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    Attenuation Characteristics of Coda Waves in Mainland Gujarat (India) Arun K. Gupta, Anup K. c, Sumer Chopra, Santosh Kumar, B.K. Rastogi PII: DOI: Reference:

S0040-1951(12)00018-2 doi: 10.1016/j.tecto.2012.01.002 TECTO 125340

To appear in:

Tectonophysics

Received date: Revised date: Accepted date:

3 August 2011 2 January 2012 2 January 2012

Please cite this article as: Gupta, Arun K., c, Anup K., Chopra, Sumer, Kumar, Santosh, Rastogi, B.K., Attenuation Characteristics of Coda Waves in Mainland Gujarat (India), Tectonophysics (2012), doi: 10.1016/j.tecto.2012.01.002

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ACCEPTED MANUSCRIPT Attenuation Characteristics of Coda Waves in Mainland Gujarat (India)

Institute of Seismological Research, Gandhinagar-382 009, Gujarat, India E-mail:[email protected]

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Ministry of Earth Sciences, New Delhi-110 003, India

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Arun K Gupta1, Anup K Sutar1, Sumer Chopra1, Santosh Kumar2 and B.K. Rastogi2

Abstract

The attenuation characteristics based on coda waves of Mainland Gujarat (India) has been

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investigated in the present study. The broadband waveforms of 53 local earthquakes (Mw 1.1 – 3.3) having focal depths in the 6.0–33.6 km range recorded at five stations of

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Mainland Gujarat region has been used for the analysis.

The frequency - dependent

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relationships (Q=Q0fn) for coda-Q (Qc) and dependency of coda-Q on lapse time windows have been determined for the said region. The average lapse time dependent coda-Q Qc=(87±13)f(1.01±0.06) (lapse time : 30 s),

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relations estimated for the region are:

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Qc=(112±20)f(0.94±0.08) (lapse time : 40 s) and Qc=(120±22)f(0.76±0.07) (lapse time : 50 s). The increase in Qc values with lapse time shows the depth dependence of Qc as longer lapse time windows will sample larger area. The observed quality factor is strongly dependent on frequency and lapse time, which indicates that the upper lithosphere, is more heterogeneous and seismotectonically active, while the lower lithosphere is homogeneous and relatively less active. A comparison of the coda-Q estimated for Mainland Gujarat region with those of nearby Kachchh and Saurashtra regions shows that Mainland Gujarat region is more heterogeneous. The rate of decay of attenuation (Q-1) with frequency for the relations obtained here is found to be comparable with those of

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ACCEPTED MANUSCRIPT other regions of the world though the absolute values differ The obtained relations are expected to be useful for the estimation of source parameters of the earthquakes in the

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Mainland Gujarat region where no such relations were available earlier. These relations

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are also important for the simulation of earthquake strong ground motions in the region.

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Keywords: Coda wave; Attenuation; Lapse time; Mainland Gujarat

1. Introduction

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Seismic wave attenuation, expressed by the dimensionless quantity known as quality factor (Q), represents the decay of wave amplitude or energy caused by

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heterogeneity or anelasticity or both in the earth crust. It is one of the most important

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basic physical parameters which is directly related to the seismicity and tectonic activity of study region. The attenuation characteristics of seismic waves has been widely

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estimated using coda waves in the crust of a region (Pulli, 1984; Van Eck, 1988; Ambeh

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and Fairhead, 1989; Catherine, 1990; Gupta et al., 1996; Kumar et al., 1997; Mandal and Rastogi, 1998; Gupta and Ashwani, 2002; Paul et al., 2003, Sharma et al.,2008 and 2011). Several researchers (Mitchell, 1995; Frankel et al., 1990; Aleqabi and Wysession, 2006) have used coda waves for structure and tectonic interpretation to investigate the tectonic properties of the seismically active regions as the attenuation of the seismic waves is affected by the tectonic pattern of the crust. The study of attenuation of seismic waves is also important for seismic hazard assessment by studying the ground-motion attenuation (Anderson et al., 1996) and for monitoring nuclear explosions (Mayeda et al., 2003). The attenuation (Q-1), for local or regional earthquakes is determined from the rate

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ACCEPTED MANUSCRIPT of time decay of coda wave amplitude or analysis of direct waves (P and S waves) and Lg wave amplitude (Aki, 1969; Aki and Chouet, 1975; Sato, 1977; Aki, 1980; Frankel et al.,

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1990; Yoshimoto et al., 1993; Chung and Sato, 2001; Davis and Clayton, 2007). The

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relations estimated for attenuation may be used to determine the earthquake source

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strong ground motions (Chopra et al., 2010).

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parameters for understanding source processes (Abercrombie, 1997), and to predict the

The attenuation of seismic waves is affected by several factors like geometrical

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spreading, scattering due to inhomogeneities in the media, inelasticity and multipathing. The attenuation properties of the media are governed by the amplitude of seismic waves

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at various distances from an earthquake source. The frequency dependent relations for Q

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(= Q0fn) have been developed by many workers for different regions of the world. The Q0 values are found to be varied according to the tectonic conditions and geological Aki (1980) found that the frequency dependency (n) of Q

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history of the regions.

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increases with intensity of tectonic activity. The attenuation characteristics based on coda waves has been investigated in the present study using the single back scattering model of Aki and Chouet (1975). The broadband seismograms of 53 events that occurred in Narmada and its adjoining area of Mainland Gujarat have been used in this analysis.

The frequency - dependent

relationships for coda-Q (Qc) have been estimated at five stations in Mainland Gujarat region. The dependency of coda-Q on lapse time windows has also been investigated. These attenuation characteristics based on coda waves are the first estimates for Mainland Gujarat region. However the frequency dependent Q relations for the nearby Kachchh

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ACCEPTED MANUSCRIPT region (Mandal et al., 2004, Gupta et al., 2006 and Sharma et al., 2008), Saurashtra region (Sharma et al., 2011) and three distinct zones (Kachchh, Saurashtra and Mainland

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Gujarat) of Gujarat region (Chopra et al., 2010) are available. Chopra et al. (2010) have

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studied the attenuation of high frequency P and S waves in Kachchh (9 stations),

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Saurashtra (5 stations) and used only one station in Mainland Gujarat. The frequency

active and stable regions of the world.

