M4.1 earthquake 69 km NNW of Pante Makasar, Timor Leste

Tuesday, July 9, 1991, 01:54:02 UTC · 8.617°S, 124.160°E

A magnitude 4.1 earthquake struck 69 km NNW of Pante Makasar, Timor Leste on Tuesday, July 9, 1991, 01:54:02 UTC, at a depth of 165.5 km (intermediate).

Magnitude: 4.1; Light · mb
Depth: 166 km; Intermediate
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

21 tons of TNT

That is about 1/707 of the Hiroshima bomb. A magnitude 5.0 releases about 22 times more energy.

Tectonic setting

93 km

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

Depth: intermediate

166 km

Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.

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 2 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.2 on July 9, 1991. 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 264 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 9 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 418 recorded deaths. The most severe:

1896
Timor: Alor Island
18 Apr 1896 · 77 km away · intensity VIII
250 deathsModerate damage ($1–5M)
1987M6.5
Timor: Pantar, Mount Sirung
26 Nov 1987 · 41 km away
125 deaths$5 million damagetsunami
1991M6.5
Timor: Kalabahi, Dili
4 Jul 1991 · 81 km away
28 deaths$8 million damage
1982M5.9
Flores Island: Eastern
25 Dec 1982 · 121 km away
13 deaths$1 million damagetsunami
1961M6.5
Flores: Endeh
16 Mar 1961 · 242 km away · intensity VIII
2 deathsModerate damage ($1–5M)
1814
Timor Island, Kupang, Kissar Island
1814 · 187 km away
Severe damage ($5–24M)tsunami

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

Nearby trackers