(2)The Tottori Earthquake (September 10, 1943, M 7.2)


The Tottori Earthquake occurred in a shallow location on land, and its focal region was near the Tottori Plain. Seismic intensity 6 in JMA scale was observed in Tottori City, and 5 in Okayama City (Fig.8-12). The damage was concentrated in the Tottori Plain where the soft ground extends and the damage in Tottori City in particular accounted for 80% of all the damage. The earthquake caused 1,083 fatalities and completely collapsed 7,485 houses (Fig.8-13). Roads, embankments, and other public works were damaged.

There were more than 100 aftershocks of M 4 or larger until April 1944. The largest aftershock (M 6.2) occurred the following day, on September 11 (Fig.8-14). In the aftershock area, there was an earthquake of M 6.2 in 1983.

This earthquake caused slipping at the surface on the Shikano and Yoshioka faults. This slipping extended for about 8 km on the Shikano fault. At the southwest edge, the northern side of the fault had subsided 75 cm relative to the southern side, and had moved a maximum of 150 cm to the east. This earthquake created a new fault known as the Yoshioka fault which runs 4.5 km long, roughly parallel to the Shikano fault at the north. The northern side of the fault subsided a maximum of 50 cm in relation to the southern side, and moved a maximum of 90 cm to the east. A trenching of the Shikano fault clearly shows that an earthquake had occurred in the same location 4,000 to 8,000 years before the Tottori Earthquake.

Two M 6.2 earthquakes occurred on March 4 and 5, about six months before the Tottori Earthquake, near the source region of the Tottori Earthquake. Earlier, two destructive earthquakes had occurred in this area, six months apart, during the Edo period (in the year of 1710, M 6.5 and 1711, M 6 1/4).