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dependent relationships for Qc obtained here have been compared with those of other The present study of coda wave attenuation in

Mainland Gujarat region will enhance our knowledge about the medium properties of the

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studied region.

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2. Geology and Seismotectonics of Mainland Gujarat

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Gujarat state is situated in a highly tectonised zone along the western border of the Indian continental plate. The breakup of the Indian plate started from Gujarat region

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as the rifting process migrated from north to south. Since the breakup of Indian

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continental plate from the African plate at least three major tectonic episodes – JurassicEarly Cretaceous rifting, Late Cretaceous-Early Eocene drifting and Late Miocene to ongoing inversion affected this region (Biswas, 1987). There are four distinct tectonic regimes within the boundaries of the Gujarat state: 1) Narmada rift zone, 2) Saurashtra horst, 3) Cambay rift zone, and 4) Kachchh rift zone (Biswas, 1987). Physiographically, Gujarat state comprises of three distinct zones: Kachchh, Saurashtra and Mainland Gujarat (Fig.1). Stratigraphically, Mainland Gujarat comprises of Precambrian crystallines, sedimentary rocks of Cretaceous, Tertiary and Quaternary periods and the Deccan basalt (Merh, 1995). Mainland Gujarat is largely occupied by a

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ACCEPTED MANUSCRIPT flat alluvial plain. Cambay basin is a major tectonic feature in the central portion. It is surrounded by Deccan traps in the east and west and Aravalli system of Precambrian age

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in the north-east. In the southern part, the EW trending Narmada fault system is a zone of

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weakness following Narmada–Son Geofracture (NSG) comprising of Narmada-Son fault

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(NSF) in the north and Satpura fault (SF) in the South. The Cambay basin occupies a

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long narrow rift extending from south of Narmada to the Jaisalmer-Mari arch of Rajasthan to the north in NNW-SSE direction. Northward the rift becomes narrower and ends up as Barmer basin in Rajasthan. It extends to the south across the Narmada rift,

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along the west coast fault in the offshore shelf. It is a sub-surface structure below the alluvial plains of Gujarat (Biswas, 1987).

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The Cambay and Narmada are conjugate rifts displacing each other while

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crossing in the region of Gulf of Cambay, which is supposedly the tri-junction point over the plume head along the west coast fault in the offshore shelf. Significantly, this is the

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zone of maximum subsidence in the present tectonic framework where Surat deep

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depression is located. The NSG has been the site of resurgent tectonics since NeoArchaean times including neotectonic rejuvenation and recent seismicity (Biswas, 1987). In the present neo-tectonic cycle, the NSF is the active strike-slip fault, undergoing right lateral movement and responsible for frequent earthquake (Biswas, 1987). Historical and instrumental records indicate that the compressive stresses still continue to accumulate along the NSF due to continued northward movement of the Indian plate. This is evidenced by the fault plane solution studies of the earthquakes at Broach M5.4 (23 March 1970) and Jabalpur M5.8 (22 May 1997), which suggest a thrusting mechanism (Gupta et al., 1972, 1997; Chandra, 1977; Acharya et al., 1998).

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ACCEPTED MANUSCRIPT However, the underlying cause of the seismicity in the NSF zone is not yet understood (Quittmeyer and Jacob, 1979).

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Mainland Gujarat region falls under zone III of the seismic zoning map of India

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which indicates the moderate damage risk zone. This zone may experience an intensity

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of VII on the MSK scale. A zone factor of 0.16 has been assigned to this zone which

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indicates the effective peak horizontal ground acceleration of 0.16g that may be generated during a maximum credible earthquake considered in the zone. Historically this region has experienced several earthquakes of magnitude between 4 and 5.7 (Fig. 1). The

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Cambay fault of Mainland Gujarat has produced a number of moderate size earthquakes in the eastern boundary of Saurashtra, largest being magnitude 6 near Bhavnagar in 1919.

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Valsad area of south Gujarat has witnessed swarm type of seismic activity in 1986 (Rao

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et al, 1991). The region has also witnessed earthquake of magnitude 3.2 on May 20, 2008 near Surat (ISR Annual report, 2008). Figure 1 shows the tectonics of the Mainland

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Gujarat region along with the major rift zones. The epicenters of the earthquakes and

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locations of recording stations in the Mainland Gujarat are also shown in fig. 1. 3. Methodology

Aki and Chouet (1975) proposed a method to estimate the Qc using the single backscattering model. Single backscattering model assume that the coda waves are backscattered body waves generated by numerous heterogeneities present in the Earth’s crust and upper mantle. Under this assumption the coda amplitudes, Ac(f,t) in a seismogram can be expressed for a central frequency ‘f’ over a narrow band width signal, as a function of the lapse time t, measured from the origin time of the seismic event, as (Aki, 1980):

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ACCEPTED MANUSCRIPT Ac(f,t) = S(f)t-aexp(-ft/ Qc)

(1)

where S(f) represents the source function at frequency f, and is considered a constant as it

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is independent of time and radiation pattern, and therefore, not a function of factors

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influencing energy loss in the medium; a is the geometrical spreading factor, and taken as 1 for body waves, and Qc is the apparent quality factor of coda waves representing the Rautian and Khalturin (1978) suggested that the coda

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attenuation in a medium.

parameters S(f) and Qc are independent of source-site distance if coda start time is taken

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as twice the travel time of S-waves. The equation (1) can be rewritten as: (2)

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ln(Ac(f,t)t) = lnS(f)-(f/Qc)t

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4. Data and Analysis

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The linear equation (2) with slope -f/Qc can be used to estimate Qc .

