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Complex faulting in the Quetta Syntaxis: fault source modeling of the October 28, 2008 earthquake sequence in Baluchistan, Pakistan, based on ALOS/PALSAR InSAR data
© Usman and Furuya. 2015
- Received: 9 June 2015
- Accepted: 11 August 2015
- Published: 3 September 2015
The Quetta Syntaxis in western Baluchistan, Pakistan, is the result of an oroclinal bend of the western mountain belt and serves as a junction for different faults. As this area also lies close to the left-lateral strike-slip Chaman fault, which marks the boundary between the Indian and Eurasian plates, the resulting seismological behavior of this regime is very complex. In the region of the Quetta Syntaxis, close to the fold and thrust belt of the Sulaiman and Kirthar Ranges, an earthquake with a magnitude of 6.4 (Mw) occurred on October 28, 2008, which was followed by a doublet on the very next day. Six more shocks associated with these major events then occurred (one foreshock and five aftershocks), with moment magnitudes greater than 4. Numerous researchers have tried to explain the source of this sequence based on seismological, GPS, and Environmental Satellite (ENVISAT)/Advanced Synthetic Aperture Radar (ASAR) data. Here, we used Advanced Land Observing Satellite (ALOS)/Phased Array-type L-band Synthetic Aperture Radar (PALSAR) InSAR data sets from both ascending and descending orbits that allow us to more completely detect the deformation signals around the epicentral region. The results indicated that the shock sequence can be explained by two right-lateral and two left-lateral strike-slip faults that also included reverse slip. The right-lateral faults have a curved geometry. Moreover, whereas previous studies have explained the aftershock crustal deformation with a different fault source, we found that the same left-lateral segment of the conjugate fault was responsible for the aftershocks. We thus confirmed the complex surface deformation signals from the moderate-sized earthquake. Intra-plate crustal bending and shortening often seem to be accommodated as conjugate faulting, without any single preferred fault orientation. We also detected two possible landslide areas along with the crustal deformation pattern.
- ALOS/PALSAR data
- Crustal deformation
- Source modeling
- Conjugate faulting
International Seismological Center (ISC) data for events with magnitudes (Mw) greater than 4, related to the shock sequence of October 28, 2008 in Baluchistan, Pakistan. Times indicated are universal time (UTC). The corresponding FMS are shown in Fig. 2
Time (UTC) (HH:MM:SS)
Based on the spatial distribution of aftershocks and the focal mechanisms, Yadav et al. (2012) attributed the earthquake sequence to the activation of the right-lateral strike-slip Urghargai fault (Fig. 2) that had been proposed by Kazmi (1979). The GPS study suggested NW–SE-oriented dextral movement associated with the shock sequence of October 2008 (Khan et al. 2008). Based on seismological data, Lisa and Jan (2010) proposed that either the NNW-trending Urghargai fault\or two parallel faults could be the source of the earthquake doublet.
In order to identify the location and geometry of the source faults, however, co-seismic deformation signals derived from the interferometric synthetic aperture radar (InSAR) technique are much more useful because of the dense and wide spatial coverage (Massonnet et al. 1993; Amarjargal et al. 2013). Using C-band (5.6 cm wavelength) Environmental Satellite (ENVISAT) Advanced Synthetic Aperture Radar (ASAR) images, Pinel-Puysségur et al. (2014) and Pezzo et al. (2014) derived the co-seismic deformation signals and revealed the complexity of the responsible fault sources. However, because of low coherence, the ENVISAT/ASAR data lacked signals near the epicentral area, which led to different fault models despite the use of the same satellite data. Here, we use Advanced Land Observing Satellite’s Phased Array-type L-band (23.6 cm wavelength) Synthetic Aperture Radar (ALOS/PALSAR) images to derive the co-seismic deformation signals that are more complete in terms of spatial coverage near the epicentral area. Although Pinel-Puysségur et al. (2014) showed one InSAR image based on ALOS/PALSAR, the InSAR data covered only part of the deforming areas because the analyzed track was shifted to the east. Based on the InSAR images, we generate our fault source model and discuss its implications for the regional strain partitioning and the style of intra-plate deformation.
