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M 7.8, Dusky Sound, July 15 2009
This earthquake in Fiordland was New Zealand's largest for nearly 80 years.
- Location: Dusky Sound
- Date (NZ Standard Time): Wednesday, July 15 2009 at 9:22 pm
- Epicentre: 45.75°S, 166.58°E
- Focal Depth: 12 km
- Maximum Intensity: MM 7
- Magnitude: MW 7.8
- Casualties: No casualties reported
- GeoNet Summary:
The earthquake's epicentre was located in Dusky Sound at the south-west corner of the South Island. Its magnitude of 7.8 made its size comparable with the Buller (or Murchison) earthquake of 1929 and the damaging Hawke's Bay earthquake of 1931. The earthquake rupture started at about 30 km depth and ruptured upwards and to the south, focusing energy offshore. The motion was more like a lurch than a snap (meaning the energy was released more slowly); this is typical for a subduction thrust event. This explains why the damage was much less than many people expected for this size of earthquake. The motion was slower (with lower frequency shaking) and "rolling" rather than the sharp (higher frequency shaking) movements that cause building damage; this also explains the low number of landslides.
