Brief Background Material
The quake was centered along the southern portion of the Tonga-Kermadec subduction zone, the tectonic boundary between the Pacific and Australia plates, just prior to where it bends around the North Island of New Zealand. Large earthquakes are common along this extensive tectonic boundary but this quake occurred within a seismic gap where few historic quakes of this magnitude and depth have occurred relative to the other portions of the zone.

It was the strongest earthquake off the North Island coast since 1997 but that M7.2 quake was centered well to the north near L'Esperance Rock in the Kermadec Islands. Below is a list of M6.5+ quakes between 32°S and 40°S since 1970. Notice that the M6.5 temblor in 1994 is the only quake in the vicinity in the past 30 years.

11/08/79 15:56:43 32.31S 179.20W 440 6.5
12/30/84 21:36:56 36.66S 177.51W 39 6.8
09/26/85 07:27:51 34.69S 178.66W 51 7.0
02/17/87 06:16:12 32.79S 179.30W 10 6.6
08/23/86 23:47:48 34.55S 179.29W 32 6.5
03/02/87 01:42:34 37.97S 176.76W 19 6.8
08/10/93 09:46;35 38.52S 177.55W 14 6.5
12/15/94 11:20:22 37.28S 177.52W 33 6.5
02/05/95 22:51:05 37.76S 178.75E 21 7.5
02/10/95 01:45:03 37.85S 178.60E 28 6.5
01/30/96 22:29:57 32.92S 178.30W 33 6.9
05/25/97 23:22:33 32.12S 179.79E 332 7.2
01/08/21 06:52:06 36.96S 179.84W 33 6.9

Additional Seismic information links:

• Seismo-Watch Links to New Zealand Activity
• NEIC-USGS Earthquake Bulletin
  • Historical Seismicity
  • P-Wave Travel Times
  • Phase (Arrival Time) Data
• Institute of Geological & Nuclear Sciences
  • GNS Seismological Observatory
  • GNSSO Earthquake Report

Seismograms from selected global stations:

• South Karori, New Zealand
• Pohakaloa, Hawaii
• Albuquerque, New Mexico
• La Paz, Bolivia
• IGNS - Cannon Point << way cool!

Mainstream media news reports:

• Earthquake Rocks Parts of New Zealand (AP) - Aug. 21 6:34 AM ET