Characterization of the causative fault system for the 2001 Bhuj earthquake of Mw 7.7

Mandal, Prantik; Rastogi, B. K.; Satyanaraya, H.V.S.; Kousalya, M.; Vijayraghavan, R.; Satyamurty, C.; Raju, I. P.; Sarma, A. N. S.; Kumar, Narendra

doi:10.1016/j.tecto.2003.08.026

Cited by 113 publications

(61 citation statements)

References 27 publications

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“…The average P-wave velocity of the Mesozoic sediments was estimated to be 2.4 km/sec from the controlled seismics results (GUPTA et al, 2001;KAILA et al, 1981;MANDAL et al, 2004a). Recently, the inversion of teleseismic receiver function revealed that the Moho depth for the Kachchh region varies from 39-49 km and an average Moho depth of 40 km at Bhachau (MANDAL, 2006).…”

Section: -D Velocity Inversionmentioning

confidence: 99%

“…4c). Focal mechanism solutions of a few of the major aftershocks obtained from waveform inversion of broadband data indicate a dominant reverse movement on the NWF (MANDAL et al, 2004a).…”

Section: Minimum 1-d Velocity Model For the Regionmentioning

confidence: 99%

“…4a, b). Most of the earthquakes continue to occur between the north Wagad fault (NWF) and the Kachchh mainland fault (KMF) (MANDAL et al, 2004a). The surface expression of NWF is hidden beneath the Banni plains comprising soft sediments and extending along Wagad uplift (BISWAS, 1987).…”

Section: Minimum 1-d Velocity Model For the Regionmentioning

confidence: 99%

“…The Kachchh area lies in seismic zone V of India, and has experienced two earthquakes of M w ‡ 7.7 within a span of 182 years (BIS, 2003;MANDAL et al, 2004a). In addition, we know that the region has experienced several moderate-size earthquakes since 1668 (RAJENDRAN and RAJENDRAN, 1998).…”

Section: Introductionmentioning

confidence: 99%

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Sediment Thicknesses and Qs vs. Qp Relations in the Kachchh Rift Basin, Gujarat, India Using Sp Converted Phases

Mandal

2007

Pure appl. geophys.

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Delineation of the top sedimentary structure and its Q s vs. Q p relationship using the travel-time difference of direct S and converted Sp phase is key to understanding the seismic hazard of any sedimentary basin area. We constructed filtered displacement waveforms from local ETNA Episensor acceleration recordings as well as local velocity recordings of aftershocks of the 2001 Bhuj earthquake recorded by the Kachchh seismological network of the National Geophysical Research Institute (NGRI), Hyderabad, India during 2001-2004. Stations are within 15-70km of epicenters, and the resulting displacement waveforms are generally simple, displaying prominent P, Sp, and S wave pulses. Particle motion of P and S waves suggest near-vertical raypaths consistent with preliminary depth estimates. The direct S wave on the horizontal component is characterized by lower frequency content than the converted Sp phase on the vertical component. This difference in frequency content between S and Sp phases can be explained in terms of different attenuation effects for P and S waves in the unconsolidated sediments. The Sp phase is generated by S-to-P phase conversion at the base of Mesozoic sediments of the Kachchh basin. Travel-time inversion (VELEST) of 2565 P and 2380 S arrivals from 658 well located aftershocks recorded at 8-14 three-component local seismic stations led to 1 D velocity models indicated very slow sediments in the upper 0-2 km depth range (Vp: 2.92 km/s and Vs: 0.90 km/s) and an increasing trend of velocities with depth at 2-40 km depth. The estimated sediment thicknesses beneath 12 accelerograph and 6 seismograph sites from the estimated velocity model and the travel-time difference between S and converted Sp phases reaches a maximum of (1.534 ± 0.117) km beneath Bandri (near the location of 2001 Bhuj mainshock) and attains a minimum sediment thickness of (0.858 ± 0.104) km beneath Ramvav and Burudia. The spectral ratios between Sp and S from 159 three-component accelerograms have been used to study seismic wave attenuation in the Kachchh rift basin. The estimated Q s vs. Q p relations for 12 accelerograph sites vary from Q s = 0.184 Q p (at Chobari) to Q s = 0.505 Q p (at Dudhai). For stations Chobari, Chopdwa, Jahawarnagar, Vondh and Tapar, the spectral ratio slopes and hence the calculated Q s vs. Q p relations are effectively the same, and the correlation coefficients are quite high (0.91-0.93). Stations Adhoi, Manfara, New Dudhai, Dudhai and Sikara have similar Q s vs. Q p relationships to each other and also have high correlation coefficients (0.78-0.87). The spectral ratios for stations Anjar and Ramvav are small and poorly constrained, resulting in less reliable Q s vs. Q p relations. This could be due to noisy data, fewer available waveforms, or scattering due to velocity heterogeneities and/or interface irregularities.

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Section: -D Velocity Inversionmentioning

confidence: 99%

“…4c). Focal mechanism solutions of a few of the major aftershocks obtained from waveform inversion of broadband data indicate a dominant reverse movement on the NWF (MANDAL et al, 2004a).…”

Section: Minimum 1-d Velocity Model For the Regionmentioning

confidence: 99%

Section: Minimum 1-d Velocity Model For the Regionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sediment Thicknesses and Qs vs. Qp Relations in the Kachchh Rift Basin, Gujarat, India Using Sp Converted Phases

Mandal

2007

Pure appl. geophys.

