2011年安庆M_S4.8地震SmS震相观测与研究
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摘要
2011年1月19日发生的安庆MS4.8地震,在较远范围引起了明显震感.通过仔细辨认此次地震不同频段的波形记录,发现在一些台站记录到了清晰的SmS震相.采用CAP方法反演了其震源机制解,并利用理论地震图与实际观测数据对比进一步确认了SmS震相的存在.结合已有实验结果,推断在人类有感频率(1Hz至几Hz)范围内,震中距70—200km内SmS震相往往是振幅最大的震相,是引起远距离有感的主要原因.利用理论地震图研究了震源深度对SmS震相的影响.结果表明,震源深度可改变SmS震相发育的临界震中距,震源越深对应的临界震中距越小.进一步通过对比SmS与S的振幅比,定性讨论了震源机制解中倾角、滑动角和地壳浅层衰减等因素对SmS震相的影响.结果表明,倾角和滑动角对其振幅比影响呈现比较复杂的关系,而SmS与S振幅比随地壳浅层衰减的增大而减小,说明浅层衰减对SmS震相影响较大.综合分析认为,除当地地壳速度结构的影响外,SmS震相的发育受到震源机制解的倾角、滑动角,震源深度以及地壳浅层衰减等多种因素的影响.
The M S 4.8Anqing earthquake on 19Jan 2011was obviously felt even at long distances.SmS phases are identified in seismic records of some stations by examining the filtered waveforms and comparing them with synthetic seismograms.Based on our study result,we argued that the SmS phase,usually the strongest one in epicenter distance range of 70to 200km,is the main reason of feeling at such long distances.Some previous studies suggest that the SmSphases are controlled by the local crustal structure.We perform some tests using synthetic seismograms.The results show that focal depth can change the critical distance of SmS.The larger focal depth makes the critical distance smaller. Also effects of focal mechanism on SmS are investigated qualitatively by comparing the amplitude ratio between SmS and S.The amplitude ratio between SmS and S becomes smaller with larger attenuation in the shallow crust,indicating SmS is sensitive to that.Overall,the SmS phase can be affected by many factors besides local crustal structures,such as dip angle,rake angle of the focal mechanism,focal depth and attenuation.
The M S 4.8Anqing earthquake on 19Jan 2011was obviously felt even at long distances.SmS phases are identified in seismic records of some stations by examining the filtered waveforms and comparing them with synthetic seismograms.Based on our study result,we argued that the SmS phase,usually the strongest one in epicenter distance range of 70to 200km,is the main reason of feeling at such long distances.Some previous studies suggest that the SmSphases are controlled by the local crustal structure.We perform some tests using synthetic seismograms.The results show that focal depth can change the critical distance of SmS.The larger focal depth makes the critical distance smaller. Also effects of focal mechanism on SmS are investigated qualitatively by comparing the amplitude ratio between SmS and S.The amplitude ratio between SmS and S becomes smaller with larger attenuation in the shallow crust,indicating SmS is sensitive to that.Overall,the SmS phase can be affected by many factors besides local crustal structures,such as dip angle,rake angle of the focal mechanism,focal depth and attenuation.
引文
①http:∥www.csndmc.ac.cn/newweb/secondpage.jsp?id=1021
邓起东,张培震,冉勇康,杨晓平,闵伟,楚全芝.2002.中国大陆活动构造基本特征[J].中国科学:D辑,32(12):1020--1030.
黄建平,傅容珊,许萍,黄建华,郑勇.2006.利用重力和地形观测反演中国及邻区地壳厚度[J].地震学报,28(3):250--258.
李光,童远林,郑颖平.2008.安徽及邻区地震烈度衰减关系研究[J].华南地震,28(3):49--55.
罗艳,倪四道,陈颙.2010.超临界距离上SmS震相对强地面振动衰减关系影响的初步探讨[J].中国地震,26(2):131--141.
罗艳,倪四道,曾祥方,谢军,陈颙,龙锋.2011.一个发生在沉积盖层里的破坏性地震:2010年1月31日四川遂宁—重庆潼南地震[J].科学通报,56(2):147--152.
吕坚,郑勇,倪四道,高建华.2008.2005年12月26日九江—瑞昌MS5.7,MS4.8地震的震源机制解与发震构造研究[J].地球物理学报,51(1):158--164.
