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Evidence for serpentinization of the forearc mantle wedge along the Nicoya Peninsula, Costa Rica
Author(s) -
DeShon Heather R.,
Schwartz Susan Y.
Publication year - 2004
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 - 10.1029/2004gl021179
Subject(s) - forearc , geology , subduction , seismology , mantle wedge , mantle (geology) , wedge (geometry) , peninsula , receiver function , geodesy , tectonics , geophysics , geometry , lithosphere , geography , archaeology , mathematics
Characterizing the hydration state of the forearc mantle wedge yields valuable information on frictional stability at the downdip edge of subduction megathrusts. Simultaneous inversion of P ‐ and S ‐wave arrival times collected as part of the Costa Rica Seismogenic Zone Experiment yields 1D and 3D P ‐ and S ‐wave velocity models ( V P and V S ) for the Nicoya Peninsula segment of the Middle America Trench. Nicoya Peninsula 1D velocity models show similar velocity gradients to country‐wide 1D velocity models from 5–30 km depth but diverge at expected Moho depths due to proximity to the subducting Cocos plate. 3D V P values range from 7.2–7.6 km/sec in the forearc mantle wedge. Receiver functions computed at Global Seismic Network station JTS in northwestern Costa Rica confirm these V P values, yield V P / V S of ∼1.85, and place the continental Moho at 36 ± 4 km depth. V P and V P / V S are consistent with 15–25% serpentinization of the forearc mantle wedge.