Digital data of earthquakes that occurred during 2007–2010 in Mainland Gujarat

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region and recorded by the broadband seismograph (BBS) network of Institute of Seismological Research (ISR), Gandhinagar are analyzed for the estimation of Qc in the present analysis. ISR, Gandhinagar has installed five permanent 120 s broadband (CMG3T, Guralp) sensors having 24 bit CMG-DCM recorders with an external hard disk (4GB) and GPS synchronized timing system instruments at Kadana (KAD), Sipu (SIP), Vadodara (VAD), Kevdia (KEV) and Ukai (UKE) stations. All the five recording stations are connected through VSAT and continuous data is being recorded at all these stations at the sampling rate of 50 samples/s (Chopra et al.,2008). Table 1 gives the locations and site conditions of the recording stations. The events were located in SEISAN (Havskov 7

ACCEPTED MANUSCRIPT and Ottemoller, 2000) program. The Koyna model (Kaila et al. 1981) constrained by Deep Seismic Sounding is used for locating earthquakes in Mainland Gujarat. The

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velocity model of Koyna is given in Table 2. The error in an epicenter is 5 km, and the

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error in origin time is 1 s. The magnitudes of the events have been estimated by fitting the

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Brune’s (1970) model to the source displacement spectra of observed seismograms. Out

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of 100 local earthquakes, seismograms of 53 events having Mw (1.1-3.3) were selected based on signal-to-noise ratio and correlation criteria for estimation of Qc. Figure 1 shows the locations of the earthquakes and recording stations.

The maximum and

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minimum epicentral distances for the earthquakes are 113 km and 20 km respectively. Only waveforms with good signal-to-noise ratio (S/N ≥2) are used for the

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analysis. S/N ratios are calculated for each central frequency for each record separately.

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We have also checked how the Qc estimates are affected when S/N is increased (≥5). It is observed that the estimated Qc values for both cases are almost the same or lie within the

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error range. As for S/N ≥ 2, the number of data available is higher, and as this does not

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significantly affect the result, we have decided to use S/N ≥ 2. In the same manner the criteria of correlation coefficient ≥0.50 is applied to obtain reliable Qc values. In order to estimate Qc, it is necessary to eliminate contamination caused by the direct S-phases (Rautian and Khalturin 1978; Herraiz and Espinosa 1987). In order to do so, Rautian and Khalturin (1978) suggested that the beginning of the coda window should be placed at a time measured from the origin time of an earthquake that is about twice the S-wave travel time (ts). This time is called lapse time. We call it start time tstart following Havskov et al. (1989). Spudich and Bostwick (1987) have shown that for ts ≤ tstart ≤ 2ts, near-site reverberations can be the dominant component of the coda, at least

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ACCEPTED MANUSCRIPT for frequencies less than about 10 Hz. In the present study, we have analyzed the data set by selecting the start times tstart at 2ts .

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The coda window length should be large enough to get stable results. Havskov

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and Ottemoller (2005) suggest a minimum value of 20 s. There is no limit on the

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maximum lapse time. However, it is assumed that S/N ≥ 2 could be obtained for very few

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records for lapse time > 50 sec; hence, it was set as the upper limit. Three lapse time window lengths of duration 30s, 40s and 50s are selected and we fix the window length as 20 s. Figure 2 shows an example of coda portion used for analysis (the boxed portion)

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when window length is 20 s and tstart = 2ts. The Q values are calculated through the CODAQ subroutine of SEISAN (Havskov and Ottemoller; 2003). The S-wave time is

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calculated through the P wave time using Vp/Vs = 1.74. The top panels in Fig. 2a show

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the 20-s window length of coda waves considered for the estimation of Qc for tstart equal to 2ts. The origin time, Pwave and Swave arrival time of the earthquake is shown in the

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seismogram. Coda of all the seismograms are filtered using the Butterworth band pass

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filter (eight poles) at central frequencies of 1.5, 3.0, 6.0, 12.0 and 18.0 Hz. The root mean square (RMS) amplitudes of filtered seismograms are estimated using a moving time window of 2.56 sec width with 1.28 sec interval.

Figure 2 displays the filtered

seismograms and plots of ln[A(f,t).t] versus t for an event recorded at UKE for different central frequencies along with the least square fitted lines. The slopes (m) of these lines are used to estimate Qc (= -f/m). Table 3 shows average value of Qc for the region at different lapse times and central frequencies. An increasing frequency band is used for increasing central frequency to avoid ringing and to take constant relative bandwidths as suggested by Havskov and Ottemoller (2005). The comparison of the number of

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ACCEPTED MANUSCRIPT seismograms selected for each frequency and lapse time to observe the average Qc is described by the factor N in Table 3. Table 4 shows the parameters of frequency

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dependent Q for different lapse times at different stations whereas Table 5 shows the

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worldwide comparison of Q value.

In the single scattering model the estimated attenuation of coda wave is the

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average decay of amplitude of back-scattered waves on the surface of ellipsoid volume having earthquake source and station as foci (Pulli, 1984). On this basis the approximate

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ellipsoidal volume for five seismic stations is estimated, which shows average attenuation properties of the area around station. The observed Qc reflects the average attenuation

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properties of the volume of ellipsoid at an average depth, h = hav + a2, where hav is the average focal depth of the events and

is the small semi axis of the ellipsoid

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for Δ as average epicentral distance (Pulli, 1984; Havskov et al., 1989; Canas et al.,1995).

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The large semi-axis of the ellipsoidal volume is a1=ct/2 for lapse time t and velocity c of the S wave (c = 3.5 km/s). The average lapse time is taken as t = tstart + W/2 where tstart

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is the starting time of the coda window and W is the coda window length. The depths calculated for the ellipsoidal volume for different stations of data are given in Table 6. 5. Results and Discussions The seismograms have been filtered at five different central frequencies of 1.5 (1– 2 Hz), 3 (2–4 Hz), 6 (4–8 Hz), 12 (9–15 Hz), and 18 Hz (16–20 Hz) using a Butterworth band-pass filter. On the filtered seismograms, RMS amplitudes of coda waves in a window length of 256 samples and lapse time of 30, 40 and 50 s have been used to estimate Qc. The frequency dependent average Qc values of the region at different lapse

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ACCEPTED MANUSCRIPT times is given in Table 3 and Q0 (quality factor at 1 Hz) along with n, the degree of frequency dependence are given in Table 4. We note from Table 3 that Qc values

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increase with increase in frequency and for all the three lengths of lapse time window

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considered here. The average values of Qc for the lapse time windows of 30, 40 and 50 s

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with standard error varies, respectively, from 133±66, 173±88 and 175±60 at 1.5 Hz to This shows the frequency

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1633±386, 1634±448 and 1686±265 at 18 Hz (Table 3). dependent nature of Q estimates.

