顾及地形与地壳结构的破裂模型反演研究—以2008年汶川地震为例

The 2008 Mw7.9 Wenchuan earthquake that occurred in the Longmen Shan fault zone manifested complicated characteristics. Constrained by observation data with high resolution and high precision acquired by geodetic measurements like GPS and InSAR, various rupture models have been inferred. Although they reveal some common features, controversies still exist between them, such as the amount and depth of maximum slip, slip on the deep decollement. All published rupture models utilize elastic half-space dislocation theory which neglects steep topography and significant lateral difference across the Longmen Shan, thus perhaps involve significant error. This project proposes to employ 3D FEM to simulate topography and lateral heterogeneity in crust, so as to analysis the effects of topography and crustal heterogeneity on co-seismic surface displacement field, and invert for detailed characteristics of the rupture model more accurately, including whether significant slip existed on the low-dip decollement at 20km or so depth, and whether shallow slip deficit existed in the Wenchuan earthquake. This project will help to complement methodology of coseismic rupture model inversion in the Longmen Shan, and can provide new hints for research on the tectonic deformation mechanism and seismogenic process in the Longmen Shan.

2008年发生在龙门山断裂带的Mw7.9级汶川地震表现出复杂的破裂特征。以GPS与InSAR等大地测量技术获取的高分辨率高精度的地表同震位移场为约束，国内外学者相继反演了同震破裂模型，虽然这些模型都成功揭示了一些共同特征，但是在最大滑动量和深部滑脱面的滑动分布等方面仍存在较大争议。已有的破裂模型都采用了弹性半无限空间位错模型，几乎都忽略了龙门山造山带剧烈的地形起伏及其两侧地壳结构显著的横向差异，因此带来了误差。本项目拟采用顾及地形起伏和地壳结构横向差异的三维有限元方法，定量研究地形效应和地壳非均匀性对同震形变场的扰动，以便更准确地反演同震破裂的精细特征，厘清龙门山地下20km左右深处低倾角滑脱面上是否存在明显的同震滑动，汶川地震是否存在浅部滑动亏损等关键问题。本研究将有助于完善龙门山地区同震破裂模型研究的理论方法，也可为研究龙门山地区的构造变形机制和孕震过程提供参考。

2008年发生在龙门山断裂带的Mw7.9级汶川地震表现出复杂的破裂特征。以GPS与InSAR等大地测量技术获取的高分辨率高精度的地表同震位移场为约束，国内外学者相继反演了同震破裂模型，虽然这些模型都成功揭示了一些共同特征，但是在最大滑动量和深部滑脱面的滑动分布等方面仍存在较大争议。已有的破裂模型都采用了弹性半无限空间位错模型，几乎都忽略了龙门山造山带剧烈的地形起伏及其两侧地壳结构显著的横向差异，因此带来了误差。本项目拟采用顾及地形起伏和地壳结构横向差异的三维有限元方法，定量研究地形效应和地壳非均匀性对同震形变场的扰动，以便更准确地反演同震破裂的精细特征，厘清龙门山地下20km左右深处低倾角滑脱面上是否存在明显的同震滑动，汶川地震是否存在浅部滑动亏损等关键问题。本研究将有助于完善龙门山地区同震破裂模型研究的理论方法，也可为研究龙门山地区的构造变形机制和孕震过程提供参考。