The 2008 Nura Mw6.7 earthquake: A shallow rupture on the Main Pamir Thrust revealed by GPS and In SAR
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摘要
The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia.We present Interferometric Synthetic Aperture Radar(In SAR) measurements of its coseismic ground deformation that are available for a major earthquake in the region.Analysis of the In SAR data shows that the earthquake ruptured a secondary fault of the Main Pamir Thrust for about 20 km. The fault plane striking N46 E and dipping 48 SE is dominated by thrust slip up to 3 m, most of which is confined to the uppermost 2e5 km of the crust, similar to the nearby 1974 Mw7.0 Markansu earthquake. The elastic model of interseismic deformation constrained by GPS measurements suggests that the two earthquakes may have resulted from the failures of two high-angle reverse faults that are about 10 km apart and rooted in a locked de collement at depths of 5e6 km. The elastic strain is built up by a freely creeping de collement at about 16 mm/a.
The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia.We present Interferometric Synthetic Aperture Radar(In SAR) measurements of its coseismic ground deformation that are available for a major earthquake in the region.Analysis of the In SAR data shows that the earthquake ruptured a secondary fault of the Main Pamir Thrust for about 20 km. The fault plane striking N46 E and dipping 48 SE is dominated by thrust slip up to 3 m, most of which is confined to the uppermost 2e5 km of the crust, similar to the nearby 1974 Mw7.0 Markansu earthquake. The elastic model of interseismic deformation constrained by GPS measurements suggests that the two earthquakes may have resulted from the failures of two high-angle reverse faults that are about 10 km apart and rooted in a locked de collement at depths of 5e6 km. The elastic strain is built up by a freely creeping de collement at about 16 mm/a.
The 2008 Nura Mw6.7 earthquake occurred in front of the Trans-Alai Range, central Asia.We present Interferometric Synthetic Aperture Radar(In SAR) measurements of its coseismic ground deformation that are available for a major earthquake in the region.Analysis of the In SAR data shows that the earthquake ruptured a secondary fault of the Main Pamir Thrust for about 20 km. The fault plane striking N46 E and dipping 48 SE is dominated by thrust slip up to 3 m, most of which is confined to the uppermost 2e5 km of the crust, similar to the nearby 1974 Mw7.0 Markansu earthquake. The elastic model of interseismic deformation constrained by GPS measurements suggests that the two earthquakes may have resulted from the failures of two high-angle reverse faults that are about 10 km apart and rooted in a locked de collement at depths of 5e6 km. The elastic strain is built up by a freely creeping de collement at about 16 mm/a.
引文
[1]Tapponnier P,Molnar P.Active faulting and cenozoic tectonics of the Tien Shan,Mongolia,and Baykal regions.J Geophys Res 1979;84:3425e59.
[2]Mohadjer S,Bendick R,Ischuk A,Kuzikov S,Kostuk A,Saydullaev U,et al.Partitioning of India-Eurasia convergence in the Pamir-Hindu Kush from GPS measurements.Geophys Res Lett 2010;37:L04305.http://dx.doi.org/10.1029/2009GL041737.
[3]Burtman V,Molnar P.Geological and geophysical evidence for deep subduction of continental crust beneath the Pamir.Geol Soc Am Special Pap 1993;281:1e76.
[4]Strecker MR,Frisch W,Hamburger MW,Ratschbacher L,Semiletkin S,Zamoruyev A,et al.Quaternary deformation in the eastern Pamirs,Tadzhikistan and Kyrgyzstan.Tectonics1995;14:1061e79.
[5]Coutand I,Strecker MR,Arrowsmith JR,Hilley G,Thiede RC,Korjenkov A,et al.Late cenozoic tectonic development of the intramontane Alai Valley,(Pamir-Tien Shan region,central Asia):an example of intracontinental deformation due to the Indo-Eurasia collision.Tectonics 2002;21:1053.http://dx.doi.org/10.1029/2002TC001358.
[6]Arrowsmith JR,Strecker MR.Seismotectonic range-front segmentation and mountain-belt growth in the Pamir-Alai region,Kyrgyzstan(India-Eurasia collision zone).Geol Soc Am Bull 1999;111:1665e83.
[7]Lukk AA,Nersesov JL,Pevnev AK,Yunga SL.Present day movements of the western part of the Peter I range from geodetic and seismological data.Izvestiya Acad Sci USSR Phys Solid Earth 1980;16:32e41.