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Figure 3 shows the fitting of the power law Qc = Q0fn for each station and gives the average frequency dependent relationships as: Qc=(87±13)f(1.01±0.06) (lapse time: 30

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s), Qc=(112±20)f(0.94±0.08) (lapse time: 40 s) and Qc=(120±22)f(0.76±0.07) (lapse time: 50 s) for mainland Gujarat. It is clear from Figure 3 and Table 4 that SIP site located in

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granitic basement shows Q0 decreasing with increasing lapse time as compare to other

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sites and average Q values. This seems to be basically due to the relatively large standard error in Q estimation. We tried to compare the results of Q0 estimation in Mainland

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Gujarat with other regions of the World (Rodriguiez et al. (1983), Rovelli (1984), Roecker et al. (1982), Havskov et al. (1989), Ambeh and Fairhead (1989),Van Eck (1988), Hellweg et al. (1995), Rovelli (1982), Pujades et al. (1991), Ibanez et al. (1990), (1998), Akinci et al. (1994), Sherbaum and Kisslinger (1985), Kvamme and Havskov (1989), Rhea (1984), Pulli (1984), Pujades et al. (1991)). A plot was made to compare the results with some of the other systems of the world (figure 4). We note that rate of decay of attenuation (Q-1) with frequency for the relations obtained in the present study are comparable with those of other regions of the world. It has been observed that the average Q0 variation of Mainland Gujarat is very close to the active region of Dead Sea 11

ACCEPTED MANUSCRIPT (Table 5) which is a part of Jordan rift structure. This may be due to similarity of geological and tectonic setup of Mainland Gujarat and Dead Sea regions. Cambay rift is

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main tectonic structure in center of Mainland Gujarat which is largely occupied by a flat

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alluvial plain and comprises of Precambrian crystallines, sedimentary rocks of

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Cretaceous, Tertiary and Quaternary periods and the Deccan basalt (Merh, 1995). Dead

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Sea region is characterized by a large fill of sediments up to 6 to 8 km on top of the more consolidated Cretaceous sediments of 2 km and its subsequent crystalline Precambrian basement rock and evaporates including diapirs (Van Eck, T., 1988). The variation in Qc

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values at different sites may be attributed to the heterogeneities present in the regions

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and/or difference in the distances of the events from the recording stations.

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It has been observed from Table 4 that Q0 values increase with the increase in lapse-time along with n for all the stations and their averages. The degree of frequency

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dependence, n, has been found to be high for tectonically active region as compared to

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that of tectonically stable regions (Table 5). The value of n varies from 0.70 to 1.10 for the active regions (Hellweg et al., 1995; Rovelli, 1982; Gupta et al., 1995). The high values of n estimated here indicate that Mainland Gujarat is seismotectonically active. No significant variation in n with lapse time window lengths has been found for smaller lapse time window lengths (e.g. Ibnaez et al., 1990; Akinci et al., 1994). The value of n obtained here for different lapse time window lengths can be considered as stationary as it has not changed much for different lapse times. The increase in Qc values with lapse time found in this study show the depth dependence of Qc as larger area will be sampled with longer lapse time windows. The increase of Qc with lapse time has been observed

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ACCEPTED MANUSCRIPT by other researchers for other regions (e.g. Roecker et al., 1982; Havskov, 1989; Akinci, 1994; Gupta et al., 1996; Sharma et al., 2011). The estimated maximum depth of

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ellipsoidal volume varying from 58.1 to 120.9 km (Table 6) which indicate that the

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region is seismically active and upper lithosphere is quite heterogeneous (Naresh et al,

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2005).

The increase in Qc with lapse time can also, as pointed out by Woodgold (1994), be attributed to other factors like consideration of non-zero source receiver distance with

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anisotropic scattering and assumption of single scattering model where multiple scattering is important. The coda start time has been taken as twice of the S-wave travel

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time for all the three lapse times considered here and therefore only back scattered waves

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arrive at this time (Aki and Chouet, 1975). Gao et al. (1983) has reported that the effects of multiple scattering are not important for local events with lapse time less than 100 s.

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The lapse time window lengths of local events analyzed here are less than 100 s. In view

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of this, the lapse time dependence of coda-Q in the studied region can be attributed to the variation of attenuation with depth.

The coda-Q estimates of nearby Kachchh region are available (Mandal et al., 2004, Gupta et al., 2006 and Sharma et al., 2008). Sharma et al. (2011) have studies the Q estimates for Saurashtra and Chopra et al. (2010) have studied Q for P and S waves for three distinct zones (Kachchh, Saurashtra and Mainland Gujarat) of Gujarat region. Chopra et al. (2010) have reported Q of S-wave, Qs=118f0.65 for Kevadia (KEV) station of Mainland Gujarat which is comparable to the estimated Qc =(89±6)f(1.02±0.03) (lapse

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ACCEPTED MANUSCRIPT time : 30 s), Qc =(108±14)f(0.92±0.06) (lapse time : 40 s) and Qc =(108±16)f(0.95±0.07) (lapse time : 50 s) in present study for the same station. The estimated average Qc =

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(87±13)f(1.01±0.06) at 30 s lapse time is low as compared to that of Saurashtra region

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(Qc=170f0.97 for Junagarh and Qc=224f0.98 for Jamnagar areas at lapse time 30s by Sharma

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et al., 2011) and comparable to the Kachchh region (Qc = 102f

0.98

by Mandal et al.,

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2004; Qc = 106f1.11 by Gupta et al., 2006 and Qc=148f 1.01 by Sharma et al., 2008) (Figure 5). This shows that the region is more heterogeneous as compared to that of adjacent Saurashtra and Kachchh regions. The region is infested with many of criss-crossed

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fracture and dykes, which may be the reason of getting low coda Q values.

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The frequency dependent relations developed here are useful for the estimation of

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source parameters of the earthquakes in the Mainland Gujarat region where no such relations were available earlier. These relations can also be used for the simulation of

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6. Conclusions

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earthquake strong ground motions in the region.

