the Seismological Society of America (Aguilera, 1920), and his rupture map was reproduced by Richter (1958, p. 595, Figure 31-2). Nevertheless, Aguilera’s and Goodfellow’s studies are not widely known today, and they are not given credit for their pioneering achievements in reviews of the history of seismology (for example, Davison, 1927; Agnew, 2002) or earthquake geology (historical vignettes in Yeats et al., 1997). Here I review the major accomplishments in Goodfellow’s and Aguilera’s contributions and place them in a historical context. The 3 May 1887 Sonora event is the largest historical earthquake of the southern Basin and Range tectonic-physiographic province and produced worldwide the longest recorded normalfault surface rupture in historic time. The end-to-end length of the rupture trace (Figure 2) measures 101.8 km. The magnitude of the event is estimated as Mw = 7.5±0.3 based on this distance and the surface rupture length versus magnitude regression for normal fault earthquakes by Wells and Coppersmith (1994, Table 2A). The rupture dips ~74° W (Suter and Contreras, 2002) and has a maximum vertical slip of 5.1 m, whereas the horizontal slip is negligible (Herd and McMasters, 1982). The earthquake reactivated three segments (Figure 2) of a normal fault zone that extends more than 300 km along the western margin of the Sierra Madre Occidental plateau (Figure 1). The

▲ Figure 1. Location map showing the rupture trace of the 1887 Sonora, Mexico, earthquake (within box, marked by bold black lines). B: Bavispe River; V: Óputo (now Villa Hidalgo); H: Huásabas; G: Granados; M: Oposura (now Moctezuma); gray solid line: international boundary; gray dashed lines: state boundaries; box: region covered by Figure 2.

fault zone separates the plateau from the Sonoran Basin and Range province (Brand, 1937), a series of north-south trending fault-bounded mountain ranges separated by river valleys. A seismotectonic map of this region including epicenters, focal mechanisms, and the traces of Basin and Range faults is provided in Suter and Contreras (2002, Figure 2). The occurrence and location of microseismicity (Natali and Sbar, 1982), the 26 May 1907 M I 5.2 Colonia Morelos, and the 7 May 1913 M I 5.0 and 20 December 1923 M I 5.7 Granados-Huásabas events (Suter, 2001) can be explained by an increase in static shear stress at the tips of the three rupture segments and on neighboring faults by the 1887 rupture (Suter and Contreras, 2002). The 1887 earthquake destroyed the town of Bavispe (Figures 1 and 2), where 42 lives were lost out of a population of 700 (Goodfellow, 1887b), and severely damaged the towns of Fronteras, Nacori Chico, Bacadéhuachi, Granados, Huásabas, Óputo (now Villa Hidalgo), Oposura (now Moctezuma), Sahuaripa, and Janos

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▲ Figure 2. Digital elevation model (SRTM, 3 arc-sec resolution) of northeastern Sonora (location marked in Figure 1) showing the rupture trace of the 1887 Sonora earthquake marked by white bold lines (from Suter and Contreras, 2002, modified); 1: Pitáycachi segment; 2: Teras segment; 3: Otates segment. A: Agua Prieta, B: Bavispe; D: Douglas; F: Fronteras; H: Huachineras; S: San Bernardino; V: Óputo (now Villa Hidalgo); a: Bavispe River; b: San Bernardino (Batepito) River; c: Cajón Bonito; d: Cañón de los Embudos; e: Arroyo Pitáycachi; f: Arroyo de la Cabellera; g: Cerro Pitáycachi; h: Sierra de la Cabellera (Cabellera Mountains); i: Sierra El Tigre (mountain range within the big bend of the Bavispe River); k: Sierra Pilares de Teras (Teras mountain range; northernmost part of Sierra El Tigre); dashed white line: international boundary. Arrows show locations where photographs of the surface rupture were taken by Camillus S. Fly (Figures 6-10).

(Figure 1). These towns were built on river terraces composed of water-saturated alluvium, which is prone to severe ground shaking. Towns located on firmer ground, such as Tombstone and Bisbee (Figure 1), suffered less (DuBois and Smith, 1980).

GOODFELLOW’S EXPEDITIONS Tombstone, Arizona Territory (Figure 1), was the largest town in the epicentral region of the 1887 earthquake; its peak population in 1882–1884 was probably about 10,000 (Walker and Bufkin, 1986). Two Tombstone residents, the photographer

