M7.3 earthquake 195 km E of Biak, Indonesia

Wednesday, April 2, 1947, 05:39:16 UTC · 1.102°S, 137.839°E

A magnitude 7.3 earthquake struck 195 km E of Biak, Indonesia on Wednesday, April 2, 1947, 05:39:16 UTC, at a depth of 15.0 km (shallow). It is the strongest earthquake within 300 km since an M7.6 on October 26, 1926.

Magnitude: 7.3; Major · mw
Depth: 15 km; Shallow
Felt reports: 0; Did You Feel It?
Est. shaking: VII; Very strong (ShakeMap)
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

1.3 megatons of TNT

That is about 89 times the Hiroshima bomb. It released about 2,818 times the energy of a magnitude 5.0.

Tectonic setting

45 km

from the nearest mapped plate boundary, between the Birds Head and Caroline 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 has not published any M2.5+ earthquake within 200 km in the 30 days after this event.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 36 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. The most severe:

1914M8.1
New Guinea: Irian Jaya: Japen
26 May 1914 · 128 km away · intensity IX
Moderate damage ($1–5M)tsunami
1921
New Guinea: Irian Jaya: Sentani
10 Oct 1921 · 171 km away · intensity VII
Moderate damage ($1–5M)
1916M8.1
New Guinea: Irian Jaya
13 Jan 1916 · 294 km away
1926M7.9
New Guinea: Irian Jaya
26 Oct 1926 · 277 km away
1915M6.0
Nw. Irian Jaya
6 Nov 1915 · 205 km away
tsunami

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

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