5:15 PM - 7:15 PM
[SSS09-P03] Estimation of seismic wave propagation paths using Snell's law
Keywords:anomalous seismic intensity zone, deep-focus intra-slab earthquake
On May 9, 2022, a deep-focus earthquake occurred at 340 km depth beneath the Ise Bay, and the maximum seismic intensity was observed in Fukushima Prefecture. Seismic intensity usually appears in concentric circles around the epicenter, but in this earthquake the distribution extended north to south from northern Kanto to the Tohoku region, far from the epicenter. This phenomenon is called an anomalous seismic intensity zone. It is thought that a reason for the anomalous intensity zones is that seismic waves pass through a medium (within a slab) with different physical properties such as seismic velocity and attenuation. Because the waves can pass through the slab faster and with less attenuation, they reach the far surface with the original amplitude.
On the other hand, near Ise Bay directly above the epicenter, the seismic waves that escape from the slab travel through the mantle, an area where seismic waves are slow and attenuated greatly. As a result, the seismic waves have smaller amplitudes and arrive later than those that travel within the slab.
We calculate the propagation path of seismic waves while taking into account complex amplitude changes, and investigate the distribution of anomalous seismic intensity.
On the other hand, near Ise Bay directly above the epicenter, the seismic waves that escape from the slab travel through the mantle, an area where seismic waves are slow and attenuated greatly. As a result, the seismic waves have smaller amplitudes and arrive later than those that travel within the slab.
We calculate the propagation path of seismic waves while taking into account complex amplitude changes, and investigate the distribution of anomalous seismic intensity.