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“…The model was constrained by results from a geophysical survey and controlled source seismics(KAILA et al, 1981;GUPTA et al, 2001). The detail of 1-D travel-time inversion can be found inMANDAL et al (2004a).Recently, MANDAL et al (2004b) relocated a total of 600 events using 3-D velocity tomography, which define an EW trending plane extending from 10 to 40 km depth and covering an area of 60 Â 40 km 2 , which dips south at an angle of 45 o(Figs. 4 a, b and c).…”

mentioning

confidence: 99%

Estimation of Site Response in Kachchh, Gujarat, India, Region Using H/V Spectral Ratios of Aftershocks of the 2001 Mw 7.7 Bhuj Earthquake

Mandal

Chadha

Satyamurty

et al. 2005

Pure appl. geophys.

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Site response in the aftershock zone of 2001 Bhuj M w 7.7 earthquake has been studied using the H/V spectral ratio method using 454 aftershocks (M w 2.5-4.7) recorded at twelve threecomponent digital strong motion and eight three-component digital seismograph sites. The mean amplification factor obtained for soft sediment sites (Quaternary/Tertiary) varies from 0.75-6.03 times for 1-3 Hz and 0.49-3.27 times for 3-10 Hz. The mean amplification factors obtained for hard sediment sites (hard Jurassic/Mesozoic sediments) range from 0.32-3.24 times for 1-3 Hz and 0.37-2.18 times for 310 Hz. The upper bounds of the larger mean amplification factors for 1-3 Hz are found to be of the order of 3.13-6.03 at Chopadwa, Vadawa, Kavada, Vondh, Adhoi, Jahwarnagar and Gadhada, whereas, the upper bounds of the higher mean amplification factors at 3-10 Hz are estimated to be of the order of 2.00-3.27°at Tapar, Chopadwa, Adhoi, Jahwarnagar, Gandhidham and Khingarpur. The site response estimated at Bhuj suggests a typical hard-rock site behavior. Preliminary site response maps for 1-3 Hz and 310 Hz frequency ranges have been prepared for the area extending from 23-23.85°N and 69.65-70.85°E. These frequency ranges are considered on the basis of the fact that the natural frequencies of multi-story buildings (3 to 10 floor) range between 1-3 Hz, while the natural frequencies for 1 to 3 story buildings vary from 3-10 Hz. The 1-3 Hz map delineates two distinct zones of maximum site amplification (>3 times): one lying in the NW quadrant of the study area covering Jahwarnagar, Kavada and Gadadha and the other in the SE quadrant of the study area with a peak of 6.03 at Chopadwa covering an area of 70 km · 50 km. While the 3-10 Hz map shows more than 2 times site amplification value over the entire study area except, NE quadrant, two patches in the southwest corner covering Bhuj and Anjar, and one patch at the center covering Vondh, Manfara and Sikara. The zones for large site amplification values ($3 times) are found at Tapar, Chopadwa, Adhoi and Chobari. The estimated site response values show a good correlation with the distribution of geological formations as well as observed ground deformation in the epicentral zone.

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GPS and InSAR derived evidences of intra‐basin stress and strike‐slip tectonics in the vicinity of 2001 (M7.7) earthquake, Kachchh, western India

et al. 2022

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The current geodetic investigation is based on nearly a decade of continuous Global Positioning System (GPS) data towards the western part of the Indian Plate (2009–2019). This research focused on the Kachchh Rift Basin (KRB), the seismically most active intra‐plate region of the Indian Plate, which has seen three ≥ M 7.0 earthquakes in the last two centuries. The GPS stations on the northern and southern margins show SSW and NNE directed motion, indicating that the KRB is currently under the influence of regional compressive stress on both flanks and the same is reflected in the form of earthquake activity in the center portion. Furthermore, the existence of intra‐basin stress, in addition to regional stress, increases strain accumulation and results in the creation of a Principal Deformation Zone (PDZ) in the central part of the KRB. The average annual deformation in the middle of KRB remains 1.0 ± 0.5 mm/year, while sites near the South Wagad Fault (SWF) experience 1.2 mm/year of fault parallel motion. The dominant fault normal motion along the flanks with a maximum fault parallel motion in the middle intimates the existence of strike‐slip tectonics in the central Kachchh. The geometric relationship of strike‐slip faults in a compressive margin and strain accumulation in pre‐existing faults (PDZ) is responsible for current strike‐slip and thrust motion in the Kachchh, including the 2001 Bhuj earthquake (M 7.7). Our geodetic model is well‐corroborated with the geological observations of the wrench fault model of strike‐slip faults. PS‐InSAR results in the northern part of the region between Khadir and Bela Islands show ≤6.0 mm of annual LOS displacement. GPS results indicate ≈ 1.3 to 1.4 ± 0.5 mm/year of fault parallel motion along the transverse Ekal Amrapar Fault (EAF). The non‐significant variation in GRACE‐derived TWS values (from 2009 to 2018) rules out non‐tectonic deformation in the vicinity of EAF and thus points to tectonic activity as the cause of the derived deformation in the region.

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Characterization of the causative fault system for the 2001 Bhuj earthquake of Mw 7.7

Cited by 113 publications

References 27 publications

Sediment Thicknesses and Qs vs. Qp Relations in the Kachchh Rift Basin, Gujarat, India Using Sp Converted Phases

Sediment Thicknesses and Qs vs. Qp Relations in the Kachchh Rift Basin, Gujarat, India Using Sp Converted Phases

Estimation of Site Response in Kachchh, Gujarat, India, Region Using H/V Spectral Ratios of Aftershocks of the 2001 Mw 7.7 Bhuj Earthquake

GPS and InSAR derived evidences of intra‐basin stress and strike‐slip tectonics in the vicinity of 2001 (M7.7) earthquake, Kachchh, western India

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