Camillus Sidney Fly (Vaughn, 1989; Cooper, 1989; Rowe, 1997) and the physician and naturalist Dr. George Emory Goodfellow, made important contributions to the early studies of this earthquake. Goodfellow’s intellectual curiosity and wide range of interests also are expressed by his numerous articles in medical journals about frontier surgery and an article in Scientific American about the Gila monster, a poisonous lizard (Chaput, 1996). Fly took pictures documenting the earthquake surfacerupture (Figures 6–10, below) and the damage caused by the temblor in Bavispe (DuBois and Smith, 1980, Figures 12–15). To my knowledge, these are the earliest photographs of an earthquake surface-rupture worldwide and probably among the earliest landscape photographs taken in northeastern Sonora. They are dispersed in various repositories, such as the Arizona Historical Society in Tucson, the Arizona State Archives in Phoenix, the University of California, Berkeley (Steinbrugge Collection), and the Bisbee Mining & Historical Museum and have never been published in their entirety. Here I include five Fly photographs of the surface rupture (Figures 6–10, below), courtesy of the Karl V. Steinbrugge Collection, National Information Service for Earthquake Engineering, University of California, Berkeley. At the time of the earthquake, Fly already was familiar with this remote area, having taken photographs the year before at Cañón de Los Embudos (Figure 2) to document the war camp of a group of Chiricahua Apaches led by Gerónimo and their surrender negotiations with General George Crook (Van Orden, 1989). These photographs, printed as engravings in Harper’s Weekly (24 April 1886), had made Fly widely known. Coincidentally, the negotiations took place only ~3 km upstream from the place where, in the following year, the earthquake surface-rupture would cross Cañón de los Embudos. Goodfellow had rushed a preliminary note to Science on 7 May 1887 (Goodfellow, 1887a), only four days after the earthquake. His letter, dated “Tombstone, A.T., May 7,” appeared in the Science issue of 20 May 1887. In a second letter to Science, dated 14 July 1887, Goodfellow (1887b) reported about a first trip to the earthquake zone in Sonora, on which he accompanied Professor Ferdinand Lee Clark of Honolulu (Tombstone Daily Epitaph, 9 July 1887), and included a sketch map of the rupture trace (Figure 3). He described the surface rupture as a fault with a general north-south strike, a dip from 45° to vertical, and an average throw of eight feet (~2.4 m). Goodfellow then left Tombstone later in July or in early August 1887 together with Fly for a second extended trip to Sonora, where he made a more detailed observational study of the earthquake. After his return, Goodfellow prepared a comprehensive report about his observations. The Tombstone Daily Prospector reported on 14 September 1887 that “Dr. Goodfellow is busily engaged in preparing his report of the recent scientific investigations made by him in Sonora. It is learned that he has not yet fully determined whether to publish it himself or to turn it over to the U.S. Geological Survey.” The Tombstone Epitaph reported on 6 January 1888 that “Dr. Goodfellow is busily engaged during his leisure moments in preparing maps, tracings, etc. showing the

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suggests that these prints were originally part of the report about the earthquake authored by Goodfellow. Goodfellow’s itinerary can be retraced from his 1888 article. He surveyed the surface rupture in a southern direction to the Bavispe River and 8 km beyond (Figure 3; Pitáycachi rupture segment on Figure 2). Fly’s photographs document the surface rupture at several places (Figures 6–10, below) and the camp of the field party near the junction of the Batepito (San Bernardino) and Bavispe rivers (Figures 2 and 3). From there, Goodfellow and Fly must have traveled along the river to Bavispe (Figures 1 and 2), where Fly took pictures of the destruction caused by the earthquake. From Bavispe, Goodfellow moved on to Bacadéhuachi, Granados, Óputo, and Fronteras (Figure 1), from where he provided macroseismic observations. No Fly photographs are known from this part of Goodfellow’s trip beyond Bavispe, and it is likely that Fly returned from Bavispe on his own directly to Tombstone. The photographs by Fly are the only known historical photographs of the 1887 earthquake, with the exception of a picture by James Douglas showing ground fissures near Agua Prieta (Figure 2), which was printed as an engraving in Harper’s Weekly (2 July 1887), where it accompanied a note by Thomas Sterry Hunt and James Douglas about the earthquake (see also Sterry Hunt and Douglas, 1887, 1888a, 1888b), and which was reproduced as a halftone print in DuBois and Smith (1980, Figure 9).

AGUILERA’S EXPEDITION

▲ Figure 3. Sketch map of the rupture trace by Goodfellow (1887b), who mapped the surface rupture in the south ~8 km beyond its intersection with the Bavispe River. The rupture trace mapped by Goodfellow as well as Aguilera (Figure 5) has an end-to-end length of 56 km and is now known as the Pitáycachi segment of the surface rupture. The scale is approximate.

results of the earthquake disturbance in Sonora, which when completed will be forwarded to the U.S. Geological Survey in Washington.” When Tombstone hosted the first Cochise County Teacher’s Institute, Goodfellow contributed a talk about the Sonora earthquake on 8 February 1888 (Tombstone Daily Prospector, 9 February 1888). Goodfellow’s report, which included photographs by Fly and maps, was sent to Captain C. E. Dutton of the U.S. Geological Survey. A six-page summary of his report (without the maps and photographs), edited by Dutton, appeared on 6 April 1888 in Science (Goodfellow, 1888). However, the full version of Goodfellow’s report is lost; neither the original nor any copy appears to have survived (DuBois and Smith, 1980, p. 17). The technical nature of the captions of the Fly photographs in the Steinbrugge Collection

Aguilera was dispatched to the epicentral region on 1 July 1887 from Hermosillo (Figure 1), where he was employed by the Scientific Commission of Sonora (Comisión Científica de Sonora) as Head of the Department of Naturalists ( Jefe de la Sección Naturalista). In his work order, which is included in his 1888 publication on page 9, he was asked not only to study the earthquake but also to describe the regional geology along his itinerary, collect rock samples, and construct a geologic map and cross sections. Aguilera was accompanied by a military crew carrying out triangulation that resulted in a topographic map of the expedition area. In Aguilera’s 1888 report, credit for the topographic work is given to Juan B. Laurencio and Nicolás Lazo de la Vega, who possibly are depicted in Figure 4. Aguilera and Laurencio also held positions at the Comisión GeográficoExploradora, the Mexican federal mapping agency of its time, located in Jalapa, Veracruz. It is likely that Aguilera was assigned to the Scientific Commission of Sonora not because of the earthquake but to do field mapping for the first geologic map of the Republic of Mexico (1:3,000,000 scale), which was published in 1889 (facsimile in de Cserna, 1990, pl. 1). The itinerary of the expedition, ~750 km long, is marked on the geologic and topographic maps in Aguilera’s 1888 report. The field party traveled from Hermosillo to Oposura (now Moctezuma) (Figure 1) and from there to Bavispe, where they spent 15 days in August 1887 documenting the damage to the village and mapping ground fissures (Aguilera, 1888, p. 37). From Bavispe, they moved to the junction of the Bavispe


