The 19 September 2017 (Mw7.1) Intermediate‐Depth Mexican Earthquake: A Slow and Energetically Inefficient Deadly Shock

Abstract

Abstract We investigate dynamic source parameters of the Mw7.1 Puebla‐Morelos intermediate‐depth earthquake (h = 57 km) of 19 September 2017, which devastated 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 (Δτ = 14.9±5.6 MPa) and a remarkably low radiation efficiency (ηr = 0.16 ± 0.09). Fracture energy was large (G = (1.04 ± 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 of 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 intermediate‐depth earthquakes.

Keywords

• 19 September 2017
• Puebla‐Morelos Mexican earthquake
• dynamic source inversion
• Particle Swarm Optimization method
• slow and highly dissipative rupture process
• friction‐induced melts in fault core