Remarkable ground uplift and reverse fault ruptures for the 2013 Bohol earthquake (Mw 7.1), Philippines, revealed by SAR pixel offset analysis
Abstract
By applying a pixel offset analysis using RADARSAT-2 SAR data to an inland crustal earthquake that occurred on Bohol Island, Philippines on 15 October 2013, we succeeded in mapping a ground displacement associated with the earthquake. The most concentrated crustal deformation with ground displacement exceeding 1 m is located in the northwest part of the island. The crustal deformation is zonally distributed and extends a length of approximately 50 km in the ENE-WSW direction. The ground in the mountainous area moved toward the satellite, while the ground in the northern coastal zone moved away from the satellite. A clear displacement discontinuity with a length of about 5 km, probably corresponding to earthquake surface faults, can be identified in the northeastern region. Our fault model consisting of two rectangular planes shows nearly pure reverse-fault motion on south-southeast-dipping planes with moderate dip angles. A local rupture occurs in the northeast at shallow depths and produces surface ruptures. By applying an additive color process using SAR amplitude images, significant changes in backscatter intensity were detected along the coast from Maribojoc to Loon; these changes suggest that the seafloor uplifted and the shoreline resultantly shifted seaward. The area showing the shoreline change is in good spatial agreement with the locally distributed large ground uplift predicted from our fault model. We identified a good correlation between the ground upheaval produced by the reverse-fault motion and elevation in the mountainous area, which is consistent with the idea that repeated historical reverse faulting developed the present-day topography.
- Publication:
-
Geoscience Letters
- Pub Date:
- December 2014
- DOI:
- 10.1186/2196-4092-1-7
- Bibcode:
- 2014GSL.....1....7K
- Keywords:
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- SAR;
- Pixel offset;
- Additive color process;
- Bohol earthquake;
- Crustal deformation;
- Earthquake surface fault;
- Shoreline changes;
- Fault model