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TitleStrain release at the trench during shallow slow slip: the example of Nicoya Peninsula, Costa Rica
 
AuthorJiang, YORCID logo; Liu, Z; Davis, E E; Schwartz, S Y; Dixon, T H; Voss, N; Malservisi, R; Protti, M
SourceGeophysical Research Letters vol. 44, issue 10, 2017 p. 4846-4854, https://doi.org/10.1002/2017GL072803 Open Access logo Open Access
Image
Year2017
Alt SeriesNatural Resources Canada, Contribution Series 20160443
PublisherWiley-Blackwell
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf; html
AreaNicoya Peninsula; Costa Rica
Subjectstectonics; Nature and Environment; Science and Technology
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2017 05 26
AbstractThe near-trench behavior of subduction megathrust faults is critical for understanding earthquake hazard and tsunami generation. The shallow subduction interface is typically located in unconsolidated sediments that are considered too weak to accumulate elastic strain. However, the spectrum of shallow fault slip behavior is still elusive, due in large part to the lack of near-field observations. Here we combine measurements from seafloor pressure sensors near the trench and an onshore GPS network in a time-dependent inversion to image the initiation and migration of a well-documented slow slip event (SSE) in 2007 at the Nicoya Peninsula, Costa Rica. Our results show that the shallow SSE initiated on the shallow subduction interface at a depth of ~15Êkm, where pore fluid pressure is inferred to be high, and propagated all the way to the trench. The migrating event may have triggered a second subevent that occurred 1Êmonth later. Our results document the release of elastic strain at the shallow part of the subduction megathrust and suggest prior accumulation of elastic strain. In conjunction with near-trench shallow slow slip recently reported for the Hikurangi subduction zone and trench breaching ruptures revealed in some large earthquakes, our results suggest that near-trench strain accumulation and release at the shallower portions of the subduction interface is more common than previously thought. ©2017. Her Majesty the Queen in Right of Canada. Geophysical Research Letters. Reproduced with the permission of the Minister of Natural Resources Canada.
Summary(Plain Language Summary, not published)
The near-trench behavior of subduction megathrust faults is critical for controlling tsunami generation. The shallowest subduction interface is typically located in unconsolidated sediments that are considered too weak to accumulate elastic strain. However, the spectrum of shallow fault slip behavior is still elusive, due in large part to the lack of near-field observations. Here we combine measurements from seafloor pressure sensors near the trench and onshore GPS to show that shallow slow slip events (SSEs) offshore the Nicoya Peninsula propagate all the way to the trench. Using time-dependent inversion, we image the initiation and migration of a well-documented SSE that initiated on the shallow subduction interface at a depth of 15 km where pore fluid pressure is inferred to be high. The migrating SSE may have triggered a second SSE one month later. Our results suggest accumulation of elastic strain and transitional friction conditions in the shallowest parts of at least some subduction megathrusts.
GEOSCAN ID310533

 
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