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The 19 September 2017 ( M w 7.1) Intermediate‐Depth Mexican Earthquake: A Slow and Energetically Inefficient Deadly Shock
Author(s) -
Mirwald Aron,
CruzAtienza Víctor M.,
DíazMojica John,
Iglesias Arturo,
Singh Shri K.,
Villafuerte Carlos,
Tago Josué
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl080904
Subject(s) - seismic moment , dissipative system , seismology , subduction , scaling , shock (circulatory) , geology , physics , fault (geology) , geometry , thermodynamics , mathematics , medicine , tectonics
We investigate dynamic source parameters of the M w 7.1 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 (Δ τ = 14.9±5.6 MPa) and a remarkably low radiation efficiency ( η r = 0.16 ± 0.09). Fracture energy was large ( G = (1.04 ± 0.3) × 10 16 J), producing a slow dissipative rupture ( V r / V s = 0.34 ± 0.04) with scaling‐consistent radiated energy ( E r = (1.8 ± 0.9)·10 15 J) and energy‐moment ratio ( E r / M 0 = 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.