Frictional properties of subduction input sediments at an erosive convergent continental margin and related controls on décollement slip modes - the Costa Rica Seismogenesis Project (CRISP).

Kurzawski, Robert M., Niemeijer, André, Stipp, Michael, Charpentier, Delphine, Behrmann, Jan Hinrich and Spiers, Christopher James (2018) Frictional properties of subduction input sediments at an erosive convergent continental margin and related controls on décollement slip modes - the Costa Rica Seismogenesis Project (CRISP). Open Access Journal of Geophysical Research: Solid Earth, 123 (10). pp. 8385-8408. DOI 10.1029/2017JB015398.

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Supplementary data:

Abstract

The spectrum of slip modes occurring along shallow portions of the plate boundary décollement in subduction zones includes aseismic slip, slow slip, and seismogenic slip. The factors that control slip modes directly influence the hazard potential of subduction zones for generating large magnitude earthquakes and tsunamis. We conducted an experimental study of the frictional behaviour of subduction input sediments, recovered from two IODP expeditions to the erosive subduction margin offshore Costa Rica (Exp. 334, 344),employing rotary shear under hydrothermal conditions. The velocity dependence of friction was explored, using simulated gouges prepared from all major lithologies, covering a wide range of conditions representative for the initial stages of subduction. Temperature, effective normal stress, and pore fluid pressure were varied systematically up to 140 °C, 110 MPa and 120 MPa respectively. Sliding velocities up to 100 μm/s, relevant for earthquake rupture nucleation and slow slip, were investigated. The only sediment type that produced frictional instabilities (i.e. laboratory earthquakes) was the calcareous ooze carried by the incoming Cocos Plate, which by virtue of its slip weakening behaviour is also a likely candidate for triggering slow slip events. We evaluate this mechanism of producing unstable slip and consider alternatives. Therefore, locking and unlocking of plate boundary megathrusts are not only related to variations in pore fluid pressure, but may also depend on the presence of pelagic carbonate‐rich lithologies. Subduction systems containing such input are likely low‐latitude, where extensive deposition of carbonates takes place above the CCD.

Document Type: Article
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2017JB015398
ISSN: 0148-0227
Projects: IODP, CRISP
Expeditions/Models/Experiments:
Date Deposited: 21 Aug 2018 07:01
Last Modified: 01 Apr 2019 23:38
URI: http://oceanrep.geomar.de/id/eprint/44048

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