The September 19, 2017 (Mw 7.1), Intermediate-Depth Mexican Earthquake: A Slow and Energetically Inefficient Deadly Shock

Date: 4/26/2019

Time: 06:00 PM

Room: Grand Ballroom

We investigate dynamic source parameters of the M_W7.1 Puebla-Morelos intermediate depth earthquake (IDE) (h = 57 km) of September 19, 2017, that caused a devastation in Mexico City. Our simple, elliptical source model, coupled with a new Particle Swarm Optimization algorithm, revealed rupture propagation within the subducted Cocos plate, featuring a high stress drop (∆τ = 14.2 ± 5.8 MPa) and a remarkably low radiation efficiency (ηr = 0.16 ± 0.09). Fracture energy was large (G = (1.0 ± 0.3) × 10¹⁶ J), producing a slow dissipative rupture (Vr/Vs = 0.34 ± 0.04) with scaling-consistent radiated energy (Er = (1.8 ± 0.9) × 10¹⁵ J) and energy-moment ratio (Er/M0 = 3.2 × 10⁻⁵). About 84% of the available potential energy for the dynamic rupture was dissipated in the focal region, likely producing friction-induced melts in the fault-core with 0.2-1.2 cm width due to heat production (700−1200◦C temperature rise). Such source features seem to be a universal signature of IDEs.

Reference: Mirwald, A., V. M. Cruz-Atienza, J. Díaz-Mojica, A. Iglesias, S. K. Singh, C. Villafuerte and J. Tago. The September 19, 2017 (Mw7.1), intermediate-depth Mexican earthquake: a slow and energetically inefficient deadly shock. Accepted in the Geophysical Research Letters, January 2019.

Presenting Author: Victor M. Cruz-Atienza

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