Reviewed by USGSNew Zealand110y ago
M6.8 earthquake 56 km SSE of Castlepoint, New Zealand
Sunday, August 5, 1917, 15:50:25 UTC · 41.379°S, 176.458°E
A magnitude 6.8 earthquake struck 56 km SSE of Castlepoint, New Zealand on Sunday, August 5, 1917, 15:50:25 UTC, at a depth of 15.0 km (shallow). It is the strongest earthquake within 300 km since an M6.9 on August 8, 1904.
- Magnitude
- 6.8
- Strong · mw
- Depth
- 15 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- V
- Moderate (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
215 kilotons of TNT
That is about 14 times the Hiroshima bomb. It released about 452 times the energy of a magnitude 5.0.
Tectonic setting
46 km
from the nearest mapped plate boundary, between the Kermadec and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
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 has not published any M2.5+ earthquake within 100 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 1 M5.0+ earthquake within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
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 3 recorded deaths. The most severe:
- 1848M6.0
Awatere River, Marlborough
18 Oct 1848 · 207 km away
3 deathstsunami
- 1855M8.0
Wellington,Waiouru,Wanganui,Otaki
23 Jan 1855 · 123 km away
Severe damage ($5–24M)tsunami
- 1848M7.9
N.
15 Oct 1848 · 164 km away
Limited damage (under $1M)tsunami
- 1843M7.5
Wanganui
8 Jul 1843 · 205 km away
tsunami
- 1904M7.5
E Of North Island
8 Aug 1904 · 108 km away
tsunami
- 1895M6.0
Taupo
18 Aug 1895 · 289 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.