Magnitude 7.2 SOUTH ISLAND OF NEW ZEALAND
2003 August 21 12:12:50 UTC
Preliminary Earthquake Report
U.S. Geological Survey, National Earthquake Information Center
World Data Center for Seismology, Denver
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Magnitude | 7.2 | |
| Date-Time |
Thursday, August 21, 2003 at 12:12:50 (UTC) - Coordinated Universal Time Friday, August 22, 2003 at 12:12:50 AM local time at epicenter Time of Earthquake in other Time Zones |
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| Location | 45.12S 167.17E | ||
| Depth | 28.0 kilometers | ||
| Region | SOUTH ISLAND OF NEW ZEALAND | ||
| Reference |
120 km (75 miles) W of Queenstown, New Zealand 170 km (105 miles) NNW of Invercargill, New Zealand 275 km (170 miles) WNW of Dunedin, New Zealand 750 km (465 miles) SW of WELLINGTON, New Zealand |
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| Location Quality | Error estimate: horizontal +/- 9.0 km; depth fixed by location program | ||
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Location Quality Parameters |
Nst=52, Nph=53, Dmin=105.6 km, Rmss=1.12 sec, Erho=9.0 km, Erzz=0 km, Gp=56.7 degrees | ||
| Source | USGS NEIC (WDCS-D) | ||
| Remarks | Minor damage in Otago and Southland. Chimneys fell and walls cracked at Dunedin, Invercargill and Te Anau. More than 200 landslides were observed and minor damage occurred to park infrastructure in Fiordland National Park. A small tsunami with a maximum wave height of 0.6 meters was recorded in Jackson Bay in Westland. Felt strongly on much of the South Island. Felt as far north as Wellington on the North Island. Also felt at Sydney, New South Wales and Hobart, Tasmania, Australia. |
|
Tectonic Summary
New Zealand straddles the boundary of the Australian and Pacific
plates. Along New Zealand, the Australian plate moves to the northeast
at a rate of 35 to 45 mm/yr relative to the Pacific plate. In the
central
South Island, this plate motion results in predominantly strike-slip
movement along the Alpine Fault. In southwestern South Island, relative
plate motion is accommodated by oblique subduction of the Australian
plate
along the Puysegur trench and deformation of the overriding Pacific
plate
inland of the trench. The Southern Alps of New Zealand result
from this oblique plate convergence.
The recent (03/08/21) thrust earthquake occurred near the southern tip of South Island in a region known as Fiordland. The preliminary location, depth, and estimate of fault orientation are consistent with the earthquake having resulted from slip on the thrust interface between the Pacific and Australian plates. The deformed and subducted Australian plate beneath Fiordland and below the thrust interface is also highly active, and several surface strands of the Alpine Fault are observed in the vicinity of the earthquake epicenter in the overriding Pacific plate above the thrust interface. Over the past two decades, several large earthquakes have occurred in Fiordland. A magnitude 7.0 event on August 10, 1993 caused power outages in the Te Anau area and was felt throughout South Island and as far away as Sydney, Australia. A magnitude 6.4 earthquake struck on May 31, 1989 and was felt strongly in the southwestern part of South Island and a magnitude 6.7 quake struck on June 3, 1988.
|
NB:
The region name is an automatically generated name
from the Flinn-Engdahl (F-E) seismic and geographical regionalization scheme.
The boundaries of
these regions are defined at one-degree intervals and therefore differ from
irregular political boundaries.
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