From the USGS here:
The January 1, 2024, M7.5 earthquake on the west coast of Japan, on the island of Honshu, occurred as a result of shallow reverse faulting in the Earth’s crust. Focal mechanism solutions for the earthquake indicate faulting occurred on a moderately dipping reverse fault striking to the southwest or northeast. Japan is a seismically active region, with most earthquakes occurring off the east coast, where the Pacific plate subducts beneath Japan. This earthquake occurred on the west coast of Japan where crustal deformation created by the broader plate motions is accommodated in shallow faults. Shallow earthquakes cause more damage than intermediate- and deep-focus ones since the energy generated by the shallow events is released closer to the surface and therefore produces stronger shaking relative to earthquakes located deeper within the Earth. This coastal earthquake produced both strong shaking on land and generated a tsunami.
While earthquakes are common in Japan, the region surrounding the January 1, 2024, earthquake sees lower rates of seismicity as compared to the major subduction zone along its east coast. Still, since 1900, 30 other M6 and larger earthquakes have occurred within 250 km of the January 1 event. Three of these occurred on or near the Noto Peninsula, where the January 1 event is located. On May 5, 2023, a M6.2 earthquake on the Noto Peninsula killed one person and damaged hundreds of buildings. On April 16, 1964, a M7.6 occurred 205 km east-northeast of the January 1 event, resulting in 36 fatalities and roughly 3,500 destroyed homes.
