June 20, 2021
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On June 19 at 15:08 (JST), there was a magnitude (M) 5.4 (provisional) earthquake at a depth of approximately 15 km in the Noto region, Ishikawa prefecture and maximum seismic intensity 6 Lower was observed in Ishikawa prefecture and some damage was caused. The focal mechanism showed a reverse fault type with a compression axis in an NNW-SSE direction. This event occurred within the crust.
* In the vicinity of the recent event, the number of earthquakes is increasing since about 2018, then the seismic activity became high since December 2020, and it has become higher since about July 2021. In the series of the seismic activity, from December 1, 2020 till June 20, 2022 at 12 o'clock (JST) there occurred 160 earthquakes with seismic intensity 1 or over: of these 27 earthquakes with seismic intensity 3 or over. After the recent event, till June 20 at 12 o'clock (JST), there occurred 12 earthquakes with seismic intensity 1 or over.
In the series of the seismic activity, the largest earthquake is the recent event. In addition, an M5.1 earthquake on September 16, 2021 caused maximum seismic intensity 5 Lower and an M5.0 earthquake on June 20, 2022 at 10:31 (JST) caused maximum seismic intensity 5 Upper.
* The series of the seismic activity occurs in the area about 15 km in an E-W direction and about 15 km in an N-S direction. Especially the activity is high in the northern and eastern parts, where the recent event and the M5.0 earthquake on 20th at 10:31 (JST) occurred. In the eastern region, the M5.1 earthquake on September 16, 2021 occurred, and the number of earthquakes of M3.0 or over has increased since March 2022.
* According to the GNSS observation, since about December 2020, the following crustal deformation has been observed: the cumulative displacement of 1 cm over in the south-southeast direction and the uplift of 4 cm or so at the Suzu observatory in Suzu City, Ishikawa prefecture and the cumulative displacement of 1 cm over in the south-southwest direction at the Noto observatory in Noto Town. The deformation at the Suzu observatory continues at present. On the other hand, the deformation at the Noto observatory seems to have decayed since about January 2022.
Note that any significant crustal deformation has not been observed till now.
* In the area of strong shaking, we should pay attention for a week or so, to the possibility of an earthquake which causes maximum seismic intensity 6 Lower or so. Especially for 2 or 3 days after the earthquake, there is a possibility that a large earthquake occurs.
Based on the situation of the seismic activity and the crustal deformation, the series of the seismic activity will continue for the time being and we should pay attention for a strong shaking.
Note: GNSS is a general name of satellite positioning system such as GPS.