M5.6 earthquake 271 km SW of Merizo Village, Guam

Tuesday, October 26, 1971, 19:05:06 UTC · 11.881°N, 142.609°E

A magnitude 5.6 earthquake struck 271 km SW of Merizo Village, Guam on Tuesday, October 26, 1971, 19:05:06 UTC, at a depth of 18.4 km (shallow). It is the strongest earthquake within 300 km since an M6.2 on October 24, 1971.

Magnitude: 5.6; Moderate · mw
Depth: 18 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 earthquake

In context

How big was it, and why here?

Energy released

4 kilotons of TNT

That is about 1/4 of the Hiroshima bomb. It released about 9 times the energy of a magnitude 5.0.

Tectonic setting

52 km

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

Depth: shallow

18 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 75 km

USGS has not published any M2.5+ earthquake within 75 km in the 30 days after this event.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 61 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 7 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

1849M7.5
Guam
25 Jan 1849 · 247 km away · intensity IX
Severe damage ($5–24M)tsunami
1909M8.0
Guam
9 Dec 1909 · 269 km away · intensity VIII
Moderate damage ($1–5M)tsunami
1892M7.5
Guam
16 May 1892 · 247 km away · intensity VIII
Moderate damage ($1–5M)tsunami
1825
Ladrones Island
Apr 1825 · 247 km away · intensity VIII
Moderate damage ($1–5M)tsunami
1834
Agana
May 1834 · 247 km away
Moderate damage ($1–5M)
1903
Guam
10 Feb 1903 · 247 km away · intensity VII
Limited damage (under $1M)tsunami

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

Nearby trackers