腾冲地区地壳速度结构的有限差分成像
|
摘要
利用流动台网和固定台站的地震观测数据,采用有限差分层析成像方法反演了腾冲及邻近地区的地壳P波速度结构,分析了腾冲火山区的岩浆活动和龙陵七级地震的深部构造成因.研究结果表明,腾冲火山区的地壳结构具有明显的非均匀性,浅表层偏低的速度主要为盆地内部的松散沉积层、新生代火山堆积及断裂附近的流体裂隙和热泉活动所致;5～15km之间的高速体可能代表了早期火山通道内冷却固结的岩浆侵入体或难挥发的超铁镁质残留体;地壳深部的低速体则反映了熔融或半熔融的岩浆体,推断火山区下方的岩浆活动与龙陵七级地震震源区地壳深部的岩浆侵入来自同一源区——现今壳内岩浆活动的主要区域.龙陵震源区的地壳速度结构横向变化较大,怒江断裂东侧和龙陵断裂西侧为高速特征,介质应变强度较大,为应力积累的主要载体;两断裂之间的低速区向下延伸至下地壳,可能与地壳深部的岩浆侵入有关;龙陵断裂和怒江断裂明显控制了这一区域的岩浆活动,七级地震正是发生在断裂下方的速度边界附近.地壳介质强度的横向变化导致了震源区应力积累的不均一性,深部岩浆的聚集和动力作用是龙陵地区发生强震的主要原因.
This paper applies the finite difference tomography method to invert for the P-wave velocity structure in the Tengchong area using earthquake data from a temporary network and other permanent stations,and analyzes the magmatic activity of the Tengchong volcanoes and the deep tectonic genesis of Longling M7.3/M7.4 earthquakes.The results show the mean velocity in the crust with clear heterogeneity is a little lower.The lower velocities in the shallow layers are caused by unconsolidated basin deposits,Cenozoic volcanic deposits,fluid fractures and hot springs.The high-velocity zone at 5~15 km depth probably represents the cooled and solidified magmatic intrusions or the less volatile ultramafic remnants.The low-velocity structure in the deep indicates the molten or semi-molten magma.It is probable that the magmatic activity beneath the volcanoes and heat flow intrusions in the deep crust of Longling earthquake zone are from the same magmatic hearth area,which is the main area of the present magmatic activities.A strong lateral heterogeneity is observed in Longling earthquake zone.The east of the Nujiang fault belt and the west of the Longling fault belt have the characters of high-velocity with the high strength of rock,which are the main bearing body of stress accumulation.However,the low-velocity anomaly between the two faults extends to lower crust,probably caused by magmatic intrusions in the deep crust.The magmatic activity in this area is controlled clearly by the Longling fault and the Nujiang fault.The Longling M7.3 and M7.4 earthquakes occurred near the velocity boundary beneath the faults.The main reasons of the strong earthquakes in the Longling area contain the heterogeneity of stress accumulation caused by the lateral variation of the crustal medium strength,the deep magmatic aggregation and dynamic effects.
This paper applies the finite difference tomography method to invert for the P-wave velocity structure in the Tengchong area using earthquake data from a temporary network and other permanent stations,and analyzes the magmatic activity of the Tengchong volcanoes and the deep tectonic genesis of Longling M7.3/M7.4 earthquakes.The results show the mean velocity in the crust with clear heterogeneity is a little lower.The lower velocities in the shallow layers are caused by unconsolidated basin deposits,Cenozoic volcanic deposits,fluid fractures and hot springs.The high-velocity zone at 5~15 km depth probably represents the cooled and solidified magmatic intrusions or the less volatile ultramafic remnants.The low-velocity structure in the deep indicates the molten or semi-molten magma.It is probable that the magmatic activity beneath the volcanoes and heat flow intrusions in the deep crust of Longling earthquake zone are from the same magmatic hearth area,which is the main area of the present magmatic activities.A strong lateral heterogeneity is observed in Longling earthquake zone.The east of the Nujiang fault belt and the west of the Longling fault belt have the characters of high-velocity with the high strength of rock,which are the main bearing body of stress accumulation.However,the low-velocity anomaly between the two faults extends to lower crust,probably caused by magmatic intrusions in the deep crust.The magmatic activity in this area is controlled clearly by the Longling fault and the Nujiang fault.The Longling M7.3 and M7.4 earthquakes occurred near the velocity boundary beneath the faults.The main reasons of the strong earthquakes in the Longling area contain the heterogeneity of stress accumulation caused by the lateral variation of the crustal medium strength,the deep magmatic aggregation and dynamic effects.