ALOS/PALSAR data used in this research (dates are formatted as MM-DD-YYYY)
Perpendicular baseline (m)
We also found breaks in the deformation pattern close to the central part of RLF1, suggesting a bend in the fault surface at this area (Figs. 3a and 4a). The InSAR data indicates that this part has moved towards the satellite for both ascending and descending observations (Figs. 3a and 4a). Examination of the fault mechanism solutions (Fig. 2), which are numbered in sequence according their occurrence during the observation time, indicates that there is a reverse component in most of the shocks, and fault mechanism no. 4 in Fig. 2 exhibits almost pure reverse faulting. These observations suggest the possibility of uplift in this area.
Besides these two major phase boundaries, we also identified a shorter phase jump to the NW that strikes NE–SW (Figs. 3a and 4a), and another phase jump that strikes NW–SE (Figs. 3a and 4a). For the aftershock differential interferogram, the range change amplitude was 13 cm for the both positive and negative sense (Fig. 5a). Comparing the location of the phase boundary in Fig. 5a, we found that the phase step location exactly matches the location of the LLF1 in Figs. 3a and 4a. Field observations indicated no clear co-seismic surface rupture (Khan et al. 2008), thus the phase boundaries noted above have no corresponding surface faults. Although cracks on the ground have been observed at some locations (Rafi et al. 2009), there are no clear corresponding signals in Figs. 3a and 4a.
Apart from the curved fault geometry for right-lateral faults in our model (RLF1 and RLF2), there are also other significant differences. In the Pinel-Puysségur et al. (2014) study, the InSAR data were noisy near the location of fault segment FP for the co-seismic interferogram, and the affected area was subsequently masked. Comparison of our model with that of Pinel-Puysségur et al. (2014) shows that segment F╹2 is very close to the location of LLF2 in our model. However, the conjugate faults of the Pinel-Puysségur et al. (2014) model have a larger angle between them, and their intersection point is shifted towards the western side compared to the conjugate geometry of our model. Pinel-Puysségur et al. (2014) also suggested that the aftershocks of December 9, 2008 were caused by a different fault segment, FP, rather than the same segment of conjugate faulting (LLF1 in our model). In addition, segment RLF2 is entirely missing in their study. On the other hand, Pezzo et al. (2014) lacked many of the signals around the epicentral area. Fault 4 in Pezzo et al. (2014) appears to be located quite close to the location of our fault LLF2, but segment 3 is unnecessary. The aftershock of December 9, 2008 was explained by segment 5, which appears to be located very close to fault LLF1 of our model. Segment 1 crosses segment 5 and penetrates into the block between segments 4 and 5. However, no such breaks have been found in the ALOS/PALSAR data, in the area between LLF1 and LLF2 of our model. Rather, the ALOS/PALSAR data has led us to conclude that segment RLF2 extends further in the SE direction.
Some fundamental parameters of proposed faults
Cal. mag. (Mw)
Covering shock sequence
Covering shock sequence
Covering shock sequence
Covering shock sequence
Although the crustal deformation associated with the seismic event of October 28, 2008 have been independently studied by Pinel-Puysségur et al. (2014) and Pezzo et al. (2014), using ENVISAT/ASAR data, their inferred source models contained several differences that were presumably due to the low-coherence problem of the C-band data. In this research, the same crustal deformations were studied using ALOS/PALSAR L-band data that had high coherence and thus, could nearly completely reveal the crustal deformations around the epicentral region. The results indicated that the shock sequence could be explained by two right-lateral and two left-lateral faults, and the right-lateral faults had a curved geometry. Moreover, whereas previous studies have explained the aftershock crustal deformation using a different fault source, we found that the same left-lateral segment of the conjugate fault system was responsible for the aftershocks.
We are very much thankful to the anonymous reviewers for their critical review. We are also indebted to the editor Dr. Taku Ozawa for carefully reading the manuscript and providing us valuable suggestions. Also, we are grateful to our colleagues Dr. Takatoshi Yasuda and Mr. Shutaro Umemura for their time to time useful comments. PALSAR level 1.0 data was provided by the PALSAR Interferometry Consortium to Study our Evolving Land surface (PIXEL). Ownership of PALSAR data belongs to the Japan Aerospace Exploration Agency (JAXA) and the Ministry of Economy, Trade and Industry (METI/Japan).
