Publication Date:
2017-04-11
Description:
Highlights:
• We present new active and passive seismological data offshore Maule, Chile.
• We discuss the outer rise seismicity and Vp, Vs and Poisson's ratio models.
• We compare our results with published data available in the area and with bathymetric features.
• We confirm hydration of the upper oceanic lithosphere and partial serpentinization of the upper mantle.
We have studied the dependency between incoming plate structure, bending-related faulting, lithospheric hydration, and outer rise seismic activity offshore Maule, Chile. We derived a 2D Poisson's ratio distribution from P- and S-wave seismic wide angle data collected in the trench-outer rise. High values of Poisson's ratio in the uppermost mantle suggest that the oceanic lithosphere is highly hydrated due to the water infiltration through bending-related normal faults outcropping at the seafloor. This process is presumably facilitated by the presence of a seamount in the area. We conclude that water infiltrates deep into the lithosphere, when it approaches the Chile trench, producing a reduction of crustal and upper mantle velocities, supporting serpentinization of the upper mantle. Further, we observed a mantle Vp anisotropy of 8%, with the fast velocity axis running normal to the abyssal hill fabric and hence in spreading direction, indicating that outer rise processes have yet not affected anisotropy.The first weeks following the megatrust Mw = 8.8 Maule earthquake in 2010 were characterized by a sudden increase of the outer rise seismic activity, located between 34° S and 35°30' S. We concluded that this phenomenon is a result of an intensification of the water infiltration process in the outer rise, presumably triggered by the main shock, whose epicenter was located some 100 km to the south east of the cluster.
Type:
Article
,
PeerReviewed
Format:
text
DOI:
10.1016/j.jog.2015.06.007
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