IODP Expedition 319, NanTroSEIZE Stage 2: First IODP Riser Drilling Operations and Observatory Installation Towards Understanding Subduction Zone Seismogenesis

摘要

The Nankai Trough Seismogenic Zone Experiment(NanTroSEIZE) is a major drilling project designed toinvestigate fault mechanics and the seismogenic behaviorof subduction zone plate boundaries. Expedition 319 is thefirst riser drilling operation within scientific ocean drilling.Operations included riser drilling at Site C0009 in the forearcbasin above the plate boundary fault, non-riser drillingat Site C0010 across the shallow part of the megasplay faultsystem – which may slip during plate boundary earthquakes – and initial drilling at Site C0011 (incoming oceanicplate) for Expedition 322. At Site C0009, new methods weretested, including analysis of drill mud cuttings and gas, andin situ measurements of stress, pore pressure, and permeability.These results, in conjunction with earlier drilling,will provide (a) the history of forearc basin development(including links to growth of the megasplay fault system andmodern prism), (b) the first in situ hydrological measurementsof the plate boundary hanging wall, and (c) integrationof in situ stress measurements (orientation and magnitude)across the forearc and with depth. A vertical seismic profile(VSP) experiment provides improved constraints on thedeeper structure of the subduction zone. At Site C0010,logging-while-drilling measurements indicate significantchanges in fault zone and hanging wall properties overshort (< 5 km) along-strike distances, suggesting differentburial and/or uplift history. The first borehole observatoryinstruments were installed at Site C0010 to monitorpressure and temperature within the megasplay fault zone,and methods of deployment of more complex observatoryinstruments were tested for future operations.doi:href="http://dx.doi.org/10.2204/iodp.sd.10.01.2010" target="_blank">10.2204/iodp.sd.10.01.2010