13:45 〜 15:15
[SCG46-P01] Analysis of the potential interactions between intraslab intermediate-depth and shallow earthquakes in the Japan and the Chile trench subduction zones
キーワード：intermediate-depth intraslab earthquakes, interactions, megathrusts, statistical seismology, foreshocks
An increase of both shallow and intermediate-depth intraslab seismicity has been observed days to years before some great subduction earthquakes, sometimes accompanied by seismic spatial patterns forming along dip lineaments over some hours. These observations suggest that a link exists between these deep and shallow foreshocks, but it is still poorly understood and not characterized in a systematic manner. The aim of this study is to systematically and statistically identify the potential correlations between intermediate-depth and shallow seismicity, and to characterize their duration and spatial pattern.
For this purpose, we develop a statistical method based on cross-correlation to assess the relevance of deep-shallow interactions. We focus on the seismicity of the Japan and the Chile trench subduction zones, during the decades prior to the Tohoku-oki (Mw 9.0, 2011) and Iquique (Mw 8.2, 2014) earthquakes, respectively. The temporal correlation values between the deep and shallow events are calculated on various sliding-windows with durations from days to years, and then compared to the ones obtained using parts of seismicity catalogs far in space and therefore uncorrelated to evaluate their significance. In a second time, we also use DBScan to search seismic lineaments patterns linking intermediate-depth and shallow seismicity and check the evolution of the obtained clusters’ parameters through time, especially before big events.
If the seismic spatial patterns are still under analysis, our study based on cross-correlation shows some windows with a strong link between shallow and intermediate depth events, sometimes on different timescales, including the months just before the two megathrusts. However, periods that don’t precede great seismicity can present the same kind of interactions, indicating that the latter can’t be used as precursors.
For this purpose, we develop a statistical method based on cross-correlation to assess the relevance of deep-shallow interactions. We focus on the seismicity of the Japan and the Chile trench subduction zones, during the decades prior to the Tohoku-oki (Mw 9.0, 2011) and Iquique (Mw 8.2, 2014) earthquakes, respectively. The temporal correlation values between the deep and shallow events are calculated on various sliding-windows with durations from days to years, and then compared to the ones obtained using parts of seismicity catalogs far in space and therefore uncorrelated to evaluate their significance. In a second time, we also use DBScan to search seismic lineaments patterns linking intermediate-depth and shallow seismicity and check the evolution of the obtained clusters’ parameters through time, especially before big events.
If the seismic spatial patterns are still under analysis, our study based on cross-correlation shows some windows with a strong link between shallow and intermediate depth events, sometimes on different timescales, including the months just before the two megathrusts. However, periods that don’t precede great seismicity can present the same kind of interactions, indicating that the latter can’t be used as precursors.