基于曲面断层结构的2007年所罗门群岛地震同震滑动分布反演

Coseismic Slip Distribution Inversion of 2007 Solomon Islands Earthquake Based on Curved Fault Surface Structure

2007年4月1日,南太平洋岛国所罗门群岛的俯冲带地区发生了Mw 8.1级地震。利用日本宇宙航空研究开发机构(Japan Aerospace Exploration Agency, JAXA)的ALOS/PALSAR卫星雷达影像数据,采用二通差分干涉技术获得了覆盖所罗门群岛地震震区的同震地表形变场,根据四叉树方法对原始观测数据进行降采样,利用弹性半空间三角形位错模型进行断层几何参数反演;并结合断层深度剖分图的特征,构建更为合理的上下两个不同倾角连接的断层面模型,通过提出的断层剖分技术确定了最佳同震滑动分布模型。为了测试断层倾角的最佳估计,对不同断层倾角进行测试,对比合成孔径雷达干涉测量(interferometic synthetic aperture radar, InSAR)技术获取的同震观测数据和不同模型预测的InSAR干涉图,发现上下断层面倾角分别为10°和23°的模型更为合理。据此模型得到该断层同震滑动分布主要发生在距地表40 km深度范围内;最大同震滑移量为5.227 m,深度为2 km。

On 1 th April 2007, an Mw 8.1 earthquake occurred in the subduction zone of Solomon Islands. A coseismic deformation field covering the earthquake area of Solomon Islands is constructed from Japan Aerospace Exploration Agency(JAXA) ALOS/PALSAR radar images with 2-pass differential interferometry. A quadtree method is used to sample down the original observed datasets. Then, the triangle dislocation model in elastic half-space is used to invert the geometric parameters of faults. Combined with the characteristics of fault depth subdivision map, a more reasonable fault plane model connecting the upward and downward dip angles is constructed. The best coseismic slip distribution model is determined by the proposed fault subdivision technique. In order to test the best estimation of the fault dip angle, different fault dip angles are tested, the coseismic observation data obtained by interferometic synthetic aperture radar(InSAR) techndogy and the InSAR interferogram predicted by different models are compared. The tests indicate that the model is more reasonable when the dip angles of upper and lower fault planes are 10° and 23°, respectively. According to the proposed model, the coseismic slip distribution of the fault mainly occurs in the depth range of 40 km from the surface. The maximum coseismic slip is 5.227 m,and the depth is 2 km.