▲ Figure 4. Photograph by Camillus S. Fly possibly showing the Aguilera and Goodfellow field parties in August 1887 near Bavispe, at a place where major fissures formed a small graben in the flood plain of the Bavispe River. The labeled persons are interpreted to be G: George E. Goodfellow; A: José G. Aguilera; L: Major Juan B. Laurencio, topographer of the Aguilera expedition; and K: Emilio Kosterlitzky.

and San Bernardino rivers and mapped the earthquake surface rupture scarp that passes along the eastern margin of the San Bernardino valley (Figure 5; Pitáycachi rupture segment on Figure 2). The expedition then proceeded on the U.S. side of the international boundary from San Bernardino to Agua Prieta (Figure 5), from where they returned to Moctezuma and Hermosillo. Aguilera published the results of his expedition in 1888; the preface to his article was written in Hermosillo on 18 March 1888. The first half of his article is taken up by the geologic description of his itinerary and the collected samples, whereas the second half is related to the 3 May 1887 earthquake. The article includes four plates: an isoseismal map (scale: 1:6,000,000) covering the southwestern United States and Mexico; a geologic map of northeastern Sonora (scale: 1:1,000,000); a topographic map of northeastern Sonora (scale: 1:1,000,000; contour interval: 250 m) that shows the surface rupture and ground fissures caused by the earthquake; and a plate with five geologic cross sections. Aguilera (1888, p. 7) considered the topographic and geologic maps necessary tools to document and interpret the earthquake-related field observations and to formulate a hypothesis about the cause of the earthquake. The Aguilera and Goodfellow expeditions met in Bavispe in August 1887. The encounter is mentioned by Goodfellow (1888, p. 162). A group portrait taken by Fly near Bavispe, at a place where major fissures developed in the flood plain of the Bavispe River, possibly shows the two field parties (Figure 4). In the Steinbrugge Collection, this photograph has the caption “Depressions or seismic troughs in river bed. View from Babispe, looking northwest. (Fly)” A comparison with photographs in Chaput (1996) suggests that the person labeled G is very likely Goodfellow, who was 32 years of age when this picture was taken. Based on a comparison with a photograph in de Cserna (1990, Figure 14), Aguilera is possibly the person labeled A. Aguilera was the only civilian in the Mexican field

party and was 30 years old at the time the picture was taken. The second person from the right (labeled L) is possibly Major Juan B. Laurencio, topographer of the Aguilera expedition. Based on comparisons with photographs in Smith (1970) and Truett (2004), the civilian on the outer right (labeled K) is likely to be Emilio Kosterlitzky (1853–1928), who worked in 1887 in Bavispe for the Mexican customs guard or Gendarmería Fiscal, and who registered the aftershocks of the 3 May 1887 earthquake (Orozco y Berra, 1887, p. 522).

THE SURFACE RUPTURE OF THE 1887 EARTHQUAKE Goodfellow (1887b) and Aguilera (1888) mapped the scarp of what is now known as the Pitáycachi segment of the surface rupture (Figure 2). Their maps are reproduced here as Figures 3 and 5, respectively. According to these maps, the surface rupture extends from 10 km south of the international border in the north to 8 km beyond its intersection with the Bavispe River in the south. Remarkably, the end-to-end rupture length of 56 km obtained from modern topographic maps, based on the rupture trace marked by Aguilera on Figure 5, coincides with the rupture length of ~35 miles indicated by Goodfellow (1888). Goodfellow and Aguilera described the surface rupture as having a sinuous trace parallel to the mountain front, with the western block downthrown. According to both authors, the rupture scarp developed over its entire length in alluvium and is characterized by a continuous crevice passing along its base. Goodfellow mentions an exception at Cerro Pitáycachi, where bedrock is cut off by the rupture (Figure 8) and south of the Bavispe River, where the trace passes within bedrock. Goodfellow and Aguilera did not survey the Teras rupture segment and evidently were not aware of the existence of the Otates segment (Figure 2). Coincidentally, on his way to Bavispe, Aguilera had crossed the Sierra El Tigre only ~15 km south


▲ Figure 5. Enlarged detail of the topographic map by Aguilera (1888) showing the tectonic rupture scarp of the 3 May 1887 earthquake along the eastern margin of the San Bernardino Valley (bold line with numerous northward bifurcations), ground fissures in the San Bernardino Valley (short bold lines), and his itinerary (thin line composed of straight-line segments). The contour interval is 250 m. The scale is approximate.

