5:15 PM - 6:45 PM
[SSS07-P13] Detection of the anisotropic structure of small-scale heterogeneities in Kyushu
Keywords:heterogeneities, anisotropic structure, peak delay times
Short-period seismic waves show the excitation of the coda waves and envelope broadenings due to the scattering by small-scale heterogeneities. When the heterogeneity has an anisotropic structure, those effects depend on the propagation direction. According to the multiple forward scattering theory, the envelope broadening is significant in the direction along the long scale of the heterogeneity. Northern and southern Kyushu consist of different geological structures reflecting the geological history of the Kyushu. The stretched geological structure in between them can be seen in the geological map. In this study, we analyze the waveforms of seismic waves propagating parallel and perpendicular to the anisotropic geological structure Kyushu to investigate the effect of the anisotropic structure on observed waveforms.
We selected earthquakes on the north-south and east-west sides of the anisotropic geological structure in Kyushu. We used the horizontal component of waveforms recorded at stations between the north-south and east-west earthquake pairs. We first applied the bandpass filter of 2 – 4 Hz and created envelopes of waveforms. The envelope broadening effect is characterized by measuring the peak delay time from S-wave arrival. We analyzed the difference in the propagation distance dependence of the peak delay time for different propagation directions.
The peak delay times are increased with the increase of the propagation distance for both propagation directions. However, we did not recognize the significant directional dependence. Observed peak delay times showed large variation. Therefore, further analyses of more event and station pairs are necessary for the statistical evaluation and to improve the spatial resolution.
We selected earthquakes on the north-south and east-west sides of the anisotropic geological structure in Kyushu. We used the horizontal component of waveforms recorded at stations between the north-south and east-west earthquake pairs. We first applied the bandpass filter of 2 – 4 Hz and created envelopes of waveforms. The envelope broadening effect is characterized by measuring the peak delay time from S-wave arrival. We analyzed the difference in the propagation distance dependence of the peak delay time for different propagation directions.
The peak delay times are increased with the increase of the propagation distance for both propagation directions. However, we did not recognize the significant directional dependence. Observed peak delay times showed large variation. Therefore, further analyses of more event and station pairs are necessary for the statistical evaluation and to improve the spatial resolution.