Quake-maker shakes Christchurch

The T-Rex truck thumps the ground to help simulate an earthquake. Photo / Supplied

The world's largest seismic vibration machine will begin testing the ground under quake-hit Christchurch today.

The giant 29,000-kilogram truck, nicknamed 'TRex', will use large hydraulics to shake the ground to determine the properties of soils up to 250 metres deep.

The machine arrived in Lyttelton last week, and it's the first time it's been used outside of America.

A team from the University of Canterbury and the University of Texas will do their first test near Lyttelton today before going on to 20 sites across the city over the next three weeks.

Researchers have assured residents that the shaking won't be felt more than 15m away.

University of Canterbury earthquake engineer Dr Brendon Bradley said an understanding of Christchurch's soil properties at great depths was important because it impacted how seismic waves were amplified, reflected, and refracted as they travelled up to the earth's surface.

"The ground motion recorded in the February 11 2011 earthquake illustrated significant basin-effects," he said.

"These were caused by reverberations of the soft sedimentary soils that Christchurch is founded on.

"Using state of the art information on soil properties throughout Christchurch obtained by TRex and previous testing we can begin to link cause and effect and better understand where such effects will occur elsewhere during future earthquakes worldwide."