of the southern termination of the Otates segment, between Óputo and Huachineras (Figure 2). Goodfellow (1888) mentions a possible southern continuation of the surface rupture, ~24 km long, beyond the mapped segment (Figure 3) into the Teras mountain range (Figure 2) based on observations relayed to him by some prospectors. According to the itinerary marked on his rupture map (Figure 5), Aguilera did not visit the part of the rupture located south of the Bavispe River, which looks on his map identical to the trace shown by Goodfellow (Figure 3). Fly’s photographs (Figures 6–10) document the surface rupture at several locations. The northernmost picture (Figure 6), a close-up between Arroyo Pitáycachi and Cañón de los Embudos, most likely at 109.135 long. W / 31.088 lat. N. (Figure 2), shows the scarp to be subvertical, ~4.4 m high, and composed of alluvial gravel cemented by caliche; a fissure or crevice can be seen at the base of the scarp. This photograph

also indicates that the ground surface is not rotated toward the scarp, which suggests a simple planar near-surface geometry of the rupture. Figure 7 shows the earthquake rupture ~3 km south of Figure 6, near Arroyo Pitáycachi (Figure 2), where the scarp is ~3.3 m high and composed of alluvial gravel. Figure 8 shows surface faulting near Cerro Pitáycachi (Figure 2). According to Goodfellow, this is the only place north of the Bavispe River where he observed bedrock (felsic volcanic rock and a dike) forming the face of the rupture scarp. The surface rupture dips here 68° W and has a height of ~2.8 m. Figure 9 shows the surface rupture in the vicinity of Arroyo de la Cabellera (Figure 2). In the Steinbrugge Collection, this photograph has the caption “Fault opposite the Cabellera Mountains. Here it splits into three. The center one is the main fissure. Difference of level is four feet upper, six feet middle, four feet lower. View looks east. (Fly)” Following Goodfellow (1888, p. 163), this triplicate


▲ Figure 6. Previously unpublished 1887 photograph by Camillus S. Fly of the earthquake rupture scarp in an ocotillo forest between Arroyo Pitáycachi and Cañón de los Embudos, most likely at 109.135 long. W / 31.088 lat. N. (Figure 2). The view is from the northwest. The scarp is subvertical, composed of alluvial gravel cemented by caliche, and its height is estimated here as ~4.4 m. The two persons are standing in a fissure or crevice that developed along the scarp. The ground surface is not rotated toward the scarp, which suggests a simple planar near-surface geometry of the rupture.

division opposite the Cabellera Mountains is more than a mile in length. The photograph (Figure 9) shows in the foreground the lower (westernmost) of the three ruptures (Figure 2) and in the background part of the central rupture (marked by arrows) in alluvial deposits. Figure 10 shows the rupture scarp directly south of the Bavispe River (Figure 2). In the Steinbrugge Collection, this photograph has the caption “Location of fault after it crosses the Yaqui at San Rafael. The dark line shows the course of the fissure as it passes into the Teras Mountains. View looks south. (Fly)” The line corresponds to the tectonic contact between Tertiary volcanic rocks and fault-scarp colluvium. This highlighting of the rupture trace and the technical nature of the captions to Figures 9 and 10 suggest strongly that the Fly photographs in the Steinbrugge Collection were originally part of the report about the earthquake authored by Goodfellow. Aguilera (1888, p. 41–44) measured scarp heights (from south to north) that increase from zero at the Bavispe River to 0.6–1.0 m somewhat north of the river, and 2.7 m where the scarp crosses the Batepito-Bavispe road. Farther north, he reports an odd measurement of 8 m at Arroyo de la Cabellera (Figure 2; the valley south of Peñasquito on Figure 5), a consistent height of 4 m between La Cabellera and Cerro Pitáycachi (Figure 2), and farther north a decrease to 2.5 m at Cañón de los Embudos (Figure 5) and 0.2 m at Barranca de Cuchuvérachi

(called Elias Creek by Goodfellow and now known as Cajón Bonito, Figure 2). Aguilera also measured at several places the scarp inclination, for which he obtained values of 75–90°. Following Goodfellow, the scarp height is five feet and less (6.1 m) between Arroyo de la Cabellera and Cerro Pitáycachi (Figure 2), and the average scarp height measures “a little over seven feet” (~2.2 m). Several parts of Aguilera’s article indicate that he interpreted the earthquake rupture to be of a tectonic nature and to have a deep-seated geometry: (1) In the geology part of his article, he described the transition zone between the plateau of the Sierra Madre Occidental in the east and the lowlands near the Gulf of California in the west as a large-scale staircase pattern, with the steep, fault-bounded side of the mountain ranges always facing west (Figure 2). On his geologic map (facsimile in Suter, 2006), Aguilera used a cartographic unit of volcanic rocks that belong mostly to the vast cover of the middle Tertiary Sierra Madre Occidental volcanic province and units of Pliocene and Quaternary rocks that belong to the fill of extensional basins. These units define on his map a series of north-south trending fault-bounded mountain ranges separated by the valleys of


▲ Figure 7. Previously unpublished 1887 photograph by Camillus S. Fly of the earthquake rupture scarp near Arroyo Pitáycachi (Figure 2), ~3 km south of Figure 6; the rupture scarp in the background is marked by an arrow. The view is from the northwest. The scarp is ~3.3 m high and composed of alluvial gravel. The two hills in the background are located in the footwall of the Pitáycachi fault, composed of Tertiary volcanic rocks, and capped by Quaternary alluvial-fan deposits.

▲ Figure 8. Previously unpublished 1887 photograph by Camillus S. Fly of the earthquake rupture scarp near Cerro Pitáycachi (Figure 2), which is the mountain peak in the background. The view is from the west. Following Goodfellow, this is the only place where bedrock (felsic volcanic rocks and a dike) forms the face of the rupture scarp. The surface rupture, which dips here 68° W, cuts off the dike at 109.159° long. W / 31.035° lat. N (white arrow). The scarp height measures ~2.8 m.


