2004年苏门答腊地震粘滞性松弛效应对华南地区地壳水平活动的影响

摘要/Abstract

摘要： 2004年苏门答腊地震后, 不同学者根据不同观测数据(地震波、 GPS), 得到了此次地震的断层滑动模型。反演过程中使用半无限空间模型时, 无法利用远场观测数据进行约束, 势必影响远场形变的解释。基于Hoechner等使用的断层几何模型和GPS同震位移数据, 本研究利用球体位错理论反演方法反演了2004年苏门答腊地震断层滑动模型, 得到的矩震级为9.24, 最大滑移量为30.4 m, 由于考虑了曲率的效应, 该模型在远场同震位移的计算结果与GPS数据吻合较好。然后, 选取了2001—2004年和2004—2007年两期的GPS水平位移速度场, 研究2004年苏门答腊地震对华南地区地壳水平活动的影响, 从两期的GPS水平位移速度场差异可以看出地震后华南块体有向西南方向的运动趋势, 华南块体受到此次地震明显的震后影响。最后, 基于反演得到的断层模型, 利用Tanaka等提出的粘弹性球体位错理论对华南块体两期GPS水平位移速度场差异进行模拟, 得到华南块体内部粘滞性系数为2×10¹⁹ Pa·s, 当考虑地幔粘滞性松弛效应后, 两期的速度场差异的均方根值由3.2 mm减少为1.9 mm。可见在研究2004年前后中国大陆GPS水平位移速度场时, 若继续以华南块体为基准, 需考虑此次地震的地幔粘滞性松弛效应。

关键词: 2004年苏门答腊地震, GPS水平位移速度场, 粘滞性松弛效应, 华南块体

Abstract: After 2004 Sumatra earthquake, different authors obtain the fault slip models from different observation data, such as seismic waves and GPS data. However, the inversion of the co-seismic model from observed co-seismic displacements can not use far-field data as the constraint while adopting half-space medium, and then the inverted model is difficult in explaining far-field data. In this paper, based on the fault geometry model and GPS data provided by Hoechner et al., we inverted the slip model of 2004 Sumatra earthquake by using the inversion algorithm based on spherical dislocation theory. We found that the moment magnitude of the fault model is 9.24, and the maximum slip reach 30.4 m, calculated co-seismic displacements of our fault model agree well with far-field GPS observations after considering the effect of earth curvature. Then, in order to study the effect of 2004 Sumatra earthquake on crustal movement in Southern China, we select two periods of GPS velocity fields (2001—2004 and 2004—2007). From the differences of them, we can see Southern China block has a significant trend of southwest movement after this earthquake, which implied South China block has been affected by the viscoelastic relaxation of this earthquake significantly. Using the viscoelastic dislocation theory of Tanaka, we simulated the differences of two periods of GPS velocity fields in south China block based on our fault model. We found that the optimal viscosity of this area is about 2×10¹⁹ Pa·s when taking the effect of viscoelastic relaxation into account, the RMS (root mean square) of the differences reduced from 3.2 mm to 1.9 mm. In studying crust deformation before and after the 2004 Sumatra earthquake, the viscoelastic relaxation of this earthquake should be considered when based on south China block continuously.

Key words: Viscoelastic relaxation, The 2004 Sumatra earthquake, GPS horizontal velocity fields, South China block

中图分类号:

P315.7

刘泰, 付广裕, 邹镇宇. 2004年苏门答腊地震粘滞性松弛效应对华南地区地壳水平活动的影响[J]. 地震, 2019, 39(2): 37-45.

LIU Tai, FU Guang-yu, ZOU Zhen-yu. Effect of Viscoelastic Relaxation following the 2004 Sumatra Earthquake on Horizontal Crustal Movement in South China[J]. EARTHQUAKE, 2019, 39(2): 37-45.

