Surface deformation of the Mw 6.4 and Mw 7.1 Ridgecrest earthquakes measured from subpixel correlation of Copernicus Sentinel-2 optical images

Saif Aati, & Jean-Philippe Avouac

Published August 13, 2019, SCEC Contribution #9503, 2019 SCEC Annual Meeting Poster #232

We use sub-pixel correlation of optical images to measure surface deformation in the epicentral area of the Mw6.4 Searles Valley and the Mw 7.1 Ridgecrest earthquakes, which struck California on July 4, and 5 respectively. This study provides an opportunity to test the geometric quality of the Copernicus Sentinel-2 data distributed by the European Space Agency. The good spatial resolution (GSD of 10m), the short revisit time of ~5 days and the wide swath width (~290km) of Copernicus Sentinel-2 images make them particular adequate to study surface changes due in particular to earthquakes. We used images acquired before and after the two Ridgecrest earthquakes. No Sentinel image was acquired in the 30 hours between the two shocks so our measurement reflect the deformation that has resulted from both of them. We processed the images with COSI-Corr, using the phase correlator which can in principle yield a subpixel accuracy that can reach 1/50 pixel. The measurements clearly show the surface ruptures due to the two earthquakes and allow measuring surface slip with an accuracy of ~20cm. The measurements also show geometric artifacts due to the satellite jitter, CCD misalignment and orthrectification errors. These artifacts are present because the data distributed by EAS have been already orthorectified the images and the COSI-Corr technique to correct for these effects cannot be applied directly. We will discuss and test alternative strategies to mitigate these effects.

Key Words
Image correlation, Cosi-Corr, Surface deformation, Sentinel-2

Citation
Aati, S., & Avouac, J. (2019, 08). Surface deformation of the Mw 6.4 and Mw 7.1 Ridgecrest earthquakes measured from subpixel correlation of Copernicus Sentinel-2 optical images . Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Ridgecrest Earthquakes