Three-dimensional rupture patterns of the 2019 Ridgecrest, California earthquake sequence revealed by correlation of high-resolution WorldView optical satellite imagery

Robert Zinke, James Hollingsworth, Gilles Peltzer, Eric J. Fielding, James F. Dolan, Chris Milliner, Yousef Bozorgnia, & Alexandra Sarmiento

Published August 14, 2019, SCEC Contribution #9557, 2019 SCEC Annual Meeting Poster #226

We measure horizontal and vertical surface deformation from the 4 July 2019 MW 6.4 and 5 July 2019 MW 7.1 earthquake sequence near Ridgecrest, CA using correlation of high-resolution WorldView optical satellite imagery. Specifically, we correlated pre- and post-earthquake imagery (collected 31 July 2016 and 14 July 2019) acquired at oblique (20–30°) look angles. We used subpixel correlation methods (Ames Stereo Pipeline and COSI-Corr) to determine disparity maps between the images, then applied a simple ray tracing approach to directly triangulate horizontal and vertical coseismic displacements at 16 m intervals at the ground surface. This methodology is advantageous in that it does not require construction of multiple DEMs, or resampling of a pre-earthquake DEM for vertical differencing. Thus, the resulting deformation maps document both broad-scale and fine-scale surface rupture patterns. Coseismic displacement is evident along fault strands ranging in length from multiple km to 100’s m, and expressed by multiple meters to 10’s cm of offset. Surface rupture patterns are structurally complex, commonly consisting of multiple sub-parallel faults strands. Deformation maps show numerous high-strain or discrete shears (primary faults) embedded within broader, lower-strain shear zones comprising subsidiary fault strands and distributed shearing spanning 100’s m to km from the primary fault traces. Our high-resolution 3D results reveal systematic relationships between horizontal and vertical fault offsets controlled by local fault kinematics. Instances include > 1 m of down-dropping of the ground surface across a several km2 area within a large fault stepover, and more localized down-dropping along sub-km-scale releasing bends on high-slip fault segments. Overall, our results agree with InSAR and SAR pixel offset results, and these methods constitute a mutually complementary data set. Comparisons of our deformation maps with field data will allow for further quantification of the nature and distribution of surface faulting patterns.

Key Words
Ridgecrest earthquake, optical image correlation, structural geodesy

Citation
Zinke, R., Hollingsworth, J., Peltzer, G., Fielding, E. J., Dolan, J. F., Milliner, C., Bozorgnia, Y., & Sarmiento, A. (2019, 08). Three-dimensional rupture patterns of the 2019 Ridgecrest, California earthquake sequence revealed by correlation of high-resolution WorldView optical satellite imagery . Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Ridgecrest Earthquakes