Monitoring spatio-temporal variation in the Earth's crust using seismic coda and ambient noise

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Due to the movement of tectonic plates stress gradually builds-up at large fault zones, which is suddenly released in an earthquake. These temporal changes in stress cause temporal changes in seismic velocity. During large earthquake strong shaking and cracking occurs, which also causes temporal variations in seismic velocity. Such nonlinear effects must be taken into account in strong motion modeling and seismic hazard analysis. Recently, new seismological techniques to monitor temporal variations of elastic wave velocity using ambient seismic noise and seismic coda waves have been developed. This progress significantly improved resolution and temporal spacing of observations. Using these new methods, we will analyze velocity changes of the Earth's crust associated with six shallow earthquakes with moment magnitude larger than 6.5, which occurred on shore in Japan between 2000 and 2009. Additionally, we will analyze crustal velocity changes for Tokyo area. Measured data will be compared to predictions of different models to clarify the causes of the observed temporal velocity variations.