Feasibility of Underground Stress Estimation by Combined Use of Time-Lapse P-P and P-S Seismic Data

In the following discussion a new methodology is developed which relates seismic travel time changes to subsurface stress variation. Rock saturation state which has a combined effect with pressure on seismic data is assumed to be irrelevant since time lapse seismic here is not intended for oil reservoir monitoring but to examine if it can be used as a tool to monitor subsurface stress variation around seismically active faults. This technique is based on empirical relationship between rock stress and velocity that is derived during laboratory ultrasound core measurements. The relationship is then theoretically connected to seismic P-P and P-S travel times to develop a relationship between seismic travel time variation and changes in stress magnitude. When common values of stresses are applied in the equation, promising seismic P-P and P-S travel time sensitivity is observed. This strong sensitivity of time-lapse seismic travel times to stress variation can be used to monitor stress condition at hazardous area around faults.