An exploratory study for rapid estimation of critical source parameters of great subduction-zone earthquakes in Mexico

摘要

The rapid and reliable estimation of moment magnitude M_w, location, and size of rupture area, and radiated energy E_s of great Mexican subduction zone earthquakes is critical for a quick assessment of tsunami and/or damage potential of the event and for issuing an early tsunami alert. To accomplish this goal, the Mexican broadband seismic network needs to be supplemented by permanent GPS stations along the Pacific coast, spaced about 65 km apart or less. The data from the GPS network must be transmitted to a central location and processed in near-real time to track the position of the stations. Assuming that this can be implemented, we develop a procedure for near-real time estimation of the critical source parameters. We demonstrate the viability of the procedure by processing near-source GPS data and regional seismograms for the earthquakes of Colima-Jalisco in 1995 (M_w=8.0) and Sumatra-Andaman in 2004 (M_w=9.0-9.3). The procedure yields estimates of M_w and E_s in excellent agreement with those reported from earlier solutions. In the case of the Colima-Jalisco earthquake, the estimated location and size of rupture area agree with that mapped from aftershock locations. Presently, there are 13 permanent GPS stations along the Pacific coast of Mexico with an average spacing of ~200 km which operate in an autonomous mode. It is urgent to increase the number of stations to ≥28 thus decreasing the spacing of stations to ≤65 km. Data must be transmitted in near-real time to a central station to track the position of the stations, preferably every second.