The Chugoku region has few active faults, and their activity is a B- class or lower. The primary active faults include the Itsukaichi fault and the Iwakuni fault zone, which run from Hiroshima City to a location near Iwakuni, the Kikukawa fault in northern Shimonoseki, and the Yamasaki fault zone stretching from Hyogo Prefecture to Okayama Prefecture. These active faults run in a northeast-southwest or northwest-southeast direction, and their movement is consistent with compression in an east-west direction. The crustal movement in Chugoku region is smaller than in other regions of the Japanese archipelago. In the central and eastern sections, the surface of the earth tends to be compressed in a roughly east-west direction in continuation from the Chubu and Kinki regions. Compression occurs in this area, but to a lesser extent than in the Chubu and Kinki regions (Fig.8-5). Many linear valleys called "lineaments" run in a northeast-southwest direction in western Hiroshima Prefecture. These are viewed as having appeared through erosion along the faults in an older age. These faults are unlikely to be active.

One large earthquake that has occurred in a shallow location on land in the Chugoku region since the Meiji period (beginning in 1868) is the 1943 Tottori Earthquake (M 7.2). The source region of the 1872 Hamada Earthquake (M 7.1) was partly at sea, but the mechanism for the earthquake occurrence is thought to be identical to those that occur in shallow locations on land. Over the past several decades, large earthquakes have occurred in shallow locations on land along the Sea of Japan coast, from the Hokuriku region through the Kinki region to the Chugoku region. In addition to the Tottori Earthquake, these include the 1948 Fukui Earthquake (M 7.1) and the 1927 North Tango Earthquake (Kita-Tango Earthquake) (M 7.3). These large earthquakes have caused particularly severe damage locally because they occurred in shallow locations on land. The source regions of the Tottori and Fukui earthquakes in particular were very close to urban areas with a thick accumulation of weak strata, causing widespread damage. The earthquake occurring in the year of 868 at Harima-Yamashiro (larger than M 7) is thought to have occurred on the Yamasaki fault zone, and recent M 6 level earthquakes (1984, M 5.6, etc.) are known to have occurred there. Shallow earthquakes sometimes occur on reverse faults in the southwestern Sea of Japan (Japan Sea), such as the 1940 earthquake (M 6.6). Damage caused by tsunami have occurred on the Korean Peninsula, so it is possible they could also occur along the Sea of Japan coast.

One of the characteristics of the Shikoku region is a series of right-lateral active faults (Median Tectonic Line fault zone) along the Median Tectonic Line. There are almost no active faults in the south. The Median Tectonic Line fault zone in the Shikoku region has mostly right-lateral strike-slip faults with an A class activity. The vertical slip harmonizes with the distribution of the mountainous areas. In the southern Sanuki Mountains it rises to the north, rises to the south in the northern Ishizuchi Mountains, rises to the north on the Takanawa Peninsula, and rises to the south from Matsuyama westward. Active faults with a low activity have been found on the Muroto Peninsula and near Cape Ashizuri, and it is considered that they are closely related to the great earthquakes along the Nankai Trough. In the Shikoku region, damage from shallow inland earthquakes is almost unknown, even in historical accounts.

The interval of activity for most active faults is 1,000 years or longer, but this does not indicate that no earthquakes can occur here even if no earthquake occurrence has been reported so far.