环太平洋俯冲带内双地震带及其成因机制研究进展
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摘要
俯冲带作为地球最为庞大的循环系统的重要组成部分,已成为地球科学的研究热点之一.很多俯冲带,特别是环太平洋俯冲带内的中深源地震,在空间上呈明显的分层分布,并且各层地震具有不同的震源机制,即所谓的双地震带现象.本文简要介绍了环太平洋双地震带形态特征与震源机制的空间分布,并回顾了双地震带的几种成因模型.根据形态特征和震源机制的差异,中源深度的双地震带可以分为两类,其中,一类双地震带对应上、下二层分别为压缩和张性的地震分布;另一类双地震带的震源分布较浅,且其浅部地震以横向压缩为主.此外,日本本州东北俯冲带的地震分布可能是由三层地震带组成的,而且汤加、伊豆-小笠原地区还发现深源深度的双地震带.通过对双地震带的形态特征以及其热力学条件的研究,人们从抗弯作用、脱水脆化、相变断层等多方面,尝试建立解释双地震带成因的模型.目前,大多数研究利用数值计算结果,结合蛇纹石脱水脆化、相变断层模型,能够不同程度地分别解释中源和深源双地震带成因.不过,这些模型几乎相互独立,并不能同时解释中源和深源双地震带.有人试图尝试用统一模型解释中深源地震成因,例如,先前存在的断层模型,不过该模型还不很具有说服力.也可能是多种因素的联合作用,共同影响着俯冲板内的温度场、应力场分布.
As our Planet's largest recycling system,subduction zone has become one of the most significant leading research aspects of earth science.Intermediate-deep earthquakes in some subduction zones,especially most of circum-Pacific subdution zones,occur in two distinct layers,forming two seismic zones with different focal mechanisms,separated vertically by an aseismic zone about 40 km thick.The discovery and simultaneous studies of double seismic zones greatly contribute to the further studies on stress regimes of subduction zones.Briefly introduced spatial location,morphology and stresses distribution of Double seismic zones within some subductions around the Pacific ocean.In addition to the two types of shallow Double seismic zones with depth range from 60 to 200 km,there are deeper(>325 km) Double seismic zones beneath Tonga and Izu-Bonin arcs.According to the morphology and thermodynamic conditions of Double seismic zones,several models including unbending,dehydration embrittlement and transformational faulting,have been proposed as possible causes for intermediate-deep earthquakes and Double seismic zones.Comparing with numerical modeling results,many researches considered serpentine dehydration and transformational faulting as the dominant causes for intermediate and deep Double seismic zones,respectively.However,there is no a uniform model,which can be accepted as a mechanism for both intermediate and deep double seismic zones.Although it is very questionable and disputable,the hypothesis that intermediate-deep events occur on pre-existing or fossil faults may be a intriguing and paradoxical feature of intermediate-deep double seismic zones.Furthermore,the combination of several factors,such as unbending and dehydration,perhaps contributes more or less to the complexity of the thermal and stress regimes within the subduction zone.
As our Planet's largest recycling system,subduction zone has become one of the most significant leading research aspects of earth science.Intermediate-deep earthquakes in some subduction zones,especially most of circum-Pacific subdution zones,occur in two distinct layers,forming two seismic zones with different focal mechanisms,separated vertically by an aseismic zone about 40 km thick.The discovery and simultaneous studies of double seismic zones greatly contribute to the further studies on stress regimes of subduction zones.Briefly introduced spatial location,morphology and stresses distribution of Double seismic zones within some subductions around the Pacific ocean.In addition to the two types of shallow Double seismic zones with depth range from 60 to 200 km,there are deeper(>325 km) Double seismic zones beneath Tonga and Izu-Bonin arcs.According to the morphology and thermodynamic conditions of Double seismic zones,several models including unbending,dehydration embrittlement and transformational faulting,have been proposed as possible causes for intermediate-deep earthquakes and Double seismic zones.Comparing with numerical modeling results,many researches considered serpentine dehydration and transformational faulting as the dominant causes for intermediate and deep Double seismic zones,respectively.However,there is no a uniform model,which can be accepted as a mechanism for both intermediate and deep double seismic zones.Although it is very questionable and disputable,the hypothesis that intermediate-deep events occur on pre-existing or fossil faults may be a intriguing and paradoxical feature of intermediate-deep double seismic zones.Furthermore,the combination of several factors,such as unbending and dehydration,perhaps contributes more or less to the complexity of the thermal and stress regimes within the subduction zone.
