M7.8 earthquake 108 km SW of Kirakira, Solomon Islands

Saturday, October 3, 1931, 19:13:21 UTC · 11.118°S, 161.195°E

A magnitude 7.8 earthquake struck 108 km SW of Kirakira, Solomon Islands on Saturday, October 3, 1931, 19:13:21 UTC, at a depth of 15.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.

Magnitude: 7.8; Major · mw
Depth: 15 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: VI; Strong (ShakeMap)
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

8.4 megatons of TNT

That is about 557 times the Hiroshima bomb. It released about 17,579 times the energy of a magnitude 5.0.

Tectonic setting

5 km

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

Depth: shallow

15 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 200 km

USGS lists 8 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M7.8 on October 10, 1931. 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 23 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 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 50 recorded deaths. The most severe:

1931M7.8
San Cristobal Island
3 Oct 1931 · 28 km away
50 deathsSevere damage ($5–24M)tsunami
1926M6.9
Solomon Islands
16 Sep 1926 · 244 km away
Moderate damage ($1–5M)tsunami
1926M7.5
Guadalcanal
25 Jan 1926 · 246 km away
Limited damage (under $1M)tsunami
1931M7.7
Solomon Islands
10 Oct 1931 · 128 km away
1926M7.5
Solomon Islands
12 Apr 1926 · 126 km away

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

Nearby trackers