This study reports the attenuation characteristics of Mainland Gujarat (India) region. The frequency dependent relationships for coda-Q have been estimated using three lapse times 30 s, 40 s and 50 s with fixed 20 s coda window length. The coda-Q estimates increase with increase in lapse time window indicates the depth dependence of attenuation. The rate of decay of attenuation is found to be comparable with those of other worldwide results. The variation of Qc with frequency and lapse time shows that the upper crustal layers are seismically more active compared to the lower lithosphere. The decreasing value of the frequency parameter with increasing lapse time shows that

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ACCEPTED MANUSCRIPT the lithosphere acquires homogeneity with depth.

Based on Q relations, the Mainland

region is found to be more heterogeneous as compare to the nearby Kachchh and

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Saurashtra regions. The frequency dependent relations estimated here are very useful for

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source parameters in the Mainland Gujarat region.

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the modeling of earthquake strong ground motions as well as estimation of earthquake

Acknowledgements

The authors are grateful to Gujarat State Disaster Management Authority and

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Department of Science and Technology, Government of Gujarat for financial support in establishment of seismological network. The authors are very thankful to Dr. Anna

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Dobrynina for his critical review and useful comments for enhancing the quality of the

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References

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paper.

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Abercrombie, R. E., 1997. Near-surface attenuation and site effects from comparison of surface and deep boreholes recordings. Bull. Seismol.Soc. Am. 87, 731–744. Acharya, S.K., Kayal, J.R., Roy, A., Chaturvedi, R.K., 1998. Jabalpur earthquake of May 22, 1997: constraint from a aftershock study. J. Geol. Soc. India 51, 295– 304. Aki, K., 1969. Analysis of seismic coda of local earthquakes as scattered waves. J. Geophys. Res. 74, 615–631. Aki, K. ,1980. Attenuation of shear waves in the lithosphere for frequencies from 0.05 to 25 Hz. Phys. Earth Planet. Interiors 21, 50–60.

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ACCEPTED MANUSCRIPT Aki, K., Chouet, B.,1975. Origin of coda waves: Source, attenuation and scattering effects. J. Geophys. Res. 80, 3322–3342.

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Aleqabi, G. I., Wysession, M. E. , 2006. QLg distribution in the Basin and Range

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Province of the western United States. Bull. Seismol. Soc. Am. 96, 348–354.

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Ambeh, W.B., Fairhead, J.D., 1989. Coda-Q estimates in the Mount Cameroon volcanic

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region,West Africa. Bull. Seismol. Soc. Am. 79, 1589–1600. Anderson, J. G., Lee, Y., Zeng, Y.,Day, S. , 1996. Control of strong motion by the upper 30 meters. Bull. Seismol. Soc. Am. 86, 1749–1759.

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Akinci, A., Taktak, A.G., Ergintav, S., 1994. Attenuation of coda waves in Western Anatolia. Phys. Earth Planet Inter. 87, 155–165.

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Brune, J.N., 1970. Tectonic stress and spectra of shear waves from earthquakes. J.

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Geophy. Res. 75, 4997–5009.

Biswas, S. K., 1987. Regional framework, structure and evolution of the western

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marginal basins of India. Tectonophysics. 135, 302–327.

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Canas, J.A., Pujades, L., Blanco, M.J., Soler, V., Carracedo, J.C., 1995. Coda-Q distribution in the Canary Islands. Tectonophysics. 246, 245–261. Catherine, R.D.W., 1990. Estimation of Q in Eastern Canada using coda waves. Bull. Seismol. Soc. Am. 80, 411-429. Chopra, S., Dinesh Kumar, Rastogi, B.K. , 2010. Attenuation of High Frequency P and S Waves in the Gujarat Region, India. Pure Appl.Geophys.168( 5), 797-813. Chopra, S., Yadav, R. B. S., Patel, H., Kumar, S., Rao, K. M., Rastogi, B. K., Hameed, A., Srivastava, S., 2008. The Gujarat (India) seismic network. Seismol. Res. Lett. 79(6), 806–815.

16

ACCEPTED MANUSCRIPT Chung, T. W., Sato, H., 2001. Attenuation of high-frequency P and S waves in the crust of southeastern South Korea. Bull. Seismol. Soc. Am. 91, 1867–1874.

T

Chandra, U., 1977. Earthquakes of Peninsular India-A Seismo- tectonic study. Bull.

IP

Seismol. Soc. Am. 67, 1387–1413.

CR

Davis, P. M., Clayton, R. W. , 2007. Application of the telegraph model to coda Q

10.1029/2006JB004542. Frankel, A., McGarr, A.,

Bicknell, J.,

NU S

variations in southern California. J. Geophys. Res. 112, B09302, doi

Mori, J.,

Seeber, L.,Cranswick, E., 1990.

MA

Attenuation of high-frequency shear waves in the crust: Measurements from New York State, South Africa and Southern California. J. Geophys. Res. 95, 17441–

ED

17457.

PT

Gao, L.S., Biswas, N.N., Lee, L.C., Aki, K., 1983. Effects of multiple scattering on coda waves in three dimensional medium. Pure Appl. Geophys. 121, 3–15.

CE

Gupta, S.C., Ashwani Kumar, Singh, V.N., Basu, S., 1996. Lapse- time dependence of

AC

Qc in the Garhwal Himalaya, Bull. Indian. Soc. Earthquake Technol. 33, 147– 159.

Gupta, S.C., Singh, V.N., Kumar, A., 1995. Attenuation of coda waves in the Garhwal Himalaya, India, Phys. Earth Planet. Inter. 87, 247–253. Gupta, S.C., Ashwani Kumar, 2002. Seismic wave attenuation characteristics of three Indian regions. A comparative study. Curr. Sci. 82, 407–413. Gupta, S. C., A. Kumar, Shukla, A. K., Suresh, G., Baidya, P. R. 2006. CodaQ in the Kachchh Basin, Western India using aftershocks of the Bhuj earthquake of January26, 2001. Pure Appl.Geophys. 163(8), 1583–1595.

17

ACCEPTED MANUSCRIPT Gupta, H.K., Mohan, I., Narain, H., 1972. The Broach earthquake of March 23, 1970. Bull. Seismol. Soc. Am. 62, 47– 61.