[8]Yang S,Li J,Wang Q.The deformation pattern and fault rate in the Tianshan Mountains inferred from GPS observations.Sci China(Series D)2008;51:1064e80.
[9]Zubovich A,Wang X,Scherba Y,Schelochkov G,Reilinger R,Reigber C,et al.GPS velocity field for the Tien Shan andsurrounding regions.Tectonics 2010;29:TC6014.http://dx.doi.org/10.1029/2010TC002772.
[10]Ischuk A,Bendick R,Rybin A,Molnar P,Khan SF,Kuzikov S,et al.Kinematics of the Pamir and Hindu Kush regions from GPS geodesy.J Geophys Res 2013;118:2408e16.http://dx.doi.org/10.1002/jgrb.50185.
[11]Fan G,Ni J,Wallace T.Active tectonics of the Pamirs and Karakorum.J Geophys Res 1994;99:7131e60.
[12]Tang Lanlan,Zhao Cuiping,Wang Haitao.Study on the source characteristics of the 2008 Ms6.8 Wuqia,Xinjiang earthquake sequence and stress field on the northeastern boundary of Pamir.Chin J Geophys 2012;55(4):1228e39[in Chinese].
[13]Li T,Chen J,Thompson JA,Burbank DW,Xiao W.Equivalency of geologic and geodetic rates in contractional orogens:new insights from the Pamir Frontal Thrust.Geophys Res Lett2012;39:L15305.http://dx.doi.org/10.1029/2012GL051782.
[14]Sippl C,Schurr B,Yuan X,Mechie J,Schneider FM,Gadoev M,et al.Geometry of the Pamir-Hindu Kush intermediate-depth earthquake zone from local seismic data.J Geophys Res2013;118:1438e57.http://dx.doi.org/10.1002/jgrb.50128.
[15]Engdahl ER,van der Hilst R,Buland R.Global teleseismic earthquake relocation with improved travel times and procedures for depth determination.Bull Seismol Soc Am1998;88:722e43.
[16]Wang Q,Zhang P,Freymueller J,Bilham R,Larson K,Lai X,et al.Present-day crustal deformation in China constrained by global positioning system measurements.Science2001;294:574e7.
[17]Ni J.Contemporary tectonics in the Tien Shan region.Earth Planet Sci Lett 1978;41:347e54.
[18]Hamburger MW,Sarewitz DR,Pavlis TL,Popandopulo GA.Structural and seismic evidence for intracontinental subduction in the Peter the first range,central Asia.Geol Soc Am Bull 1992;104:397e408.
[19]Su Jinrong,Guo Zhi.A study of focal mechanisms of the Ms6.7 earthquake 5 October 2008 in southwestern TianshanPamir.Chin J Geophys 2013;56(2):504e12[in Chinese].
[20]Elliott JR,Parsons B,Jackson JA,Shan X,Sloan RA,Walker RT.Depth segmentation of the seismogenic continental crust:the 2008 and 2009 Qaidam earthquakes.Geophys Res Lett2011;38:L06305.http://dx.doi.org/10.1029/2011GL046897.
[21]Wang Q,Qiao X,Lan Q,Freymueller J,Yang S,Xu C,et al.Rupture of deep faults in the 2008 Wenchuan earthquake and uplift of the Longmen Shan.Nat Geosci 2011;4:634e40.
[22]Molnar P,Ghose S.Seismic moments of major earthquakes and the rate of shortening across the Tien Shan.Geophys Res Lett 2000;27:2377e80.
[23]Ghose S,Mellors RJ,Korjenkov AM,Hamburger MW,Pavlis TL,Pavlis GL,et al.The Ms?7.3 1992 Suusamyr,Kyrgyzstan,earthquake in the Tien Shan:2.aftershock focal mechanisms and surface deformation.Bull Seismol Soc Am 1997;87:23e38.
[24]Ma Shutian,Yao Zhenxing,Ji Chen.March 19,1996 Atushi,Xinjiang,earthquake(MS?6.9):study of the source mechanism and relative problem.Chin J Geophys1997;40(06):782e90[in Chinese].
