M8.0 earthquake 2006 Tonga Earthquake

Wednesday, May 3, 2006, 15:26:40 UTC · 20.187°S, 174.123°W

A magnitude 8.0 earthquake struck 2006 Tonga Earthquake on Wednesday, May 3, 2006, 15:26:40 UTC, at a depth of 55.0 km (shallow). USGS received 41 “Did You Feel It?” reports, with a maximum reported intensity of VIII (severe). It is the strongest earthquake within 300 km since an M8.1 on April 30, 1919.

Magnitude: 8.0; Great · mwc
Depth: 55 km; Shallow
Felt reports: 41; Max intensity VIII
Est. shaking: VII; Very strong (ShakeMap)
PAGER alert: None; Not issued
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 400 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

15 megatons of TNT

That is about 1,002 times the Hiroshima bomb. It released about 31,623 times the energy of a magnitude 5.0.

Tectonic setting

87 km

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

Depth: shallow

55 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

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
Nukuʿalofa, Tongatapu, Tonga	VII · Very strong	11	164 km
Apia, Apia Urban Area, Samoa	III · Weak	8	749 km
Neiafu, Vavaʿu, Tonga	VII · Very strong	4	180 km
Alofi, _no region, Niue	V · Moderate	2	461 km
Atiu, Atiu, Cook Islands	III · Weak	2	1674 km
Auckland, Auckland, New Zealand	VIII · Severe	1	2144 km
Vaini, Tongatapu, Tonga	V · Moderate	1	167 km
Avarua, Rarotonga, Cook Islands	IV · Light	1	1501 km
Vila, Shefa, Vanuatu	III · Weak	1	1870 km

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 400 km

USGS lists 196 M2.5+ earthquakes within 400 km in the following 30 days; the largest was M6.0 on May 17, 2006. 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 1,133 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 12 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

1919M8.1
Tonga Islands
30 Apr 1919 · 265 km away
Limited damage (under $1M)tsunami
1865M8.0
Tonga Islands
18 Nov 1865 · 100 km away
Limited damage (under $1M)tsunami
2006M7.9
Tonga Islands
3 May 2006 · 0 km away · intensity VII
Limited damage (under $1M)tsunami
1903M8.0
Tonga Islands
4 Jan 1903 · 94 km away
1948M7.9
Tonga Islands
8 Sep 1948 · 91 km away
tsunami
1902M7.8
Tonga Islands
9 Feb 1902 · 24 km away

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

Nearby trackers