3:30 PM - 4:30 PM
[J05-P-01] Investigation of remote earthquake triggering after the 2011 M9.0 Tohoku-oki earthquake
After the occurrence of the 2011 M9.0 Tohoku-oki earthquake, increased seismicity has been observed over the Japanese Islands due to increased static and/or dynamic stresses (e.g., Toda et al., 2011; Miyazawa, 2011). Miyazawa (2011) showed that a dynamically-triggered earthquake front propagated along Japan following the Tohoku-oki earthquake.
In this study, we investigated the triggering mechanism and remote activation in more detail. We first analyzed Hi-net (NIED) continuous waveform data to identify remote activation in the first minutes after the occurrence of the Tohoku-oki mainshock. We located events that are not listed in the JMA catalogue, with magnitudes from 1.2 to 3.4, which correspond to the arrival of Tohoku-oki surface waves in areas like Aichi, Hyogo and Tokushima prefectures, as well as Kyushu, at about 1350 km from the Tohoku-oki epicenter.
To determine the dominant triggering surface-wave phases, we analysed low-frequency waveform displacements at locations where remote triggering has been observed. The occurrence time for some of the analysed triggered events in Kyushu correlates well with the arrival of large surface-wave displacements on the transverse component, suggesting that the Love-waves, rather than the Rayleigh-waves, may have played the main role in triggered these remote earthquakes. The associated dynamic stresses are large, with values of ~150 kPa in southernmost Kyushu. These observations imply that induced sharing motion may have been responsible for the triggering of some of the detected remote events.
We also looked at the JMA earthquake catalog to observe the duration of increased seismic activity in areas of remote earthquake triggering. We found a clear increase in seismicity that lasted from a few days to about two weeks, depending on the activated area. The geothermal/volcanic areas in Kyushu show the longest and most clear seismicity activation.
In this study, we investigated the triggering mechanism and remote activation in more detail. We first analyzed Hi-net (NIED) continuous waveform data to identify remote activation in the first minutes after the occurrence of the Tohoku-oki mainshock. We located events that are not listed in the JMA catalogue, with magnitudes from 1.2 to 3.4, which correspond to the arrival of Tohoku-oki surface waves in areas like Aichi, Hyogo and Tokushima prefectures, as well as Kyushu, at about 1350 km from the Tohoku-oki epicenter.
To determine the dominant triggering surface-wave phases, we analysed low-frequency waveform displacements at locations where remote triggering has been observed. The occurrence time for some of the analysed triggered events in Kyushu correlates well with the arrival of large surface-wave displacements on the transverse component, suggesting that the Love-waves, rather than the Rayleigh-waves, may have played the main role in triggered these remote earthquakes. The associated dynamic stresses are large, with values of ~150 kPa in southernmost Kyushu. These observations imply that induced sharing motion may have been responsible for the triggering of some of the detected remote events.
We also looked at the JMA earthquake catalog to observe the duration of increased seismic activity in areas of remote earthquake triggering. We found a clear increase in seismicity that lasted from a few days to about two weeks, depending on the activated area. The geothermal/volcanic areas in Kyushu show the longest and most clear seismicity activation.