Characterization of physical properties for sediments and sedimentary rocks from Japan Trench, ODP Leg 186

Two sites (Sites 1150 and 1151) located in the land-ward deep-sea terrace of the Japan Trench were drilled during theOcean Drilling Program (ODP) Leg 186. Site 1150 is seismicallyactive, whereas Site 1151, aseismic. Measurements of sedimentphysical properties were made on both whole-round core andvariation with depth, although its absolute values are slightly dif-ferent. It is most likely attributable to coring disturbance. Mag-netic susceptibility is characterized by the highest value at thelithologic unit I. Depth variation of water content and porosityshows gradual decreasing pattern, except for lithologic unit I, sim-ilar to that of natural Gamma radiation. The abnormal charac-teristics of unit I are likely related to the under-consolidationcaused by rapid deposition (100200 m/myr) as well as imperme-able nature of the sediment previs higher in the unit I, but below which is relatively constant withdepth. P-wave velocity gradually increases from 1500 to 2000 m/swith depth, caused by sediment compaction and/or consolidation.Sediment physical properties of both sites are very similar, althoughp-wave velocity is slightly higher (~20 m/s on the average) at Site151. This indicates that sediment source, mineral compositionand sediment diagenesis are not significantly different at bothsites, implying that seismic activities such as earthquake do not likely cause marked changes of sediment physical properties. KCI Citation Count: 0