吕坚,俞言祥,高建华,高登平,汤兰荣.2009.江西及邻区地震烈度衰减关系研究[J].地震研究,32(3):269--274.
汪素云,俞言祥,高阿甲,阎秀杰.2000.中国分区地震动衰减关系的确定[J].中国地震,16(2):99--106.
韦生吉,倪四道,崇加军,郑勇,陈颙.2009.2003年8月16日赤峰地震:一个可能发生在下地壳的地震?[J].地球物理学报,52(1):111--119.
谢祖军,郑勇,倪四道,熊熊,张炳,王行舟.2012.2011/01/19安庆ML4.8地震的震源机制解和深度研究[J].地球物理学报,55(5):1624--1634.
张国民,汪素云,李丽,张晓东,马宏生.2002.中国大陆地震震源深度及其构造含义[J].科学通报,47(9):663--668.
郑秀芬,欧阳飚,张东宁,姚志祥,梁建宏,郑洁.2009.“国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑[J].地球物理学报,52(5):1412--1417.
Atkinson G M,Wald D J.2007.“Did you feel it?”intensity data:A surprisingly good measure of earthquake groundmotion[J].Seism Res Lett,78(3):362--368.
Burger R W,Somerville P G,Barker J S,Herrmann R B,Helmberger D V.1987.The effect of crustal structure onstrong ground motion attenuation relation in eastern North America[J].Bull Seism Soc Amer,77(2):420--439.
Chen K C.2003.Strong ground motion and damage in the Taipei basin from the Moho reflected seismic waves during theMarch 31,2002,Hualien,Taiwan earthquake[J].Geophys Res Lett,30(11):1551.
Frankel A.1994.Implications of felt area-magnitude relations for earthquake scaling and the average frequency of percep-tible ground motion[J].Bull Seism Soc Amer,84(2):462--465.
Goldman D E,Gierke H E.1961.Effects of shock and vibration on man,Chapter 44[M]∥Harris C M,Crede C E eds.Shock and Vibration Handbook.New York,NY:McGraw-Hill:1--58.
Liu K S,Tsai Y B.2009.Large effects of Moho reflections(SmS)on peak ground motion in Northwestern Taiwan[J].Bull Seism Soc Amer,99(1):255--267.
Kanamori H.1977.The energy release in great earthquakes[J].J Geophys Res,82(20):2981--2987.
Kafka A L.1990.Rg as depth discriminant for earthquakes and explosion:A case study in New England[J].Bull SeismSoc Amer,80(2):373--394.
Mori J,Helmberger D V.1996.Large-amplitude Moho reflection(SmS)from Landers aftershocks,southern California[J].Bull Seism Soc Amer,86(6):1845--1852.
Somerville P,Yoshimura J.1990.The influence of critical Moho reflections on strong ground motions recorded in SanFrancisco and Oakland during the 1989Loma Prieta earthquake[J].Geophys Res Lett,17(8):1203--1206.
Somerville P G,Smith N F,Graves R W.1994.The effect of critical Moho reflections on the attenuation of strongmotion from the 1989Loma Prieta earthquake[R]∥The Loma Prieta,California,Earthquake of October 17,1989-Strong Ground Motion.U S Geol Survey Profess Pap,1551-A,A67-A75.
Zhan Z W,Ni S D,Helmberger D V,Clayton R W.2010.Retrieval of Moho-reflected shear wave arrivals from ambientseismic noise[J].Geophys J Int,182(1):408--420.
Zhao L S,Helmberger D V.1994.Source estimation from broadband regional seismograms[J].Bull Seism Soc Amer,84(1):91--104.
Zhu L P,Rivera L A.2002.A note on the dynamic and static displacements from a point source in multi-layered media[J].Geophys J Int,148(3):619--627.
邓起东,张培震,冉勇康,杨晓平,闵伟,楚全芝.2002.中国大陆活动构造基本特征[J].中国科学:D辑,32(12):1020--1030.
黄建平,傅容珊,许萍,黄建华,郑勇.2006.利用重力和地形观测反演中国及邻区地壳厚度[J].地震学报,28(3):250--258.
李光,童远林,郑颖平.2008.安徽及邻区地震烈度衰减关系研究[J].华南地震,28(3):49--55.