参考文献

[1] Ammon C J, Ji C, Thio H K, et al. Rupture Process of the 2004 Sumatra-Andaman Earthquake[J]. Science, 2005, 308(5725): 1133.
[2] Banerjee P, Pollitz F F, Bürgmann R. The Size and Duration of the Sumatra-Andaman Earthquake from Far-Field Static Offsets[J]. Science, 2005, 308(5729): 1769-1772.
[3] Chen J L, Wilson C R, Tapley B D, et al. GRACE detects coseismic and postseismic deformation from the Sumatra—Andaman earthquake[J]. Geophys Res Lett, 2007, 34(13): 173-180.
[4] Lay T, Kanamori H, Ammon C J, et al. The great Sumatra-Andaman earthquake of 26 December 2004[J]. Science, 2005, 308(5725): 1127.
[5] Kreemer C, Blewitt G, Hammond W C, et al. Global deformation from the great 2004 Sumatra-Andaman Earthquake observed by GPS: Implications for rupture process and global reference frame[J]. Earth Planets Space, 2006, 58(2): 141-148.
[6] Han S C, Shum C K, Bevis M, et al. Crustal Dilatation Observed by GRACE after the 2004 Sumatra-Andaman Earthquake[J]. Science, 2006, 313(5787): 658.
[7] Hoechner A, Babeyko A Y, Sobolev S V. Enhanced GPS inversion technique applied to the 2004 Sumatra earthquake and tsunami[J]. Geophys Res Lett, 2008, 35(8): 135-157.
[8] Banerjee P, Pollitz F, Nagarajan B, et al. Coseismic Slip Distributions of the 26 December 2004 Sumatra-Andaman and 28 March 2005 Nias Earthquakes from GPS Static Offsets[J]. Bull Seismol Soc Am, 2007, 97(1): S86-S102.
[9] Rhie J, Dreger D, Burgmann R, et al. Slip of the 2004 Sumatra-Andaman Earthquake from Joint Inversion of Long-Period Global Seismic Waveforms and GPS Static Offsets[J]. Bull Seismol Soc Am, 2007, 97(1): S115-S127.
[10] 瞿武林, 张贝, 黄禄渊, 等. 2004年苏门答腊地震的几个断层滑动模型的全球同震位移对比[J]. 地球物理学报, 2016, 59(8): 2843-2858.
[11] Chlieh M, Avouac J P, Hjorleifsdottir V, et al. Coseismic Slip and Afterslip of the Great M_W9.15 Sumatra—Andaman Earthquake of 2004[J]. Bull Seismol Soc Am, 2007, 97(1): S152-S173.
[12] Fu G Y, Sun W K. Global co-seismic displacements caused by the 2004 Sumatra-Andaman earthquake (M_W9.1)[J]. Earth Planets Space, 2006, 58(2): 149-152.
[13] Sun W K, Okubo S, Fu G Y, et al. General formulations of global co-seismic deformations caused by an arbitrary dislocation in a spherically symmetric earth model—applicable to deformed earth surface and space-fixed point[J]. Geophys J Int, 2009, 177(3): 817-833.
[14] 付广裕, 孙文科. 2004年苏门答腊地震引起的远场形变[J]. 大地测量与地球动力学, 2008, 28(2): 1-7.
[15] 顾国华. 印尼8.7级大震前后GPS观测站的地壳水平与垂直位移时间序列结果[J]. 地震, 2006, 26(2): 19-28.
[16] 牛安福, 吉平, 高福旺, 等. 印尼强地震引起的同震形变波[J]. 地震, 2006, 26(1): 131-137.
[17] 杨国华, 江在森, 王敏, 等. 印尼地震对我国川滇地区地壳水平活动的影响[J]. 大地测量与地球动力学, 2006, 26(1): 9-14.
[18] 江在森, 方颖, 武艳强, 等. 汶川8.0级地震前区域地壳运动与变形动态过程[J]. 地球物理学报, 2009, 52(2): 505-518.
[19] 邹镇宇, 江在森, 武艳强, 等. 基于GPS速度场变化结果研究汶川地震前后南北地震带地壳运动动态特征[J]. 地球物理学报, 2015, 58(5): 1597-1609.
[20] Zhou X, Cambiotti G, Sun W K, et al. The coseismic slip distribution of a shallow subduction fault constrained by prior information: The example of 2011 Tohoku (M_W9.0) megathrust earthquake[J]. Geophys J Int, 2014, 199(2): 981-995.
[21] Tanaka T, Okuno J, Okubo S. A new method for the computation of global viscoelastic post-seismic deformation in a realistic earth model (I)—vertical displacement and gravity variation[J]. Geophys J Int, 2006, 164(2): 273-289.
[22] Tanaka T, Okuno J, Okubo S. A new method for the computation of global viscoelastic post-seismic deformation in a realistic earth model (II)—Horizontal displacement[J]. Geophys J Int, 2007, 170(3): 1031-1052.
[23] Dziewonski A M, Anderson D L. Preliminary reference Earth model[J]. Phys. Earth Planet Inter, 1981, 25: 297-356.
[24] Yabuki T, Matsu’ura M. Geodetic data inversion using a Bayesian information criterion for spatial distribution of fault slip[J]. Geophys J Int, 2007, 109(2): 363-375.
[25] Fu G Y, Sun W K. Surface coseismic gravity changes caused by dislocations in a 3-D heterogeneous earth[J]. Geophys J Int, 2008, 172(2): 479-503.
[26] Fu G Y, Sun W K, Fukuda Y, et al. Coseismic displacements caused by point disocations in a three dimensional heterogeneous, spherically earth model[J]. Geophys J Int, 2010, 183(2): 706-726.
[27] 黄立人, 符养, 段五杏, 等. 由GPS观测结果推断中国大陆活动构造边界[J]. 地球物理学报, 2003, 46(5): 609-615.
[28] Gao S H, Fu G Y, Liu T, et al. A new code for calculating post-seismic displacements as well as Geoid and gravity changes on a layered visco-elastic spherical earth[J]. Pure and Applied Geophysics, 2017, 174: 1167-1180.
[29] 张国庆, 付广裕, 周新, 等. 利用震后黏弹性位错理论研究苏门答腊地震(M_W9.3)的震后重力变化[J]. 地球物理学报, 2015, 58(5): 1654-1665.
[30] 刘泰, 付广裕, 周新, 等. 2011年日本M_W9.0地震震后形变机制与震源区总体构造特征[J]. 地球物理学报, 2017(9): 3406-3417.