引文
[1]阚荣举,赵晋明.腾冲火山地区的壳幔构造.∥陈运泰,阚荣举,滕吉文等.中国固体地球物理学进展.北京:海洋出版社,1994:23-30.Kan R J,Zhao J M.The crust-mantle structure ofTengchong volcanic area.∥Chen Y T,Kan R J,Teng J W,et al eds.Chinese Solid Geophysics Progress.Beijing:OceanPress(in Chinese),1994:23-30.
[2]Lei J S,Zhao D P,Su Y J.Insight into the origin of theTengchong intraplate volcano and seismotectonics in southwestChina from local and teleseismic data.J.Geophys.Res.,2009,114,B053202,doi:10.1029/2008JB005881.
[3]Lei J S,Xie F R,Mishra O P,et al.The 2011Yingjiang,China,earthquake:A volcano-related fluid-driven earthquake?Bulletin of the Seismological Society of America,2012,102(1):417-425,doi:10.1785/0120110143.
[4]Wang Y,Zhang X M,Jiang C S,et al.Tectonic controls onthe late Miocene-Holocene volcanic eruptions of the Tengchongvolcanic field along the southeastern margin of the Tibetanplateau.J.Asian.Earth Sci.,2007,30(2):375-389.
[5]Chen F,Satir M,Ji J,et al.Nd-Sr-Pb isotopes ofTengchong Cenozoic volcanic rocks from western Yunnan,China:evidence for an enriched-mantle source.J.Asian.Earth Sci.,2002,21(1):39-45.
[6]Huang J L,Zhao D P.High-resolution mantle tomography ofChina and surrounding regions.J.Geophys.Res.,2006,11(B9),doi:10.1029/2005JB004066.
[7]Hu J F,Hu Y L,Xia J Y,et al.Crust-mantle velocitystructure of S wave and dynamic process beneath Burma Arcand its adjacent regions.Chinese J.Geophys.,2008,51(1):140-148.
[8]Li C,van der Hilst R,Meltzer A,et al.Subduction of theIndian lithosphere beneath the Tibetan Plateau and Burma.Earth Planet.Sci.Lett.,2008,274(1-2):157-168,doi:10.1016/j.epsl.2008.07.016.
[9]Wang C Y,Huangfu G.Crustal structure in Tengchongvolcano-geothermal area,western Yunnan,China.Tectonophysics,2004,380(1-2):69-87.
[10]楼海,王椿镛,皇甫岗等.云南腾冲火山区上部地壳三维地震速度层析成像.地震学报,2002,24(3):243-251.Lou H,Wang C Y,Huangfu G,et al.Three-demensionalseismic velocity tomography of the upper crust in Tengchongvolcanic area,Yunan Province.Acta Seismologica Sinica(inChinese),2002,24(3):243-251.
[11]黄甫岗.腾冲火山研究综述.地震研究,1997,20(4):431-437.Huangfu G.Review of studies on Tengchong volcanoes.Journal of Seismological Research(in Chinese),1997,20(4):431-437.
[12]黄金莉,宋晓东,汪素云.川滇地区上地幔顶部Pn速度细结构.中国科学(D辑),2003,33(增刊):144-150.Huang J L,Song X D,Wang S Y.Fine structure of Pnvelocity beneath Sichuan-Yunnan region.Science in China(Series D),2003,46(S2):201-209.
[13]姜朝松,王绍晋,叶建庆等.腾冲火山区小震震源机制特征.地震研究,2005,28(2):141-143.Jiang C S,Wang S J,Ye J Q,et al.Focal mechanismfeatures of small shocks in the Tengchong volcanic area.Journal of Seismological Research(in Chinese),2005,28(2):141-143.
[14]杨晓涛,胥颐,刘建华等.腾冲火山区的地震层析成像及其构造意义.地球物理学报,2011,54(8):2050-2059.Yang X T,Xu Y,Liu J H,et al.Seismic tomography in theTengchong volcanic area and its tectonic implication.ChineseJ.Geophys.(in Chinese),2011,54(8):2050-2059.
[15]Liang C T,Song X D,Huang J L.Tomographic inversion ofPn travel times in China.J.Geophys.Res.,2004,109:B11304,doi:10.1029/2003JB002789.
[16]Vidale J.Finite-difference calculation of travel time.Bull.Seis.Soc.Am.,1988,78(6):2062-2076.
