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Rupture Dynamics of the 2012 Nicoya M w 7.6 Earthquake: Evidence for Low Strength on the Megathrust
Author(s) -
Yao Suli,
Yang Hongfeng
Publication year - 2020
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 - 10.1029/2020gl087508
Subject(s) - geology , seismology , subduction , earthquake rupture , interplate earthquake , drop (telecommunication) , pore water pressure , coefficient of friction , geotechnical engineering , tectonics , materials science , telecommunications , fault (geology) , computer science , composite material
Frictional properties on subduction interfaces are essential for understanding earthquake nucleation, rupture propagation, and tsunami generation during megathrust earthquakes. Because they cannot be directly observed, they have been inferred from different approaches. However, none of them have reported constraints immediately before a megathrust earthquake. Here we quantify the frictional strength on the megathrust prior to the 2012 M w 7.6 Nicoya earthquake by conducting spontaneous rupture simulations with constraints from near‐field observations. Our preferred dynamic rupture model shows a remarkable fit on the near‐field data. The simulation results indicate an average strength drop of <5 MPa. Considering typical ranges for the dynamic friction coefficient f d ≤ 0.2 and the static friction coefficient f s = 0.6 , we infer that the average strength on the megathrust is ≤ 7.5 MPa. Such low strength is attributed to the near‐lithostatic pore pressure along the subduction interface, which is implied by seismic studies in this region.