▲ Figure 9. Photograph of the 3 May 1887 earthquake rupture scarp near Arroyo de la Cabellera (Figure 2) taken by Camillus S. Fly in 1887. In the Steinbrugge Collection, the caption of this photograph reads: “Fault opposite the Cabellera Mountains. Here it splits into three. The center one is the main fissure. Difference of level is four feet upper, six feet middle, four feet lower. View looks east. (Fly)” Following Goodfellow (1888, p. 163), this triplicate division opposite the Cabellera Mountains is more than a mile in length. The photograph shows the lower (westernmost) of the three ruptures (scarp height: 1.15 m) at 109.157° long. W / 30.885° lat. N (Figure 2). The middle rupture can be seen at two locations in the background (arrows). The rupture scarps and the hill in the foreground are composed of Quaternary alluvial fan deposits and the hills in the background of Lower Cretaceous siliciclastic sediments (La Morita Formation). The high mountains in the background belong to the Tertiary Sierra Madre Oriental volcanic province; the prominent peak in the center forms part of the southern rim of Arroyo de la Cabellera canyon.

major rivers, a landscape pattern typical of the southern Basin and Range physiographic province; (2) Aguilera (1888, p. 40) reported significant subsidence of an intensely fissured 2-km2 area near Batepito (Figure 5), within the hanging wall ~8 km west of the fault trace, and explained this subsidence by motion along the fault. (According to Goodfellow [1888, p. 163], “At Batepito Ranch, an area two miles long by one wide was four or more inches deep with water immediately succeeding the first shock on May 3”); (3) Based on his macroseismic observations, Aguilera (1888, p. 52) assumed the epicenter to be located in this subsided region (Figure 11) and estimated a focal depth of 18 km (see below); (4) In his discussion of the probable cause of the earthquake, Aguilera (1888, p. 56) considered it most likely that the seismic vibrations were caused by movement along a fault displacing the Tertiary volcanic rocks, and whose trace is covered by Quaternary sediments, which resulted from the continuous increase in the weight of the Quaternary rocks overcoming the shear resistance and the horizontal stress.

Goodfellow (1888, p. 162–163) repeatedly pondered whether the earthquake rupture is deep-seated or the result of surficial slip and concluded that “there seems a preponderance of evidence favoring the first opinion.” He also mentioned the possibility of previous displacements along the same fault: “A point which attracted my attention, and which seemed significant, was the appearance of the foot-wall of the slip in many places, particularly where it abutted closely on the mountains. This was the polished surface, as if the same place had been the seat of similar perturbations in the past.” The acceptance of a tectonic nature of the surface rupture by both Aguilera and Goodfellow is probably implicitly also based on their observation of secondary ruptures at bends of the primary rupture trace. Aguilera mapped at many places northward bifurcations of the rupture scarp (Figure 5), from which he inferred a northward direction of the rupture propagation (1888, p. 45); this is likely to be the earliest inference worldwide of an earthquake rupture direction based on field observations. Goodfellow (1888, p. 163) described these bifur-


▲ Figure 10. Previously unpublished 1887 photograph by Camillus S. Fly of the earthquake rupture scarp south of the Bavispe River (Figure 2). In the Steinbrugge Collection, the caption of this photograph reads: “Location of fault after it crosses the Yaqui at San Rafael. The dark line shows the course of the fissures as it passes into the Teras Mountains. View looks south. (Fly)” The near (northern) end of the dark line is located at 109.187 long. W / 30.810 lat. N.

cations as follows: “Some things to be noticed about the fault, in connection with its sinuous course, are the small fissures at each bend with any great degree of angularity. These occur on the salients of each angle, but have no great length, in no place extending over a few hundred yards, except opposite the Cabellera Mountains [Figure 2], where there is a triplicate division over a mile in length [Figure 9]. This gives the main fault the appearance of having been compressed lineally from the south, most of them having the free end to the north. They are mostly ground-throws, not simply cracks.” Aguilera (1888, p. 44) also described systems of what he called second- and third-order ruptures, located within a 300m wide zone on either side of the main rupture. Following Aguilera, the orientation of the second-order faults is parallel to the main fault or forms acute angles of 15–20° with it, whereas the orientation of the third-order faults is approximately perpendicular to the main fault. Aguilera’s second- and third-order faults can be interpreted as Riedel shear fractures, which are characteristic subsidiary fractures of strike-slip faults (Yeats et al., 1997). However, neither Goodfellow nor Aguilera report any horizontal displacement along the main rupture.