[17]Vidale J E.Finite-difference calculation of traveltimes inthree dimensions.Geophysics,1990,55(5):521-526.
[18]Hole J A.Nonlinear High-resolution three-dimensionalseismic travel time tomography.J.Geophys.Res.,1992,97(B5):6553-6562.
[19]Hole J A,Brocher T M,Klemperer S L,et al.Three-dimensional seismic velocity structure of the San FranciscoBay area.J.Geophys.Res.,2000,105(B6):13859-13874.
[20]Hole J A,Zelt C A.3-D finite-difference reflectiontraveltimes.Geophys.J.Int.,1995,121(2):427-434.
[21]Paige C C,Saunders M A.LSQR:An algorithm for sparselinear equations and sparse least squares.ACM Trans.Math.Softw.,1982,8(1):43-71.
[22]王椿镛,Mooney W D,王溪莉等.川滇地区地壳上地幔三维速度结构研究.地震学报,2002,24(1):1-16.Wang C Y,Mooney W D,Wang X L,et al.Study on 3-Dvelocity structure of crust and upper mantle in Sichuan-Yunnan region,China.Acta Seismologica Sinica(in Chinese),2002,24(1):1-16.
[23]白志明,王椿镛.云南地区上部地壳结构和地震构造环境的层析成像研究.地震学报,2003,25(2):117-127.Bai Z M,Wang C Y.Tomographic investigation of the uppercrustal structure and seismotectonic environments in Yunnanprovince.Acta Seismologica Sinica(in Chinese),2003,25(2):117-127.
[24]秦嘉政,皇甫岗,李强等.腾冲火山及邻区速度结构的三维层析成象.地震研究,2000,23(2):157-165.Qin J Z,Huangfu G,Li Q,et al.3-D chromatography ofvelocity structure in Tengchong volcano areas and nearby.J.Seismol.Res.(in Chinese),2000,23(2):157-165.
[25]De Natale G,Troise C,Trigila R,et al.Seismicity and 3-Dsubstructure at Somma-Vesuvius volcano:evidence formagma quenching.Earth Planet.Sci.Lett.,2004,221(1-4):181-196.
[26]Lees J M.Seismic tomography of magmatic systems.J.Volcanol.Geotherm.Res.,2007,167(1-4):37-56.
[27]Park J,Morgan J K,Zelt C A,et al.Volcano-tectonicimplications of 3-D velocity structures derived from jointactive and passive source tomography of the island of Hawaii.J.Geophys.Res.,2009,114:B09301,doi:10.1029/2008JB005929.
[28]Sherburn S,White R S,Chadwick M.Three-dimensionaltomographic imaging of the Taranaki volcanoes,NewZealand.Geophys.J.Int.,2006,166(2):957-969.
[29]Molina I,Kumagai H,Pennec L,et al.Three-dimensionalP-wave velocity structure of Tungurahua Volcano,Ecuador.J.Volcanol.Geotherm.Res.,2005,147(1-2):144-156.
[30]Benz H M,Smith R B.Simultaneous inversion for lateralvelocity variations and hypocenters in the Yellowstone regionusing earthquake and refraction data.J.Geophys.Res.,1984,89(B2):1208-1220.
[31]Nercessian A,Hirn A,Tarantola A.Three-dimensionalseismic transmission prospecting of the Mont Dore Volcano,France.Geophys.J.Rastr Soc.,1984,76(2):307-315.
[32]Ankeny L A,Braile L W,Olsen K H.Upper crustalstructure beneath the Jemez Mountains volcanic field,NewMexico,determined by three-dimensional simultaneous inversionof seismic refraction and earthquake data.J.Geophys.Res.,1986,91(B6):6188-6198.
[33]Shangguan Z G,Zhao C P,Li H Z,et al.Evolution ofhydrothermal explosions at Rehai geothermal field,Tengchongvolcanic region,China.Geothermics,2005,34(4):518-526.
[34]曹令敏.地震层析成像方法的研究及其在金属矿复杂模型模拟中的应用[博士论文].北京:中国地质大学,2011.Cao L M.Research on seismic tomography and its applicationto complicated velocity model of the metal mine[Ph.D.thesis](in Chinese).Beijing:China University ofGeosciences,2011.
