Vivinavi : Yachiyo : (Japan) Yachiyo

August 11, 2024 15:30 Announced

[Summary]
A magnitude 7 ． 1 earthquake occurred at 16:43 on August 8 with its epicenter in the Hyuga Sea. 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.

[Text]
An earthquake of magnitude 7 ． 1 （ moment magnitude 7 ． 0 ） 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 higher 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 （ August 11 ） 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 ）
10th 00:00 to 24:00 2 times （ Seismic intensity 2 ： 1 time, Seismic intensity 1 ： 1 time ）
11th 00:00 to 12:00 1 time （ 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 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.

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Yachiyo City Hall Emergency Management Division
Address ： 312-5 Owada-Shinden, Yachiyo 276-8501
TEL ： 047-421-6716
FAX ： 047-483-1094