January 2, 2024
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On January 1 at 16:10 (JST), there was a magnitude (M) 7.6 (provisional) earthquake at a depth of approximately 15 km in the Noto region, Ishikawa Prefecture. In addition to maximum seismic intensity 7 observed at Shika Town, Hakui County, Ishikawa Prefecture, shaking above seismic intensity 6 Lower was observed in a wide area of the Noto region and damage was caused. Also, in Ishikawa Prefecture long-period ground motion class 4 was observed. The focal mechanism showed a reverse fault type with a compression axis in an NW-SE direction. This event occurred within the crust.
* At present the high seismic activity continues. The range of seismic activity since January 1 extends about 150 km in an NE-SW direction. From 1st at 16 o'clock till 2nd at 13 o'clock (JST), there occurred 169 earthquakes with seismic intensity 1 or over observed (maximum seismic intensity: number of earthquakes, 7: 1, 5 Upper: 3, 5 Lower: 6).
* The recent event caused tsunami observed at the Sea of Japan side of the area extending from Hokkaido to Kyushu, such that of height 1.2 m over (preliminary) observed at Wajima Port observatory (Ports and Harbours Bureau), and of height 0.9m (preliminary) observed at Kanazawa observatory (Ports and Harbours Bureau).
* According to the GNSS observation, associated with the recent event, the crustal deformations were observed in a wide area centering on the Noto Peninsula: the displacement of 1.2 m or so in the west-southwest direction and the uplift of 1.1 m or so at Wajima observatory (GSI). Also, the analysis of the Synthetic Aperture Radar Images by Advanced Land Observing Satellite "the Daichi-2" showed the uplift of maximum 4 m or so and westward displacement of maximum 1 m or so was detected at the western Wajima City.
* Associated with the M7.6 earthquake on January 1, large accelerations were observed, such as 2,828 gal (synthesis of 3 components) at K-NET Togi observatory, Shika Town.
* Since January 1 the area of the seismic activity is expanding. 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 7 or so. Especially for 2 or 3 days after the earthquake, there is a possibility that a large earthquake occurs. Also, in the case of a large earthquake at the ocean bottom, we should pay attention for tsunami.
* In the crust of the Noto region, Ishikawa Prefecture, where the recent earthquake occurred, 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 January 2, 2024 at 13 o'clock (JST) there occurred 675 earthquakes with seismic intensity 1 or over observed: of these 160 earthquakes with seismic intensity 3 or over observed. In the series of the seismic activity, the recent event is the largest earthquake. In addition, on May 5, 2023 there occurred an M6.5 earthquake.
* According to the result of the GNSS observation, since about December 2020 till the occurrence of the M6.5 earthquake, the following crustal deformation had continued: the cumulative displacement of 1 cm over in the horizontal direction and the uplift of 4 cm or so in Suzu City, Ishikawa Prefecture. The GNSS observation and the analysis of the Synthetic Aperture Radar Images by Advanced Land Observing Satellite "the Daichi-2," at the time of the M6.5 event, showed the crustal deformation of maximum 20 cm or so was found at the surrounding area of the epicenter. The deformation in different tendency from the pre-earthquake stage observed at several observatories after the M6.5 event has recently decayed, and it seems that the tendency in the pre-earthquake stage has returned.
* The series of seismic activity was mainly in the northwestern part and the sea area north of the Noto Peninsula. The seismic activity area after January 1 traverses the northern Noto Peninsula in an NE-SW direction, reaches the northeastern sea area off the Noto Peninsula in the northeastern side and reaches the activity area of "the Noto Hanto Earthquake in 2007" in the southwest side.
* The seismic fault estimated from the focal mechanism of the M7.6 earthquake on January 1, the distribution of the seismic activity and the analysis of GNSS observation, is a reverse fault mainly dipping southwest, extending about 150 km or so in an NE-SW direction.
* The recent event is a large earthquake along the Sea of Japan coast accompanying tsunami, similar to the 1983 Central Japan Sea Earthquake (M7.7), the 1993 Offshore Southwest of Hokkaido Earthquake (M7.8).
* In the ocean bottom offshore northeast and the north coast of the Noto Peninsula, several active faults are known to exist. These active faults are estimated to be of reverse fault type dipping southeast with strikes generally in an NE-SW direction.
* Based on the situation of the seismic activity and the crustal deformation, the series of the seismic activity will continue for the time being.
# :"The 2024 Noto Peninsula Earthquakes" (named by JMA) denotes the series of earthquakes after January 1, 2024 and the series of seismic activity in the Noto region since December 2020.
Note: GNSS is a general name of satellite positioning system such as GPS.