Earthquake.now

M5.4 Earthquake near Koshima, Japan — 21 March 2026

A moderate earthquake of magnitude 5.4 was recorded near Koshima, Japan on , with an epicentre 91 km south-southeast of Koshima, at a focal depth of 25.5 km.

5.4 Moderate

Time (UTC): 2026-03-21 11:12:04

Time (your timezone): —

Magnitude: 5.4 (moderate)

Focal depth: 25.5 km (shallow)

Epicentre: 29.4276, 130.7270

Location: 91 km SSE of Koshima, Japan

USGS link to NOAA tsunami information: Not linked

Review status: Reviewed

Source: USGS event page

How strong was this earthquake?

Moderate earthquakes can damage poorly built or unreinforced structures near the epicentre, while well-engineered buildings typically escape serious harm. Shaking is often strong enough to wake sleeping residents over a wide area.

A magnitude 5.4 earthquake radiates roughly 1,898 tons of TNT equivalent in seismic energy.

The USGS assigns this earthquake a significance score of 449, which is below the USGS threshold of more than 600 for its significant-earthquake list. The ranking combines magnitude with available Did You Feel It responses and PAGER alert level; it is not a direct measurement of damage.

What the magnitude scale actually measures →

Where was the epicentre?

The epicentre was located at 29.4276, 130.7270 — 91 km south-southeast of Koshima. The closest other recorded event was a magnitude 4.7 earthquake 8 km west-northwest of here on 09 September 2025.

Why the 26 km depth matters

At 26 km this was a shallow earthquake. Shallow events release their energy close to the surface, so for a given magnitude they produce noticeably stronger shaking — and more damage — than deeper ones. Roughly three quarters of all earthquakes worldwide occur at shallow depths.

This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, an event this size can be felt widely and may cause minor local damage. Its shallow focus makes stronger surface shaking more likely than for a deeper event of the same magnitude.

Read more on how focal depth changes what you feel →

What does the tsunami information flag mean?

The USGS record does not carry a link to NOAA tsunami information. That field is not an all-clear and does not state whether a tsunami occurred. In this case, a damaging tsunami would be less likely because at M5.4 it falls below the magnitude 6.5 threshold that generally applies before a submarine earthquake displaces enough water to generate a damaging tsunami; it occurred inland rather than beneath the sea floor. For an active coastal alert, use tsunami.gov or your local warning authority.

How earthquakes generate tsunamis, and what the alert levels mean →

Aftershocks and local seismic history

2 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 4.6.

155 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 6.2 event near Nishinoomote on 02 April 2025. This M5.4 event released about 16 times less energy than that event.

How long aftershock sequences last, and how large they get →

Where this event sits in the record

This earthquake is part of the March 2026 worldwide record. Browse the full monthly archive to compare periods.

Nearest recorded earthquakes to this epicentre

Other magnitude 5 earthquakes worldwide

All magnitude 5 earthquakes →

Questions about this earthquake

How strong is a magnitude 5.4 earthquake?

Moderate earthquakes can damage poorly built or unreinforced structures near the epicentre, while well-engineered buildings typically escape serious harm. Shaking is often strong enough to wake sleeping residents over a wide area. A magnitude 5.4 earthquake radiates roughly 1,898 tons of TNT equivalent in seismic energy.

How deep was the earthquake near Koshima?

At 26 km this was a shallow earthquake. Shallow events release their energy close to the surface, so for a given magnitude they produce noticeably stronger shaking — and more damage — than deeper ones. Roughly three quarters of all earthquakes worldwide occur at shallow depths.

Was the M5.4 earthquake near Koshima felt?

This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, an event this size can be felt widely and may cause minor local damage. Its shallow focus makes stronger surface shaking more likely than for a deeper event of the same magnitude.

What does the USGS tsunami field mean for this event?

The USGS record does not carry a link to NOAA tsunami information. That field is not an all-clear and does not state whether a tsunami occurred. In this case, a damaging tsunami would be less likely because at M5.4 it falls below the magnitude 6.5 threshold that generally applies before a submarine earthquake displaces enough water to generate a damaging tsunami; it occurred inland rather than beneath the sea floor. For an active coastal alert, use tsunami.gov or your local warning authority.

Have there been aftershocks?

2 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 4.6.

How often do earthquakes happen near Koshima?

155 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 6.2 event near Nishinoomote on 02 April 2025. This M5.4 event released about 16 times less energy than that event.