Christchurch, New Zealand, earthquake had similarities to threat in Charleston

Bo Petersen
Posted: Sunday, May 25, 2014

provided by Prudential Carolina Real EstateThe Archdale Plantation home lay in partial ruin after the 1886 earthquake.

The morning after the Great Earthquake of 1886 devastated Charleston, people were out in the streets among the aftershocks, picking up bricks to rebuilt their historic structures. Don't necessarily count on that happening again, the Lowcountry was warned recently.

After a powerful earthquake shattered Christchurch, New Zealand, in 2011, and collapsing structures killed many of 185 people who died, "almost no one is willing to repair the Christchurch Cathedral," said Steve Jaume, College of Charleston geophysicist. "Other historic buildings in Christchurch are being demolished even though they can be repaired."

That was just one of the unsettling takeaways from a presentation by a group of New Zealand researchers on the 2010-2011 sequence of large magnitude earthquakes that caused $40 billion in damage to an historic town much like Charleston in a similar fault zone.

Like Christchurch, "the area around Charleston is not a high risk zone," said David Johnston, director of the Joint Centre for Disaster Research at Massey University, New Zealand.

A powerful magnitude 7 quake struck in the region around Christchurch in September, 2010, but caused little damage and no deaths. No one expected what came next. A storm caused severe flooding and a landslide cut off the main supply route to the city.

Then, in February 2011 a magnitude 6 aftershock of the September quake struck beneath the city, causing the deaths and catastrophic damage.

"It is not necessarily the danger you expect that will hurt you the most," Jaume said. "Murphy's Law rules: If it can happen, it will happen."

The coastal area around Charleston is particularly vulnerable to earthquakes. Three faults underground converge on each other somewhere below the Ashley River near Middleton Place, the edges of tectonic plates pressing against each other. A number of unnoticed tiny quakes occur each year, and noticeable temblors at least every few years.

The devastating 1886 Charleston earthquake is thought to have been a 7.3 magnitude on the Richter scale. It killed 100 people, leveled nine of every 10 brick buildings in Charleston and damaged nine of every 10 in Summerville.

Charleston appears to be in better shape than Christchurch to withstand a powerful quake because of "very good building standards" that anticipate temblors, Johnston said. But people can still make other economical improvements. Even a smaller earthquake can kill by knocking off building structures such as gables and parapets.

"One thing we learned in New Zealand: We talked (beforehand) about hazards but not enough about consequences," he said. "You need to talk about what the options are that people have."

The New Zealanders' presentation was sponsored by the U.S. Geological Survey.

http://www.postandcourier.com/article/20140525/PC16/140529663