Vivinavi : Chiba : (Japan) Chiba

Nankai Trough Earthquake Related Explanatory Information （ No.4 ）

■ Date and Time ： August 12, 2024, 15:30
■ Overview ：

At around 16:43 on August 8, an 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 （ including the epicenter area of the August 8 earthquake from 16:00 on August 8 to 12:00 today （ ） 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, intensity 1 ： 8 times ）
2 times from 00:00 to 24:00 on 10th （ intensity 2 ： 1 time, intensity 1 ： 1 time ）
2 times from 00:00 to 24:00 on 11th （ intensity 3 ： 1 time, intensity 1 1 time ）
1 time from 00:00 to 12:00 on 12th （ Seismic intensity 1 ： 1 time ）
Also, at strain stations, step-like changes associated with magnitude 7 ． 1 earthquake have been observed, but other than the changes usually seen after earthquakes, no changes have been observed so far. However, no changes other than those usually seen after earthquakes have been observed so far. Deep low-frequency earthquakes in the Kii Peninsula and Ise Bay （ Microtremors ） associated with the activity have been observed in nearby strain gauges, 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 therefore, at 19:15 on August 8, the Nankai Trough Earthquake Temporary Information （ 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 a tremor 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 13th.
We will announce any new changes as they are observed.


[Distributed by]
Funabashi City Emergency Management Division

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