Constraining the Source of the Mw 8.1 Chiapas, Mexico Earthquake of 8 September 2017 Using Teleseismic and Tsunami Observations

Abstract

The September 2017 Chiapas (Mexico) normal-faulting intraplate earthquake (Mw 8.1) occurred within the Tehuantepec seismic gap offshore Mexico. We constrained the finite-fault slip model of this great earthquake using teleseismic and tsunami observations. First, teleseismic body-wave inversions were conducted for both steep (NP-1) and low-angle (NP-2) nodal planes for rupture velocities (Vr) of 1.5–4.0 km/s. Teleseismic inversion guided us to NP-1 as the actual fault plane, but was not conclusive about the best Vr. Tsunami simulations also confirmed that NP-1 is favored over NP-2 and guided the Vr = 2.5 km/s as the best source model. Our model has a maximum and average slips of 13.1 and 3.7 m, respectively, over a 130 km × 80 km fault plane. Coulomb stress transfer analysis revealed that the probability for the occurrence of a future large thrust interplate earthquake at offshore of the Tehuantepec seismic gap had been increased following the 2017 Chiapas normal-faulting intraplate earthquake.