Significant earthquakes of 2004

November 11, 2004 Earthquake: Kepulauan Alor, Indonesia

November 11, 2004 · M7.5 · 34 deaths · 781 houses destroyed

A magnitude 7.5 earthquake struck Kepulauan Alor, Indonesia on November 11, 2004 at 21:26:41 UTC, 10 km below the surface. It killed 34 people.

Map

Where it struck, with the other significant earthquakes within 200 km. Circles are sized and colored by magnitude; select one for its page.

The earthquake

Date
November 11, 2004
Time
21:26:41 UTC
Place
Kepulauan Alor, Indonesia
Magnitude
7.5 (Mw)
Magnitude scales
Mw 7.5 · Ms 7.3 · mb 6.5
Focal depth
10 km (6 mi)
Epicenter
8.152° S, 124.868° E
Country
Indonesia
Region
South and Southeast Asia and Indian Ocean

Mw: moment magnitude, based on the slip on the fault and the area that slipped. Ms: surface-wave magnitude. mb: body-wave (P-wave) magnitude. NCEI’s headline magnitude is the best of these for the earthquake.

The toll

Deaths
34
Injuries
400
Damage
Severe (about $5 to $25 million)
Houses destroyed
781
Houses damaged
16,712

Where the literature gives no number, NCEI records a description on a scale of 1 to 4, printed here in its words. Damage is in millions of US dollars of the year of the event, not adjusted for inflation.

From Wikipedia

On 12 November 2004, at 05:26:41 WITA (21:26:41 UTC, 11 November), a moment magnitude (Mw) 7.5 earthquake struck the Alor Archipelago in East Nusa Tenggara, Indonesia. The island of Alor was devastated by the earthquake, with 17,500 of the 36,300 homes on the island damaged or destroyed. At least 34 fatalities, 400 injuries and 30 missing were recorded on the island.

Text from Wikipedia, “2004 Alor earthquake”, licensed CC BY-SA 4.0. Quoted as written; the full article has the rest.

Wikidata records: 34 deaths. These are counts entered by Wikidata’s editors; they may differ from the official count, and this page never adds them to another figure. Q12483788, CC0.

What happened

The USGS’s account of the effects of this earthquake.

At least 34 people killed, 400 injured, 781 buildings destroyed and 16,712 damaged on Alor. Landslides blocked roads in some areas. Felt (VIII) at Kalabahi. Felt (V) as far away as Dili, East Timor.

From the USGS event page for usp000d85g. U.S. Geological Survey text and figures are in the public domain.

Tectonic setting

Why earthquakes happen here, from the USGS tectonic summary.

The November 11, 2004, M 7.5 earthquake near Kepulauan Alor, Indonesia, occurred as the result of shallow thrust faulting on or near the convergent boundary between the Banda Sea microplate to the north and the Timor microplate to the south. Focal mechanism solutions indicate that rupture occurred on either a steep, near-vertical reverse fault or on a shallow, southward-dipping thrust fault. Of these two possible fault orientations, finite-fault modeling of globally recorded seismic data is more consistent with slip on the southward-dipping thrust fault. At the location of the earthquake, the Banda Sea microplate thrusts beneath the Timor microplate to the south at a velocity of about 30 mm/yr. The two microplates are sandwiched along with other microplates between the larger Sunda, Philippine Sea, Australia, and Pacific plates. The location, depth, and focal mechanism solutions of the November 11th earthquake are consistent with it having occurred on the thrust interface between these two local microplates. A similar earthquake occurred only 20 km to the west in July 1991, a M 6.9 earthquake that resulted in 23 fatalities and 181 injuries.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Thrust-faulting events of the size of the November 11, 2004, earthquake are typically about 80x40 km (length x width); modeling of this earthquake implies dimensions of about 70x50 km, predominantly up-dip and east of the hypocenter.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)

From the USGS event page for usp000d85g. U.S. Geological Survey text and figures are in the public domain.

Magnitude estimates

The magnitudes the USGS catalog lists for this earthquake, by scale and by who computed them. NCEI’s own scales are in the table above.

Mag.ScaleComputed byNotes
7.5Mwc, centroid momentUSGS National Earthquake Information CenterPreferred · Reviewed
7.49Mw, momentISC-GEM global catalogFinal · ±0.1
7.5Mwc, centroid momentGlobal CMT projectPreliminary
7.4Me, energyChoy, USGS energy magnitudeReviewed
7.5Mww, W-phase momentDuputel, W-phase inversionPreliminary
7.47Mw, momentUSGS finite-fault modelFinite-fault model · Reviewed

What the record says

NCEI’s account, from the sources it cites.

At least 34 people killed, 400 injured, 781

buildings destroyed and 16,712 damaged on Alor.

Landslides blocked roads in some areas. Felt (VIII) at

Kalabahi. Felt (V) as far away as Dili, East Timor. (reference #1053)

Sources NCEI cites

The publications NCEI lists for this record. The numbers match the “reference #” notes in its account above.

  1. #1053 National Earthquake Information Center (NEIC) (1971 to 2013). Preliminary Determination of Epicenters (PDE), a weekly and monthly publication, National Earthquake Information Center, U.S. Geological Survey, Golden, Colorado, 1971 to 2013.

Other significant earthquakes nearby

Within 200 km, the deadliest first.

More

Significant earthquakes of 2004The 2000sEvery quake the USGS located in 2004Recent earthquakes near hereThis day in weather history

Sources

Significant earthquakes from NOAA’s National Centers for Environmental Information, Global Historical Hazard Database, cited as NCEI/WDS, doi:10.7289/V5PN93H7. Public domain. Read 2026-10-01. NCEI earthquake 5810. The written accounts and the magnitude estimates are from the USGS earthquake catalog, event usp000d85g, matched to this record by time, place and magnitude.