引文
[1]Stern R J.Subduction zones[J].Rev.Geophys.,2002,40(4):1012~1049.
[2]SlancováA,S∧picák A,Ha∧nusV,et al.How the state ofstress varies in the W-B zone indications from focal mecha-nisms in the W-B zone beneath Sumatra and Java[J].Geo-phys.J.Int.,2000,143:909~930.
[3]Isacks B,Molnar P.Mantle earthquake mechanisms and thesinking of the lithosphere[J].Nature,1969,223(5211):1121~1124.
[4]石耀霖,王其允.斜俯冲板块边界变形分配的力学分析[J].地球物理学报,1994,37(5):607~612.
[5]臧绍先,宁杰远.西太平洋俯冲带的研究及其动力学意义[J].地球物理学报,1996,39(2):188~202.
[6]孙文斌,和跃时.西太平洋Beniof带的形态及其应力状态[J].地球物理学报,2004,47(2):433~440.
[7]Stein S.Deep earthquakes:a fault too big?[J].Science,1995,268:49~50.
[8]Tibi R,Estabrook C H,Bock G.the 1996 June 17 flores seaand the 1994 March 9 Fiji-tonga earthquakes:source processesand deep earthquake mechanisms[J].Geophys.J.Int.,1999,138:625~642.
[9]Sykes L R.Seismicity and deep structure of island arcs[J].J.Geophys.Res.,1966,71:2981~3006.
[10]Veith K F.The nature of the dual zone of seismicity in theKurils arc[J].Eos Trans.AGU,1977,58,1232
[11]Hasegawa A,Umino N,Takagi A.Double-planed structureof the deep seismic zone in the northeastern Japan arc[J].Tectonophysics,1978,47(1~2):43~58.
[12]Kawakatsu H.Double seismic zones:kinematics[J].J.Geo-phys.Res.,1986,91(B5):4811~4825.
[13]Ohmi S,Hori S.Seismic wave conversion near the upperboundary of the Pacific plate beneath the Kanto district,Ja-pan[J].Geophys.J.Int.,2000,141:136~148.
[14]Kao H,Rau R J.Detailed structures of the subducted Philip-pine Sea plate beneath northeast Taiwan:A new type ofdouble seismic zone[J].J.Geophys.Res.,1999,104(B1):1015~1033.
[15]Wiens D A,McGuire J J,Shore P J.Evidence for transfor-mational faulting from a deep double seismic zone in Tonga[J].Nature,1993,364:790~793
[16]Iidaka T,Furukawa Y.Double seismic zone for deep earth-quakes in the Izu-Bonin subduction zone[J].Science,1994,263:1116~1118.
[17]Hasegawa A,Houriuchi S,Umino N.Seismic structure ofthe northeastern Japan convergent margin:A synthesis[J].J.Geophys.Res.,1994,99(B11):22,295~22,311.
[18]Kawakatsu H,Seno T.Triple seismic zone and the regionalvariation of seimicity along the northern Honshu arc[J].J.Geophys.Res.,1983,88:4215~4230.
[19]Igarashi T,Matsuzawa T,Umino N,et al.Spatial distribu-tion of focal mechanisms for interpolate and intraplate earth-quakes associated with the subducting Pacific plate beneaththe northeastern Japan arc:A triple-planed deep seismic zone[J].J.Geophys.Res.,2001,106(B2):2177~2191.
[20]Peacock S M.Are double seismic zones caused by serpentinedehydration reactions in subducting oceanic mantle?[J].Ge-ology,2001,29:299~302.
[21]Seno T,Zhao D,Kobayashi Y,et al,Dehydration of serpen-tinized slab mantle:seismic evidence from southwest Japan[J].Earth Planets Space,2001,53:861~871.
[22]Hacker B R,Peacock S M,Abers G A,et al.Subductionfactory 2.Are intermediate-depth earthquakes in subductingslabs linked to metamorphic dehydration reactions?[J].J.Geophys.Res.,2003,108(B1):2030~2045.