罗艳,倪四道,陈颙.2010.超临界距离上SmS震相对强地面振动衰减关系影响的初步探讨[J].中国地震,26(2):131--141.
罗艳,倪四道,曾祥方,谢军,陈颙,龙锋.2011.一个发生在沉积盖层里的破坏性地震:2010年1月31日四川遂宁—重庆潼南地震[J].科学通报,56(2):147--152.
吕坚,郑勇,倪四道,高建华.2008.2005年12月26日九江—瑞昌MS5.7,MS4.8地震的震源机制解与发震构造研究[J].地球物理学报,51(1):158--164.
吕坚,俞言祥,高建华,高登平,汤兰荣.2009.江西及邻区地震烈度衰减关系研究[J].地震研究,32(3):269--274.
汪素云,俞言祥,高阿甲,阎秀杰.2000.中国分区地震动衰减关系的确定[J].中国地震,16(2):99--106.
韦生吉,倪四道,崇加军,郑勇,陈颙.2009.2003年8月16日赤峰地震:一个可能发生在下地壳的地震?[J].地球物理学报,52(1):111--119.
谢祖军,郑勇,倪四道,熊熊,张炳,王行舟.2012.2011/01/19安庆ML4.8地震的震源机制解和深度研究[J].地球物理学报,55(5):1624--1634.
张国民,汪素云,李丽,张晓东,马宏生.2002.中国大陆地震震源深度及其构造含义[J].科学通报,47(9):663--668.
郑秀芬,欧阳飚,张东宁,姚志祥,梁建宏,郑洁.2009.“国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑[J].地球物理学报,52(5):1412--1417.
Atkinson G M,Wald D J.2007.“Did you feel it?”intensity data:A surprisingly good measure of earthquake groundmotion[J].Seism Res Lett,78(3):362--368.
Burger R W,Somerville P G,Barker J S,Herrmann R B,Helmberger D V.1987.The effect of crustal structure onstrong ground motion attenuation relation in eastern North America[J].Bull Seism Soc Amer,77(2):420--439.
Chen K C.2003.Strong ground motion and damage in the Taipei basin from the Moho reflected seismic waves during theMarch 31,2002,Hualien,Taiwan earthquake[J].Geophys Res Lett,30(11):1551.
Frankel A.1994.Implications of felt area-magnitude relations for earthquake scaling and the average frequency of percep-tible ground motion[J].Bull Seism Soc Amer,84(2):462--465.
Goldman D E,Gierke H E.1961.Effects of shock and vibration on man,Chapter 44[M]∥Harris C M,Crede C E eds.Shock and Vibration Handbook.New York,NY:McGraw-Hill:1--58.
Liu K S,Tsai Y B.2009.Large effects of Moho reflections(SmS)on peak ground motion in Northwestern Taiwan[J].Bull Seism Soc Amer,99(1):255--267.
Kanamori H.1977.The energy release in great earthquakes[J].J Geophys Res,82(20):2981--2987.
Kafka A L.1990.Rg as depth discriminant for earthquakes and explosion:A case study in New England[J].Bull SeismSoc Amer,80(2):373--394.
Mori J,Helmberger D V.1996.Large-amplitude Moho reflection(SmS)from Landers aftershocks,southern California[J].Bull Seism Soc Amer,86(6):1845--1852.
Somerville P,Yoshimura J.1990.The influence of critical Moho reflections on strong ground motions recorded in SanFrancisco and Oakland during the 1989Loma Prieta earthquake[J].Geophys Res Lett,17(8):1203--1206.
Somerville P G,Smith N F,Graves R W.1994.The effect of critical Moho reflections on the attenuation of strongmotion from the 1989Loma Prieta earthquake[R]∥The Loma Prieta,California,Earthquake of October 17,1989-Strong Ground Motion.U S Geol Survey Profess Pap,1551-A,A67-A75.
Zhan Z W,Ni S D,Helmberger D V,Clayton R W.2010.Retrieval of Moho-reflected shear wave arrivals from ambientseismic noise[J].Geophys J Int,182(1):408--420.
Zhao L S,Helmberger D V.1994.Source estimation from broadband regional seismograms[J].Bull Seism Soc Amer,84(1):91--104.
Zhu L P,Rivera L A.2002.A note on the dynamic and static displacements from a point source in multi-layered media[J].Geophys J Int,148(3):619--627.
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