基于ASAR影像亚像元匹配技术研究汶川地震同震形变特征

Coseismic displacement analysis of the 2008 Wenchuan earthquake based on sub-pixel matching using ASAR images

利用汶川地震前后的ENVISAT ASAR影像,采用交叉相关性方法对影像进行了亚像元级别的配准,获取了沿卫星斜距向和方位向上的同震形变图,对地震地表破裂带的分布及断层运动特性进行了分析.提取了沿北川—映秀断裂分布的长230 km的地震地表破裂带,以及沿灌县—江油断裂分布的长约65 km的地震地表破裂带.通过对两个方向地表位移进行分析可知,北川—映秀断裂带的南段以逆冲运动为主导,兼一定的右行走滑运动,向北逐渐转为右行走滑为主的运动特征,并具有一定的逆冲特性;而灌县—江油断裂主要以逆冲作用为主.研究表明,该方法与InSAR、GPS技术以及野外调查的研究结果基本一致,并从另一个角度揭示了汶川地震地表破裂带的分布特征和断层运动性质,因此可以同其它方法一起作为地震同震形变场研究的有效技术手段.

ENVISAT ASAR images were used to measure coseismic displacement field of the 2008 Wenchuan earthquake in both the line of sight and azimuth directions of the sensor.Cross-correlation method was utilized to match the images before and after the earthquake in precision of sub-pixel level.And then we analyzed surface rupture geometry and motion feature of the Longmenshan fault zone.Two large scale surface ruptures are identified on the map.One is distributed along Beichuan——Yingxiu fault,about 230 km long.And the other is distributed along Guanxian——Jiangyou fault,about 65 km long.The two deformation maps also illuminate motion characteristc of the Longmenshan fault zone.The southwest part of Beichuan——Yingxiu fault is characterized by thrust-dominant motion,while the northeast part shows right-lateral slip.The Guanxian——Jiangyou fault is a thrust-dominant fault.This result is in well accordance with InSAR/GPS and field surveys and reveals coseismic displacement features of the Wenchuan earthquake from a new sight.So sub-pixel matching method,together with other methods,will serve as an effective technique in the research of surface ruptures and fault activity.