MACROSEISMIC OBSERVATIONS AND AGUILERA’S ISOSEISMAL MAP OF THE 1887 EARTHQUAKE The intensity observations of the 3 May 1887 earthquake by Goodfellow (1887a, 1887b, 1888) and Aguilera (1888) as well as the ones catalogued by Orozco y Berra (1887, 1888) are

included in the detailed compilation of the historical accounts of this earthquake by DuBois and Smith (1980), DuBois et al. (1982), and Sbar and DuBois (1984). The paper by Aguilera (1888) includes an isoseismal map, which is in all likelihood the first published intensity map for an earthquake in North America. An excerpt of the map is reproduced here on a reduced scale as Figure 11. The map, which employs the 1–10 RossiForel scale, does not provide the entry data points and values. The earthquake was felt as far north as Santa Fé, New Mexico, as far west as Yuma, Arizona, and as far east and south as Mexico City. Aguilera estimated the felt area as 1,200,000 km2 and located the epicenter of the 1887 earthquake in the center of the innermost isoseismal (intensity: 10), near Batepito, ~8 km west of the surface rupture trace (Figure 11). The isoseismals are elongated in NNW–SSE direction, which Aguilera (1888, p. 37–38) explained by directional differences in the intensity attenuation properties of the rocks. The U.S. Geological Survey had distributed a large number of letters of inquiry shortly after the earthquake with questions related to the exact time the shocks were felt; duration and any other particulars giving an idea of the intensity of the shock; apparent direction in which the wave traveled; accompanying sounds; effect on springs, wells, mountain ranges, etc. (El Paso Times, 7 May 1887; Arizona Daily Star, 8 May 1887; Dutton 1889a, p. 165). According to a press release by the Survey, about two hundred reports were received on the subject, on which Dutton based an estimate that the earthquake was felt in about two-thirds of each of the territories of Arizona and New Mexico and was not comparable in violence and extent


▲ Figure 11. Excerpt from the isoseismal map of the 3 May 1887 earthquake by José G. Aguilera (1888). The map employs the 1–10 Rossi-Forel scale. The only entry point not shown on the excerpt is Mexico City, with an intensity of one. Aguilera assumed the epicenter of the 1887 earthquake to be located in the center of the innermost isoseismal (intensity 10), near Batepito, ~8 km west of the surface rupture trace (Figure 5).


to the 31 August 1886 Charleston, South Carolina, earthquake (Arizona Daily Star and Tombstone Daily Epitaph, 10 June 1887). Unfortunately, the answers to the circular of the U.S. Geological Survey are lost (DuBois and Smith, 1980, p. 17). Based on Aguilera’s isoseismal map (Figure 11), it is likely that he had access to the macroseismic information gathered by the U.S. Geological Survey, because the isoseismals pass through major towns such as Yuma, Globe, Phoenix, Benson, Tombstone, El Paso, Socorro, Albuquerque, and Santa Fé. The map probably also is based on information from the Observatorio Meteorológico Central de México, which had received telegrams with felt reports from several locations in Mexico. Numerous macroseismic observations also were made by Goodfellow, partly for areas that were not visited by Aguilera. Because Goodfellow (1888) repeatedly refers to isoseismals, it is likely that an isoseismal map was part of the lost full version of his report, whereas no figures are included in the abridged version published in Science.

SOURCE PARAMETERS OF THE 1887 EARTHQUAKE Macroseismic observations and isoseismal patterns were used in the pre-instrumental period to determine earthquake source parameters (Dutton, 1889b; Dutton, 1904; Davison, 1927). Aguilera (1888, p. 53) assumed the epicenter of the 1887 earthquake to be located at 109°05’55’’W / 30°48’24’’N, in the center of the innermost isoseismal (Figure 11), a subsided and intensely fissured area near the Batepito ranch, ~8 km west of the surface rupture trace (Figure 5). Furthermore, he calculated a focal depth of 18 km based on an obsolete technique that assumed (i) the epicenter to be located in the center of the innermost isoseismal; (ii) the intensity attenuation to be quadratic; and (iii) the distance from the epicenter to the location where the change in intensity attenuation is a maximum (i.e., where the second derivative of the attenuation function is zero) to bear to the focal depth the ratio 1: 3 . Aguilera refers to this technique as the method developed by Dutton and Hayden of the U.S. Geological Survey. Details of this technique and the underlying theory, which are not considered valid any more, are given by Dutton (1889b, 1904). Davison (1927, p. 150) lists seven earthquakes for which Dutton’s method was applied to calculate the focal depth. However, because his list does not include the 1887 Sonora earthquake, he was evidently unaware of Aguilera’s study. Based on records by Emilio Kosterlitzky, Aguilera (1888, p. 36) noted that the intervals between the aftershocks of the 3 May 1887 earthquake increased with time. Six to eight aftershocks were felt daily immediately after the earthquake, whereas in August, when Aguilera spent 15 days in Bavispe, he felt only two aftershocks. Two lists of aftershocks of the 1887 earthquake by Kosterlitzky and Aguilera are provided in Orozco y Berra (1887, p. 522–523). However, they both cover incomplete time periods. A search in the Kosterlitzky archive (Special Collections of the University of Arizona Library) did not provide additional information.

INSTRUMENTAL OBSERVATIONS The 1887 earthquake generally is considered a pre-instrumental event. Nevertheless, several early instrumental observations are associated with it. The earthquake disturbed the needle of the magnetograph of the Coast and Geodetic Survey in Los Angeles, California (Dutton, 1904, p. 55), and possibly was recorded by the set of Ewing seismographs at the Lick Observatory on Mount Hamilton, California (Holden, 1887, p. 76), which had been installed earlier the same year (Davison, 1927, p. 147). Seismic experiments were carried out by Goodfellow (1888, p. 164): “I had rigged up a seismograph, if such a contrivance can be entitled to the name, consisting of a bullet suspended in a large beer-bottle. This, with moderate accuracy, gave me the direction of the vibrations, and all seemed to come from the northern end of the Teras mountains [stepover between the Pitáycachi and Teras segments, Figure 2]. While I was in the neighborhood, certainly, all seismic disturbances had their origin from those mountains, irrespective of my situation.” Goodfellow’s observations are confirmed by Aguilera (1888, p. 53), who reports the aftershocks he felt in Bavispe as coming from the northwest and, while he traveled counterclockwise around the epicentral region, as coming consistently from the region near the junction of the Batepito (San Bernardino) and Bavispe rivers (Figures 2 and 5).

