The Relationship Between the Miyazaki Offshore Earthquake and the Nankai Trough

 

The Relationship Between the Miyazaki Offshore Earthquake and the Nankai Trough

On August 8, 2024, a magnitude 7.1 earthquake occurred off the coast of Miyazaki Prefecture, in the Hyuga-nada region. This earthquake registered a seismic intensity of lower 6 on the Japanese scale in Nichinan City, Miyazaki Prefecture. The Japan Meteorological Agency (JMA) has issued an "Nankai Trough Earthquake Temporary Information" and is investigating the possible connection between this event and the potential for a future Nankai Trough earthquake​​.

1. Details and Impact of the Earthquake

The earthquake struck at approximately 4:43 PM, with its epicenter located about 30 kilometers deep. Although tsunami advisories were issued for Miyazaki and Kochi Prefectures, they were later lifted​. Due to the proximity of this earthquake to the presumed source region of the Nankai Trough, experts have immediately started examining any potential links to a larger Nankai Trough earthquake.

2. Potential Links to the Nankai Trough Earthquake

The Nankai Trough earthquake is expected to occur along the boundary between the Philippine Sea Plate and the Eurasian Plate, potentially causing a massive earthquake that would affect a large portion of Japan. Given that the recent Miyazaki offshore earthquake occurred near this plate boundary, there is concern that it might act as a trigger for a larger event.

The JMA has convened an evaluation committee of experts to analyze the situation. Initial findings suggest "slow slip" phenomena have been detected, where the tectonic plates gradually shift without causing a major earthquake. However, it remains uncertain whether these slow slips directly indicate an imminent major earthquake​.

3. Earthquake Mechanism

The mechanism behind Nankai Trough earthquakes involves the subduction of the Philippine Sea Plate beneath the Eurasian Plate, leading to the accumulation of stress, which is eventually released in the form of a massive earthquake. The "slow slip" phenomena mentioned earlier refer to subtle movements of the plates, which have sometimes been observed before large seismic events. Nevertheless, not all slow slips lead to major earthquakes, requiring careful monitoring and analysis​.

4. Recent Research and Predictions

Recent research efforts have focused on observing crustal movements and low-frequency earthquakes (tremors) in the Nankai Trough region. The data gathered from these observations is critical for assessing the potential for a future Nankai Trough earthquake. The 2024 Miyazaki offshore earthquake has drawn significant attention as part of these efforts, highlighting the need for continued vigilance regarding seismic activity​​.

5. Strengthening Disaster Preparedness

In response to the Miyazaki offshore earthquake, disaster preparedness efforts are being reinforced. The government and local authorities are enhancing measures such as disaster drills, the preparation of evacuation centers, and the promotion of earthquake insurance. On an individual level, people are advised to prepare emergency kits, secure furniture, and establish evacuation routes.

Conclusion

The Miyazaki offshore earthquake has raised significant concerns about its potential connection to the Nankai Trough earthquake. Although there is currently no definitive evidence that the Nankai Trough earthquake is imminent, the ongoing seismic activity warrants close observation. Increasing awareness of disaster preparedness and ensuring readiness are essential for ensuring safety. Staying informed with the latest updates and expert analyses will help guide appropriate actions in the future.