基于向-位错模型的同震断层运动反演——以龙门山断层为例  

The Co-seismic Slip and Rotation of the Longmenshan Fault Based on Disclination-dislocation Model Inversed from GPS Data

作　　者：张永志[1] 张本平[1] 王卫东[1] 王帅[1] 

机构地区：[1]长安大学地质工程与测绘学院,陕西西安710054

出　　处：《地球学报》2016年第3期294-300,共7页Acta Geoscientica Sinica

基　　金：国家自然科学基金(编号:41374028;41304013);长安大学中央高校基本科研业务费专项资金(编号:CHD2012TD004);中国地质调查局国土资源大调查项目(编号:1212010914015)联合资助

摘　　要：针对2008年发生汶川8.0级地震的龙门山断裂铲状分布和断层倾滑面倾角随深度变化特点,本文提出了描述龙门山断层同震运动(滑动和转动)的向-位错组合模型。结合地质数据采用回归分析法模拟了断层在倾滑过程中断层面倾滑方向随断层深度的分布特征;利用四川地区实测的三维同震GPS数据结合粒子群算法,采用向-位错模型对汶川地震断层面的同震滑动和随深度的方向转动(向错)进行了反演计算,并将反演的同震滑动区域和大小分布与USGS断层滑动结果进行了对比分析。理论分析和模型计算表明:(1)在汶川8.0级地震发生过程中,由于断层的倾滑面为倾角由上向下逐渐变小的曲面,断层面上的倾滑方向也随断层面法线的改变而变化,即断层面在破裂过程中存在明显的向错现象;(2)龙门山发震断层的倾滑面转动方向随深度变化为一开口向上的抛物线,震中位于转动角变化的极值点附近;(3)在断层几何参数相同的情况下,采用向-位错组合模型反演的同震滑动区域和USGS的滑动区域具有较好的一致性,滑动大小的差异主要由断层模型之间的差异、测量误差等多种因素引起。In order to describe the listric Longmenshan fault （the dip angle of the fault plane changed with depth） where Ms8.0 Wenchuan earthquake occurred in 2008, the authors put forward the fault model combining disclination with dislocation. The dip angle and the disclination of the Longmenshan fault that changed with depth were calculated from geological data by regression analysis. At the same time, according to the disclination-dislocation model, the co-seismic slip and rotation at different depths of the Longmenshan fault due to Wenchuan Ms8.0 earthquake were inversed by PSO algorithm from GPS data. A comparison was made between slip area and magnitude calculated in this study and the data offered by USGS. Based on theoretical analysis and model computation, some conclusions have been reached： （1） Because the dip angle of the Longmenshan fault plane became smaller with the depth, and the slip direction of fault plane changed during the rapture process of the shock, the disclination of the fault took place obviously during the Wenchuan Ms8.0 earthquake; （2） The distribution of disclination along depth approximately obeyed the upward parabola, and the earthquake occurred near the curve＇s extreme point; （3） Under the same fault parameters, the total slip on fault plane inversed by PSO from GPS data has a similar spatial distribution to but different magnitudes from the data given by USGS, and the difference of magnitude may be related to such factors as the co-seismic disclination components and measurement errors.

关 键 词：向-位错模型 同震GPS数据 粒子群算法 反演 断层运动 

分 类 号：P315.33[天文地球—地震学] P542.3[天文地球—固体地球物理学]