“Severe” Quake Strikes Near Haast, West Coast

A “severe” shallow earthquake has struck  the west coast of the South Island.

Reference Number 3764993[View Felt Reports in Google Maps]
Universal Time August 30 2012 at 19:38
NZ Standard Time Friday, August 31 2012 at 7:38 am
Latitude, Longitude 44.10°S, 168.72°E
Focal Depth 5 km
Richter magnitude 5.3
Region West Coast
Location
  • 40 km south-west of Haast
  • 70 km north-west of Wanaka
  • 200 km west of Timaru
  • 240 km north-west of Dunedin

The quake, which happened at 7.38am quake was centred 40km southwest of Haast,  10km inland from the fishing port of Jackson Bay.

GNS Science described the earthquake’s intensity as severe and reported it had been felt as far afield as Dunedin.

More than 270 people had this morning reported they felt the quake to GeoNet… more here

New Zealanders were quick to respond to the earthquake saying

“felt it in ranfurly,, seemed to go on for a bit ,,”

“Was only 5km deep so would have been much stronger than a deeper quake.”

“Now they have revised it to 3km deep so was really shallow!”

“Just had a look on geonet and it seems to be all around the Alpine Fault lately. I did feel that Haast one here in Christchurch, a small wavey jump is how I’d describe it. We’re about 600km away from the epicentre so it would have given yous guys down south a hell of a fright!”

“Epicentre on Geonet looks like it’s very close to bang on the Alpine fault, perhaps a km or two east.”

Alpine Fault – A major Earthquake in waiting

The Alpine Fault, Wikipedia

Over the last thousand years, there have been four major ruptures along the Alpine Fault causing earthquakes of about magnitude 8. These occurred in approximately 1100, 1450, 1620 and 1717 AD, at intervals between 100 and 350 years. The 1717 quake appears to have involved a rupture along nearly 400 km of the southern two thirds of the fault. Scientists say that a similar earthquake could happen at any time as the interval since 1717 is longer than between the earlier events.

GNS Science researchers have compiled an 8000-year timeline of 24 major quakes on the (southern end of the) fault from sediments at Hokuri Creek, near Lake McKerrow in north Fiordland. In earthquake terms, the 850km-long fault is remarkably consistent, rupturing on average each 330 years, at intervals ranging from 140 years to 510 years.

Large ruptures can also trigger earthquakes on the faults continuing north from the Alpine Fault. There is paleotsunami evidence of near-simultaneous ruptures of the Alpine fault and Wellington (and/or other major) faults to the North having occurred at least twice in the past 1,000 years. source

For more about the Alpine Fault click here http://www.otago.ac.nz/geology/research/structural_geology/alpinefault/index.html