Reviewed by USGSTonga23y ago
M4.3 earthquake 276 km WNW of Haveluloto, Tonga
Monday, August 18, 2003, 17:09:00 UTC · 20.157°S, 177.647°W
A magnitude 4.3 earthquake struck 276 km WNW of Haveluloto, Tonga on Monday, August 18, 2003, 17:09:00 UTC, at a depth of 400.0 km (deep).
- Magnitude
- 4.3
- Light · mb
- Depth
- 400 km
- Deep
- 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
43 tons of TNT
That is about 1/354 of the Hiroshima bomb. A magnitude 5.0 releases about 11 times more energy.
Tectonic setting
153 km
from the nearest mapped plate boundary, between the Tonga and Australian plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: deep
400 km
Deep earthquakes (over 300 km) happen deep inside subducting plates. They rarely cause damage, but can be felt faintly over very large distances.
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 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M4.1 on August 18, 2003. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 1,378 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.0TongaJanuary 4, 1903 · 277 km E of this epicenter
- 7.8159 km W of Pangai, TongaDecember 14, 1950 · 192 km E of this epicenter
- 7.8Fiji regionJanuary 1, 1919 · 104 km NW of this epicenter
- 7.8192 km WSW of Haveluloto, TongaOctober 14, 1997 · 234 km SE of this epicenter
- 7.7Fiji regionAugust 19, 2002 · 259 km SW of this epicenter
- 7.6178 km E of Levuka, FijiFebruary 22, 1909 · 261 km NW of this epicenter
- 7.6240 km E of Levuka, FijiMarch 9, 1994 · 249 km N of this epicenter
- 7.5262 km WNW of Haveluloto, TongaMay 21, 1962 · 21 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 11 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1937M8.1
Fiji Islands
16 Apr 1937 · 164 km away
- 1903M8.0
Tonga Islands
4 Jan 1903 · 277 km away
- 1909M7.8
Fiji Islands
22 Feb 1909 · 279 km away
- 1919M7.8
Fiji Islands
1 Jan 1919 · 104 km away
tsunami
- 1950M7.7
Tonga Islands
14 Dec 1950 · 187 km away · intensity VI
- 1997M7.7
Tonga Islands
14 Oct 1997 · 234 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.