[25]Simons M,Fialko Y,Rivera L.Coseismic deformation from the 1999 Mw 7.1 Hector Mine,California,earthquake as inferred from In SAR and GPS observations.Bull Seismol Soc Am 2002;92:1390e402.
[26]Rosen P,Hensley S,Peltzer G,Simons M.Updated repeat orbit interferometry package released.EOS Trans Am Geophys Union 2004;85.http://dx.doi.org/10.1029/2004EO050004.
[27]Farr TG,Kobrick M.Shuttle radar topography mission produces a wealth of data.EOS Trans Am Geophys Union2000;81:583e5.
[28]Goldstein RM,Werner CL.Radar interferogram filtering for geophysical applications.Geophys Res Lett 1998;25:4035e8.
[29]Chen C,Zebker H.Network approaches to two-dimensional phase unwrapping:intractability and two new algorithms.J Opt Soc Am A Opt Image Sci Vis 2000;17:401e14.
[30]Hanssen RF.Radar interferometry:data interpretation and error analysis.Norwell,MA,USA:Kluwer Academic Publishers;2001.p.308.
[31]Lohman R,Simons M.Some thoughts on the use of In SAR data to constrain models of surface deformation:noise structure and data downsampling.Geochem Geophys Geosys 2005;6:Q01007.http://dx.doi.org/10.1029/2004GC000841.
[32]Wright T,Parsons B,England P,Fielding E.In SAR observations of low slip rates on the major faults of western Tibet.Science 2004;305:236e9.
[33]Bechor NBD,Zebker HA.Measuring two-dimensional movements using a single In SAR pair.Geophys Res Lett2006;33:L16311.http://dx.doi.org/10.1029/2006GL026883.
[34]Okada Y.Surface deformation due to shear and tensile faults in a half-space.Bull Seismol Soc Am 1985;75:1135e54.
[35]Stark P,Parker R.Bounded-variable least-squares:an algorithm and applications.J Comput Stat 1995;10:129e41.
[36]Bilham R,Larson K,Freymueller JT.Project Idylhim members.GPS measurements of present-day convergence across the Nepal Himalaya.Nature 1997;386:61e4.
[37]Hsu YJ,Simons M,Yu SB,Kuo LC,Chen HY.A twodimensional dislocation model for interseismic deformation of the Taiwan mountain belt.Earth Planet Sci Lett2003;211L:287e94.
[38]Savage J.A dislocation model of strain accumulation and release at a subduction zone.J Geophys Res 1983;88:4984e96.
[39]Hsu YJ,Yu SB,Simons M,Kuo LC,Chen HY.Interseismic crustal deformation in the Taiwan plate boundary zonerevealed by GPS observations,seismicity,and earthquake focal mechanisms.Tectonophysics 2009;479:4e18.
[40]Jackson J,Molnar P,Patton H,Fitch T.Seismotectonic aspects of the Markansu valley,Tadjikstan,earthquake of August II,1974.J Geophys Res 1979;84:6157e67.
[41]Das S,Scholz H.Why large earthquakes do not nucleate at shallow depths.Nature 1983;305:621e3.
[42]Bindi D,Go mez-Capera A,Parolai S,Abdrakhmatov K,Stucchi M,Zschau J.Location and magnitudes of earthquakes in Central Asia from seismic intensity data:model calibration and validation.Geophys J Int2013;192:710e24.
[43]Stein RS,King GP.Seismic potential revealed by surface folding:1983 Coalinga,California,earthquake.Science1984;224:869e72.
[44]Chen W,Molnar P.Seismic moment of major earthquake and the average rate of slip in central Asia.J Geophys Res1977;82:2945e67.
[2]Mohadjer S,Bendick R,Ischuk A,Kuzikov S,Kostuk A,Saydullaev U,et al.Partitioning of India-Eurasia convergence in the Pamir-Hindu Kush from GPS measurements.Geophys Res Lett 2010;37:L04305.http://dx.doi.org/10.1029/2009GL041737.
[3]Burtman V,Molnar P.Geological and geophysical evidence for deep subduction of continental crust beneath the Pamir.Geol Soc Am Special Pap 1993;281:1e76.
[4]Strecker MR,Frisch W,Hamburger MW,Ratschbacher L,Semiletkin S,Zamoruyev A,et al.Quaternary deformation in the eastern Pamirs,Tadzhikistan and Kyrgyzstan.Tectonics1995;14:1061e79.