T

Gupta, H.K., Chadha, R.K., Rao, M.N., Narayna, B.L., Mandal, P.,Ravikumar, M.,

IP

Kumar, N., 1997. The Japalbur earthquake of May 22, 1997. J. Geol. Soc. India

CR

50, 85– 91.

NU S

Havskov, J., Ottemoller, L., 2000. SEISAN earthquake analysis software, Seism. Res. Lett. 70, 532–534.

Havskov, J., Ottemoller, L., 2003. SEISAN: The Earthquake Analysis Softwares for

MA

Windows, Solaris and Linux, Version 8.0. Institute of Solid Earth Physics, University of Bergen, Norway.

ED

Havskov J, Ottemoller L ., 2005. SEISAN (version 8.1): the earthquake analysis software

PT

for Windows, Solaris, Linux, and Mac OSX Version 8.0. pp 254. Havskov, J., Malone, S., McClury, D., Crosson, R., 1989. Coda-Q for the State of

CE

Washington. Bull. Seismol. Soc. Am., 79, 1024–1038.

AC

Herraiz, M, Espinosa,A.F., 1987. Coda waves: a review. Pure Appl. Geophys. 125, 499– 577.

Hellweg, M., Spandich, P., Fletcher, J.B., Baker, L.M., 1995. Stability of coda Q in the region of Parkfield, California: view from the U.S. Geological Survey Parkfield Dense Seismograph Array. J. Geophys. Res.100, 2089–2102. Ibanez, J.M., del Pezzo, E., de Miguel, F., Herraiz, M., Alguagh, G., Morales, J., 1990. Depth dependent seismic attenuation in the Granada zone (southern Spain), Bull. Seismol. Soc. Am. 80, 1222–1234.

18

ACCEPTED MANUSCRIPT Imtiyaz, A. Parvez, Anup K. Sutar, Mridula, M., Mishra, S. K., Rai, S. S., 2008. Coda Q Estimates in the Andaman Islands Using Local Earthquakes. Pure Appl. Geophys.

T

165, 1861–1878

IP

ISR, Annual report, 2008. Institute of Seismological Research, Gandhinagar. pp.1-43

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(unpublished)

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Kanao, M., Ito, K.,1991. Attenuation of S-waves and coda waves in the inner zone of southwestern Japan. Disaster Prev. Res. Inst., Kyoto Univ., Bull. 41 2, 356, pp. 87–107.

MA

Kaila, K. L., Murphy, P. R. K., Rao, V. K. , Kharetchko, G. E., 1981. Crustal structure from deep seismic sounding along the Koyna 11 (Kelsi-Loni) profile in Deccan

ED

trap area, India, Tectonophysics. 73, 365–384.

79, 1575–1588.

PT

Kvamme, L.B. and Havskov, J., 1989. Q in southern Norway, Bull. Seismol. Soc.Am.,

CE

Kumar, A., Pandey, A.D., Sharma, M.L., Gupta, S.C., Verma, A.K., Gupta, B.K., 1997.

AC

Processing and preliminary interpretation of digital data obtained from telemetered seismic array in the Garhwal Himalaya, 10th Symp. of Earthquake Engineering,University of Roorkee, Roorkee. 141–152. Latchman, Joan L., William, B. Ambeh, Lloyd, L. Lynch, .1996. Attenuation of seismic waves in the Trinidad and Tobago area. Tectonophysics. 253(1-2), 111-127 Mandal, P. and Rastogi, B.K., 1998. A frequency-dependent relation of coda Qc for Koyna-Warna region, India. Pure Appl. Geophys. 153, 163–177.

19

ACCEPTED MANUSCRIPT Mandal, P., Jainendra, Joshi, S., Kumar, S., Bhunia, R., Rastogi, B.K., 2004. Low codaQc in the epicentral region of the 2001 Bhuj Earthquake of M w 7.7. Pure Appl.

IP

Merh, S. S., 1995. Geology of Gujarat. Geol Soc Ind. pp. 222.

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Geophys. 161, 1635–1654.

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Mitchell, B., 1995. Anelastic structure and evolution of the continental crust and upper

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mantle from seismic surface wave attenuation. Rev.Geophys. 33(4), 441–462. Mayeda, K., Hofstetter, A., O’Boyle, J. L., Walter, W. R. 2003. Stable and transportable

Soc. Am. 93, 224–239.

MA

regional magnitudes based on coda-derived moment rate spectra. Bull. Seismol.

Naresh, Kumar, Imtiyaz, A. Parvez , Virk, H.S. 2005. Estimation of coda wave

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attenuation for NW Himalayan region using local earthquakes. Phys. of the Earth

PT

and Planet. Int. 151, 243–258

Paul, A., Gupta, S., Pant, C. C., 2003. Coda Q estimates for Kumaun Himalaya, Proc.

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Indian Acad. Sci. 112, 569–576.

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Pulli, J.J.,1984. Attenuation in New England. Bull. Seismol. Soc. Am., 74, 1149–1166. Pujades, L., Canas, J.A., Egozcue, J.J., Puigvi, M.A., Pous, J., Gallart, J.,Lana, X., Casas, A., 1991. Coda Q distribution in the Iberian Peninsula, Geophys. J. Int., 100, 285– 301. Quittmeyer, R.C., Jacob, K.H., 1979. Historical and modern seismicity of Pakistan, Afghanistan, northwestern India and southeastern Iran. Bull. Seismol. Soc. Am. 69, 773– 823.

20

ACCEPTED MANUSCRIPT Rao, D.T., Jambusaria, B.B., Srivastava, S., Srivastava N.P., Hamid, A., Desai, B.N., Srivastava, H.N., 1991. Earthquake swarm activity in south Gujarat. Mausam. 42,

T

89-98.

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Rautian, T.G., Khalturin, V.I., 1978. The use of the coda for the determination of the

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earthquake source spectrum, Bull. Seismol.Soc.Am., 68, 923–948.

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Rhea, S., 1984. Q determined from local earthquakes in the South Carolina Coastal Plain, Bull. Seismol. Soc. Am., 74, 2257–2268.

Rovelli, A., 1982. On the frequency dependence of Q in Friuli from short period digital

MA

records, Bull. Seismol. Soc. Am., 72, 2369–2372.

