Dusky Sound Earthquake

Date: July 15, 2009 • Location: Te Anau, New Zealand

A .mw-parser-output .tooltip-dotted{border-bottom:1px dotted;cursor:help}Mw 7.8 earthquake struck a remote region of Fiordland, New Zealand, the country's largest earthquake magnitude since the 1931 Hawke's Bay earthquake.

Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram. Magnitude scales vary based on what aspect of the seismic waves are measured and how they are measured. Different magnitude scales are necessary because of differences in earthquakes, the information available, and the purposes for which the magnitudes are used.