Japan Earthquake: 6.6 Magnitude Tremor Strikes Off Coast of Miyazaki

A powerful 6.6 magnitude earthquake struck off the coast of Miyazaki Prefecture on Japan’s southern island of Kyushu at 4:43 p.m. local time on August 8, 2024. According to the Japan Meteorological Agency (JMA), the tremor reached a seismic intensity of 6-minus on the Japanese Shindo scale in Nichinan City. Authorities issued a tsunami advisory for the Pacific coast of Kyushu and Shikoku, though no major damage or casualties were immediately reported.

What Caused the Miyazaki Earthquake?

The earthquake occurred at a depth of approximately 30 kilometers, according to the United States Geological Survey (USGS). The region is located near the Nankai Trough, a subduction zone where the Philippine Sea Plate slides beneath the Eurasian Plate. The JMA noted that the quake was likely a “megathrust” event, which is consistent with the geological history of the Nankai Trough—a site known for producing periodic, high-magnitude seismic activity.

Is a “Mega-Quake” Imminent?

Following the August 8 tremor, the JMA issued its first-ever “Nankai Trough Earthquake Extra Information” advisory. This warning indicates that the probability of a larger earthquake occurring in the region is higher than normal. The government’s Cabinet Office advises residents in affected prefectures to review their evacuation routes and ensure emergency supplies are ready. However, the agency clarified that this is not a prediction that a massive quake will definitely occur, but rather a precautionary measure to increase public preparedness.

How Does This Compare to Previous Seismic Events?

While the Miyazaki earthquake was significant, it serves as a reminder of Japan’s vulnerability to tectonic shifts. The following table highlights the difference between the recent event and historical precedents in the region:

Safety Protocols for Residents

The Fire and Disaster Management Agency recommends the following steps during and after seismic activity:

• Drop, Cover, and Hold On: Seek shelter under a sturdy table to protect against falling objects.
• Stay Informed: Monitor official JMA alerts via the NHK World-Japan portal for real-time updates.
• Evacuate Early: If near the coast, move to higher ground immediately if a tsunami warning is upgraded or if the shaking makes it difficult to stand.
• Check Gas and Electricity: Turn off main power and gas valves to prevent secondary fire hazards after the shaking stops.

While the immediate threat from the August 8 tremor has subsided, the JMA continues to monitor crustal movements in the Nankai Trough. Residents are encouraged to remain vigilant, as seismic activity in this region can remain elevated for several days following an initial rupture.