Reviewed by USGSTonga17y ago
M4.5 earthquake 166 km SSW of ‘Ohonua, Tonga
Friday, April 24, 2009, 10:25:34 UTC · 22.793°S, 175.339°W
A magnitude 4.5 earthquake struck 166 km SSW of ‘Ohonua, Tonga on Friday, April 24, 2009, 10:25:34 UTC, at a depth of 10.0 km (shallow). It is the strongest earthquake within 300 km since an M4.7 on April 19, 2009.
- Magnitude
- 4.5
- Light · mb
- Depth
- 10 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
85 tons of TNT
That is about 1/178 of the Hiroshima bomb. A magnitude 5.0 releases about 6 times more energy.
Tectonic setting
84 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
10 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 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.8 on April 28, 2009. 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 1,266 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.8south of TongaOctober 11, 1975 · 235 km S of this epicenter
- 7.8192 km WSW of Haveluloto, TongaOctober 14, 1997 · 166 km NW of this epicenter
- 7.8111 km SSE of Pangai, TongaJune 26, 1913 · 283 km NE of this epicenter
- 7.6south of the Fiji IslandsDecember 18, 1963 · 266 km SW of this epicenter
- 7.6191 km S of ‘Ohonua, TongaMarch 19, 2009 · 75 km E of this epicenter
- 7.5110 km E of ‘Ohonua, TongaSeptember 8, 1948 · 230 km NE of this epicenter
- 7.4south of TongaMarch 18, 1905 · 264 km SE of this epicenter
- 7.2south of the Fiji IslandsNovember 24, 1960 · 229 km SW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 10 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 1 recorded deaths. The most severe:
- 1977M7.2
Tonga Trench
22 Jun 1977 · 58 km away · intensity IV
1 death$1 million damagetsunami
- 1937M8.1
Fiji Islands
16 Apr 1937 · 223 km away
- 1948M7.9
Tonga Islands
8 Sep 1948 · 243 km away
tsunami
- 1975M7.8
S Of Tonga
11 Oct 1975 · 235 km away
- 1982M7.7
Tonga Trench
19 Dec 1982 · 158 km away
tsunami
- 1997M7.7
Tonga Islands
14 Oct 1997 · 166 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.