M3.9 earthquake 27 km S of Sinabang, Indonesia

Wednesday, April 20, 2005, 17:28:03 UTC · 2.234°N, 96.372°E

A magnitude 3.9 earthquake struck 27 km S of Sinabang, Indonesia on Wednesday, April 20, 2005, 17:28:03 UTC, at a depth of 30.0 km (shallow).

Magnitude: 3.9; Minor · 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

11 tons of TNT

That is about 1/1,410 of the Hiroshima bomb. A magnitude 5.0 releases about 45 times more energy.

Tectonic setting

45 km

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

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 24 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M6.2 on April 28, 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 396 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 15 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 231,429 recorded deaths. The most severe:

2004M9.1
Sumatra: Aceh: Off West Coast
26 Dec 2004 · 126 km away
227,899 deaths$10 billion damagetsunami
1907M8.2
Nw Sumatra: Gunungsitoli, Barus
4 Jan 1907 · 106 km away
2,188 deathsSevere damage ($5–24M)tsunami
2005M8.6
Sumatera: Sw
28 Mar 2005 · 83 km away
1,319 deaths$37 million damagetsunami
1936
N Sumatera: Tapanuli, Karo
9 Sep 1936 · 188 km away · intensity VIII
17 deathsModerate damage ($1–5M)
2002M7.3
Sumatera: Simeulue
2 Nov 2002 · 73 km away
3 deathsSevere damage ($5–24M)
1987M6.6
Sumatera: N, Tarutung-Lake Toba,
25 Apr 1987 · 277 km away
2 deaths$1 million damage

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

Nearby trackers