← Back to Sessions

Modeling and Simulation of Response Spectra at Regional Distances for the September 19, 2022 (Mw 7.7) and September 22, 2022 (Mw 6.9) Michoacan, Mexico Earthquakes and Comparison With Observed Data

Description: 

On September 19, 2022 a 7.7 Mw subduction earthquake occurred in the coast of Michoacan, Mexico, along the tectonic interface between the Cocos and the North American plates. Various broadband and accelerometric seismological stations of the National Seismological Service of Mexico (SSN), recorded the ground motions produced by this earthquake. The closest station that recorded these motions was the MMIG-Maruata, observing maximum accelerations of Ans=1.09g in the North-South component and Aew=0.72g in the East-West component. The vertical acceleration observed had a maximum value of Az=0.68g. The largest aftershock occurred on September 22, 2022 with a magnitude 6.9 Mw and depth of 12.0km, located 23.0km SE from the mainshock. The closest station with available data for this earthquake was Zihuatanejo (ZIIG) showing a maximum acceleration of Ans=0.56g in the North-South component.
In this work, we generated different theoretical ground motion scenarios and compared them with observations. To do this, on the one hand we performed a simulation of these two earthquakes by modelling the rupture of both seismic events, taking into account their locations, focal mechanisms and assuming different GMPEs for the interplate subduction tectonic regime; then we obtained the corresponding theoretical response spectra. On the other hand, an analysis of the seismic recordings obtained by the seismological stations was carried out to obtain the corresponding response spectra from the recorded accelerograms. After this, we compared the theoretical spectra obtained from the simulations of the different proposed scenarios with the observed spectra. From the modeled scenarios, our results show that depending on the GMPE assumed, spectral amplitudes are mostly underestimated at close distances from the source, and overestimated beyond a given distance to the source. An important observation results for the different central Mexico recording sites, where in most cases, the observation at large periods are allways underestimated by models. From these results, different explanations for the observed regional amplifications are proposed

Session: Numerical Modeling in Seismology: Developments and Applications

Type: Oral

Date: 4/20/2023

Presentation Time: 05:00 PM (local time)

Presenting Author: María Belén Benito Oterino

Student Presenter: Yes

Invited Presentation: 

Authors