【摘要】 本文主要以GPS、精密水准观测和卫星SAR遥感图像分析2008年汶川特大地震同震位移特征.GPS数据包括:(1)四川盆地和川西高原地区各类国家等级GPS网点复测;(2)沿破裂带国家天文大地网GPS复测.前者推算的同震位移测定精度优于2cm,后者6～8cm.SAR遥感资料包括:(1)ALOS卫星升轨相位干涉图像,精度优于8cm;(2)ALOS和ENVISAT卫星影像合成的三维位移图,精度优于0.5m.同震位移场显示,断层下盘(四川盆地)变形总体呈扇形集中指向震中,断层上盘(龙门山)变形总体上呈逆时针旋转态势,最大的实测水平位移5.5m.汶川、理县、茂县等地测站位移指向破裂带方向,而平武、青川等地测站逐渐转变为平行,乃至远离破裂带方向,与汶川地震逆冲兼走滑的破裂特征一致.断层上盘大幅隆升,下盘靠近断层的区域以下沉为主,远场表现为幅度很小的隆升,垂直升降区域间,有一条与龙泉山断裂带平行的升降过渡带,调节龙泉断层的应力状态.用实测变形场检验多个地震波破裂模型表明,近场(距离断层50km)模型形变准确度可达40～50cm,远场精度优于5cm.更多还原

【Abstract】 We analyze the coseismic surface displacement field produced by the 2008 Wenchuan(Mw7.9) earthquake using various geodetic data including GPS measurements,SAR images,in combination with other data such as leveling,gravity and near-field strong motion records.The GPS data come from resurveys on several high-precision GPS networks and a triangulation network.Coseismic displacements at GPS sites are estimated to within 2 cm and triangulation points within 6~8 cm in precision.Two kinds of SAR data are used in the paper,including light-of-sight SAR interferograms with a precision better than 8 cm and three-dimensional surface displacements using SAR sub-pixel correlation to within 0.5 meters in precision.The coseismic displacements constructed by various types of data are characterized by the deformation pattern of a coherent motion of the footwall and anticlockwise rotation of the hanging wall.Site horizontal offsets in the Sichuan Basin are found to direct toward to the epicenter.Otherwise,the GPS sites in Wenchuan,Lixian and Maoxian along the Longmen Shan moved normal to the surface rupture as well.However,the GPS sites in Pingwu and Qingchuan were displaced initially parallel to and finally away from the rupture zone,in consistent with the rupture mechanism of thrusting-slip and right lateral strike-slip faulting.Whereas the hanging wall was uplifted significantly,the subsidence in the footwall was localized near the rupture zone.The far-field uplift in the Sichuan Basin is found with a hinge line(separating uplift from subsidence) parallel to the Longquan Shan fault.Finally,we test seismological slip models by fitting the coseismic displacement field,from which a mean misfit of 40~50 cm is derived for the GPS sites within 50 km to the rupture zone,and 5 cm for ones in the far-field.更多还原