Reviewed by USGSNew Zealand22y ago
M7.1 earthquake 255 km W of Riverton, New Zealand
Monday, November 22, 2004, 20:26:23 UTC · 46.676°S, 164.721°E
A magnitude 7.1 earthquake struck 255 km W of Riverton, New Zealand on Monday, November 22, 2004, 20:26:23 UTC, at a depth of 10.0 km (shallow). USGS received 12 “Did You Feel It?” reports, with a maximum reported intensity of V (moderate). It is the strongest earthquake within 300 km since an M7.2 on August 21, 2003.
- Magnitude
- 7.1
- Major · mwc
- Depth
- 10 km
- Shallow
- Felt reports
- 12
- Max intensity V
- Est. shaking
- V
- Moderate (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
674 kilotons of TNT
That is about 45 times the Hiroshima bomb. It released about 1,413 times the energy of a magnitude 5.0.
Tectonic setting
19 km
from the nearest mapped plate boundary, between the Pacific and Australian plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
10 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
Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.
| Place | Intensity | Reports | Distance |
|---|---|---|---|
| Invercargill, Southland, New Zealand | V · Moderate | 4 | 281 km |
| Dunedin, Otago, New Zealand | IV · Light | 3 | 452 km |
| Christchurch, Canterbury, New Zealand | III · Weak | 2 | 714 km |
| Wanaka, Otago, New Zealand | IV · Light | 1 | 409 km |
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 4 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M4.3 on December 5, 2004. 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 81 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.6off the west coast of the South Island of New ZealandMay 25, 1981 · 236 km S of this epicenter
- 7.5173 km WSW of Riverton, New ZealandSeptember 1, 1945 · 100 km E of this epicenter
- 7.4180 km W of Riverton, New ZealandOctober 12, 1979 · 75 km E of this epicenter
- 7.256 km NW of Te Anau, New ZealandAugust 21, 2003 · 256 km NE of this epicenter
- 7.0Auckland Islands, New Zealand regionSeptember 12, 1964 · 263 km S of this epicenter
- 7.015 km WNW of Te Anau, New ZealandDecember 16, 1938 · 261 km NE of this epicenter
- 7.063 km WNW of Te Anau, New ZealandAugust 10, 1993 · 231 km NE of this epicenter
- 7.0Auckland Islands, New Zealand regionFebruary 22, 1936 · 278 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 2003M7.2
Dunedin,Invercargill,Te Anau,Fiordland
21 Aug 2003 · 256 km away
Limited damage (under $1M)tsunami
- 2004M7.1
Invercargill, Southland, Otago
22 Nov 2004 · 0 km away
Limited damage (under $1M)tsunami
- 1826M8.0
Fjordland
1826 · 168 km away
- 1981M7.6
W Of North Island
25 May 1981 · 236 km away
tsunami
- 1979M7.5
W Of North Island
12 Oct 1979 · 75 km away · intensity V
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.