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- Abe T, Furuya M, Takada Y (2013) Nonplanar fault source modeling of the 2008 Mw 6.9 Iwate–Miyagi inland earthquake in northeast Japan. Bull Seismol Soc Am 103(No. 1):507–518View ArticleGoogle Scholar
- Amarjargal S, Kato T, Furuya M (2013) Surface deformations from moderate-sized earthquakes in Mongolia observed by InSAR. Earth Planets Space 65:713–723View ArticleGoogle Scholar
- Bannert D, Bender FK, Bender H, Grüneberg F, Kazmi AH, Raza HA, Shams FA (1995) Geology of Pakistan. Gebrüder Borntraeger, BerlinGoogle Scholar
- Bernard M, Shen-Tu B, Holt WE, Davis DM (2000) Kinematics of active deformation in the Sulaiman lobe and range, Pakistan. J Geophys Res 105:13,253–13,279View ArticleGoogle Scholar
- Fukuyama E (2015) Dynamic faulting on a conjugate fault system detected by near-fault tilt measurements. EPS. doi:10.1186/s40623-015-0207-1 Google Scholar
- Furuya M, Yasuda T (2011) The 2008 Yutian normal faulting earthquake (Mw 7.1), NW Tibet: non-planar fault modeling and implications for the Karakax fault. Tectonophysics 511:125–133. doi:10.1016/j.tecto.2011.09.003 View ArticleGoogle Scholar
- Furuya M, Kobayashi T, Takada Y, Murakami M (2010) Fault source modeling of the 2008 Wenchuan earthquake based on ALOS/PALSAR data. Bull Seismol Soc Am 100(5B):2750–2766. doi:10.1785/0120090242 View ArticleGoogle Scholar
- Geuzaine C, Remacle JF (2009) Gmsh: a three-dimensional finite element mesh generator with built-in pre- and post-processing facilities. Int J Numer Meth Eng 79(11):1309–1331View ArticleGoogle Scholar
- Haq SSB, Davis DM (1997) Oblique convergence and lobate mountain belts of Western Pakistan. Geology 25:23–26View ArticleGoogle Scholar
- International Seismological Centre (2012) On-line Bulletin, http://www.isc.ac.uk, Int Seis Cent, Thatcham, United Kingdom. Accessed 01 Jan 2013
- Jarvis A, Reuter H I, Nelson A, Guevara E (2008) Hole-filled seamless SRTM data V4, International Centre for Tropical Agriculture (CIAT). http://srtm.csi.cgiar.org. Accessed October 2012
- Jónsson S, Zebker H, Segall P, Amelung F (2002) Fault slip distribution of the 1999 Mw 7.1 Hector Mine, California, earthquake, estimated from satellite radar and GPS measurements. Bull Seismol Soc Am 92(no. 4):1377–1389View ArticleGoogle Scholar
- Kazmi AH (1979) Active faults systems in Pakistan. In: Geol Surv Pak. Geodynamic of Pakistan, Quetta, BaluchistanGoogle Scholar
- Khan MA et al (2008) Preliminary geodetic constraints on plate boundary deformation on the western edge of the Indian plate from TriGGnet (Tri-University GPS Geodesy Network). J Him Geosci 41:71–87Google Scholar
- Kobayashi T, Takada Y, Furuya M, Murakami M (2009) Locations and types of ruptures involved in the 2008 Sichuan earthquake inferred from SAR image matching. Geophys Res Lett 36:L07302. doi:10.1029/2008GL036907 Google Scholar
- Lisa M, Jan MQ (2010) Geoseismological study of the Ziarat (Balochistan) earthquake (doublet?) of 28 October 2008. Curr Sci 98(1):50–57Google Scholar
- Lohman RB, Simons M (2005) Some thoughts on the use of InSAR data to constrain models of surface deformation: noise structure and data downsampling. Geochem Geophys Geosys. doi:10.1029/2004GC000841 Google Scholar
