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The 2010 M w 8.8 Maule, Chile earthquake: Nucleation and rupture propagation controlled by a subducted topographic high
Author(s) -
Hicks Stephen P.,
Rietbrock Andreas,
Haberland Christian A.,
Ryder Isabelle M. A.,
Simons Mark,
Tassara Andrés
Publication year - 2012
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 - 10.1029/2012gl053184
Subject(s) - geology , forearc , seismology , aftershock , subduction , slip (aerodynamics) , epicenter , interplate earthquake , foreshock , trench , tectonics , chemistry , physics , organic chemistry , layer (electronics) , thermodynamics
Knowledge of seismic properties in an earthquake rupture zone is essential for understanding the factors controlling rupture dynamics. We use data from aftershocks following the Maule earthquake to derive a three‐dimensional seismic velocity model of the central Chile forearc. At 36°S, we find a high v p (>7.0 km/s) and high v p / v s (∼1.89) anomaly lying along the megathrust at 25 km depth, which coincides with a strong forearc Bouguer gravity signal. We interpret this as a subducted topographic high, possibly a former seamount on the Nazca slab. The Maule earthquake nucleated at the anomaly's updip boundary; yet high co‐seismic slip occurred where the megathrust is overlain by lower seismic velocities. Sparse aftershock seismicity occurs within this structure, suggesting that it disrupts normal interface seismogenesis. These findings imply that subducted structures can be conducive to the nucleation of large megathrust earthquakes, even if they subsequently hinder co‐seismic slip and aftershock activity.