| 6 October 2000 |
| Headquarters for Earthquake Research Promotion |
| Earthquake Research Committee |
Seismic Activity in Western Tottori Prefecture
There have been a number of earthquakes following this event, but the incidence has lessened over time. The epicenters of these events, as of the present time of 6:00 p.m., have been distributed in a zone stretching 25 km NNW-SSE. From this, it can be concluded that the activity constitutes aftershocks to the original event. The focal mechanism was a strike slip type with an east-west pressure axis, and, from the distribution of aftershocks, it is believed there was a left lateral strike slip in the NNW-SSE strike of the source fault. The aftershocks are in a narrow area for an earthquake of such large magnitude. The largest aftershocks up to the present time of 6:30 p.m. were M4.7 events (tentative data) at about 1:34 and 1:36 p.m. There was also an M4.2 aftershock (tentative data) at about 4:21 p.m., which registered a maximum seismic intensity of 5 lower.
*The results of recent GPS observation show low levels of strain in the area, but the area does show a trend to compression along an east-west axis, which matches with the focal mechanism of the current event.
*There are no known events of M6.0 or greater in western Tottori Prefecture in recent years, but in 1990 in the vicinity of its zone of activity, there was activity including three M5 class events distributed in the same direction as the current event.
*It is estimated that there is a 40% chance of an aftershock of M6.0 or greater occurring within 24 hours of the main shock.
*It is conjectured that there is a short active NW-SE fault near the current area of seismic activity.