地壳分层和地壳厚度对汶川地震同震效应的影响
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摘要
基于有限矩形位错理论及USGS地震波反演的断层模型,结合研究区地壳-上地幔平均波速分层结构,构建均匀地壳模型,利用PSGRN/PSCMP软件模拟计算地壳分层和地壳厚度对汶川地震同震形变和重力变化的影响,模拟结果表明:地壳分层和地壳厚度对同震效应的影响与断层产状和计算点与断层相对位置有关;两模型模拟结果差异分布形式与同震效应分布类似;其差异百分比分布明显受同震效应零线制约,远离零线为正,对于地壳分层,其影响在10%～20%之间,而负影响以及正影响超过30%的则集中出现在零线附近;地壳分层对地表经向位移、纬向位移、垂直位移和重力变化的平均影响分别为18.4%、18.0%、15.8%和16.2%;地壳厚度为40km时,其对汶川同震经向位移、纬向位移、垂直位移和重力变化的平均影响分别为4.6%、5.3%、3.8%和3.8%;壳厚度为70km时,其平均影响分别为3.5%、4.6%、3.0%和2.5%。
Using the PSGRN/PSCMP software and the fault model offered by USGS and on the basis of finite rectangular dislocation theory and the local layered wave velocity structures of the crust-upper-mantle,the influences of crust layering and thickness to coseismic gravity changes and deformation of Wenchuan earthquake have been simulated.The results indicate that:the influences have relation to the attitude of faults and the relative position between calculated points and fault.The difference distribution form of simulated results between the two models is similar to the distribution of coseismic effect.For the per-centum distribution,it's restricted by the zero line of the coseismic effects obviously.It's positive far from the zero line.For the crust thickness,the effect is about 10%~20%.The negative and the effect over 30% focus around the zero line.The average influences of crust layering and thickness for the longitudinal deformation,latitudinal deformation,vertical deformation and gravity changes are 18.4%、18.0%、15.8% and 16.2%,respectively when the crust thickness is 40km,the average influences are 4.6%,5.3%,3.8% and 3.8%,while the crust thickness is 70 km,the average influences are 3.5%,4.6%,3.0% and 2.5% respectively.
Using the PSGRN/PSCMP software and the fault model offered by USGS and on the basis of finite rectangular dislocation theory and the local layered wave velocity structures of the crust-upper-mantle,the influences of crust layering and thickness to coseismic gravity changes and deformation of Wenchuan earthquake have been simulated.The results indicate that:the influences have relation to the attitude of faults and the relative position between calculated points and fault.The difference distribution form of simulated results between the two models is similar to the distribution of coseismic effect.For the per-centum distribution,it's restricted by the zero line of the coseismic effects obviously.It's positive far from the zero line.For the crust thickness,the effect is about 10%~20%.The negative and the effect over 30% focus around the zero line.The average influences of crust layering and thickness for the longitudinal deformation,latitudinal deformation,vertical deformation and gravity changes are 18.4%、18.0%、15.8% and 16.2%,respectively when the crust thickness is 40km,the average influences are 4.6%,5.3%,3.8% and 3.8%,while the crust thickness is 70 km,the average influences are 3.5%,4.6%,3.0% and 2.5% respectively.
引文
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12Chen Ji,UCSB and Gavin Hayes.NEIC,preliminary result of the May12,2008Mw7.9eastern Sichuan,China earth-quake[ED/OL].http://earthquake.usgs.gov/eqcenter/eqinthenews/us2008ryan/.200805.
13王椿墉,等.松潘-甘孜造山带地壳速度结构[J].地震学报,2003,25(3):229-241.(Wang Chunyong,et al.Crus-tal structure beneath the Songpan-Ganze orogenic belt[J].Acta Seismologica Simica,2003,25(3):229-241)
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15吴建平,明跃红,王椿墉.川滇地区速度结构的区域地震波形反演研究[J].地球物理学报,2006,49(5):1369-1376.(Wu Jianping,Ming Yuehong and Wang Chunyong.Regional waveform inversion for crustal and upper mantle velocity structure below Chuandian region[J].Chinese Journal of Geophysics,2006,49(5):1369-1376)
16Talwandl M,et al.A crustal section across the Puerto Pico Trench[J].J.Geophys.Res,1959,64(10):1545-1556.
