Coseismic displacements and Mw estimation of the El Mayor-Cucapah earthquake, Mexico, from GPS source spectra

Abstract

El Mayor-Cucapah earthquake Mw 7.2 on April 4, 2010, occurred on Mexicali Valley near the international border between California, USA and Baja California, Mexico. The objective of this paper was to examine GPS as a complementary tool for seismic studies and to estimate earthquake seismic moment and Mw. For this purpose the capabilities of high-rate GPS (5 Hz) data located in the northern part of the seismic rupture has been explored to obtain the kinematic coseismic displacements. GPS data were processed using Precise Point Positioning method with GIPSY-OASIS II software, then applying the Fast Fourier Transform to the position time series, spectral parameters, seismic moment and Mw were calculated. A good agreement was found in terms of signal correlation of the GPS displacements, by comparing strong-motion seismic records integrated to displacement, using filtering parameters for two sets of instruments. Kinematic GPS displacement spectra clearly shows the low frequency displacement spectral level (~0.2 Hz) when compared with double integration of strong-motion data. It is easy to calculate the static coseismic motion from GPS data, however it is very difficult to calculate it from strong-motion data. A simple earthquake source model is suitable for the GPS dataset used in this work, estimated on Mw=7.19±0.13, was in according with Mw 7.2 obtained in other studies of the El Mayor-Cucapah earthquake.