M6.1 earthquake 107 km W of Te Anau, New Zealand

Wednesday, August 5, 2009, 08:31:40 UTC · 45.554°S, 166.356°E

A magnitude 6.1 earthquake struck 107 km W of Te Anau, New Zealand on Wednesday, August 5, 2009, 08:31:40 UTC, at a depth of 10.0 km (shallow). USGS received 25 “Did You Feel It?” reports, with a maximum reported intensity of III (weak). It is the strongest earthquake within 300 km since an M7.8 on July 15, 2009.

Magnitude: 6.1; Strong · mwc
Depth: 10 km; Shallow
Felt reports: 25; Max intensity III
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

21 kilotons of TNT

That is about the energy of the Hiroshima bomb. It released about 45 times the energy of a magnitude 5.0.

Tectonic setting

0 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	III · Weak	11	183 km
Gore, Southland, New Zealand	III · Weak	3	208 km
Queenstown, Otago, New Zealand	II · Weak	3	188 km
Otautau, Southland, New Zealand	III · Weak	2	144 km
Dunedin, Otago, New Zealand	II · Weak	2	323 km
Riverton, Southland, New Zealand	III · Weak	1	156 km
Arrowtown, Otago, New Zealand	III · Weak	1	206 km
Ohai, Southland, New Zealand	III · Weak	1	130 km
Te Anau, Southland, New Zealand	III · Weak	1	108 km

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 16 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M5.2 on August 25, 2009. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 100 M5.0+ earthquakes 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 6 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

2009M7.8
Off West Coast Of South Island
15 Jul 2009 · 28 km away
Limited damage (under $1M)tsunami
2003M7.2
Dunedin,Invercargill,Te Anau,Fiordland
21 Aug 2003 · 79 km away
Limited damage (under $1M)tsunami
2004M7.1
Invercargill, Southland, Otago
22 Nov 2004 · 177 km away
Limited damage (under $1M)tsunami
2007M6.8
South Island: Fiordland
15 Oct 2007 · 129 km away
Limited damage (under $1M)
1826M8.0
Fjordland
1826 · 30 km away
1979M7.5
W Of North Island
12 Oct 1979 · 134 km away · intensity V

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers