MARCH 8 2011 01:25h

New Zealand earthquake mapped by satellite


CHRISTCHURCH, New Zealand, March 7 (UPI) -- A satellite has mapped the aftermath of the earthquake that devastated Christchurch, New Zealand, showing how the ground deformed, researchers say.

Radar data from the Japanese Alos spacecraft show the magnitude 6.3 tremor that killed more than 160 people Feb. 22 was centered directly under the city's southeastern suburbs, the BBC reported Monday.

The "map" made by combining a sequence of radar images acquired before and after the quake showed that in some places the ground rose almost 20 inches while other areas sank.

"It's like a contour map but it's showing to the southeast of Christchurch that the ground motion is towards Alos. That's uplift," John Elliott at Oxford University in the United Kingdom said.

"And then right under Christchurch, we see subsidence. That's partly due to liquefaction but it's mainly due to the way the Earth deforms when you snap it like an elastic band."

Liquefaction afflicts loose sediments in an earthquake and has been compared to a lateral landslide.

Scientists are using the Alos information to understand the future seismic hazards in this part of New Zealand, including "blind" faulting -- faulting at risk of rupture but which shows little surface evidence of its existence, so the potential danger it poses is not easily recognized.

"To get an earthquake right under their city will have been a surprise to nearly every single person," Elliott said of the residents of Christchurch.