Reviewed by USGSNew Zealand64y ago
M6.8 earthquake in Kermadec Islands, New Zealand
Monday, May 20, 1963, 11:38:05 UTC · 30.685°S, 178.170°W
A magnitude 6.8 earthquake struck in Kermadec Islands, New Zealand on Monday, May 20, 1963, 11:38:05 UTC, at a depth of 65.0 km (shallow). It is the strongest earthquake within 300 km since an M7.3 on March 26, 1963.
- Magnitude
- 6.8
- Strong · mw
- Depth
- 65 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: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
239 kilotons of TNT
That is about 16 times the Hiroshima bomb. It released about 501 times the energy of a magnitude 5.0.
Tectonic setting
107 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
65 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 M5.6 on June 4, 1963. 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 131 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 · 155 km E of this epicenter
- 7.5Kermadec Islands, New ZealandNovember 16, 1917 · 98 km N of this epicenter
- 7.3Kermadec Islands regionSeptember 14, 1959 · 225 km NE of this epicenter
- 7.3Kermadec Islands, New ZealandMarch 26, 1963 · 91 km NE of this epicenter
- 7.2Kermadec Islands, New ZealandAugust 2, 1941 · 115 km NE of this epicenter
- 7.2Kermadec Islands, New ZealandApril 17, 1919 · 21 km NE of this epicenter
- 7.1Kermadec Islands, New ZealandJune 29, 1910 · 105 km E of this epicenter
- 7.1Kermadec Islands, New ZealandSeptember 16, 1941 · 177 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:
- 1917M8.0
Kermadec Islands
1 May 1917 · 200 km away
tsunami
- 1959M7.7
Kermadec Islands
14 Sep 1959 · 268 km away
- 1943M7.6
S Of
14 Sep 1943 · 136 km away
- 1917M7.5
S Of
16 Nov 1917 · 198 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.