Hydrogeological system of erosional convergent margins and its influence on tectonics and interplate seismogenesis.

Ranero, César R., Grevemeyer, Ingo , Sahling, Heiko, Barckhausen, U., Hensen, Christian, Wallmann, Klaus , Weinrebe, Reimer Wilhelm, Vannucchi, P., von Huene, Roland and McIntosch, K. (2008) Hydrogeological system of erosional convergent margins and its influence on tectonics and interplate seismogenesis. Open Access Geochemistry, Geophysics, Geosystems, 9 (3). Q03S04. DOI 10.1029/2007GC001679.

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[1] Fluid distribution in convergent margins is by most accounts closely related to tectonics. This association has been widely studied at accretionary prisms, but at half of the Earth's convergent margins, tectonic erosion grinds down overriding plates, and here fluid distribution and its relation to tectonics remain speculative. Here we present a new conceptual model for the hydrological system of erosional convergent margins. The model is based largely on new data and recently published observations from along the Middle America Trench offshore Nicaragua and Costa Rica, and it is consistent with observations from other erosional margins. The observations indicate that erosional margins possess previously unrecognized distinct hydrogeological systems: Most fluid contained in the sediment pores and liberated by early dehydration reactions drains from the plate boundary through a fractured upper plate to seep at the seafloor across the slope, rather than migrating along the décollement toward the deformation front as described for accretionary prisms. The observations indicate that the relative fluid abundance across the plate-boundary fault zone and fluid migration influence long-term tectonics and the transition from aseismic to seismogenic behavior. The segment of the plate boundary where fluid appears to be more abundant corresponds to the locus of long-term tectonic erosion, where tectonic thinning of the overriding plate causes subsidence and the formation of the continental slope. This correspondence between observations indicates that tectonic erosion is possibly linked to the migration of overpressured fluids into the overriding plate. The presence of overpressured fluids at the plate boundary is compatible with the highest flow rates estimated at slope seeps. The change from aseismic to seismogenic behavior along the plate boundary of the erosional margin begins where the amount of fluid at the fault declines with depth, indicating a control on interplate earthquakes. A previously described similar observation along accreting plate boundaries strongly indicates that fluid abundance exerts a first-order control on interplate seismogenesis at all types of subduction zones. We hypothesize that fluid depletion with depth increases grain-to-grain contact, increasing effective stress on the fault, and modifies fault zone architecture from a thick fault zone to a narrower zone of localized slip.

Document Type: Article
Keywords: subduction zones, tectonic erosion, seismogenesis, fluid flow
Research affiliation: OceanRep > SFB 574 > B5
OceanRep > SFB 574
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > SFB 574 > A1
OceanRep > SFB 574 > A5
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2007GC001679
ISSN: 1525-2027
Projects: Future Ocean, SFB574
Contribution Number:
SFB 574111
Date Deposited: 06 Feb 2009 14:45
Last Modified: 23 Sep 2019 23:20
URI: http://oceanrep.geomar.de/id/eprint/940

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