[23]Yamasaki T,Seno T.Double seismic zone and dehydrationembrittlement of subducting slab[J].J.Geophys.Res.,2003,108(B4):2212~2232.
[24]Perrillat J P,Daniel I,Koga K T,et al.Kinetics of an-tigorite dehydration:A real-time X-ray diffraction study[J].Earth Planet.Sci.Lett.,2005,236:899~913.
[25]Dobson D P,Meredith P G,Boon S A.Simulation of Sub-duction Zone Seismicity by Dehydration of Serpentine[J].Science,2002,298:1407~1410.
[26]Kirby S H,Durham W B,Stern L A.Mantle phase changeand deep earthquake faulting in subducting lithosphere[J].Science,1991,252:216~225.
[27]Silver P G,Beck S L,Wallace T C.et al.Rupture character-istics of the deep Bolivian earthquake of 9 June 1994 and themechanism of deep focus earthquakes[J].Science,1995,268:69~73.
[28]Kirby S H,Stein S,Okal E A,et al.Metastable mantlephase transformations and deep earthquakes in subducting o-ceanic lithosphere[J].Rev.Geophys.,1996,34(2):261~306.
[29]Bina C R.Patterns of deep seismicity reflect buoyancy stres-ses due to phase transitions[J].Geophys.Res.Lett,1997,24:3301~3304.
[30]Wang K.Unbending combined with dehydration embrittle-ment as a cause for double and triple seismic zones[J].Geo-phys.Res.Lett.,2002,29(18):1889~1892.
[31]Samowitz I R,Forsyth D W.Double seismic zone beneaththe Mariana island arc[J].J.Geophys.Res,1981,86:7013~7021.
[32]Kawakatsu H.Double seismic zone in Tonga[J].Nature,1985,316:53~55.
[33]Kawakatsu H.Downdip tensional earthquakes beneath thetonga arc:a double seismic zone?[J],J.Geophys.Res.,1986,91(B6):6432~6440.
[34]Kao H,Chen W P.The double seismic zone in Kuril-Kam-chatka:the tale of two two overlapping single zones[J].J.Geophys.Res.,1994,99(B4):6913~6930.
[35]Kao H,Chen W P.Transition from interplate slip to doubleseismic zone along the Kuril-Kamchatka arc[J].J.Geophys.Res.,1995,100(B7):9881~9903.
[36]Kao H,Liu L.A hypothesis for the seismogenesis of doubleseismic zone[J].Geophys.J.Int.,1995,123:71~84.
[37]Comte D,Suarez G.An inverted double seismic zone in Chil-e:evidence of phase transition in the subducted slab[J].Sci-ence,1994,263:212~215.
[38]Comte D,Dorbath L,Pardo M,Monfret T,Haessler H.Adouble-layered seismic zone in Arica,Northern Chile[J].Geophys.Res.Lett.,1999,26(13):1965~1968.
[39]Rietbrock A,Waldhauser F.A narrowly spaced double seis-mic zone in the subducting Nazca plate[J].Geophys.Res.Lett.,2004,31,L10608.
[40]Ratchkovsky N A,Pujol J,Biswas N N.Stress Parttern indouble seismic zone beneath Cook Inlet,south central Alaska[J].Tectonophysics,1997,281:163~171.
[41]Reyners M,Robinson R,McGinty P.Plate coupling in thenorthern South Island and southernmost North Island,NewZealand,as illuminated by earthquake focal mechanisms[J].J.Geophys.Res.,1997,120(B7):15,197~15,210.
[42]Cassidy J,Waldhauser F F.Evidence for both crustal andmantle earthquakes in the subducting Juan de Fuca plate[J].Geophys.Res.Lett.,2003,30(2):1095~1098.
[43]Wang K,Rogers G C.An explanation for the double seismiclayers north of the Mendocino triple junction[J].Geophys.Res.Lett.,1994,21(2):121~124.
[44]McGurire J J,Wiens D A.A double seismic zone in new Brit-ain and the morphology of the Solomon Plate at intermediatedepths[J].Geophys.Res.Lett,1995,22(15):1965~1968.
[45]Wiens D A,McGurire J J,Shore P J,et al.A deep earth-quake aftershock sequence and implications for the rupturemechanism of deep earthquakes[J].Nature,1994,372:540~543.
