Reviewed by USGSTonga20y ago
M4.1 earthquake 21 km NNW of Pangai, Tonga
Saturday, July 15, 2006, 03:30:40 UTC · 19.631°S, 174.419°W
A magnitude 4.1 earthquake struck 21 km NNW of Pangai, Tonga on Saturday, July 15, 2006, 03:30:40 UTC, at a depth of 35.0 km (shallow).
- Magnitude
- 4.1
- Light · mb
- Depth
- 35 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
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
82 km
from the nearest mapped plate boundary, between the Tonga and Niuafo'ou plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
35 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 2 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.9 on July 17, 2006. 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 1,232 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.11919 Tonga EarthquakeApril 30, 1919 · 254 km NE of this epicenter
- 8.0TongaJanuary 4, 1903 · 73 km SW of this epicenter
- 8.02006 Tonga EarthquakeMay 3, 2006 · 69 km SE of this epicenter
- 7.8159 km W of Pangai, TongaDecember 14, 1950 · 153 km W of this epicenter
- 7.8111 km SSE of Pangai, TongaJune 26, 1913 · 133 km SE of this epicenter
- 7.5110 km E of ‘Ohonua, TongaSeptember 8, 1948 · 185 km S of this epicenter
- 7.4103 km ESE of Neiafu, TongaFebruary 27, 1921 · 166 km NE of this epicenter
- 7.385 km ESE of Neiafu, TongaJanuary 2, 1907 · 132 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 13 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1919M8.1
Tonga Islands
30 Apr 1919 · 246 km away
Limited damage (under $1M)tsunami
- 1865M8.0
Tonga Islands
18 Nov 1865 · 97 km away
Limited damage (under $1M)tsunami
- 2006M7.9
Tonga Islands
3 May 2006 · 69 km away · intensity VII
Limited damage (under $1M)tsunami
- 1903M8.0
Tonga Islands
4 Jan 1903 · 73 km away
- 1948M7.9
Tonga Islands
8 Sep 1948 · 158 km away
tsunami
- 1902M7.8
Tonga Islands
9 Feb 1902 · 60 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.