M4.2 earthquake 100 km W of Banda Aceh, Indonesia

Monday, February 21, 2005, 20:18:38 UTC · 5.417°N, 94.432°E

A magnitude 4.2 earthquake struck 100 km W of Banda Aceh, Indonesia on Monday, February 21, 2005, 20:18:38 UTC, at a depth of 30.0 km (shallow).

Magnitude: 4.2; Light · mb
Depth: 30 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

30 tons of TNT

That is about 1/500 of the Hiroshima bomb. A magnitude 5.0 releases about 16 times more energy.

Tectonic setting

105 km

from the nearest mapped plate boundary, between the Sunda and Burma plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: shallow

30 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 22 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.5 on March 13, 2005. 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 513 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 227,908 recorded deaths. The most severe:

2004M9.1
Sumatra: Aceh: Off West Coast
26 Dec 2004 · 292 km away
227,899 deaths$10 billion damagetsunami
1936M7.3
Banda Aceh,Lhok Sukon,Lhoksemawe
23 Aug 1936 · 82 km away · intensity VIII
9 deathsModerate damage ($1–5M)tsunami
1964M7.0
Banda Aceh
2 Apr 1964 · 150 km away · intensity VII
Severe damage ($5–24M)tsunami
1837M7.3
Banda Atjeh
29 Sep 1837 · 174 km away
Moderate damage ($1–5M)tsunami
1983M6.6
Sumatera: Banda Aceh
4 Apr 1983 · 47 km away · intensity VII
$1 million damage
1982M6.3
Little Nicobar Island
20 Jan 1982 · 177 km away · intensity VIII
Moderate damage ($1–5M)

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

Nearby trackers