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GEOPHYSICAL RESEARCH LETTERS,
VOL. 31,
L04613,
doi:10.1029/2003GL018863,
2004
Along-strike variations in underthrust sediment dewatering on the Nicoya margin, Costa Rica related to the updip limit of
seismicity
Glenn A. Spinelli
Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA
Demian M. Saffer
Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming, USA
Abstract
Along the Costa Rican subduction zone offshore the Nicoya peninsula, an offset in the updip limit of seismicity coincides
with a transition between subduction of warm crust generated at the Cocos-Nazca Spreading Center and cool crust formed at
the East Pacific Rise. We evaluate whether the observed difference in thermal state of incoming crust would result in significant
differences in sediment dehydration reaction progress along strike, thought to be a control on the updip limit of seismicity.
We combine thermal models with models of dehydration reaction kinetics for opal and smectite to estimate the distribution
of diagenetic fluid sources. The modeled distribution of diagenetic fluid sources mimics the pattern of the updip limit of
seismicity; seismicity begins ∼15–20 km landward of most of the smectite-to-illite transition. This suggests that the location
of the updip limit of seismicity may be influenced by the dissipation of fluid overpressures landward of smectite-to-illite
dehydration.
Received 17
October
2003;
accepted 20
January
2004;
published 28
February
2004.
Index Terms: 3015 Marine Geology and Geophysics: Heat flow (benthic) and hydrothermal processes; 3022 Marine Geology and Geophysics: Marine sediments—processes and transport; 3040 Marine Geology and Geophysics: Plate tectonics (8150, 8155, 8157, 8158); 7209 Seismology: Earthquake dynamics and mechanics; 8105 Tectonophysics: Continental margins and sedimentary basins.
Read Full Article (file size: 417808 bytes) Cited by
Citation: Spinelli, G. A., and D. M. Saffer
(2004),
Along-strike variations in underthrust sediment dewatering on the Nicoya margin, Costa Rica related to the updip limit of
seismicity,
Geophys. Res. Lett.,
31,
L04613,
doi:10.1029/2003GL018863.
Copyright 2004 by the American Geophysical Union.
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