[46]Zhang J F,Green II H W,Bozhilov K,Jin Z M.Faulting in-duced by precipitation of water at grain boundaries in hot sub-ducting oceanic crust[J].Nature,2004,428:633~636.
[47]Abers G A,van Keken P E,Kneller E A,et al.The thermalstructure of subduction zones constrained by seismic imaging:Implications for slab dehydration and wedge flow[J].EarthPlanet.Sci.Lett.,2006,241:387~397.
[48]Zhang H J,Thurber C H,Shelly D,et al.High resolutionsubducting slab structure beneath northern Honsu,Japan,revealed by Double-difference tomography[J].Geology,2004,32(4):361~364.
[49]Bina C R.Phase transition buoyancy contributions to stressesin subducting lithosphere[J].Geophys.Res.Lett.,1996,23:3563~3566.
[50]宁杰元,臧绍先.对俯冲带深震成因的探讨[J].地震学报,1999,21(5):523~532.
[51]Guest A,Schubert G,Gable C W.Stresses along the meta-stable wedge of olivine in a subducting slab:possible explana-tion for the Tonga double seismic layer[J].Phys.EarthPlanet.Int.,2004,141:253~267.
[52]Jiao W,Silver P G,Fei Y,et al.Do intermediate-and deep-focus earthquakes occur on preexisting weak zones?An ex-amination of the Tonga subduction zone[J].J.Geophys.Res.,2000,105(B12):28125~28138.
[53]张瑞青,李永华,姚雪绒.西北太平洋俯冲带东北地区壳幔结构研究进展[J].地球物理学进展,2006,21(4):1080~1085.
[54]刘展,赵文举,吴时国等.冲绳海槽南部基底构造特征[J].地球物理学进展,2006,21(3):814~824.
[55]刘展,孙鲁平,范丰鑫等.冲绳海槽北部基底构造特征[J].地球物理学进展,2006,21(4):1086~1092.
[56]李延兴,张静华,何建坤等.由空间大地测量得到的太平洋板块现今构造运动与板内形变应变场[J].地球物理学报,2007,50(2):437~447
[57]朱涛,马宗晋,冯锐.三维地震波速结构约束下的变黏度地幔对流及其动力学意义[J].地球物理学报,2006,49(5):1347~1358.
[2]SlancováA,S∧picák A,Ha∧nusV,et al.How the state ofstress varies in the W-B zone indications from focal mecha-nisms in the W-B zone beneath Sumatra and Java[J].Geo-phys.J.Int.,2000,143:909~930.
[3]Isacks B,Molnar P.Mantle earthquake mechanisms and thesinking of the lithosphere[J].Nature,1969,223(5211):1121~1124.
[4]石耀霖,王其允.斜俯冲板块边界变形分配的力学分析[J].地球物理学报,1994,37(5):607~612.
[5]臧绍先,宁杰远.西太平洋俯冲带的研究及其动力学意义[J].地球物理学报,1996,39(2):188~202.
[6]孙文斌,和跃时.西太平洋Beniof带的形态及其应力状态[J].地球物理学报,2004,47(2):433~440.
[7]Stein S.Deep earthquakes:a fault too big?[J].Science,1995,268:49~50.
[8]Tibi R,Estabrook C H,Bock G.the 1996 June 17 flores seaand the 1994 March 9 Fiji-tonga earthquakes:source processesand deep earthquake mechanisms[J].Geophys.J.Int.,1999,138:625~642.
[9]Sykes L R.Seismicity and deep structure of island arcs[J].J.Geophys.Res.,1966,71:2981~3006.
[10]Veith K F.The nature of the dual zone of seismicity in theKurils arc[J].Eos Trans.AGU,1977,58,1232
[11]Hasegawa A,Umino N,Takagi A.Double-planed structureof the deep seismic zone in the northeastern Japan arc[J].Tectonophysics,1978,47(1~2):43~58.
[12]Kawakatsu H.Double seismic zones:kinematics[J].J.Geo-phys.Res.,1986,91(B5):4811~4825.
[13]Ohmi S,Hori S.Seismic wave conversion near the upperboundary of the Pacific plate beneath the Kanto district,Ja-pan[J].Geophys.J.Int.,2000,141:136~148.
