Regional seismotectonic characteristics from the 2007 Laos Earthquake
Date Issued
2016
Date
2016
Author(s)
Lee, Huey-Cheng
Abstract
Large earthquakes are often accompanied by noticeable surface deformations and damages. In cases where surface ruptures are visible and field investigations are feasible, detailed information about the co-seismic deformations is generally obtained in the field. However, in cases where field evidence for surface deformations are difficult to delineate either due to smaller magnitude of the events, deeper hypocenters, or inaccessibility of the earthquake area, remote sensing observations may provide information about the co-seismic deformations. This study focuses on the 16 May 2007 Mw 6.3 earthquake that occurred in northwestern Laos where information from GPS networks or seismic stations is scarce. The event also occurred in an area which is nearly inaccessible. Therefore, SAR interferometry is a feasible solution in an attempt to understand the co-seismic deformation pattern of the event. In this study, Phased Array type L-band Synthetic Aperture Radar 1.0 (PALSAR 1.0) images of Advanced Land Observing Satellite (ALOS) were used, and they were analyzed by using the Differential Synthetic Aperture Radar interferometry (D-InSAR) method on the GMTSAR software. Two co-seismic pairs were analyzed, 2007/2/17-7/5 and 2007/2/17-8/20, in order to obtain better constraint for the co-seismic deformation patterns. In this study, a model for the subsurface fault slip was constructed from the InSAR results. The earthquake may have occurred on the Mae Chang fault, one of a series of left-lateral faults in the region. The main deformation is induced by an 18 km long, ~8 km wide fault patch with the rupture top is at ~ 4 km of and a 0.7m average slip. The attitude of the fault patch is approximately (N54E, 89N). The co-seismic deformation signal is quite apparent on both interferograms. However, the signal is ~15-20 km away from the epicenter locations of most global earthquake catalogues, and the depth of the epicenter is also different by ~10 km. This implies the global catalogues may have large errors in this region due to poor local constraints. The obtained model, nonetheless, is consistent with tectonic geomorphological observations of the area and the focal mechanism from the Global CMT catalogue. Ultimately, the fault parameters suggested from the forward model were applied to calculate coulomb stress transfer, in an attempt to explain the relationship of the main shock and the distribution of the aftershocks.
Subjects
Laos
Mae Chan fault
Differential interferometric SAR
elastic half-space dislocation model
coulomb stress transfer
Ban Mone earthquake
Type
thesis
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