Identify Potential Source Regions in the Nankai Trough Using Spatial Clustering Techniques

Identification of potential source regions, pinpointing where large earthquakes are most likely to occur, is fundamental to seismic risk assessment. Previous results often suffer from significant uncertainties due to the limitations of individual observations. To address this issue, here we apply the self-organizing map method to the Nankai trough, which has been considered to have high-seismic potential. By integrating multisource observations (b value, slip-deficit rate [SDR], and cumulative slip deficit [CSD]), we cluster regions of low b value, high SDR, and large CSD to delineate potential source regions. We identify four potential earthquake sources along the Nankai trough. Among them, the Tokai segment shows the highest potential for generating earthquakes in the near future. Using pre-2011 observations, the identified source regions agree well with the rupture zone of the 2011 Mw 9.0 Tohoku-Oki earthquake, validating the reliability of this approach.