June 29, 2026
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On July 28 at 16:27, an earthquake with a magnitude (M) of 7.1 (provisional) occurred in the Kumamoto region, Kumamoto Prefecture, at a depth of approximately 15 km. The quake recorded a maximum seismic intensity 7 in Kumamoto Prefecture, where it caused damage. Furthermore, a long-period ground motion of class 4 was also recorded in Kumamoto Prefecture. Its focal mechanism was a strike-slip fault type with a tension axis oriented in the NNW-SSE direction. The earthquake occurred within the Earth's crust.
* Following the earthquakes, intense seismic activity has continued across an area extending approximately 50 km in a NE-SW direction. As of 14:00 on July 29, a total of 194 earthquakes with a maximum seismic intensity 1 or greater have been recorded. The largest event was the M6.1 quake on July 28, at 17:08.
* Following the M7.1 earthquake, high acceleration values were recorded at several observation stations in Kumamoto Prefecture. These included 1,667 gal at the KiK-net Misumi station and 2,438 gal at the municipal seismic intensity station in Toyono Town, Uki City (both three-component composite).
* GNSS observations revealed that the M7.1 earthquake was accompanied by crustal deformation, which was recorded over a wide area centered on Kumamoto Prefecture. For example, a shift of approximately 87 cm was recorded at the Sencho observation point in Yatsushiro City. Moreover, analysis results from the synthetic aperture radar interferometry of the Advanced Land Observing Satellite-2 "Daichi 2" provided evidence of significant crustal deformation around the seismic activity area.
* The source of the M7.1 earthquake, as estimated from crustal deformation observations and seismic wave analysis, extends from the rupture initiation point towards shallower depths, and the length is estimated to be approximately 30 km.
* The seismic activity zone is located near the Futagawa and Hinagu fault zones. This activity is primarily distributed along the Takano-Shirahata and Hinagu segments of the Hinagu Fault Zone, which is made up of three parts (the Takano-Shirahata, Hinagu and Yatsushiro Sea segments). It is believed that the source fault of the M7.1 event extends across the north-eastern part of the Hinagu segment and a portion of the Takano-Shirahata segment of the Hinagu Fault Zone.
* To the northeast of this seismic activity zone lies the seismic activity zone of the 2016 Kumamoto Earthquake, which extends from the Kumamoto region, Kumamoto Prefecture to central Oita Prefecture. From the Aso region, Kumamoto Prefecture which includes this seismic activity zone, seismic activity remains high compared to that before the 2016 Kumamoto Earthquake.
* The Earthquake Research Committee assessed that, when active, the Takano-Shirahata and Hinagu segments of the Hinagu Fault Zone have the potential to generate earthquakes with magnitudes of approximately M6.8 and M7.5, respectively. The probability of such earthquakes occurring within 30 years was classified as Rank X (unknown) and Rank S* (high), respectively (#2). Furthermore, the probability of an M6.8 or greater earthquake occurring in the southern Kyushu area, including the Hinagu Fault Zone, was estimated to be between 7% and 18%.
* In this region, there have been past instances where earthquakes of a similar magnitude have occurred successively within approximately a week after a strong earthquake. Therefore, it is advisable to exercise caution for approximately a week after strong earthquakes, particularly those with a maximum seismic intensity 7. Notably, earthquakes that cause strong shaking often occur within two to three days after the initial shock. As this seismic activity zone extends over a wide area and depending on the location and magnitude of subsequent earthquakes, shaking could be stronger than that caused by this one (M7.1). Furthermore, if a large earthquake occurs on the seafloor, caution is required regarding tsunamis.
Note: GNSS refers to a generic term for satellite positioning systems, including GPS.
#1: The 2026 Kumamoto Earthquake (as designated by the Japan Meteorological Agency) refers to the M7.1 earthquake that occurred on July 28, 2026, in the Kumamoto region, Kumamoto Prefecture, and the subsequent series of aftershocks.
#2: Active faults are classified as "S-rank" if the probability of an earthquake occurring within the next 30 years is 3% or higher, "A-rank" if the probability is between 0.1% and less than 3%, "Z-rank" if the probability is less than 0.1%, and "X-rank" if the probability is unknown (meaning that the evaluation is difficult due to insufficient historical earthquake data). An asterisk (*) is appended to the rank for active faults with an elapsed-time rate(#3) of 0.7 or greater. Even for Z-rank, the simple existence of the active fault still indicates a possibility that a major earthquake could occur in the area.
#3: A value obtained by dividing the elapsed time from the most recent seismic event by the average recurrence interval at the time of evaluation. This value is 1.0 when the elapsed time reaches the average recurrence interval.