2006 Volume 59 Issue 6 Pages 525-537
The EARS (Exploration of Asperities-Reflectors System) is intended to integrate research components needed for the estimation of on-going, active plate subduction. Major component of EARS are: mapping of Earth's seismic structure, time lapse (active and continuous) monitoring, real time data telemetry and study of physical properties. In addition to ordinary 2D and/or 3D MCS surveys, combination of refraction and wide-angle reflection survey method using OBS and air guns is essential technology to map the seismological nature of the subducting plate boundary. The second component is time-lapse measurement (active and continuous monitoring). The ACROSS (Accurately and Routinely Operated Signal System) is a unique survey method that can use either seismic or electromagnetic, active and continuous signal sources. It can also be used for time-lapse measurements of oil reservoirs. Using an ACROSS seismic source and temporary seismic array across Central Japan, we carried out a feasibility study to characterize seismic arrivals through a slow slip region where a strong reflection has been observed in the region NE of Lake Hamana and large aseismic slip has also been detected by GPS. By comparing synthetic seismograms and observed records, we can interpret the major phases observed. Although, the observational offset was not large enough to identify the reflected phase from the plate boundary, the results showed high potential to use ACROSS for time-lapse and EARS studies.
