Margin architecture and seismic attenuation in the central Costa Rican forearc

Zhu, Junjiang, Kopp, Heidrun, Papenberg, Cord, Klaeschen, Dirk, Flueh, E. R. and Planert, Lars (2010) Margin architecture and seismic attenuation in the central Costa Rican forearc Marine Geology, 276 . pp. 30-41. DOI 10.1016/j.margeo.2010.07.004.

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Abstract

Seismic attenuation across the central Costa Rican margin wedge is determined fromamplitude analysis ofwideangle seismic data. Travel time and amplitude modeling are applied to ocean bottom hydrophones along two trench-parallel profiles, located 30 km (P21) and 35 km (P18) landward of the deformation front northeast of Quepos Plateau. Tomographic inversion images a progressively thinning margin wedge from the coast to the lower slope at the trench. A 1–1.5 km thick décollement zone with seismic velocities of 3.5–4.5 km/s is sandwiched between the marginwedge and the subducting Cocos plate. For strike line P21, amplitude modeling indicates a Qp value of 50–150 for the upper margin wedge with seismic velocities ranging from 3.9 km/s to 4.9 km/s. Along strike line P18, Qp values of 50–150 are determined with velocities of 4.3–5.0 km/s in the upper margin wedge, increasing to 5.1–5.4 km/s in the lower margin wedge. Quantitative amplitude decay curves support the observed upper plate Qp values. In conjunction with earlier results from offshore Nicoya Peninsula, our study documents landward decreasing attenuation across the margin wedge, consistent with a change in lithology from the sediment-dominated frontal prism to the igneous composition of the forearc middle prism

Document Type: Article
Keywords: Geodynamics; Seismic attenuation, amplitude modeling, décollement, seismic tomography, Middle America Trench
Research affiliation: OceanRep > SFB 574
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
DOI etc.: 10.1016/j.margeo.2010.07.004
ISSN: 0025-3227
Projects: SFB574
Expeditions/Models:
Date Deposited: 15 Sep 2010 12:43
Last Modified: 08 Aug 2017 08:06
URI: http://eprints.uni-kiel.de/id/eprint/8907

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