2:30 PM - 2:45 PM
[SCG57-04] Stress rotation found in the aftershock area of the 2000 Western Tottori Earthquake and its temporal variation
Keywords:stress field , stress rotation, spatial statistics, P-wave first-motion, Bayesian estimation, postseismic slip
This method was applied to the dataset that was taken from the aftershocks of the 2000 Western Tottori Earthquake. The dataset was retrieved from the one used in Kawanishi et al. [2009, JGR], which complied P-wave first-motions recorded from October 15 to November 30 in 2000. The spatial variation in the estimated azimuth of the sigma1-axis was detailed, and it shows that, around the southern part of the fault, the azimuth along the western side of the fault is larger whereas it is smaller along the eastern side. Because the Tottori earthquake has a left-lateral strike-slip motion, it is expected that the compressive stress changes parallel to the main fault occur along the western side of the fault in the southern edge and that the sigma1-axis rotates in a clockwise direction or the increase of the azimuth. Similarly, counterclockwise rotation of the sigma1-axis (or the decrease of the azimuth) is plausible along the eastern side. The revealed spatial variation of the stress rotation across the main fault agrees with this expectation.
Furthermore, the dataset was divided into two datasets from October 15 to November 4 and from November 4 to November 30 to make the two contain almost the same number of P-wave first-motions. Then, the approach was applied to these individually. For both of the datasets, the stress rotation as described above was found, and it is more remarkable for the latter dataset than the former dataset. This temporal change in the stress rotation may be associated with the postseismic slip of the 2000 Tottori Earthquake.