Relationship Between Attenuation of Coda Wave and Crustal Stress

Abstract

Stress field deep under the ground, like seismogenic depth, is important to know seismic activity, state of oil reservoir, etc. However we can only know stress field near the earth surface using the current equipment and technique. In this study we focus on seismic scattering waves having information of the earth crust where the seismic waves travel through. From the scattering waves, we try to estimate the stress field deep under the ground. At first we employ a 2-D finite different method to reveal a relationship between the seismic scattering and the crustal stress field, i.e., magnitude and direction of the stress. As the result, it is revealed that coda-Q, which is derived from attenuation ratio of a seismic wave, has a proportional relationship with magnitude of the stress and changes periodically against direction of the magnitude. Next it is examined if the relationship can be seen in real field data using seismograms obtained by Hi-net. And it is revealed that coda-Q has the relationship with change in strain obtained by GPS observation and theoretical dislocation calculated from fault movement; both are proxy of the crustal stress field. We conclude that change in crustal stress field can be estimated from monitoring of coda-Q.