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Partially demolished church in a city.
Photo Credit: Wikipedia Commons
Demolition of the Christchurch Cathedral, which was severely damaged by an earthquake in February 2011. Research partly funded by the National Science Foundation is studying liquefaction effects to strengthen building codes in the United States.

Earth-shaking research

U.S. study on liquefaction in Christchurch may have far-reaching applications

Researchers from the University of Texas at Austin External Non-U.S. government site are conducting a study in the New Zealand city of Christchurch with the hope of learning how to bolster building codes in earthquake-prone areas in the United States and abroad.

The team visited New Zealand’s second largest city this summer to conduct field research on liquefaction, the process by which water-saturated sediments, or soil, temporarily become liquid-like.

“This liquefaction fieldwork has never been done before and represents critical, basic research as well as important practical knowledge for Christchurch to move forward in its developments,” said Kenneth Stokoe External Non-U.S. government site, principal investigator on the project and professor in the Department of Civil, Architectural and Environmental Engineering External Non-U.S. government site, in a press release External Non-U.S. government site.

On Sept. 4, 2010, a 7.1-magnitue earthquake rocked the New Zealand’s Canterbury region on the South Island, with much of the damage centered near Christchurch. Nearly six months later, on Feb. 22, 2011, a shallow aftershock of 6.3-magntitude devastated the city center and killed more than 180 people in the country’s fourth-deadliest disaster in history.

Christchurch serves as the primary gateway to Antarctica for the U.S. Antarctic Program (USAP) External U.S. government site and other national programs. About 600 USAP participants were transitioning through the Christchurch area on Feb. 22, 2011, when the earthquake struck. [See previous article — Christchurch earthquake: Witnesses recall first days of crisis as search finds all USAP personnel are OK.]

The quake devastated the city central business district, which fully re-opened to the public at the end of June of this year. The iconic ChristChurch Cathedral was also severely damaged during the February 2011 earthquake. A temporary “cardboard” cathedral building took its place and opened this month.

People stand near a big truck.
Photo Credit: UT Austin
UT Austin researchers stand with the T-Rex shaker truck.
Cars buried in a road.
Photo Credit: Timothy Musson/Wikipedia Commons
Results of liquefaction in Christchurch. The fine washed-up sand solidifies after the water has run off.

As many as 7,500 homes have been abandoned because of earthquake damage, and approximately 2,400 out of 3,000 structures in the central business district have been demolished, according the UT press release.

“The study will impact the future Christchurch society through the development of more robust seismic designs of residential structures for more than 15,000 homes,” Stokoe said.

The National Science Foundation (NSF) External U.S. government site, which manages the USAP through the Division of Polar Programs External U.S. government site, provided nearly $200,000 in funding for the project through its Rapid Response Research (RAPID) program. The New Zealand government supported the earthquake-related study with $2.2 million to fund the construction of 16 ground improvement sites in different soils around Christchurch. The government also provided the team free access to the testing sites.

In 2011, NSF funded more than 40 RAPID grants for about $2.5 million for studies associated with the earthquakes that hit both Christchurch and Japan. [See previous article — Shifting through the pieces: NSF funds RAPID grants to study effects from New Zealand, Japan earthquakes.]

About 15,000 earthquakes occur in and around New Zealand each year, with about 250 big enough to be felt, according to GeoNet External Non-U.S. government site, a geological hazard monitoring system in New Zealand.

The UT project’s goal is to determine whether various ground improvement methods help inhibit liquefaction, and which of the methods tested would be most cost-effective.

The liquefaction testing was conducted using a large mobile shaker truck, called T-Rex External Non-U.S. government site, which is part of the George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES) External Non-U.S. government site. The 64,000-pound T-Rex is used to simulate a wide range of earthquake shaking levels. [See a special report about NEES from NSF External U.S. government site.]

The research may have applications for earthquake-prone cities in the United States, as well as numerous other parts of the world. The first phase of testing should be complete by August.

“We will work for another year to dig deeper into the basic research findings,” Stokoe said. “This stage mainly determines which ground improvement methods are best suited for Christchurch and will allow them to move forward in rebuilding a resilient city.”

NSF-funded research in this story: Kenneth Stokoe and Brady Cox, University of Texas at Austin, Award No. 1343524 External U.S. government site.

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