oa Relationship between Coda-Q and Loaded Stress

A coda-wave is formed by superposed signals caused by scatterers such as cracks and medium inhomogeneities in the underground materials. For an inhomogeneous medium, it is natural to deal with stochastic methodologies to interpret seismic data. In the past, it is revealed that coda-Q, which is derived from the coda-wave has relationship with frequency of earthquakes1). If the frequency of earthquakes is reflected the change of loaded stress, there is the relationship between the loaded stress and coda-Q. Our purpose is to reveal that relationship. We employ 2-D finite difference method to simulate scatter waves which is generated by cracks. When the stress is loaded to a simulation model, anisotropy of velocity is occurred along direction of the stress, and formation of the scatter waves is changed. Then value of coda-Q is changed. In this study, we find that coda-Q increases constantly according to the increasing stress and behavior of coda-Q has a tendency according to direction of the stress respectively (i.e. stress is loaded vertically or horizontally). In conclusion, we are able to estimate relative magnitude and the direction of the stress. It might lead a new method in underground monitoring.