M4.3 earthquake 65 km E of Kokopo, Papua New Guinea

Saturday, July 13, 1985, 14:59:58 UTC · 4.386°S, 152.855°E

A magnitude 4.3 earthquake struck 65 km E of Kokopo, Papua New Guinea on Saturday, July 13, 1985, 14:59:58 UTC, at a depth of 33.0 km (shallow).

Magnitude: 4.3; Light · mb
Depth: 33 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: —; No ShakeMap
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

43 tons of TNT

That is about 1/354 of the Hiroshima bomb. A magnitude 5.0 releases about 11 times more energy.

Tectonic setting

6 km

from the nearest mapped plate boundary, between the North Bismarck and South Bismarck plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: shallow

33 km

Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.

Did You Feel It?

Where it was felt

No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.

After the main event

Aftershocks within 50 km

USGS lists 9 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M6.0 on July 17, 1985. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 838 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 31 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 526 recorded deaths. The most severe:

1937
Keravia, Rabaul, Kokopo
28 May 1937 · 73 km away · intensity VIII
507 deathsLimited damage (under $1M)tsunami
1983M6.4
Ulawun, Rabaul
22 Dec 1983 · 156 km away · intensity V
10 deaths$25 million damage
1941M7.4
Bismarck Sea
13 Jan 1941 · 90 km away
4 deathsModerate damage ($1–5M)tsunami
1971M7.9
New Ireland: Bougainville
14 Jul 1971 · 170 km away · intensity IX
3 deathsUnder $1 million damagetsunami
1985M7.1
New Britain: Bialla, Piona
10 May 1985 · 242 km away · intensity VIII
1 death$1 million damage
1878
Bismarck Sea
4 Feb 1878 · 69 km away
1 deathtsunami

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers