由多个地震震源机制解求川滇地区平均应力场方向
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摘要
基于震源断层面解的空间取向和断层滑动方向,写出相应力轴张量在地理坐标系中的表达式,进而给出计算平均力轴张量及主值的方法,即通过求解相应的本征方程得到.对使用多个震源机制解的T,B,P轴参数计算平均应力场的方法,以用滑动方向拟合法反演富蕴、唐山地区平均应力场数据进行验证,二者结果一致.选择具有地震构造意义的地块或地震带内大量地震的震源机制解研究区域平均应力场.根据川滇13个地震带(区)的256次中强地震的震源机制解,给出了各带(区)应力张量的定量分析结果.该方法算法简便,使由大量地震震源机制解资料分析构造应力场的方法走向定量化.
Based on the spatial orientation and slip direction of the fault plane solutions, we present the expression of corresponding mechanical axis tensor in geographic coordinate system, and then put forward a method for calculating average mechanical axis tensor and its eigenvalues, which involves solving the corresponding eigenequation. The method for deducing mean stress field from T, B, and P axes parameters of a number of focal mechanism solutions has been verified by inverting data of mean stress fields in Fuyun region and in Tangshan region with fitting method of slip direction and both results are consistent. To study regional average stress field, we need to choose a population of focal mechanism solutions of earthquakes in the massifs where there are significant tectonic structures. According to the focal mechanism solutions of 256 moderate-strong earthquakes occurred in 13 seismic zones of Sichuan-Yunnan region, the quantitative analysis results of stress tensor in each seismic zone have been given. The algorithm of such method is simple and convenient, which makes the method for analyzing tectonic stress field with large amount of focal mechanism solution data become quantified.
Based on the spatial orientation and slip direction of the fault plane solutions, we present the expression of corresponding mechanical axis tensor in geographic coordinate system, and then put forward a method for calculating average mechanical axis tensor and its eigenvalues, which involves solving the corresponding eigenequation. The method for deducing mean stress field from T, B, and P axes parameters of a number of focal mechanism solutions has been verified by inverting data of mean stress fields in Fuyun region and in Tangshan region with fitting method of slip direction and both results are consistent. To study regional average stress field, we need to choose a population of focal mechanism solutions of earthquakes in the massifs where there are significant tectonic structures. According to the focal mechanism solutions of 256 moderate-strong earthquakes occurred in 13 seismic zones of Sichuan-Yunnan region, the quantitative analysis results of stress tensor in each seismic zone have been given. The algorithm of such method is simple and convenient, which makes the method for analyzing tectonic stress field with large amount of focal mechanism solution data become quantified.
引文
[1]陈运泰,顾浩鼎.1990.震源理论.中国科学院研究生院教材,23~24.
程万正,刁桂苓,吕弋培,等.2003.川滇地块的震源力学机制、运动速率和活动方式[J].地震地质,25(1):71~87
崔效锋,谢富仁.1999.利用震源机制解对中国西南及邻区进行应力分区的初步研究[J].地震学报,21(5):513~522
阚荣举.1980.西南地区现代构造应力场与板内强震活动[J].地震研究,3(3):45~59
阚荣举,张四昌,晏凤桐,等.1977.我国西南地区现代构造应力场与现代构造活动特征的探讨[J].地球物理学报,20(2):96~107
数学手册编写组.2002.数学手册[M].北京:高等教育出版社,88~89
许忠淮,戈澍谟.1984.用滑动方向拟合法反演富蕴地震断裂带应力场[J].地震学报,6(4):395~404
许忠淮.1985.用滑动方向拟合法反演唐山余震区的平均应力场[J].地震学报,7(4):349~361
许忠淮,汪素云,黄雨蕊,等.1987.由多个小震推断的青甘和川滇地区地壳应力场的方向特征[J].地球物理学报,30(5):476~486
AkiK,RichardsPG.1980.QuantitativeSeismology.TheoryandMethodsVol.1[M].SanFrancisco:FreemanandCompany,114
EllsworthWL,XuZH.1980.Determinationofthestresstensorfromfocalmechanismdata[J].EOSTrans,AGU,61:1117
GephartJW,ForsythDW.1984.Animprovedmethodfordeterminingtheregionalstresstensorusingearthquakefocalmechanismdata:ApplicafiontotheSanFernandearthquakesequence[J].JGeophysRes,89:9305~9320
程万正,刁桂苓,吕弋培,等.2003.川滇地块的震源力学机制、运动速率和活动方式[J].地震地质,25(1):71~87
崔效锋,谢富仁.1999.利用震源机制解对中国西南及邻区进行应力分区的初步研究[J].地震学报,21(5):513~522
阚荣举.1980.西南地区现代构造应力场与板内强震活动[J].地震研究,3(3):45~59
阚荣举,张四昌,晏凤桐,等.1977.我国西南地区现代构造应力场与现代构造活动特征的探讨[J].地球物理学报,20(2):96~107
数学手册编写组.2002.数学手册[M].北京:高等教育出版社,88~89
许忠淮,戈澍谟.1984.用滑动方向拟合法反演富蕴地震断裂带应力场[J].地震学报,6(4):395~404
许忠淮.1985.用滑动方向拟合法反演唐山余震区的平均应力场[J].地震学报,7(4):349~361
许忠淮,汪素云,黄雨蕊,等.1987.由多个小震推断的青甘和川滇地区地壳应力场的方向特征[J].地球物理学报,30(5):476~486
AkiK,RichardsPG.1980.QuantitativeSeismology.TheoryandMethodsVol.1[M].SanFrancisco:FreemanandCompany,114
EllsworthWL,XuZH.1980.Determinationofthestresstensorfromfocalmechanismdata[J].EOSTrans,AGU,61:1117
GephartJW,ForsythDW.1984.Animprovedmethodfordeterminingtheregionalstresstensorusingearthquakefocalmechanismdata:ApplicafiontotheSanFernandearthquakesequence[J].JGeophysRes,89:9305~9320
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