Reviewed by USGS108y ago
M8.1 earthquake 1919 Tonga Earthquake
Wednesday, April 30, 1919, 07:17:16 UTC · 18.322°S, 172.442°W
A magnitude 8.1 earthquake struck 1919 Tonga Earthquake on Wednesday, April 30, 1919, 07:17:16 UTC, at a depth of 25.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 8.1
- Great · mw
- Depth
- 25 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: 400 km aftershock search area
In context
How big was it, and why here?
Energy released
21 megatons of TNT
That is about 1,415 times the Hiroshima bomb. It released about 44,668 times the energy of a magnitude 5.0.
Tectonic setting
21 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
25 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 400 km
USGS lists 2 M2.5+ earthquakes within 400 km in the following 30 days; the largest was M6.6 on May 2, 1919. 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 7 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.8111 km SSE of Pangai, TongaJune 26, 1913 · 299 km SW of this epicenter
- 7.385 km ESE of Neiafu, TongaJanuary 2, 1907 · 123 km SW of this epicenter
- 7.2108 km SE of Neiafu, TongaDecember 19, 1906 · 126 km SW of this epicenter
- 6.915 km WSW of Pangai, TongaFebruary 27, 1905 · 276 km SW of this epicenter
- 6.9127 km S of Hihifo, TongaMay 8, 1913 · 213 km NW of this epicenter
- 6.8100 km SE of Hihifo, TongaDecember 20, 1914 · 203 km NW of this epicenter
- 6.2211 km SSW of Vailoatai, American SamoaJune 28, 1917 · 263 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 4 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1919M8.1
Tonga Islands
30 Apr 1919 · 8 km away
Limited damage (under $1M)tsunami
- 1865M8.0
Tonga Islands
18 Nov 1865 · 172 km away
Limited damage (under $1M)tsunami
- 1902M7.8
Tonga Islands
9 Feb 1902 · 248 km away
- 1913M7.6
Tonga Islands
26 Jun 1913 · 248 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.