M7.8 earthquake 97 km WSW of Te Anau, New Zealand

Wednesday, July 15, 2009, 09:22:29 UTC · 45.762°S, 166.562°E

A magnitude 7.8 earthquake struck 97 km WSW of Te Anau, New Zealand on Wednesday, July 15, 2009, 09:22:29 UTC, at a depth of 12.0 km (shallow). USGS received 363 “Did You Feel It?” reports, with a maximum reported intensity of VI (strong). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.

Magnitude: 7.8; Major · mwc
Depth: 12 km; Shallow
Felt reports: 363; Max intensity VI
Est. shaking: VIII; Severe (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

7.6 megatons of TNT

That is about 502 times the Hiroshima bomb. It released about 15,849 times the energy of a magnitude 5.0.

Tectonic setting

25 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

12 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	84	157 km
Dunedin, Otago, New Zealand	IV · Light	54	305 km
Queenstown, Otago, New Zealand	IV · Light	41	181 km
Christchurch, Canterbury, New Zealand	III · Weak	30	542 km
Wanaka, Otago, New Zealand	V · Moderate	12	235 km
Timaru, Canterbury, New Zealand	IV · Light	10	397 km
Gore, Southland, New Zealand	IV · Light	9	186 km
Winton, Southland, New Zealand	V · Moderate	8	144 km
Oamaru, Canterbury, New Zealand	IV · Light	8	354 km
Wellington, Wellington, New Zealand	III · Weak	8	830 km
Te Anau, Southland, New Zealand	VI · Strong	7	98 km
Tuatapere, Southland, New Zealand	VI · Strong	4	96 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 200 km

USGS lists 113 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.1 on August 5, 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 80 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 · 0 km away
Limited damage (under $1M)tsunami
2003M7.2
Dunedin,Invercargill,Te Anau,Fiordland
21 Aug 2003 · 86 km away
Limited damage (under $1M)tsunami
2004M7.1
Invercargill, Southland, Otago
22 Nov 2004 · 174 km away
Limited damage (under $1M)tsunami
2007M6.8
South Island: Fiordland
15 Oct 2007 · 135 km away
Limited damage (under $1M)
1826M8.0
Fjordland
1826 · 6 km away
1979M7.5
W Of North Island
12 Oct 1979 · 121 km away · intensity V

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

Nearby trackers