[14]Kao H,Rau R J.Detailed structures of the subducted Philip-pine Sea plate beneath northeast Taiwan:A new type ofdouble seismic zone[J].J.Geophys.Res.,1999,104(B1):1015~1033.
[15]Wiens D A,McGuire J J,Shore P J.Evidence for transfor-mational faulting from a deep double seismic zone in Tonga[J].Nature,1993,364:790~793
[16]Iidaka T,Furukawa Y.Double seismic zone for deep earth-quakes in the Izu-Bonin subduction zone[J].Science,1994,263:1116~1118.
[17]Hasegawa A,Houriuchi S,Umino N.Seismic structure ofthe northeastern Japan convergent margin:A synthesis[J].J.Geophys.Res.,1994,99(B11):22,295~22,311.
[18]Kawakatsu H,Seno T.Triple seismic zone and the regionalvariation of seimicity along the northern Honshu arc[J].J.Geophys.Res.,1983,88:4215~4230.
[19]Igarashi T,Matsuzawa T,Umino N,et al.Spatial distribu-tion of focal mechanisms for interpolate and intraplate earth-quakes associated with the subducting Pacific plate beneaththe northeastern Japan arc:A triple-planed deep seismic zone[J].J.Geophys.Res.,2001,106(B2):2177~2191.
[20]Peacock S M.Are double seismic zones caused by serpentinedehydration reactions in subducting oceanic mantle?[J].Ge-ology,2001,29:299~302.
[21]Seno T,Zhao D,Kobayashi Y,et al,Dehydration of serpen-tinized slab mantle:seismic evidence from southwest Japan[J].Earth Planets Space,2001,53:861~871.
[22]Hacker B R,Peacock S M,Abers G A,et al.Subductionfactory 2.Are intermediate-depth earthquakes in subductingslabs linked to metamorphic dehydration reactions?[J].J.Geophys.Res.,2003,108(B1):2030~2045.
[23]Yamasaki T,Seno T.Double seismic zone and dehydrationembrittlement of subducting slab[J].J.Geophys.Res.,2003,108(B4):2212~2232.
[24]Perrillat J P,Daniel I,Koga K T,et al.Kinetics of an-tigorite dehydration:A real-time X-ray diffraction study[J].Earth Planet.Sci.Lett.,2005,236:899~913.
[25]Dobson D P,Meredith P G,Boon S A.Simulation of Sub-duction Zone Seismicity by Dehydration of Serpentine[J].Science,2002,298:1407~1410.
[26]Kirby S H,Durham W B,Stern L A.Mantle phase changeand deep earthquake faulting in subducting lithosphere[J].Science,1991,252:216~225.
[27]Silver P G,Beck S L,Wallace T C.et al.Rupture character-istics of the deep Bolivian earthquake of 9 June 1994 and themechanism of deep focus earthquakes[J].Science,1995,268:69~73.
[28]Kirby S H,Stein S,Okal E A,et al.Metastable mantlephase transformations and deep earthquakes in subducting o-ceanic lithosphere[J].Rev.Geophys.,1996,34(2):261~306.
[29]Bina C R.Patterns of deep seismicity reflect buoyancy stres-ses due to phase transitions[J].Geophys.Res.Lett,1997,24:3301~3304.
[30]Wang K.Unbending combined with dehydration embrittle-ment as a cause for double and triple seismic zones[J].Geo-phys.Res.Lett.,2002,29(18):1889~1892.
[31]Samowitz I R,Forsyth D W.Double seismic zone beneaththe Mariana island arc[J].J.Geophys.Res,1981,86:7013~7021.
[32]Kawakatsu H.Double seismic zone in Tonga[J].Nature,1985,316:53~55.
[33]Kawakatsu H.Downdip tensional earthquakes beneath thetonga arc:a double seismic zone?[J],J.Geophys.Res.,1986,91(B6):6432~6440.
[34]Kao H,Chen W P.The double seismic zone in Kuril-Kam-chatka:the tale of two two overlapping single zones[J].J.Geophys.Res.,1994,99(B4):6913~6930.
[35]Kao H,Chen W P.Transition from interplate slip to doubleseismic zone along the Kuril-Kamchatka arc[J].J.Geophys.Res.,1995,100(B7):9881~9903.
