Reviewed by USGSNew Zealand59y ago
M7.1 earthquake 38 km E of Westport, New Zealand
Thursday, May 23, 1968, 17:24:18 UTC · 41.727°S, 172.060°E
A magnitude 7.1 earthquake struck 38 km E of Westport, New Zealand on Thursday, May 23, 1968, 17:24:18 UTC, at a depth of 22.5 km (shallow). It is the strongest earthquake within 300 km since an M7.3 on June 16, 1929.
- Magnitude
- 7.1
- Major · mw
- Depth
- 23 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- IX
- Violent (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
587 kilotons of TNT
That is about 39 times the Hiroshima bomb. It released about 1,230 times the energy of a magnitude 5.0.
Tectonic setting
92 km
from the nearest mapped plate boundary, between the Australian and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
23 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 lists 1 M2.5+ earthquake within 200 km in the following 30 days; the largest was M5.8 on May 24, 1968. 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 17 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.368 km S of Wakefield, New ZealandJune 16, 1929 · 100 km E of this epicenter
- 7.030 km NW of Amberley, New ZealandMarch 9, 1929 · 143 km S of this epicenter
- 6.815 km SSE of Levin, New ZealandAugust 1, 1942 · 296 km E of this epicenter
- 6.535 km NNW of Methven, New ZealandJune 26, 1946 · 188 km S of this epicenter
- 6.558 km SW of Wakefield, New ZealandJune 22, 1929 · 47 km E of this epicenter
- 6.471 km NNE of Amberley, New ZealandMay 22, 1948 · 121 km SE of this epicenter
- 6.386 km NNE of Amberley, New ZealandDecember 25, 1922 · 124 km SE of this epicenter
- 6.351 km SSW of Wakefield, New ZealandJune 22, 1929 · 54 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, which together caused about 23 recorded deaths. The most severe:
- 1929M7.5
South Island
16 Jun 1929 · 16 km away
17 deathsModerate damage ($1–5M)tsunami
- 1968M7.1
South Island: Nw Coast
23 May 1968 · 6 km away
3 deaths$3 million damage
- 1848M6.0
Awatere River, Marlborough
18 Oct 1848 · 161 km away
3 deathstsunami
- 1855M8.0
Wellington,Waiouru,Wanganui,Otaki
23 Jan 1855 · 251 km away
Severe damage ($5–24M)tsunami
- 1848M7.9
N.
15 Oct 1848 · 209 km away
Limited damage (under $1M)tsunami
- 1913M6.8
Tasman Sea
22 Feb 1913 · 47 km away · intensity VIII
Limited damage (under $1M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.