汶川地震GPS形变约束的破裂分段特征及滑移

为了解2008年汶川地震破裂分段特征及滑移，采用弹性位错模型和模拟退火算法，数值模拟汶川震区密集的GPS同震形变。结果表明，GPS同震形变场至少需要用铲状的映秀-北川五断裂加上灌县－江油断裂来模拟，该模型对GPS数据的符合程度与汶川地震滑动分布模型相当，基本反映了汶川地震破裂特征。映秀－北川断裂总长255~294km。南段以逆冲为主，分上下两层，最深达30km。中段右旋走滑和逆冲都很大，而北段以右旋走滑为主。映秀段地震周期最短为3000年。破裂上层深度14km可能是龙门山中央断裂的闭锁深度。汶川地震可能源于相邻块体的相对运动和挤压、深部滑脱或浅部闭锁，在薄弱构造处首先爆发地震。

Rupture Characteristic and Slip Constrained by GPS Coseismic Deformation Induced by the Wenchuan Earthquake

In order to study the Wenchuan Mw7.9 earthquake rupture characteristic and slip,we model the dense GPS coseismic deformation using simulated annealing algorithm based on uniform elastic half-space model. We find the GPS coseismic deformation can be modeled well using five rupture segments from Yingxiu to Beichuan combined with one rupture segment from Guanxian to Jiangyou, and the result is better than one which is inferred from seismic wave data or InSAR data. The rupture along Yingxiu-Beichuan is 255-294 km length. The south segment can be separated into upper and lower two layers, and is 30 km depth characterized by dip-slip reverse faulting. The mid-segment characterized by right 1ateral oblique faulting and dip-slip reverse faulting, and the north segment characterized by right 1ateral oblique faulting. The shortest earthquake recurrence interval is 3000-year at Yingxiu segment. The rupture depth 14 km of upper layer is probably the locking depth along the Longmenshan fault. The Wenchuan earthquake maybe arised from block relatively moving and extrusion, sliping at depth or locking at shallow,and break out at weakness.