Estimation of temporal change in crustal stress field using seismic scattering

摘要

Stress field deep under the ground around the seismogenic depth is important for understanding seismicrnactivity, the state of oil reservoir, etc. However we could only guess the stress field near the earth surfacernusing the current equipment and technique for the geodetic measurements. In this study we focus on thernseismic scattering in which elastic waves bring the information on the earth crust where the seismic wavesrntravel through to the surface. From the scattered waves, we try to estimate the variation in the stress field atrna depth in the subsurface.rnFirst we employ a 2-D finite different method to investigate a relationship between the seismicrnscattering and the crustal stress field, i.e., the magnitude and the direction of the stress. As a result, it isrnrevealed that coda-Q, which is derived from the attenuation of seismic waves, has a proportionalrnrelationship with the magnitude of the stress and the sinusoidal changes against the orientation of wavernpropagation.rnAfter confirming the relationship between the seismic scattering and coda-Q, it is examined if the samernrelationship could stand in real field data. We use seismic records acquired by Hi-net. And it is revealedrnthat coda-Q has the relationship with the change in the strain obtained by GPS observation, which is arnproxy of the crustal stress field. We conclude that the change in crustal stress field could be estimatedrnthrough monitoring of coda-Q of natural earthquakes.