[5]Coutand I,Strecker MR,Arrowsmith JR,Hilley G,Thiede RC,Korjenkov A,et al.Late cenozoic tectonic development of the intramontane Alai Valley,(Pamir-Tien Shan region,central Asia):an example of intracontinental deformation due to the Indo-Eurasia collision.Tectonics 2002;21:1053.http://dx.doi.org/10.1029/2002TC001358.
[6]Arrowsmith JR,Strecker MR.Seismotectonic range-front segmentation and mountain-belt growth in the Pamir-Alai region,Kyrgyzstan(India-Eurasia collision zone).Geol Soc Am Bull 1999;111:1665e83.
[7]Lukk AA,Nersesov JL,Pevnev AK,Yunga SL.Present day movements of the western part of the Peter I range from geodetic and seismological data.Izvestiya Acad Sci USSR Phys Solid Earth 1980;16:32e41.
[8]Yang S,Li J,Wang Q.The deformation pattern and fault rate in the Tianshan Mountains inferred from GPS observations.Sci China(Series D)2008;51:1064e80.
[9]Zubovich A,Wang X,Scherba Y,Schelochkov G,Reilinger R,Reigber C,et al.GPS velocity field for the Tien Shan andsurrounding regions.Tectonics 2010;29:TC6014.http://dx.doi.org/10.1029/2010TC002772.
[10]Ischuk A,Bendick R,Rybin A,Molnar P,Khan SF,Kuzikov S,et al.Kinematics of the Pamir and Hindu Kush regions from GPS geodesy.J Geophys Res 2013;118:2408e16.http://dx.doi.org/10.1002/jgrb.50185.
[11]Fan G,Ni J,Wallace T.Active tectonics of the Pamirs and Karakorum.J Geophys Res 1994;99:7131e60.
[12]Tang Lanlan,Zhao Cuiping,Wang Haitao.Study on the source characteristics of the 2008 Ms6.8 Wuqia,Xinjiang earthquake sequence and stress field on the northeastern boundary of Pamir.Chin J Geophys 2012;55(4):1228e39[in Chinese].
[13]Li T,Chen J,Thompson JA,Burbank DW,Xiao W.Equivalency of geologic and geodetic rates in contractional orogens:new insights from the Pamir Frontal Thrust.Geophys Res Lett2012;39:L15305.http://dx.doi.org/10.1029/2012GL051782.
[14]Sippl C,Schurr B,Yuan X,Mechie J,Schneider FM,Gadoev M,et al.Geometry of the Pamir-Hindu Kush intermediate-depth earthquake zone from local seismic data.J Geophys Res2013;118:1438e57.http://dx.doi.org/10.1002/jgrb.50128.
[15]Engdahl ER,van der Hilst R,Buland R.Global teleseismic earthquake relocation with improved travel times and procedures for depth determination.Bull Seismol Soc Am1998;88:722e43.
[16]Wang Q,Zhang P,Freymueller J,Bilham R,Larson K,Lai X,et al.Present-day crustal deformation in China constrained by global positioning system measurements.Science2001;294:574e7.
[17]Ni J.Contemporary tectonics in the Tien Shan region.Earth Planet Sci Lett 1978;41:347e54.
[18]Hamburger MW,Sarewitz DR,Pavlis TL,Popandopulo GA.Structural and seismic evidence for intracontinental subduction in the Peter the first range,central Asia.Geol Soc Am Bull 1992;104:397e408.
[19]Su Jinrong,Guo Zhi.A study of focal mechanisms of the Ms6.7 earthquake 5 October 2008 in southwestern TianshanPamir.Chin J Geophys 2013;56(2):504e12[in Chinese].
[20]Elliott JR,Parsons B,Jackson JA,Shan X,Sloan RA,Walker RT.Depth segmentation of the seismogenic continental crust:the 2008 and 2009 Qaidam earthquakes.Geophys Res Lett2011;38:L06305.http://dx.doi.org/10.1029/2011GL046897.
[21]Wang Q,Qiao X,Lan Q,Freymueller J,Yang S,Xu C,et al.Rupture of deep faults in the 2008 Wenchuan earthquake and uplift of the Longmen Shan.Nat Geosci 2011;4:634e40.
[22]Molnar P,Ghose S.Seismic moments of major earthquakes and the rate of shortening across the Tien Shan.Geophys Res Lett 2000;27:2377e80.
