Analysis of microearthquakes at the Horonobe area, north of Hokkaido, Japan, by using the multiplet-clustering analysis

Moriya, Hirokazu*; Niizato, Tadafumi  ; Kitamura, Itaru*; Hotta, Hikaru*; Ohara, Hidefumi

The source locations of earthquakes at the Horonobe area, north of Hokkaido, Japan have been relocated by using the multiplet-clustering analysis (MCA) to identify the subsurface structures and to reveal the mechanism of earthquakes. The absolute source locations of 221 earthquakes were determined by the "hypomh" algorithm to find the overall structures in this area. After that, those earthquakes were classified into 10 groups of multiplets which are the groups of events with very similar waveforms and their source locations have been relocated based on the MCA in order to reveal the fine scale structures. The multiplet-clustering analysis has revealed that the earthquake locations show the structures trending from NS to NNE-SSW with reverse or strike-slip focal mechanism.