Measuring Co-seismic Deformation from Optical Images. A Proposition for Methodological Improvements.

从光学图像测量同震形变。改进方法的建议PI：Jean-Philippe Avouac合作者：Leprint Leprince，Remi Michel断层破裂的几何形状和同震位移的分布是突出地震破裂力学的关键数据。它是感兴趣的震源研究，因为故障的几何复杂性是已知的影响破裂动力学，因此地震辐射，因为同震滑动分布可以用来测试动态破裂模型。相反，这样的数据是必要的，以约束源的运动学，可以从地震记录，因为有各种权衡之间的几何特征的故障，分布的滑动和破裂时间的故障。 断层破裂和同震滑动的几何形状一般是从野外调查和大地测量中获得的。然而，要评估在地表沿着断层迹线测得的滑动及其沿着走向变化是否与近地表复杂性有关或是否真正反映了断层滑动在深度上的分布并不简单。大地测量数据通常过于稀疏，无法严格约束滑动分布，差分干涉合成孔径雷达通常在近断层带失败，在那里，大位移导致相关性差的图像。我们开发了一种替代方法的基础上获得的地震前后的卫星光学图像的亚像素相关性。这种技术受到一些限制，主要是由于卫星姿态的不确定性或过于近似的立体效果。拟议的方法研究意在适用于任何卫星光学系统，但在现阶段，我们侧重于分析SPOT图像，利用2002年发射的SPOT 5号卫星带来的技术进步。这些进展确实应该能够校正内部（反射镜的方向、光学系统的热变形、CCD的错位）和外部几何失真源（卫星姿态和位置）。此外，特别是在SRTM使命之后，全球覆盖的高分辨率数字高程模型的可用性使得有可能准确地说明立体效果。我们使用现有的数据兰德斯和赫克托矿地震，这两个有据可查的事件，使人们有可能测试的有效性和估计的准确性从SPOT图像测量地面位移。

Measuring Co-seismic deformation from optical images. A proposition for methodological improvements PI: Jean-Philippe AvouacCollaborators: Sebastien Leprince, Remi MichelThe geometry of fault ruptures and the distribution of coseismic displacements are key data to highlight the mechanics of seismic rupture. It is of interest in earthquake source studies because fault geometric complexities are known to influence rupture dynamics, hence seismic radiation, and because the coseismic slip distribution can be used to test dynamic rupture models. Conversely, such data are necessary to constrain the source kinematics which can be derived from seismological records, because there are various trade-offs between the geometric characteristics of the fault, the distributions of slip and rupture time on the fault. Geometry of fault ruptures and coseismic slip are generally obtained from field investigations and geodetic measurements. It is however not straightforward to assess whether the slip measured at the surface along the fault trace, and it's along strike variability, relates to near-surface complications or really reflect fault slip distribution at depth. Geodetic data are generally too sparse to constrain tightly the slip distribution and differential inSAR generally fails in the near-fault zone where large displacements result in poorly correlated images. We develop an alternative approach based on sub-pixel correlation of satellite optical images acquired before and after an earthquake. This technique suffers from some limitations mostly due to the uncertainties of the satellite attitude or to too approximate account for stereoscopic effects. The proposed methodological research is meant to apply to any satellite optical system but at this stage we focus on the analysis of SPOT images, taking advantage of the technological advances due to SPOT5 that was launched in 2002. These advances should indeed allow correcting the internal (mirror's orientation, thermal deformation of the optical system, misaligned CCD) and external sources of geometric distortion (satellite attitude and position). In addition, the availability of high resolution Digital Elevation Models with global coverage, in particular following the SRTM mission, make it possible to account accurately for stereoscopic effects. We use available data for the Landers and Hector Mine earthquakes, which are both well documented events, making it possible to test the validity and estimate the accuracy of the ground displacements measured from the SPOT images.