17谭凯,李杰,王琪.大地测量约束下的阿尔泰岩石圈流变结构[J].地球物理学报,2007,50(6):1713-1718.(Tan Kai,Li Jie and Wang Qi.Lithospheric rheological structure constrained by grodetic data in Altay[J].Chinese Journal of Geophysics,2007,50(6):1713-1718)
18沈正康,等.东昆仑活动断裂带大地震之间的黏弹性应力触发研究[J].地球物理学报,2003,46(6):786-795.(Shen Zhengkang,et al.Viscoelastic triggering among large earthquakes along the east Kunlun fault system[J].Chi-nese Journal of Geophysics,2003,46(6):786-795.)
19谈洪波,申重阳,李辉.断层位错引起的地表重力变化特征研究[J].大地测量与地球动力学,2008,(4):54-62.(Tan Hongbo,Shen Chongyang and Li Hui.Characteristics of sureface gravity changes caused by a fault or faults dislo-cation[J].Journal of Geodesy and Geodynamics,2008,(4):54-62)
20谈洪波,等.断层位错引起的地表形变特征[J].大地测量与地球动力学,2009,(3):42-49.(Tan Hongbo,et al.Characteristics of sureface deformation caused by fault dis-location[J].Journal of Geodesy and Geodynamics,2009,(3):42-49)
21国家重大科学工程“中国地壳运动观测网络”项目组.GPS测定的2008年汶川Ms8.0地震的同震位移场[J].中国科学(D辑):地球科学,2008,38(10):1195-1206.(Project Group of the Crust movement Observation Network of China.The coseismic deformation of the Wen-chuanMs8.0earthquake based on GPS observation[J].Science China D,2008,38(10):1195-1206)
2滕吉文,等.2008汶川Ms8.0地震发生的深层过程和动力学响应[J].地球物理学报,2008,51(5):1385-1402.(Teng Jiwen,et al.Deep processes and dynamic responses associated with the Wenchuan Ms8.0earthquake of2008[J].Chinese Journal of Geophysics,2008,51(5):1385-1402)
3杨海燕,等.川西地区壳幔结构与汶川Ms8.0地震的孕震背景[J].地球物理学报,2009,52(2):356-364.(Yang Haiyan,et al.Crust-mantle structre in Western Si-chuan area and seismogenic background of WenchuanMs8.0earthquake[J].Chinese Journal of Geophysics,2009,52(2):356-564)
4雷建设,等.龙门山断裂带地壳精细结构与汶川地震发震机理[J].地球物理学报,2009,52(2):339-345.(Lei Jianshe,et al.Fine seismic structure under the Longmenshan fault zone and the mechanism of the Wenchuan earthquake[J].Chinese Journal of Geophysics,2009,52(2):339-345)
5徐朝繁,等.龙门山及其邻近地区深部地球物理探测[J].大地测量与地球动力学,2008,(6):31-37.(Xu Zhao-fan,et al.Deep geophysical exploration of Longmenshan and its adjacent area[J].Journal of Geodesy and Geodynamics,2008,(6):31-37)
6Sun W and Okubo S.Effects of the earth’s spherical curva-ture and radial heterogeneity in dislocation studies—for a point dislocation[J].Geophys.R.L.,2002,29(12):461-464.
7Pollitz F F.Coseismic deformation from earthquake faulting in a layered spherical earth[J].Geophys.J.Int.,1996,125:1-4.
8Fu G and Sun W.Surface coseismic gravity changes caused by dislocations in a3-D heterogeneous earth[J].Geophysi-cal Journal Inernational,2008,172(2):479-503.doi:10.1111/j.1365～246X.2007.03684.x.