[35]陈学波,李金森,赵静娴等.三江构造带基底构造特征与强震活动关系.∥陈运泰,阚荣举,滕吉文等.中国固体地球物理学进展.北京:海洋出版社,1994:41-54.Chen X B,Li J S,Zhao J X,et al.The relationship betweenthe basement structure characteristics of Sanjiang tectonicbelt and strong earthquakes.∥Chen Y T,Kan R J,Teng JW,et al eds.Chinese Solid Geophysics Progress.Beijing:Ocean Press(in Chinese),1994:41-54.
[2]Lei J S,Zhao D P,Su Y J.Insight into the origin of theTengchong intraplate volcano and seismotectonics in southwestChina from local and teleseismic data.J.Geophys.Res.,2009,114,B053202,doi:10.1029/2008JB005881.
[3]Lei J S,Xie F R,Mishra O P,et al.The 2011Yingjiang,China,earthquake:A volcano-related fluid-driven earthquake?Bulletin of the Seismological Society of America,2012,102(1):417-425,doi:10.1785/0120110143.
[4]Wang Y,Zhang X M,Jiang C S,et al.Tectonic controls onthe late Miocene-Holocene volcanic eruptions of the Tengchongvolcanic field along the southeastern margin of the Tibetanplateau.J.Asian.Earth Sci.,2007,30(2):375-389.
[5]Chen F,Satir M,Ji J,et al.Nd-Sr-Pb isotopes ofTengchong Cenozoic volcanic rocks from western Yunnan,China:evidence for an enriched-mantle source.J.Asian.Earth Sci.,2002,21(1):39-45.
[6]Huang J L,Zhao D P.High-resolution mantle tomography ofChina and surrounding regions.J.Geophys.Res.,2006,11(B9),doi:10.1029/2005JB004066.
[7]Hu J F,Hu Y L,Xia J Y,et al.Crust-mantle velocitystructure of S wave and dynamic process beneath Burma Arcand its adjacent regions.Chinese J.Geophys.,2008,51(1):140-148.
[8]Li C,van der Hilst R,Meltzer A,et al.Subduction of theIndian lithosphere beneath the Tibetan Plateau and Burma.Earth Planet.Sci.Lett.,2008,274(1-2):157-168,doi:10.1016/j.epsl.2008.07.016.
[9]Wang C Y,Huangfu G.Crustal structure in Tengchongvolcano-geothermal area,western Yunnan,China.Tectonophysics,2004,380(1-2):69-87.
[10]楼海,王椿镛,皇甫岗等.云南腾冲火山区上部地壳三维地震速度层析成像.地震学报,2002,24(3):243-251.Lou H,Wang C Y,Huangfu G,et al.Three-demensionalseismic velocity tomography of the upper crust in Tengchongvolcanic area,Yunan Province.Acta Seismologica Sinica(inChinese),2002,24(3):243-251.
[11]黄甫岗.腾冲火山研究综述.地震研究,1997,20(4):431-437.Huangfu G.Review of studies on Tengchong volcanoes.Journal of Seismological Research(in Chinese),1997,20(4):431-437.
[12]黄金莉,宋晓东,汪素云.川滇地区上地幔顶部Pn速度细结构.中国科学(D辑),2003,33(增刊):144-150.Huang J L,Song X D,Wang S Y.Fine structure of Pnvelocity beneath Sichuan-Yunnan region.Science in China(Series D),2003,46(S2):201-209.
[13]姜朝松,王绍晋,叶建庆等.腾冲火山区小震震源机制特征.地震研究,2005,28(2):141-143.Jiang C S,Wang S J,Ye J Q,et al.Focal mechanismfeatures of small shocks in the Tengchong volcanic area.Journal of Seismological Research(in Chinese),2005,28(2):141-143.
[14]杨晓涛,胥颐,刘建华等.腾冲火山区的地震层析成像及其构造意义.地球物理学报,2011,54(8):2050-2059.Yang X T,Xu Y,Liu J H,et al.Seismic tomography in theTengchong volcanic area and its tectonic implication.ChineseJ.Geophys.(in Chinese),2011,54(8):2050-2059.
[15]Liang C T,Song X D,Huang J L.Tomographic inversion ofPn travel times in China.J.Geophys.Res.,2004,109:B11304,doi:10.1029/2003JB002789.
[16]Vidale J.Finite-difference calculation of travel time.Bull.Seis.Soc.Am.,1988,78(6):2062-2076.
[17]Vidale J E.Finite-difference calculation of traveltimes inthree dimensions.Geophysics,1990,55(5):521-526.
[18]Hole J A.Nonlinear High-resolution three-dimensionalseismic travel time tomography.J.Geophys.Res.,1992,97(B5):6553-6562.
