汶川地震SAR形变场电离层影响校正与断层地表破裂线自动提取

针对汶川地震PALSAR观测的方位向形变场存在严重电离层影响,导致准确提取断层地表破裂线困难的问题,本文使用一种基于频率域的电离层影响校正方法,从方位向形变场频域数据中提取电离层信号对应的频域信息,通过建模获得空间域电离层信号,并与原始形变场进行差分运算完成电离层影响的校正,还原了汶川地震断层近场沿SAR方位向的真实地表形变场.以校正后的方位向形变场作为数据源,采用非极大值抑制二维梯度算法,准确提取汶川地震北川—映秀断层和灌县—江油断层的地表破裂线.为验证提取结果的可靠性,引入野外地质调查数据进行对比分析,定量计算两条破裂线间的距离差异,结果表明基于SAR形变场自动提取的断层破裂线与野外地质调查数据具有较高的一致性,利用SAR观测形变场可作为调查地震断层地表破裂的重要补充手段.

SAR ionosphere signal correction for deformation field of Wenchuan earthquake and extraction of fault surface rupture trace

In order to mitigate the negative effect of ionosphere signal on SAR observed azimuth deformation and extract fault rupture trace for the Wenchuan earthquake, we model the ionosphere signal using the frequency component recognized in the frequency domain of original SAR azimuth deformation field. The accurate coseismic azimuth deformation is derived after removing the ionosphere component from the original observations. We extract the Yingxiu-Beichuan and Pengguan faults surface rupture traces from the corrected SAR azimuth deformation field based on the proposed method that restricts the non-peak deformation gradient along the fault. The field investigation data are introduced for validating the accuracy of extracted fault surface rupture traces. The comparison results show that two datasets have high consistence with each other. The corrected SAR deformation field could be a significant supplement for the investigation of fault surface rupture traces.