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.

Coseismic Ground Rupture of the 15 October 2013 Magnitude (MW) 7.2 Bohol Earthquake, Bohol Island, Central Philippines

“…Our field investigation shortly after the 2013 earthquake and mapping from 1‐m resolution LiDAR DEM (Felix, ; Felix et al, ) made it possible to identify several other ground rupture traces on the southeastern portion of the island, further away from the more conspicuous surface rupture in the northeast. This corroborates observations from InSAR analysis by Kobayashi (), which shows a 50‐km‐long east‐northeast trending deformation zone with ground uplift of up to more than 1 m.…”

“…Tectonics other ground rupture traces on the southeastern portion of the island, further away from the more conspicuous surface rupture in the northeast. This corroborates observations from InSAR analysis by Kobayashi (2014), which shows a 50-km-long east-northeast trending deformation zone with ground uplift of up to more than 1 m.…”

A review of terrestrial radar interferometry for measuring surface change in the geosciences

“…For satellite SAR time series, intensity information alone can be used to calculate feature offsets that result from surface deformations, which has been documented by several studies (Huang and Li, 2011;Nagler et al, 2012;Kobayashi, 2014). For satellite SAR time series, intensity information alone can be used to calculate feature offsets that result from surface deformations, which has been documented by several studies (Huang and Li, 2011;Nagler et al, 2012;Kobayashi, 2014).…”

“…The application of both types of techniques is currently state-of-the art in many fields (Dunnicliff, 1993;Thut, 2009). Related applications were presented by Huang and Li (2011) and Nagler et al (2012) where flow lengths and patterns of glaciers were measured, and by Kobayashi (2014) who quantified post-earthquake crustal deformation. This method has been applied to quantify surface deformation in response to: tectonic shortening and regional subsidence (Massonnet et al, 1993;Hooper et al, 2012;Tosi et al, 2013), volcanic doming (Lundgren et al, 2004;Jung et al, 2011), landslides and rockslides (Catani et al, 2005;Strozzi et al, 2005;Rott and Nagler, 2006;Calabro et al, 2010;Herrera et al, 2011) and glacial and peri-glacial processes (Mohr et al, 1998;Delaloye et al, 2007;Magnusson et al, 2007;Kääb, 2008).…”

“…In cases where large areas are affected by homogeneous shifts in the surface, non-interferometric image analyses such as intensity-or feature-tracking algorithms may be applied to calculate the lengths and direction of the displacements. Related applications were presented by Huang and Li (2011) and Nagler et al (2012) where flow lengths and patterns of glaciers were measured, and by Kobayashi (2014) who quantified post-earthquake crustal deformation. Alternatively, limitations of the single techniques can be reduced through the combination of different surveying technologies (Kääb, 2008;Roering et al, 2009).…”