[19]Hole J A,Brocher T M,Klemperer S L,et al.Three-dimensional seismic velocity structure of the San FranciscoBay area.J.Geophys.Res.,2000,105(B6):13859-13874.
[20]Hole J A,Zelt C A.3-D finite-difference reflectiontraveltimes.Geophys.J.Int.,1995,121(2):427-434.
[21]Paige C C,Saunders M A.LSQR:An algorithm for sparselinear equations and sparse least squares.ACM Trans.Math.Softw.,1982,8(1):43-71.
[22]王椿镛,Mooney W D,王溪莉等.川滇地区地壳上地幔三维速度结构研究.地震学报,2002,24(1):1-16.Wang C Y,Mooney W D,Wang X L,et al.Study on 3-Dvelocity structure of crust and upper mantle in Sichuan-Yunnan region,China.Acta Seismologica Sinica(in Chinese),2002,24(1):1-16.
[23]白志明,王椿镛.云南地区上部地壳结构和地震构造环境的层析成像研究.地震学报,2003,25(2):117-127.Bai Z M,Wang C Y.Tomographic investigation of the uppercrustal structure and seismotectonic environments in Yunnanprovince.Acta Seismologica Sinica(in Chinese),2003,25(2):117-127.
[24]秦嘉政,皇甫岗,李强等.腾冲火山及邻区速度结构的三维层析成象.地震研究,2000,23(2):157-165.Qin J Z,Huangfu G,Li Q,et al.3-D chromatography ofvelocity structure in Tengchong volcano areas and nearby.J.Seismol.Res.(in Chinese),2000,23(2):157-165.
[25]De Natale G,Troise C,Trigila R,et al.Seismicity and 3-Dsubstructure at Somma-Vesuvius volcano:evidence formagma quenching.Earth Planet.Sci.Lett.,2004,221(1-4):181-196.
[26]Lees J M.Seismic tomography of magmatic systems.J.Volcanol.Geotherm.Res.,2007,167(1-4):37-56.
[27]Park J,Morgan J K,Zelt C A,et al.Volcano-tectonicimplications of 3-D velocity structures derived from jointactive and passive source tomography of the island of Hawaii.J.Geophys.Res.,2009,114:B09301,doi:10.1029/2008JB005929.
[28]Sherburn S,White R S,Chadwick M.Three-dimensionaltomographic imaging of the Taranaki volcanoes,NewZealand.Geophys.J.Int.,2006,166(2):957-969.
[29]Molina I,Kumagai H,Pennec L,et al.Three-dimensionalP-wave velocity structure of Tungurahua Volcano,Ecuador.J.Volcanol.Geotherm.Res.,2005,147(1-2):144-156.
[30]Benz H M,Smith R B.Simultaneous inversion for lateralvelocity variations and hypocenters in the Yellowstone regionusing earthquake and refraction data.J.Geophys.Res.,1984,89(B2):1208-1220.
[31]Nercessian A,Hirn A,Tarantola A.Three-dimensionalseismic transmission prospecting of the Mont Dore Volcano,France.Geophys.J.Rastr Soc.,1984,76(2):307-315.
[32]Ankeny L A,Braile L W,Olsen K H.Upper crustalstructure beneath the Jemez Mountains volcanic field,NewMexico,determined by three-dimensional simultaneous inversionof seismic refraction and earthquake data.J.Geophys.Res.,1986,91(B6):6188-6198.
[33]Shangguan Z G,Zhao C P,Li H Z,et al.Evolution ofhydrothermal explosions at Rehai geothermal field,Tengchongvolcanic region,China.Geothermics,2005,34(4):518-526.
[34]曹令敏.地震层析成像方法的研究及其在金属矿复杂模型模拟中的应用[博士论文].北京:中国地质大学,2011.Cao L M.Research on seismic tomography and its applicationto complicated velocity model of the metal mine[Ph.D.thesis](in Chinese).Beijing:China University ofGeosciences,2011.
[35]陈学波,李金森,赵静娴等.三江构造带基底构造特征与强震活动关系.∥陈运泰,阚荣举,滕吉文等.中国固体地球物理学进展.北京:海洋出版社,1994:41-54.Chen X B,Li J S,Zhao J X,et al.The relationship betweenthe basement structure characteristics of Sanjiang tectonicbelt and strong earthquakes.∥Chen Y T,Kan R J,Teng JW,et al eds.Chinese Solid Geophysics Progress.Beijing:Ocean Press(in Chinese),1994:41-54.
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心