M4.6 earthquake 80 km SSW of Kandrian, Papua New Guinea

Tuesday, October 20, 1987, 22:04:53 UTC · 6.821°S, 149.156°E

A magnitude 4.6 earthquake struck 80 km SSW of Kandrian, Papua New Guinea on Tuesday, October 20, 1987, 22:04:53 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M4.7 on October 19, 1987.

Magnitude: 4.6; 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

120 tons of TNT

That is about 1/126 of the Hiroshima bomb. A magnitude 5.0 releases about 4 times more energy.

Tectonic setting

28 km

from the nearest mapped plate boundary, between the South Bismarck and Solomon Sea 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 4 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.0 on October 29, 1987. 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 581 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 19 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 4 recorded deaths. The most severe:

1987M7.6
Huon Peninsula, Umboi Island
8 Feb 1987 · 181 km away · intensity VII
3 deaths$3 million damagetsunami
1985M7.1
New Britain: Bialla, Piona
10 May 1985 · 249 km away · intensity VIII
1 death$1 million damage
1906M8.0
New Britain
14 Sep 1906 · 26 km away
Severe damage ($5–24M)tsunami
1857M8.0
Bismarck Sea
17 Apr 1857 · 280 km away
Moderate damage ($1–5M)tsunami
1987M7.7
New Britain: Kandrian, Kimbte
16 Oct 1987 · 63 km away · intensity VIII
Moderate damage ($1–5M)tsunami
1895M7.3
W. Solomon Sea
6 Mar 1895 · 204 km away
Moderate damage ($1–5M)tsunami

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

Nearby trackers