- Maerten F, Resor P, Pollard D, Maerten L (2005) Inverting for slip on three dimensional fault surfaces using angular dislocations. Bull Seismol Soc Am 95:1654–1665. doi:10.1785/0120030181 View ArticleGoogle Scholar
- Massonnet D, Rossi M, Carmona C, Adragna F, Peltzer G, Feigl K, Rabaute T (1993) The displacement field of the Landers earthquake mapped by radar interferometry. Nature 364:138–142View ArticleGoogle Scholar
- Meade BJ (2007) Algorithms for the calculation of exact displacements, strains, and stresses for triangular dislocation elements in a uniform elastic half space. Comp and Geosci 33:1064–1075. doi:10.1016/j.cageo.2006.12.003 View ArticleGoogle Scholar
- Nakata T, Tsutsumi H, Khan SH, Lawrence RD (1991) Active faults of Pakistan: map sheets and inventories. Research Center for Regional Geography. Hiroshima University, HiroshimaGoogle Scholar
- Okada Y (1992) Internal deformation due to shear and tensile faults in a half-space. Bull Seismol Soc Am 82:1018–1040Google Scholar
- Pezzo G, Bancori JPM, Atroz S, Antonioli A, Salvi S (2014) Deformation of the western Indian plate boundary: insights from differential and multi-aperture InSAR data inversion for the 2008 Baluchistan (Western Pakistan) seismic sequence. Geophys J Int. doi:10.1093/gji/ggu106 Google Scholar
- Pinel-Puysségur B, Grandin R, Bollinger L, Baudry C (2014) Multifaulting in a tectonic syntaxis revealed by InSAR: the case of the Ziarat earthquake sequence (Pakistan). J Geophys Res Solid Earth 119:5838–5854. doi:10.1002/2013JB010564 View ArticleGoogle Scholar
- Rafi Z, Ahmad N, Rehman SU (2009) Seismotectonic analysis of Ziarat, Balochistan earthquake of 29th October, 2008. Pakistan Meteorological Department, Islamabad, Pakistan, Technical report no. PMD-32/2009Google Scholar
- Simons M, Fialko Y, Rivera L (2002) Coseismic deformation from the 1999 Mw 7.1 Hector Mine, California, earthquake as inferred from InSAR and GPS observations. Bull Seismol Soc Am 92(4):1390–1402. doi:10.1785/0120000933 View ArticleGoogle Scholar
- Takada Y, Kobayashi T, Furuya M, Murakami M (2009) Coseismic displacement due to the 2008 Iwate-Miyagi Nairiku earthquake detected by ALOS/PALSAR: preliminary results. Earth Planets Space 61:e9–e12View ArticleGoogle Scholar
- Tong X, Sandwell DT, Fialko Y (2010) Coseimic slip model of the 2008 Wenchuan earthquake derived from joint inversion of interferometric synthetic aperture radar, GPS, and field data. J Geophys Res 115:B04314. doi:10.1029/2009JB006625 Google Scholar
- Walker RT, Bergnan EA, Elliot JR, Fielding EJ, Ghods AR, Ghoraishi M, Jackson J, Nazari H, Nemati M, Oveisi B, Talebian M, Walters RJ (2013) The 2010–2011 South Rigan (Baluchestan) earthquake sequence and its implications for distributed deformation and earthquake hazard in southeast Iran. Geophys J Int. doi:10.1093/gji/ggs109 Google Scholar
- Wright TJ, Lu Z, Wicks C (2003) Source model of the Mw 6.7, 23 October 2002, Nenana Mountain earthquake (Alaska) from InSAR. Geophys Res Lett. doi:10.1029/2003GL018014 Google Scholar
- Yadav RBS, Gahalaut VK, Chopra S, Shan B (2012) Tectonic implications and seismicity triggering during the 2008 Baluchistan, Pakistan earthquake sequence. J Asian Earth Sci 45:167–178. doi:10.1785/0120120133 View ArticleGoogle Scholar