Rodriguiez, M., Havskov, J., Singh, S.K., 1983. Q from coda waves near Petatlan,

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Guerrero, Mexico, Bull. Seismol. Soc. Am., 73, 321–326.

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Rovelli, A., 1984. Seismic Q for the lithosphere of the Montenegro region (Yugoslavia):

172.

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frequency, depth, and time windowing effects, Phys. Earth Planet. Inter., 34, 159–

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Roecker, S.W., Tucker, B., King, J., Hartzfield, D., 1982. Estimates of Q in Central Asia as a function of frequency and depth using the coda of locally recorded earthquakes, Bull. Seismol. Soc. Am., 72, 129–149. Sato, H,1977. Energy propagation including scattering effect. J. Phys. Earth. 25, 27–41. Sato, H.,1984. Attenuation of envelope formation of three- component seismograms of small local earthquakes in randomly inhomogeneous lithosphere, J. Geophys. Res., 89, 1221–1241. Sherbaum, F., Kisslinger, C., 1985. Coda Q in the Adak seismic zone, Bull. Seismol. Soc. Am., 75, 615–620.

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ACCEPTED MANUSCRIPT Sharma, B., Gupta, A.K., Devi, D. K., Dinesh, Kumar, Teotia, S.S., Rastogi, B. K., 2008. Attenuation of high frequency seismic waves in Kachchh region, Gujarat, India,

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Bull. Seismol. Soc.Am. 98, 2325–2340.

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Sharma, Babita, Dinesh Kumar, S. S. Teotia, B. K. Rastogi, Arun K. Gupta, Srichand

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Prajapati, 2011. Attenuation of Coda Waves in the Saurashtra Region, Gujarat

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(India). Pure Appl. Geophys. DOI: 10.1007/s00024-011-0295-1. Spudich, P., Bostwick, T., 1987. Studies of the seismic coda using an earthquake cluster as a buried seismograph array. J. Geophys. Res. 92,10526–10546.

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Singh, D. D. , Govoni, A., Bragato,P. L., 2001. Coda Qc Attenuation and Source Parameter Analysis in Friuli (NE Italy) and its Vicinity. Pure Appl. Geophys. 158, 1737-1761.

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Am., 2, 770–779.

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Van Eck, T., 1988. Attenuation of coda waves in the Dead Sea region. Bull.Seismol. Soc.

Woodgold, C.,1994. Coda-Q in Charlevoix, Quebec, Region. Lapse time dependence and

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Spatial and temporal comparisons. Bull. Seismol. Soc. Am. 84, 1123–1131.

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Yoshimoto, K., Sato, H., Ohtake, M. , 1993. Frequency-dependent attenuation of P and S waves in the Kanto area, Japan, based on the coda-normalization method, Geophys. J. Int. 114, 165–174.

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ACCEPTED MANUSCRIPT List of Tables: Table 1: Site characteristics and epicentral locations of the recording stations

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Table 2:Velocity model for locating earthquakes in Mainland Gujarat (Kaila et al., 1981)

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Table 3: Average quality factor at different frequencies and lapse time. ±σ indicates the

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standard error and intervals show the frequency band

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Table 4: Q0 (quality factor at 1 Hz) and n values for all the stations and their averages Table 5 Worldwide comparative study of observed Q0 and n values for various active and stable regions

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Table-6: Maximum depth of the ellipsoidal volume

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ACCEPTED MANUSCRIPT List of Figures: Fig.1. The rectangular region on the map is expanded. Epicentral locations of 53 events used in present study are shown by dark circles, epicenters of historical earthquakes are

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shown by open circles, and stations used in this study are shown by triangles. The

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tectonic features are as follows: NPF: Nagar Parker fault, ABF: Allah Bund fault, IBF:

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Island Belt fault, GF: Gedi fault, KMF: Kachchh Mainland fault, KHF: Katrol Hill fault,

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NSF: Narmada Son Fault and BSF: Barwani Sukta Fault

Fig.2. Plot of event recorded at UKE station on 12/12/2010 from 66 km epicentral distance. (a) Unfiltered data trace with coda window, (b) to (f) bandpass filtered

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displacement amplitudes of coda window at 1-2 Hz,2-4Hz,4-8Hz,9-15Hz and16-20Hz respectively, (g) to (k) the RMS amplitude values multiplied with lapse time along with

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best square fits of selected coda window at central frequencies of 1.5, 3.0,6.0,12.0 and 18.0 Hz respectively. The Qc is determined from the slope of best square line.

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Abbrevations are: P: P-wave arrival time; S: S-wave arrival time.

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Fig.3. Plots of quality factors and central frequencies for all the five stations (a) to (e) and average with linear regression frequency dependent relationship (f), Qc= Q0fn at different

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lapse time 30,40 and 50 s.

Fig.4. Comparison of Qc values for Mainland Gujarat, India with the existing Q studies worldwide. Fig.5. Comparison of Qc values for Mainland Gujarat, India with the existing Q studies in India.

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Fig. 1

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25

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a 20000

origin time

counts

10000

coda window

0

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P

-20000 -30000 300

320

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356

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h

Qc(3 Hz.)=317

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356

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f=6 Hz.

i

14

Qc(6 Hz.)=441

13 12 11 10

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352 Time (sec.)

356

360

364

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f=12.0 Hz.

0 -1000

Qc(12 Hz)=923

j

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ln (A(f,t)*t)

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348

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ln (A(f,t)*t)

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ln (A(f,t)*t)

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15

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340

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f=3 Hz.

c

0

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k

Qc(18 Hz.)=1832

13 12 11

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Fig. 2

Qc(1.5 Hz)=150

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ACCEPTED MANUSCRIPT 2500

2500

30 sec. Q c=(109±20)f (0.94±0.08) 40 Sec. Qc=(122±32) f (0.85±0.11)

2000

2000

b

50 Sec. Qc=(90±04) f (1.03±0.02)

50 Sec. Qc=(90±16)f (1.00±0.08)

Qc

1500

Qc

1500

30 Sec. Qc=(67±08) f (1.10±0.05) 40 sec. Qc=(66±11) f (1.11±0.08)

a

1000

500

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1000

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500

SIPU 0 0

4

8

12

16

20

0

frequency (Hz.) 2500

30 Sec. Qc =(101±27) f (0.97±0.11)

c

40 Sec. Qc =(160±20) f (0.85±0.06) 50 Sec. Qc =(178±39) f (0.74±0.10)

2000

2000

4

8

KAD 12

16

20

frequency (Hz.)

