Reviewed by USGSNew Zealand50y ago
M4.6 earthquake in Kermadec Islands, New Zealand
Saturday, July 31, 1976, 01:32:24 UTC · 30.338°S, 177.806°W
A magnitude 4.6 earthquake struck in Kermadec Islands, New Zealand on Saturday, July 31, 1976, 01:32:24 UTC, at a depth of 24.0 km (shallow). It is the strongest earthquake within 300 km since an M6.2 on July 31, 1976.
- Magnitude
- 4.6
- Light · mb
- Depth
- 24 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
120 tons of TNT
That is about 1/126 of the Hiroshima bomb. A magnitude 5.0 releases about 4 times more energy.
Tectonic setting
112 km
from the nearest mapped plate boundary, between the Kermadec and Pacific plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
24 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 7 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.8 on August 19, 1976. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 5.8Kermadec Islands, New Zealand50y ago · 43 km E of this epicenter
- 4.9Kermadec Islands, New Zealand50y ago · 6 km SE of this epicenter
- 5.3Kermadec Islands, New Zealand50y ago · 32 km SE of this epicenter
- 5.0Kermadec Islands, New Zealand50y ago · 20 km NE of this epicenter
- 5.7Kermadec Islands, New Zealand50y ago · 9 km NE of this epicenter
- 5.6Kermadec Islands, New Zealand50y ago · 9 km SE of this epicenter
- 5.2Kermadec Islands, New Zealand50y ago · 30 km NW of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 389 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.21917 Kermadec Islands, New Zealand EarthquakeMay 1, 1917 · 146 km SE of this epicenter
- 8.01976 Kermadec Islands, New Zealand EarthquakeJanuary 14, 1976 · 213 km N of this epicenter
- 7.5Kermadec Islands, New ZealandNovember 16, 1917 · 54 km N of this epicenter
- 7.3Kermadec Islands regionSeptember 14, 1959 · 176 km N of this epicenter
- 7.3Kermadec Islands, New ZealandMarch 26, 1963 · 40 km N of this epicenter
- 7.3Kermadec Islands, New ZealandJuly 25, 1968 · 61 km SW of this epicenter
- 7.2Kermadec Islands regionJuly 2, 1974 · 227 km NE of this epicenter
- 7.2Kermadec Islands, New ZealandAugust 2, 1941 · 65 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 7 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1976M7.9
Kermadec Islands
14 Jan 1976 · 132 km away
Limited damage (under $1M)tsunami
- 1968M7.3
S Of, Raoul
25 Jul 1968 · 77 km away
Limited damage (under $1M)tsunami
- 1917M8.0
Kermadec Islands
1 May 1917 · 149 km away
tsunami
- 1976M7.8
Kermadec Islands
14 Jan 1976 · 73 km away · intensity VIII
- 1959M7.7
Kermadec Islands
14 Sep 1959 · 219 km away
- 1943M7.6
S Of
14 Sep 1943 · 86 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.