[36]Kao H,Liu L.A hypothesis for the seismogenesis of doubleseismic zone[J].Geophys.J.Int.,1995,123:71~84.
[37]Comte D,Suarez G.An inverted double seismic zone in Chil-e:evidence of phase transition in the subducted slab[J].Sci-ence,1994,263:212~215.
[38]Comte D,Dorbath L,Pardo M,Monfret T,Haessler H.Adouble-layered seismic zone in Arica,Northern Chile[J].Geophys.Res.Lett.,1999,26(13):1965~1968.
[39]Rietbrock A,Waldhauser F.A narrowly spaced double seis-mic zone in the subducting Nazca plate[J].Geophys.Res.Lett.,2004,31,L10608.
[40]Ratchkovsky N A,Pujol J,Biswas N N.Stress Parttern indouble seismic zone beneath Cook Inlet,south central Alaska[J].Tectonophysics,1997,281:163~171.
[41]Reyners M,Robinson R,McGinty P.Plate coupling in thenorthern South Island and southernmost North Island,NewZealand,as illuminated by earthquake focal mechanisms[J].J.Geophys.Res.,1997,120(B7):15,197~15,210.
[42]Cassidy J,Waldhauser F F.Evidence for both crustal andmantle earthquakes in the subducting Juan de Fuca plate[J].Geophys.Res.Lett.,2003,30(2):1095~1098.
[43]Wang K,Rogers G C.An explanation for the double seismiclayers north of the Mendocino triple junction[J].Geophys.Res.Lett.,1994,21(2):121~124.
[44]McGurire J J,Wiens D A.A double seismic zone in new Brit-ain and the morphology of the Solomon Plate at intermediatedepths[J].Geophys.Res.Lett,1995,22(15):1965~1968.
[45]Wiens D A,McGurire J J,Shore P J,et al.A deep earth-quake aftershock sequence and implications for the rupturemechanism of deep earthquakes[J].Nature,1994,372:540~543.
[46]Zhang J F,Green II H W,Bozhilov K,Jin Z M.Faulting in-duced by precipitation of water at grain boundaries in hot sub-ducting oceanic crust[J].Nature,2004,428:633~636.
[47]Abers G A,van Keken P E,Kneller E A,et al.The thermalstructure of subduction zones constrained by seismic imaging:Implications for slab dehydration and wedge flow[J].EarthPlanet.Sci.Lett.,2006,241:387~397.
[48]Zhang H J,Thurber C H,Shelly D,et al.High resolutionsubducting slab structure beneath northern Honsu,Japan,revealed by Double-difference tomography[J].Geology,2004,32(4):361~364.
[49]Bina C R.Phase transition buoyancy contributions to stressesin subducting lithosphere[J].Geophys.Res.Lett.,1996,23:3563~3566.
[50]宁杰元,臧绍先.对俯冲带深震成因的探讨[J].地震学报,1999,21(5):523~532.
[51]Guest A,Schubert G,Gable C W.Stresses along the meta-stable wedge of olivine in a subducting slab:possible explana-tion for the Tonga double seismic layer[J].Phys.EarthPlanet.Int.,2004,141:253~267.
[52]Jiao W,Silver P G,Fei Y,et al.Do intermediate-and deep-focus earthquakes occur on preexisting weak zones?An ex-amination of the Tonga subduction zone[J].J.Geophys.Res.,2000,105(B12):28125~28138.
[53]张瑞青,李永华,姚雪绒.西北太平洋俯冲带东北地区壳幔结构研究进展[J].地球物理学进展,2006,21(4):1080~1085.
[54]刘展,赵文举,吴时国等.冲绳海槽南部基底构造特征[J].地球物理学进展,2006,21(3):814~824.
[55]刘展,孙鲁平,范丰鑫等.冲绳海槽北部基底构造特征[J].地球物理学进展,2006,21(4):1086~1092.
[56]李延兴,张静华,何建坤等.由空间大地测量得到的太平洋板块现今构造运动与板内形变应变场[J].地球物理学报,2007,50(2):437~447
[57]朱涛,马宗晋,冯锐.三维地震波速结构约束下的变黏度地幔对流及其动力学意义[J].地球物理学报,2006,49(5):1347~1358.
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