Reviewed by USGSNew Zealand50y ago
M5.6 earthquake in Kermadec Islands, New Zealand
Sunday, August 29, 1976, 18:29:00 UTC · 29.627°S, 178.264°W
A magnitude 5.6 earthquake struck in Kermadec Islands, New Zealand on Sunday, August 29, 1976, 18:29:00 UTC, at a depth of 72.0 km (intermediate). It is the strongest earthquake within 300 km since an M5.8 on August 19, 1976.
- Magnitude
- 5.6
- Moderate · mb
- Depth
- 72 km
- Intermediate
- 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: 75 km aftershock search area
In context
How big was it, and why here?
Energy released
4 kilotons of TNT
That is about 1/4 of the Hiroshima bomb. It released about 8 times the energy of a magnitude 5.0.
Tectonic setting
70 km
from the nearest mapped plate boundary, between the Kermadec and Australian plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: intermediate
72 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 75 km
USGS lists 2 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M5.5 on September 13, 1976. 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 373 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 · 233 km SE of this epicenter
- 8.01976 Kermadec Islands, New Zealand EarthquakeJanuary 14, 1976 · 146 km NE of this epicenter
- 7.5Kermadec Islands regionFebruary 27, 1955 · 296 km NE of this epicenter
- 7.5Kermadec Islands, New ZealandNovember 16, 1917 · 48 km SE of this epicenter
- 7.3Kermadec Islands regionSeptember 14, 1959 · 135 km NE of this epicenter
- 7.3Kermadec Islands, New ZealandMarch 26, 1963 · 70 km SE of this epicenter
- 7.3Kermadec Islands, New ZealandJuly 25, 1968 · 131 km S of this epicenter
- 7.2Kermadec Islands regionJuly 2, 1974 · 232 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 8 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1976M7.9
Kermadec Islands
14 Jan 1976 · 93 km away
Limited damage (under $1M)tsunami
- 1968M7.3
S Of, Raoul
25 Jul 1968 · 131 km away
Limited damage (under $1M)tsunami
- 1917M8.0
Kermadec Islands
1 May 1917 · 131 km away
tsunami
- 1976M7.8
Kermadec Islands
14 Jan 1976 · 106 km away · intensity VIII
- 1959M7.7
Kermadec Islands
14 Sep 1959 · 175 km away
- 1943M7.6
S Of
14 Sep 1943 · 129 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.