N.Z. Seismologists Study Wellington Quake Risk as City Re-Opens

New Zealand seismologists are trying to determine whether the magnitude 6.5 earthquake that struck Wellington two days ago has increased the chances of a much bigger rupture occurring under the capital city.

The July 21 tremor, which was centered offshore about 57 kilometers (35 miles) south-southwest of Wellington, was New Zealand’s biggest earthquake since a magnitude 6.3 killed 185 people in the South Island city of Christchurch two years ago. It may have transferred some stress onto a larger fault below Wellington that’s capable of releasing quakes of magnitude 8 or greater, GNS Science seismologist John Ristau said.

“It is possible, we have to do more study to get a precise map of the stress pattern,” he said in an interview. “Having said that, the most recent studies found that the probability of a major earthquake along the Wellington fault is actually lower than previously thought.”

Wellington re-opened for business today even as aftershocks from the magnitude 6.5 quake continued to rattle the region. The city was largely closed yesterday after the quake, which hit shortly after 5 p.m. on Sunday evening, threw goods from store shelves, blew out windows and caused people to run screaming from buildings such as movie theaters. Four people were hospitalized with minor injuries. There were no fatalities.

Just 35 of about 2,500 buildings in the central business district sustained damage, Wellington Mayor Celia Wade-Brown said last night. About 12 of them have been cordoned off due to concerns about falling glass and masonry. Some office blocks, including the Precinct Properties New Zealand Ltd.’s HP Tower, remain closed while engineers check their structural soundness.

Statistics New Zealand delayed the release of a minor piece of data today, and canceled a news conference scheduled for tomorrow, citing water damage to its Wellington building.

There is a 7 percent chance of another magnitude 6 or greater earthquake in the region in the next 24 hours, and a 19 percent risk of one hitting over the next seven days, Ristau said.

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