Potential of 3-D vertical seismic profiles to characterize seismogenic fault zones



The potential of a 3-D vertical seismic profile (VSP) to improve resolution of seismogenic plate interfaces was explored with synthetic modeling. The 3-D VSP modeled is at a proposed site for a 1 to 1.5 km deep open hole that provides background for riser drilling. Three-dimensional VSP images could resolve 30–60 m spaced reflective horizons in a Costa Rican subduction zone. It can record a great amount of high-fidelity S wave data to invert for physical properties, directions of strain, and pore pressure above and below the plate interface fault. A 6 km × 12 km grid of shots with a surface ship will illuminate a ∼4 km × 7 km area of the plate interface fault zone with a high data density. Acquisition adds 5 to 9 days to drill ship time on site and a shooting ship. Seismic image resolution falls between that of borehole information and 3-D surface ship seismic images. A multiple-kilometer 3-D volume of high-fidelity S wave data is an exceptional addition not available with other techniques.