Tectonic Summary

The March 16, 2022, M 7.3 earthquake near the east coast of Honshu, Japan, occurred as the result of thrust faulting at or near the subduction zone plate boundary interface between the Pacific and North America plates. Moment tensor solutions indicate that slip occurred either on a moderately dipping fault striking to the south, or a moderately dipping fault striking to the north, consistent with the east-west oriented compression expected in this region. At the location of this earthquake, the Pacific plate moves approximately westward relative to the North America plate at a velocity of roughly 70 mm/yr, subducting beneath Japan at the Japan Trench and dipping to the west beneath Japan. Note that some researchers divide this region into several microplates that together define the relative motions among the larger Pacific, North America, and Eurasia plates; these include the Okhotsk and Amur microplates local to this earthquake that are part of North America and Eurasia, respectively.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Reverse (thrust) faulting events of the size of the March 16, 2022 earthquake are typically about 55 km long by 30 km wide in size.

The March 16 earthquake was preceded by a M 6.4 foreshock approximately 2 minutes earlier. A M 7.1 earthquake occurred ~15 km east of these events in February 2021. The March 16 events occurred in the vicinity of the rupture area of the March 11, 2011 M9.1 Tohoku earthquake. The March 2011 M9.1 earthquake was widely felt on the islands of Honshu and Hokkaido in Japan. Notably, that earthquake generated a significant tsunami that led to extensive destruction along the Japanese coast and propagated throughout the Pacific Ocean basin. Approximately 16,000 people perished as a result of the earthquake and subsequent tsunami. The March 16 earthquake epicenter was located ~100 km from the epicenter of the March 2011 earthquake. In the past century, 33 earthquakes of M7 or greater have occurred within 250 km of the March 16 earthquake, including 7 earthquakes >M7 since the March 2011 M9.1 earthquake.