Earthquake.now

M4.0 Earthquake near Ambunti, Papua New Guinea — 28 August 2025

A light earthquake of magnitude 4.0 was recorded near Ambunti, Papua New Guinea on , with an epicentre 44 km northeast of Ambunti, at a focal depth of 82.8 km. It ranked as the 16th strongest of 16 earthquakes recorded in Papua New Guinea in the preceding 30 days.

4.0 Light

Time (UTC): 2025-08-28 08:29:54

Time (your timezone): —

Magnitude: 4.0 (light)

Focal depth: 82.8 km (intermediate)

Epicentre: -3.9632, 143.1290

Location: 44 km NE of Ambunti, Papua New Guinea

Country: Papua New Guinea

USGS link to NOAA tsunami information: Not linked

Review status: Reviewed

Source: USGS event page

How strong was this earthquake?

Light earthquakes are widely felt near the epicentre and can rattle windows, dishes and hanging objects. Damage is uncommon and usually limited to cracked plaster or fallen loose items.

A magnitude 4.0 earthquake radiates roughly 15 tons of TNT equivalent in seismic energy.

The USGS assigns this earthquake a significance score of 246, 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 →

When it happened locally

That is about 18:02 local solar time at the epicentre, in the evening.

This event was deeper than 65% of the 549 earthquakes recorded in Papua New Guinea in our catalogue and stronger than 0% of them.

Where was the epicentre?

The epicentre was located at -3.9632, 143.1290 — 44 km northeast of Ambunti. The closest other recorded event was a magnitude 4.7 earthquake 8 km northwest of here on 25 February 2025.

The nearest other settlements in our records are Sapandei (21 km southwest), Aitape (125 km west), Wewak (145 km southeast) and Wabag (186 km southeast).

Why the 83 km depth matters

At 83 km this was an intermediate-depth earthquake. Energy from events at this depth spreads out before it reaches the surface, which usually means weaker shaking near the epicentre than a shallow quake of the same magnitude, but shaking felt across a wider area.

This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, an event this size is often felt across the surrounding area. Its intermediate depth normally reduces peak shaking near the epicentre compared with a shallow 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 M4.0 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

1 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 4.8.

49 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 6.6 event near Angoram on 20 May 2025. This M4.0 event released about 7,943 times less energy than that event.

10 earthquakes have been recorded within 100 km of this epicentre in the past year, 1 of them in the past 30 days.

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

Where this event sits in the record

This earthquake is part of the August 2025 worldwide record, and of earthquakes in Papua New Guinea during August 2025. Browse the full monthly archive to compare periods.

Nearest recorded earthquakes to this epicentre

Other recent earthquakes in Papua New Guinea

All recorded earthquakes in Papua New Guinea →

Other magnitude 4 earthquakes worldwide

All magnitude 4 earthquakes →

Questions about this earthquake

How strong was the earthquake near Ambunti?

It measured magnitude 4.0 — a light earthquake. A magnitude 4.0 earthquake radiates roughly 15 tons of TNT equivalent in seismic energy.

How deep was the earthquake near Ambunti?

The focus was 83 km below the surface, which counts as intermediate.

Was the Ambunti earthquake felt at the surface?

At magnitude 4.0 and a focal depth of 83 km, the depth spreads the energy out, so shaking is weaker overhead but reaches further.

When did the earthquake near Ambunti happen?

28 August 2025 at 08:29 UTC.

Was there a tsunami?

No. The USGS record carries no tsunami-information link for this event.

Have there been aftershocks?

1 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 4.8.

How often do earthquakes happen near Ambunti?

49 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 6.6 event near Angoram on 20 May 2025. This M4.0 event released about 7,943 times less energy than that event.