SEISMIC VELOCITIES Aguilera (1888, p. 54) estimated the mean velocity of the 1887 Sonora earthquake waves based on the times at which the earthquake was recorded in Tombstone and at railway stations in the United States (El Paso, Deming, Willcox, Benson, Tucson, Crittenden, Nogales, Fairbank, Maricopa, Phoenix, Gila Bend) and in Mexico (Hermosillo, Guaymas, Mexico City). Aguilera had obtained these arrival times from Goodfellow. In 1887, exact recording times of earthquakes were difficult to get, and the best records were made as a rule by telegraph reporters and railroad officials whose time was corrected by daily telegraph (El Paso Times, 7 May 1887). Once a day, a signal was telegraphed from an astronomical clock to every telegraph station in the country at an appointed hour, minute, and second. Thus every village reached by a telegraph line had the means of knowing each day the time of some standard meridian to a single second (Dutton, 1889b). Aguilera calculated a mean seismic wave propagation velocity of 1,772 m/s; the highest velocities were 2,730 m/s between the epicenter and Mexico City, 3,050 m/s between Tucson and Gila Bend, and 3,416 m/s between the epicenter and Tombstone. Aguilera commented that these velocities were much higher than the values assumed until recently. Previously, Dutton (1887) had commented that the time observations obtained for the Sonora earthquake gave a very high wave speed, and that preliminary examinations indicated a speed about the same as that obtained for the Charleston earthquake. The propagation velocities subsequently published for the 1886 Charleston earthquake (Dutton, 1989b) yielded a mean seismic velocity of 4.2 to 5.2 km/s based on a much larger data set.


Aguilera’s calculations of the speed of earthquake waves likely are the earliest ones worldwide based on time records showing the instant of passage of an earthquake shock. Previous calculations were based on experimental shocks and yielded lower wave velocities (Dutton, 1904). However, Aguilera’s estimates have a high uncertainty, because he rounded the travel times to entire minutes and had to make an assumption about the origin time of the earthquake.

DISCUSSION The 1887 Sonora earthquake is likely the earliest earthquake worldwide where tectonic surface faulting was recognized as such and described in detail. Inspection of surface faulting soon after the event began with the 1855 Wairarapa, New Zealand; 1861 Egion, Greece; and 1872 Owens Valley, California (Whitney, 1872; Gilbert, 1884), earthquakes. However, the predominance and amount of dextral displacement in the 1855 Wairarapa earthquake was recognized only in the 1950s (Darby and Beanland, 1992), and the 1861 Egion rupture was interpreted as a large-scale gravitational slide (Yeats et al., 1997). Furthermore, Whitney (1872) did not recognize the graben structure of Owens Valley or the tectonic character of the 1872 Owens Valley earthquake. He interpreted the surface rupture to be “local phenomena … not to be taken as indicative of a general motion of the valley in any fixed direction.” Gilbert made field observations of the 1872 Owens Valley earthquake in 1883 (Beanland and Clark, 1994) but only cursorily mentioned the rupture in his 1884 essay (Gilbert, 1884), which is not illustrated. Aguilera’s 1888 paper does not contain any bibliographical references, which was customary at that time. One is left wondering how he was educated about the study of earthquakes and where he learned the techniques he employed. Aguilera graduated from the School of Mines (Escuela de Minería) in Mexico City as a mining engineer and worked from 1882 on for the Comisión Geográfico-Exploradora, the Mexican federal mapping agency of its time, for which he carried out geologic field work in east-central Mexico. In 1884–86, before his assignment in Hermosillo, he stayed at the Smithsonian Institution in Washington, D.C. (Rubinovich Kogan et al., 1991). Charles G. Rockwood, the earliest scholar of earthquakes in the United States (Davison, 1927, p. 144) published summaries of recent work in seismology in the Reports of the Smithsonian Institution in 1884, 1885, and 1887, which must have been known to Aguilera. Moreover, it is likely that Aguilera read Gilbert’s seminal 1884 essay about tectonic faulting associated with earthquakes and the fault origin of the Basin and Range province. In this exceptionally lucid paper, Gilbert introduced a conceptual spring-block model to explain tectonic earthquakes by the frictional stick-slip behavior during the growth of faults. Furthermore, the 31 August 1886 Charleston, South Carolina, earthquake (Dutton, 1889b) happened during this period, and Aguilera likely was informed about the study of this earthquake by the U.S. Geological Survey, which used facilities at the Smithsonian Institution (Powell, 1889).

