IODP Expedition 334: An Investigation of the Sedimentary Record, Fluid Flow and State of Stress on Top of the Seismogenic Zone of an Erosive Subduction Margin
[摘要] The Costa Rica Seismogenesis Project (CRISP) is anexperiment to understand the processes that control nucleationand seismic rupture of large earthquakes at erosionalsubduction zones. Integrated Ocean Drililng Program(IODP) Expedition 334 by R/V
JOIDES Resolution is the firststep toward deep drilling through the aseismic and seismicplate boundary at the Costa Rica subduction zone offshorethe Osa Peninsula where the Cocos Ridge is subductingbeneath the Caribbean plate. Drilling operations includedlogging while drilling (LWD) at two slope sites (Sites U1378and U1379) and coring at three slope sites (Sites U1378–1380)and at one site on the Cocos plate (Site U1381). For the firsttime the lithology, stratigraphy, and age of the slope andincoming sediments as well as the petrology of the subductingCocos Ridge have been characterized at this margin.The slope sites recorded a high sediment accumulation rateof 160–1035m m y
−1 possibly caused by on-land uplift triggeredby the subduction of the Cocos Ridge. The geochemical data as well as the
in situ temperature data obtained atthe slope sites suggest that fluids are transported fromgreater depths. The geochemical profiles at Site U1381 reflectdiffusional communication of a fluid with seawater-likechemistry and the igneous basement of the Cocos plate(Solomon et al., 2011; Vannucchi et al., 2012a). Thepresent-day
in situ stress orientation determined by boreholebreakouts at Site U1378 in the middle slope and SiteU1379 in the upper slope shows a marked change in stressstate within ~12 km along the CRISP transect; that maycorrespond to a change from compression (middle slope) toextension (upper slope).
doi:
10.2204/iodp.sd.15.03.2013
