Background Seismicity
The blue hexagons denote historical large damaged earthquakes [Chronological Scientific, Maruzen; Damaged Earthquakes Pandect, University of Tokyo Press].
The yellow star indicates the epicenter of the main shock. The red circles show the aftershock distributions determined by Hi-net, and the black circles show the background seismicity from JMA unified earthquake catalogue. The blue lines indicate the active faults.
The 2004 Mid-Niigata Earthquake occurred in the area where (1) no active faults are known, (2) the background seismicity is very low, and (3) the historical large damaged earthquakes occurred in the vicinity.
|