Reviewed by USGSNew Zealand80y ago
M7.7 earthquake 46 km E of Gisborne, New Zealand
Tuesday, March 25, 1947, 20:32:20 UTC · 38.676°S, 178.533°E
A magnitude 7.7 earthquake struck 46 km E of Gisborne, New Zealand on Tuesday, March 25, 1947, 20:32:20 UTC, at a depth of 15.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 7.7
- Major · mw
- Depth
- 15 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VI
- Strong (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
4.8 megatons of TNT
That is about 320 times the Hiroshima bomb. It released about 10,116 times the energy of a magnitude 5.0.
Tectonic setting
64 km
from the nearest mapped plate boundary, between the Kermadec and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
15 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 200 km
USGS has not published any M2.5+ earthquake within 200 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 23 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.447 km WSW of Hastings, New ZealandFebruary 2, 1931 · 225 km SW of this epicenter
- 7.340 km E of Waiouru, New ZealandFebruary 13, 1931 · 224 km SW of this epicenter
- 7.044 km N of Whakatane, New ZealandNovember 22, 1914 · 189 km NW of this epicenter
- 6.962 km S of Gisborne, New ZealandSeptember 15, 1932 · 72 km SW of this epicenter
- 6.75 km SSW of Hastings, New ZealandJune 28, 1921 · 185 km SW of this epicenter
- 6.748 km ENE of Opotiki, New ZealandOctober 6, 1914 · 104 km NW of this epicenter
- 6.5105 km SSE of Hastings, New ZealandApril 22, 1931 · 216 km SW of this epicenter
- 6.4off the east coast of the North Island of New ZealandFebruary 8, 1931 · 156 km SW of this epicenter
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, which together caused about 262 recorded deaths. The most severe:
- 1931M7.7
Hawke Bay
2 Feb 1931 · 248 km away · intensity IX
261 deaths$25 million damagetsunami
- 1914
North Island
6 Oct 1914 · 102 km away · intensity VIII
1 deathModerate damage ($1–5M)tsunami
- 1932M6.8
Gisborne, Wairoa
15 Sep 1932 · 96 km away
Moderate damage ($1–5M)tsunami
- 1947M7.1
Off Coast North Island
25 Mar 1947 · 35 km away · intensity IV
Limited damage (under $1M)tsunami
- 1904M7.5
E Of North Island
8 Aug 1904 · 242 km away
tsunami
- 1931M7.1
N
13 Feb 1931 · 161 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.