西藏改则地震升降轨同震形变场特征分析与破裂模式

Coseismic Deformation Field Characteristics and Rupture Model for Gaize Earthquakes in Tibet

通过升降轨ASAR数据的获取与差分干涉处理,获取了西藏改则地震的双视线向同震形变场信息。对升降轨同震形变场的特征分析表明,改则地震主、余震均表现为典型的正断裂破裂模式,并先后形成了东、西两条规模不同的走向NE、倾向NW的正断层破裂带(可能未出露地表),以及西北盘的东、西两个沉降形变中心。从干涉条纹的切割关系判断,东沉降形变中心可能受2008年1月9日Ms 6.9级主震的控制,西沉降形变中心可能受2008年1月16日Ms 6.0级余震的控制。Ms 6.9级主震形成东南盘隆升与西北盘沉降的总体格局;Ms 6.0级余震使西北盘余震震中及以西部位进一步沉降,造成西沉降中心沉降形变量大于东沉降中心。升降轨同震形变场的获取为进一步的震源参数模拟与三维形变场解算提供了更好的约束条件与信息。

Through differential interferometry of ascending and descending orbit ASAR data, the authors obtained the Double - LOS coseismic deformation fields of Gaize earthquake in Tibet. A characteristic analysis of coseismie deformation field indicates that the Ms 6.9 mainshock and Ms 6.0 aftershock both showed the typical model of normal fault and successively gave birth to east and west normal faulted fracture zones with different sizes probably at depth, trending NE and dipping NW, with the formation of east and west subsiding centers on the northwest plate. From the incising of interferometric stripes, it can be judged that the east and west subsiding centers are controlled respectively by January 9, 2008 Ms 6.9 mainshock and January 16, 2008 Ms 6.0 aftershock. The Ms 6.9 mainshock shaped the basic pattern of subsiding in the northwest plate and uplifting in the southeast plate. And the Ms 6.0 aftershock caused the further subsidence of the epicenter and the western part of the northwest plate; therefore, the subsidence value of the west subsiding center is larger than that of the east subsiding center. The obtaining of coseismic deformation fields of ascending - descending orbits has provided the better restriction and information for further hypocenter mechanism simulation and 3 - D deformation field calculation.