Chch quake more violent than Marlborough's

Last updated 05:00 03/10/2013

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Christchurch Earthquake 2011

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The quake that caused major damage in Christchurch in February 2011 was three times more violent than the Marlborough quake on August 16, GNS Science says.

The finding is partly based on readings from 20 quake catchers, devices given out by GNS Science at a meeting in Seddon after the magnitude-6.5 quake on July 21.

Caroline Little, of GNS Science, said the tiny devices measured the violence or gravitational pull but not magnitude of quakes. They were not as sensitive or accurate as GeoNet's usual sensors but having a lot of them meant data on quake violence, depth and direction all added up.

"It is a matter of quantity over quality," the scientist and public information specialist said.

Each quake catcher was plugged into a computer USB port and the other end attached to the floor with velcro or duct tape. Only quakes of about magnitude 4.5 or more were recorded and data was sent back to Stanford University in California. Information was shared with GNS Science and the public.

"People who have the quake catchers are able to watch the earthquake shaking on their computer screen at the same time as they feel their house shaking," Little said.

The display showed the last hour of shaking and a table with all quakes recorded.

The quake catchers were designed and are part of an international network developed by Stanford University in California.

The university makes and distributes the low-cost sensors and feeds data into early warning systems.

Twelve permanent seismometers measure shaking in Marlborough, including the Sounds, Little said.

Since July, GNS Science had buried an extra 14 temporary seismometers to fill gaps in the mostly coastal permanent network. All were within 70km of Lake Grassmere, between Seddon and Ward, where the August 16 magnitude-6.6 quake was centred.

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