Reviewed by USGS97y ago
M6.4 earthquake off the east coast of the North Island of New Zealand
Sunday, February 8, 1931, 01:43:49 UTC · 39.709°S, 177.316°E
A magnitude 6.4 earthquake struck off the east coast of the North Island of New Zealand on Sunday, February 8, 1931, 01:43:49 UTC, at a depth of 15.0 km (shallow). It is the strongest earthquake within 300 km since an M7.4 on February 2, 1931.
- Magnitude
- 6.4
- Strong · 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 earthquakeDashed circle: 100 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
60 kilotons of TNT
That is about 4 times the Hiroshima bomb. It released about 126 times the energy of a magnitude 5.0.
Tectonic setting
113 km
from the nearest mapped plate boundary, between the Kermadec and Australian plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
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 100 km
USGS lists 1 M2.5+ earthquake within 100 km in the following 30 days; the largest was M6.2 on March 8, 1931. 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 13 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 · 86 km W of this epicenter
- 7.044 km N of Whakatane, New ZealandNovember 22, 1914 · 241 km N of this epicenter
- 6.9144 km SE of Waipawa, New ZealandAugust 8, 1904 · 277 km S of this epicenter
- 6.856 km SSE of Castlepoint, New ZealandAugust 5, 1917 · 199 km S of this epicenter
- 6.75 km SSW of Hastings, New ZealandJune 28, 1921 · 42 km W of this epicenter
- 6.748 km ENE of Opotiki, New ZealandOctober 6, 1914 · 204 km N of this epicenter
- 6.384 km SSE of Castlepoint, New ZealandSeptember 12, 1919 · 217 km S of this epicenter
- 6.350 km ESE of Castlepoint, New ZealandFebruary 12, 1930 · 160 km S 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, which together caused about 262 recorded deaths. The most severe:
- 1931M7.7
Hawke Bay
2 Feb 1931 · 111 km away · intensity IX
261 deaths$25 million damagetsunami
- 1914
North Island
6 Oct 1914 · 226 km away · intensity VIII
1 deathModerate damage ($1–5M)tsunami
- 1855M8.0
Wellington,Waiouru,Wanganui,Otaki
23 Jan 1855 · 260 km away
Severe damage ($5–24M)tsunami
- 1848M7.9
N.
15 Oct 1848 · 297 km away
Limited damage (under $1M)tsunami
- 1843M7.5
Wanganui
8 Jul 1843 · 199 km away
tsunami
- 1904M7.5
E Of North Island
8 Aug 1904 · 92 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.