30 Sec. Qc=(89±6) f (1.02±0.03)

d

40 Sec. Qc=(108±14) f (0.92±0.06) 50 Sec. Qc=(108±16) f (0.95±0.07)

Qc

1500

Qc

1500

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2500

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0

1000

500

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1000

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VAD

0 0

4

8

12

16

KEV 0

20

0

4

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frequency (Hz.)

2500

30 Sec. Qc=(70±06) f (1.06±0.04)

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40 Sec. Qc=(104±21) f (0.97±0.09) 50 Sec. Qc=(134±37) f (0.88±0.11)

1000

0 0

Fig. 3

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500

4

2500

16

30 Sec. Qc=(87±13) f (1.01±0.06)

e

20

f

40 Sec. Qc=(112±20) f (0.94±0.08)

2000

50 Sec. Qc=(120±22) f (0.76±0.07)

1500

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Qc

1500

12

Qc

2000

8

frequency (Hz.)

1000

500

AVG

UKE 0

8

12

16

20

frequency (Hz.)

0

4

8

12

frequency (Hz.)

27

16

20

Fig. 4

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Fig. 5

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Station code

Latitude (N)

Longitude (E)

Foundation geology

Sipu Kadana Kevdia Vadodara Ukai

SIP KAD KEV VAD UKE

24.39 23.29 21.88 22.31 21.22

72.29 73.85 73.71 73.13 73.58

Granite Basalt Basalt Hard soil Basalt

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Table 1 Station

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ACCEPTED MANUSCRIPT Table 2 Depth to the top of layer (km)

Velocity of P-wave (Km/s)

0.0 1.0

4.90

2.0

5.76

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5.33 5.89

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4.0 6.0

6.02 6.15

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8.0 10.0 13.0

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16.0 19.0 28.0 31.0

6.47 6.56 6.60 6.80 6.89 6.98 7.10

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34.0

ED

25.0

6.38

8.10

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CE

38.0

31

ACCEPTED MANUSCRIPT Table 3

133±66

40 50

48

173±88

39

323±99

58

175±60

27

286±77

38

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PT

ED

MA

28

586±24 2 617±19 7 664±16 9

N

32

N

T

30

N

3.0 Hz. (2-4) Qc±σ 246±10 2

77

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N

12 Hz. (9-15) Qc±σ

991±252 1081±32 8 1152±30 3

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1.5 Hz. (1-2) Qc±σ

89 68

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Lapse time (s)

6.0 Hz. (4-8) Qc±σ

74 76 64

18 Hz (16-20) Qc±σ 1633±38 6 1634±44 8 1686±26 5

N

75 64 52

ACCEPTED MANUSCRIPT Table 4:

40

104±21

50

134±37

Q0 109±20 122±32 90±16

Table 4 (contd.)

Q0

30

67±8

40

66 ±11

50

90±4

KAD

Q0

89± 6 108 ±14 108 ±16

VAD

Q0 101± 27

160±20 178±39

n 0.97±0.1 1 0.85±0.0 6 0.74±0.1 0

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n 1.10±0.0 5 1.11±0.0 8 1.03±0.0 2

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Lapse Times (s)

n 0.94±0.0 8 0.85±0.1 1 1.00±0.0 8

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70± 6

n 1.06±0.0 4 0.97±0.0 9 0.88±0.1 1

KEV

IP

30

SIP

CR

Q0

UKE

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Lapse Times (s)

33

n 1.02±0.0 3 0.92±0.0 6 0.95±0.0 7

AVG Q0 87±13 112±2 0 120±2 2

n 1.01±0.0 6 0.94±0.0 8 0.76±0.0 7

ACCEPTED MANUSCRIPT Table 5 Q0

n

Source

102

0.98

Guerrero, Mexico

47

0.87

Yugoslavia Hindukush

50 60

1 1

Washington State Mt. Cameroon, West Africa

63 65

0.97 1

Dead Sea Parkfield

65 79

Friuli, Italy South Iberia

80 100

1.1 0.7

158

1.05

126

0.9

155

0.89

169

0.77

183

0.76

200

1.05

Mondal et al (2004) Rodriguiez et al. (1983) Rovelli (1984) Roecker et al. (1982) Havskov et al. (1989) Ambeh & Fairhead (1989) Van Eck (1988) Hellweg et al. (1995) Rovelli (1982) Pujades et al. (1991) Naresh et al.(2005) Gupta et al. (1995) Ibanez et al. (1990) Mandal & Rastogi (1998) Akinci et al. (1994) Sherbaum & Kisslinger (1985)

Stable regions Norway

120

1.09

South Carolina South India

190 460

0.94 0.83

New England North Iberia

460 600

0.4 0.45

Mainland Gujarat

87

1.01

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Garhwal, Himalayas

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West Anatolia, Turkey

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South Spain Koyna,India

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Aleutian

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CR

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NW Himalayas

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Places Active regions Kachchh, India

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Kvamme & Havskov (1989) Rhea (1984) Mandal & Rastogi (1998) Pulli (1984) Pujades et al. (1991) Present study

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Depth (km) h= )+ a2

MA ED PT CE 35

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61.2 99.6 111.4 39.3 45.4

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a1=ct/2 c=3.5 km/s 118.0 137.9 166.3 95.2 138.5

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100.8 95.3 123.5 86.7 130.9

averag e lapse time (t) 67.4 78.8 95.0 54.4 79.1

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SIP KAD VAD KEV UKE

Average depth ) 20.9 15.6 9.5 18.7 17.6

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Table 6 average station distance s

82.1 115.2 120.9 58.0 63.0

ACCEPTED MANUSCRIPT Highlights

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The coda-Q analysis of 53 local earthquakes in Mainland Gujarat, India. Analysis in three lapse-time windows within five frequency bands. We measure the dependence of Qc on lapse-time and frequency. We present detailed comparison of Q-values for studied region.

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   

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