Numerical Simulation of Tsunami Coastal Amplitudes in the Pacific Coast of Mexico Based on Non-Uniform $k^{-2}$ Slip Distributions

Abstract

Three seismic gaps lie along the Pacific Coast of Mexico, the Tehuantepec, Guerrero, and Colima–Jalisco gaps. In the Tehuantepec seismic gap, there has not been a $M>7$ earthquake since 1902 until the $M_{w}=8.2$ in 2017 which was an intraplate event. Furthermore, there has not been significant seismic activity in the Guerrero gap for over fifty years; therefore, it is considered as potentially likely to produce a major event. Based on historical seismicity and the National Seismological Service of Mexico’s earthquakes catalog, the last major earthquake in the Colima–Jalisco gap struck in 1995 with $M_{w}=8.0$. To better understand the tsunami hazards due to the generation of near-field tsunamis in Mexico, in this work we characterize hypothetical events of magnitudes $M_{w}=8.0$, $M_{w}=8.2$, and $M_{w}=8.2$ in the Tehuantepec, Guerrero, and Colima–Jalisco gaps, respectively. We generated 99 earthquakes with stochastic $k^{-2}$ finite fault slip distributions and one earthquake with uniform slip distribution at each seismic gap. The non-planar geometry of the megathrust for each rupture area was taken into account. For each seismic gap, we compute the vertical co-seismic displacement by adding up the contribution from all point sources distributed over a grid mesh on each of the faults. Under the passive tsunami generation assumption, we simulated the tsunami wave-field propagation to obtain the coastal amplitude along the Pacific coast of Mexico. The numerical results show likely maximum peak amplitudes of $\sim 8$ m, $\sim 14$ m, and $\sim 15$ m, in Tehuantepec, Guerrero, and Colima–Jalisco gaps, respectively. The uniform slip distribution assumption over stochastic scenarios shows an average underestimation factor of 1.3 for the three seismic gaps. While our computations were carried out carefully and accurately, our models have limitations. Thus, our results cannot be used as an authoritative tsunami hazard assessment.