A magnitude 7.1 earthquake struck Kumamoto Prefecture in southern Japan on the 28th, and Japanese experts say that the mechanism of this earthquake is similar to the 2016 Kumamoto earthquake, and that aftershocks should be watched for.
According to the Japan Meteorological Agency, this earthquake is a strike-slip type. A strike-slip earthquake occurs when fault lines press against each other and slide relative to one another, triggering an earthquake. Previous research has shown that the 2016 Kumamoto earthquake was also a strike-slip earthquake.
NHK quoted Professor Shinichi Sakai of the Earthquake Research Institute at the University of Tokyo as saying that the 2016 Kumamoto earthquake was caused by the activity of two fault zones extending into Kumamoto Prefecture—the Futagawa Fault Zone and the Hinagu Fault Zone. This earthquake may have been triggered by activity in the southern part of the Hinagu Fault Zone, which did not move during the last earthquake.
Kazunari Obara, a researcher at the National Research Institute for Earth Science and Disaster Resilience, told the Nihon Keizai Shimbun that the mechanism behind this earthquake is similar to the Kumamoto earthquake ten years ago, and, as with the previous quake, there may be multiple aftershocks as well as the possibility of even stronger shaking.
Professor Aitaro Kato of the University of Tokyo Earthquake Research Institute said that this earthquake occurred to the south of the 2016 earthquake area, and that rupture of the fault could trigger a chain reaction farther south, so it is important to be on guard for aftershocks and related situations.
Sakai Shinichi said that the southern end of the Hinagu Fault Zone faces the sea, so earthquakes in this area could trigger tsunamis. People need to closely monitor seismic activity in the area and should not go near the coast or other hazardous areas when earthquakes occur.
On April 14, 2016, a magnitude 6.5 earthquake struck Kumamoto Prefecture, followed by a magnitude 7.3 quake in the early hours of April 16, and multiple aftershocks also occurred.