Seismic studies/site survey data

Site survey data have been collected in the drilling area over many years, including multiple generations of two-dimensional seismic reflection (e.g., Park et al., 2002), wide-angle refraction (Nakanishi et al., 2002), passive seismicity (e.g., Obana et al., 2004; Obara and Ito, 2005; Ito and Obara, 2006), heat flow (Yamano et al., 2003), side-scan sonar, swath bathymetry, and visual observations from submersible and ROV dives (Ashi et al., 2002). In 2006, Japan and the United States conducted a joint three-dimensional (3-D) seismic reflection survey over a ~11 km × 55 km area, acquired by PGS Geophysical, an industry service company (Moore et al., 2007). This 3-D data volume was used to refine selection of drill sites and targets in the complicated megasplay fault region, define the regional structure and seismic stratigraphy, analyze physical properties of the subsurface through seismic attribute studies in order to extend information away from boreholes, and assess drilling safety (Moore et al., 2009). A smaller 3-D survey was conducted over proposed Sites NT1-01A (C0012) and NT1-07A (C0011) in 2006 by the Japan Agency for Marine-Earth Science and Technology–Institute for Research on Earth Evolution (JAMSTEC-IFREE) (Park et al., 2008) (Figs. F3, F5, F6). Prestack depth migration of those data led to refined velocity models and revised estimates of sediment thickness and total drilling depths.

The supporting site survey data for Expedition 333 are archived at the IODP Site Survey Data Bank.