My review of the contemporary studies of the 1887 earthquake would be incomplete without documenting in more detail the involvement by Clarence Edward Dutton (1841–1912), by profession a Captain of Ordnance in the U.S. Army, who was detailed to the U.S. Geological Survey. It is Dutton who asked Goodfellow to conduct a field study of the 1887 earthquake in Mexico (Dutton, 1904, p. 54), most likely after reading his 7 May 1887 letter to Science about the earthquake, and possibly because by law the U.S. Geological Survey was not allowed to use funds for research in Mexico (Dutton, 1889b, p. 165); the Tombstone Daily Prospector reported on 9 May 1887 that “Dr. Goodfellow is engaged in gathering data to be furnished to the National Geological Society [sic], regarding the late earthquake.” Dutton also had distributed a large number of circulars requesting macroseismic information, and responses were received to most of them (Dutton, 1889a, p. 165; see above). In addition to Goodfellow’s report and the answers to the circulars, Dutton had also procured, at least in part, Aguilera’s study through the State Department (editorial comment in Science, 6 April 1888, p. 159). Based on a subsequent editorial in Science (13 April 1888, p. 171), “Capt. C. E. Dutton, of the United States Geological Survey, is now engaged in writing his monograph on the Charleston earthquake … The same volume will also contain a report on the Sonora earthquake, very abundant material for which has been collected in those portions of the United States to which the temblor extended. Mr. Goodfellow’s report upon the phenomena of the epicentral region of the disturbance in Sonora was all that was needed to complete the desirable data. Both of these monographs will be ready for the printer by June 1, and an effort will be made to hasten their publication.” In early January 1889, Dutton visited Tombstone and Bisbee, where he was guided by Goodfellow (Tombstone Daily Prospector, 5 and 9 January 1889). However, he did not visit the nearby surface rupture of the 1887 earthquake. His responsibilities had changed; he was now in charge of the Irrigation Surveys of the United States (Dutton, 1904, p. 54). In 1904, eight years years before his death, he considered it “not impossible that a coherent account of this highly interesting and instructive occurrence may yet be wrought out in scientific detail and published” (Dutton, 1904, p. 54). Could Goodfellow’s report or the responses to the circulars be preserved somewhere at the U.S. Geological Survey or in any archive? Locating Goodfellow’s full report with its maps and photographs would obviously provide information helpful in the study of the 1887 Sonora earthquake. A search by DuBois and Smith (1980, p. 17) was unsuccessful. The previously unpublished photographs of the surface rupture by Fly (Figures 6–10) in the Steinbrugge Collection were taken in 1968 from prints in possession of the late Wayne Winters, at that time editor of the Tombstone Epitaph. The technical nature of the captions of these photographs suggests that they were originally part of the report about the earthquake authored by Goodfellow.


CONCLUSIONS

ACKNOWLEDGMENTS

The 3 May 1887 Mw 7.5 Sonora, Mexico, (Basin and Range province) earthquake is likely to be the earliest earthquake worldwide where tectonic surface faulting, previous displacement along the same fault, map-scale systems of subsidiary Riedel-type shear fractures, and the near-surface direction of rupture propagation were recognized as such and described in detail. The independent observational studies of the epicentral region in summer 1887 by José Guadalupe Aguilera Serrano and George Emory Goodfellow, published in 1888 and littleknown today, merit recognition in reviews of the history of earthquake geology and seismology. They include maps and photographs (by Camillus Sidney Fly) of the surface rupture, an isoseismal map, and the source parameters and speed of propagation of the earthquake. These are the earliest maps and photographs of an earthquake surface rupture and the earliest isoseismal map of an earthquake in North America. Both authors mapped the trace, 56 km long, of what is now known as the Pitáycachi segment of the 1887 surface rupture and measured scarp heights. Goodfellow and Aguilera described the surface rupture as having a sinuous trace parallel to the mountain front, with the western block downthrown. According to both authors, the rupture scarp developed over its entire length in alluvium and was characterized by a continuous crevice passing along its base. Goodfellow mentioned an exception at Cerro Pitáycachi, where bedrock is cut off by the rupture and south of the Bavispe River, where the trace passes within bedrock. Previously unpublished 1887 photographs by Camillus Sidney Fly document the fault scarp at these two and several other locations. Aguilera’s surface rupture map shows northward bifurcations of the rupture scarp at many places, from which he inferred a northward direction of rupture propagation. Moreover, Aguilera described systems of what he called second- and thirdorder ruptures, up to 3,000 m long, located within a 300-m wide zone on either side of the main rupture and oriented like Riedel shear fractures. Aguilera’s geologic mapping of the epicentral region allowed him to make an explicit connection between the earthquake and tectonic faulting. He describes the epicentral region, the transition zone between the plateau of the Sierra Madre Occidental in the east and the lowlands near the Gulf of California in the west as a large-scale staircase pattern, with the steep, fault-bounded side of the mountain ranges always facing west. In his discussion of the probable cause of the earthquake, he considered it most likely that the seismic vibrations were caused by the movement along a fault displacing the Tertiary volcanic rocks, and whose trace is covered by Quaternary sediments, which resulted from the continuous increase in the weight of the Quaternary rocks overcoming the shear resistance and the horizontal stress. Aguilera understood that faulting was the primary earthquake process. It is likely that he was influenced by Gilbert (1884), who had introduced a conceptual spring-block model to explain tectonic earthquakes by the recurrent frictional stick-slip behavior during the growth of faults.

I am thankful to Susan Hough for her review. The photographs by Camillus S. Fly are courtesy of the Karl V. Steinbrugge Collection, National Information Service for Earthquake Engineering, University of California, Berkeley. I am indebted to Susan Fatemi for providing me with digital-image files of the collection’s Fly photographs and a text file with their captions. Financial and logistical support for this work came in part from Universidad Nacional Autónoma de México (UNAM) and Consejo Nacional de Ciencia y Tecnología (CONACYT, grant G33102-T).

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Instituto de Geología Universidad Nacional Autónoma de México Estación Regional del Noroeste Hermosillo, Sonora, Mexico [email protected]
