4:00 PM - 4:15 PM
[SSS06-08] Amplitude dependence of seismic wave attenuation
Keywords:seismic wave attenuation, Q
Quality factor, Q, indicates the anelastic attenuation, and it is known to have a weak frequency dependence based on previous observations and experimental results. The anelastic attenuation is thought to be caused mainly by microscopic deformation in minerals due to seismic wave propagation and free oscillation of the earth, and by energy dissipation due to viscous deformation in a partial melting zone. On the other hand, if the anelastic attenuation is caused by microscopic deformation of minerals, it would depend on the input amplitude due to differences in the deformation response of each process. However, at present, all analyses assume that the anelastic attenuation does not depend on the amplitude. Therefore, the objective of this study is to determine the amplitude dependence of the anelastic attenuation from seismic wave analysis.
As an analysis target, we selected the 2003 Miyagi-oki earthquake and its aftershocks, and the 2008 Iwate-Miyagi Nairiku earthquake and its aftershocks. The minimum magnitude is 3.0. We selected pairs of earthquakes with different magnitudes and epicenters within 5 km, and calculated the spectral ratios of P-wave initial motions with good S/N ratios. Finally, by fitting the theoretical spectral ratios to the observed spectral ratios, the difference in the Q-1 between the two earthquakes was determined.
As a result, a positive correlation was found between the magnitude difference and Q-1 difference. The random number test was performed to check the reliability and robustness of the results of this analysis. This result suggests that there is an amplitude dependence of the anelastic attenuation.
As an analysis target, we selected the 2003 Miyagi-oki earthquake and its aftershocks, and the 2008 Iwate-Miyagi Nairiku earthquake and its aftershocks. The minimum magnitude is 3.0. We selected pairs of earthquakes with different magnitudes and epicenters within 5 km, and calculated the spectral ratios of P-wave initial motions with good S/N ratios. Finally, by fitting the theoretical spectral ratios to the observed spectral ratios, the difference in the Q-1 between the two earthquakes was determined.
As a result, a positive correlation was found between the magnitude difference and Q-1 difference. The random number test was performed to check the reliability and robustness of the results of this analysis. This result suggests that there is an amplitude dependence of the anelastic attenuation.