[23]Ghose S,Mellors RJ,Korjenkov AM,Hamburger MW,Pavlis TL,Pavlis GL,et al.The Ms?7.3 1992 Suusamyr,Kyrgyzstan,earthquake in the Tien Shan:2.aftershock focal mechanisms and surface deformation.Bull Seismol Soc Am 1997;87:23e38.
[24]Ma Shutian,Yao Zhenxing,Ji Chen.March 19,1996 Atushi,Xinjiang,earthquake(MS?6.9):study of the source mechanism and relative problem.Chin J Geophys1997;40(06):782e90[in Chinese].
[25]Simons M,Fialko Y,Rivera L.Coseismic deformation from the 1999 Mw 7.1 Hector Mine,California,earthquake as inferred from In SAR and GPS observations.Bull Seismol Soc Am 2002;92:1390e402.
[26]Rosen P,Hensley S,Peltzer G,Simons M.Updated repeat orbit interferometry package released.EOS Trans Am Geophys Union 2004;85.http://dx.doi.org/10.1029/2004EO050004.
[27]Farr TG,Kobrick M.Shuttle radar topography mission produces a wealth of data.EOS Trans Am Geophys Union2000;81:583e5.
[28]Goldstein RM,Werner CL.Radar interferogram filtering for geophysical applications.Geophys Res Lett 1998;25:4035e8.
[29]Chen C,Zebker H.Network approaches to two-dimensional phase unwrapping:intractability and two new algorithms.J Opt Soc Am A Opt Image Sci Vis 2000;17:401e14.
[30]Hanssen RF.Radar interferometry:data interpretation and error analysis.Norwell,MA,USA:Kluwer Academic Publishers;2001.p.308.
[31]Lohman R,Simons M.Some thoughts on the use of In SAR data to constrain models of surface deformation:noise structure and data downsampling.Geochem Geophys Geosys 2005;6:Q01007.http://dx.doi.org/10.1029/2004GC000841.
[32]Wright T,Parsons B,England P,Fielding E.In SAR observations of low slip rates on the major faults of western Tibet.Science 2004;305:236e9.
[33]Bechor NBD,Zebker HA.Measuring two-dimensional movements using a single In SAR pair.Geophys Res Lett2006;33:L16311.http://dx.doi.org/10.1029/2006GL026883.
[34]Okada Y.Surface deformation due to shear and tensile faults in a half-space.Bull Seismol Soc Am 1985;75:1135e54.
[35]Stark P,Parker R.Bounded-variable least-squares:an algorithm and applications.J Comput Stat 1995;10:129e41.
[36]Bilham R,Larson K,Freymueller JT.Project Idylhim members.GPS measurements of present-day convergence across the Nepal Himalaya.Nature 1997;386:61e4.
[37]Hsu YJ,Simons M,Yu SB,Kuo LC,Chen HY.A twodimensional dislocation model for interseismic deformation of the Taiwan mountain belt.Earth Planet Sci Lett2003;211L:287e94.
[38]Savage J.A dislocation model of strain accumulation and release at a subduction zone.J Geophys Res 1983;88:4984e96.
[39]Hsu YJ,Yu SB,Simons M,Kuo LC,Chen HY.Interseismic crustal deformation in the Taiwan plate boundary zonerevealed by GPS observations,seismicity,and earthquake focal mechanisms.Tectonophysics 2009;479:4e18.
[40]Jackson J,Molnar P,Patton H,Fitch T.Seismotectonic aspects of the Markansu valley,Tadjikstan,earthquake of August II,1974.J Geophys Res 1979;84:6157e67.
[41]Das S,Scholz H.Why large earthquakes do not nucleate at shallow depths.Nature 1983;305:621e3.
[42]Bindi D,Go mez-Capera A,Parolai S,Abdrakhmatov K,Stucchi M,Zschau J.Location and magnitudes of earthquakes in Central Asia from seismic intensity data:model calibration and validation.Geophys J Int2013;192:710e24.
[43]Stein RS,King GP.Seismic potential revealed by surface folding:1983 Coalinga,California,earthquake.Science1984;224:869e72.
[44]Chen W,Molnar P.Seismic moment of major earthquake and the average rate of slip in central Asia.J Geophys Res1977;82:2945e67.