9邓明莉,孙和平,徐建桥.GPS数据约束的昆仑Ms8.1地震断层的分段模型[J].大地测量与地球动力学,2008,(4):31-37.(Den Mingli,Sun Heping and Xu Jianqiao.A sectionalized fault model of KunlunMs8.1earthquake in constraint of GPS data[J].Journal of Geodesy and Geody-namics,2008,(4):31-37)
10谈洪波,等.汶川大地震震后重力变化和形变的黏弹分层模拟[J].地震学报,2009.31(5):491-505.(Tan Hongbo,et al.Simulation of post seismic gravity change and deformation of the Wenchuan earthquake based on viscoe-lastic layered half space model[J].Acta Seismologica Simi-ca,2009,31(5):491-505)
11Wang R,Francisco Lorenzo-Martin and Frank Roth.PS-GRN/PSCMP-a new code for caluclation co-and post-seismic deformation,geoid and gravity changes based on the viscoelastic-gravitational dislocation theory[J].Com-puters and Geosciences,2006,32:527-541.
12Chen Ji,UCSB and Gavin Hayes.NEIC,preliminary result of the May12,2008Mw7.9eastern Sichuan,China earth-quake[ED/OL].http://earthquake.usgs.gov/eqcenter/eqinthenews/us2008ryan/.200805.
13王椿墉,等.松潘-甘孜造山带地壳速度结构[J].地震学报,2003,25(3):229-241.(Wang Chunyong,et al.Crus-tal structure beneath the Songpan-Ganze orogenic belt[J].Acta Seismologica Simica,2003,25(3):229-241)
14Wang C Y,Han W B and Wu J P.Crustal stuacture bene-ach the easton margin of the Tibetan plateau and its tectonic implication[J].Journal Geophysical Research,112:B07307:1-21.
15吴建平,明跃红,王椿墉.川滇地区速度结构的区域地震波形反演研究[J].地球物理学报,2006,49(5):1369-1376.(Wu Jianping,Ming Yuehong and Wang Chunyong.Regional waveform inversion for crustal and upper mantle velocity structure below Chuandian region[J].Chinese Journal of Geophysics,2006,49(5):1369-1376)
16Talwandl M,et al.A crustal section across the Puerto Pico Trench[J].J.Geophys.Res,1959,64(10):1545-1556.
17谭凯,李杰,王琪.大地测量约束下的阿尔泰岩石圈流变结构[J].地球物理学报,2007,50(6):1713-1718.(Tan Kai,Li Jie and Wang Qi.Lithospheric rheological structure constrained by grodetic data in Altay[J].Chinese Journal of Geophysics,2007,50(6):1713-1718)
18沈正康,等.东昆仑活动断裂带大地震之间的黏弹性应力触发研究[J].地球物理学报,2003,46(6):786-795.(Shen Zhengkang,et al.Viscoelastic triggering among large earthquakes along the east Kunlun fault system[J].Chi-nese Journal of Geophysics,2003,46(6):786-795.)
19谈洪波,申重阳,李辉.断层位错引起的地表重力变化特征研究[J].大地测量与地球动力学,2008,(4):54-62.(Tan Hongbo,Shen Chongyang and Li Hui.Characteristics of sureface gravity changes caused by a fault or faults dislo-cation[J].Journal of Geodesy and Geodynamics,2008,(4):54-62)
20谈洪波,等.断层位错引起的地表形变特征[J].大地测量与地球动力学,2009,(3):42-49.(Tan Hongbo,et al.Characteristics of sureface deformation caused by fault dis-location[J].Journal of Geodesy and Geodynamics,2009,(3):42-49)
21国家重大科学工程“中国地壳运动观测网络”项目组.GPS测定的2008年汶川Ms8.0地震的同震位移场[J].中国科学(D辑):地球科学,2008,38(10):1195-1206.(Project Group of the Crust movement Observation Network of China.The coseismic deformation of the Wen-chuanMs8.0earthquake based on GPS observation[J].Science China D,2008,38(10):1195-1206)
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