Vivinavi : Chiba : (Japan) Chiba

Nankai Trough Earthquake Related Explanatory Information （ No.3 ）

■ Date and Time ： 15:30, August 11, 2024
■ Summary ：

Earthquake with epicenter at Hyuga-nada at 16:43 on August 8 A magnitude 7 ． 1 earthquake occurred. After the occurrence of the earthquake on August 8, we issued a Nankai Trough Earthquake Temporary Information （ Earthquake Warning ） at 19:15 on August 8, because the possibility of a large-scale earthquake in the assumed epicenter area of the Nankai Trough earthquake was considered to have increased relative to normal conditions. After the earthquake on August 8, no seismic activity or crustal deformation has been observed in the assumed epicenter of the Nankai Trough earthquake that would indicate any particular change in the plate boundary sticking conditions. Please continue to take disaster prevention measures in response to calls from the government and local governments.



A magnitude 7 ． 1 （ moment magnitude 7 ． 0 ） earthquake occurred at 16:43 on August 8, centered in the Hyuga Sea. Seismic activity near the epicenter of this earthquake has remained active since then.
The number of earthquakes of seismic intensity 1 or greater that occurred in the ） assumed epicenter area of the Nankai Trough earthquake （ from 16:00 on August 8 to 12:00 today （ August 11 ） including the epicenter area of the August 8 earthquake （ The preliminary report ） is as follows.
8 times from 16:00 to 24:00 on the 8th （ Seismic intensity 6 ： 1 time, intensity 2 ： 2 times, intensity 1 ： 5 times ）
11 times from 00:00 to 24:00 on the 9th （ Seismic intensity 3 ： 1 time, intensity 2 ： 2 times, Seismic intensity 1 ： 8 times ）
2 times from 00:00 to 24:00 on 10th （ Seismic intensity 2 ： 1 time, Seismic intensity 1 ： 1 time ）
1 time from 00:00 to 12:00 on 11th （ Seismic intensity 3 ： 1 time ） Also, at strain stations, step-like changes associated with a magnitude 7 ． 1 earthquake have been observed, but so far no changes other than those normally seen after earthquakes have been observed. Deep low-frequency earthquake in the Kii Peninsula （ Microtremors ） associated with the activity have been observed in nearby strain gauges and other instruments, but this is a phenomenon that has been repeated in the past.
Thus, after the occurrence of the earthquake on the 8th, no seismic activity or crustal deformation has been observed in the assumed epicenter area of the Nankai Trough earthquake that would indicate any particular change in the plate boundary sticking conditions.

As a result of studying the relationship between the August 8 earthquake and the Nankai Trough earthquake, the possibility of a large-scale earthquake in the assumed epicenter area of the Nankai Trough earthquake is considered to be relatively higher than under normal conditions, and so at 19:15 on August 8, Temporary Information on Nankai Trough Earthquake （ A huge earthquake warning ） was issued.
The government is calling on the Nankai Trough Earthquake Disaster Prevention Promotion Areas to reconfirm their daily earthquake preparedness and be ready to evacuate immediately if they feel any tremors for one week after the earthquake on August 8. Please continue to take disaster prevention measures in response to calls from the government and local governments.
The JMA will continue to carefully monitor crustal activity along the Nankai Trough.

*Moment magnitude is the magnitude obtained by closely examining the scale of displacement of the epicenter fault. It may be different from the magnitude reported by the Japan Meteorological Agency in earthquake information.


We will continue to announce the status of crustal activity and other information in the "Nankai Trough Earthquake Related Information. The next announcement is scheduled for around 15:30 on the 12th.
We will announce any new changes as they are observed.


[Distributed by]
Funabashi City Emergency Management Division

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