BELLINGHAM - When civil engineering professor Dr. Aaron S. Bradshaw got a late-night phone call recently from his friend and former doctoral co-adviser, Russell Green, Bradshaw thought Green was calling to congratulate him for recently being named to the faculty of the University of Rhode Island’s Department of Civil Engineering.
Bradshaw, 37, who lives with his wife and two children in Bellingham, couldn't have been more wrong.
Green, an associate professor of civil and environmental engineering at Virgina Tech, had called to invite Bradshaw to join his six-member National Science Foundation-sponsored Geo-engineering Extreme Events Reconnaissance Team mission to Christchurch, New Zealand, to document the effects of the massive earthquake that struck the city last month.
"It was one of those opportunities I couldn't pass up," Bradshaw said Wednesday via a telephone interview from his hotel outside of the central city of Christchurch, where a 6.3-magnitude earthquake - New Zealand's deadliest natural disaster in 80 years - struck on Feb 22.
As of Friday, the death toll had reached 163, and more than 100 people were still missing.
"The most difficult part was having to leave on such short notice," Bradshaw said. "I have two young children at home and one on the way, but it's not every day you are asked to be involved in something as important as this."
The one-week mission (Bradshaw arrived in New Zealand on March 1 and was due back home today) focused on documenting geotechnical effects of extreme events as part of the U.S. National Earthquake Hazards Reduction Program.
The team members worked in close collaboration with their New Zealand colleagues from the University of Canterbury and the University of Auckland. Additionally, the team coordinated its efforts with teams organized by the Earthquake Engineering Research Institute and the American Society of Civil Engineers’ Technical Committee on Lifeline Earthquake Engineering.
The American team spent the better part of the week working with their New Zealand colleagues to perform field investigations, focusing their efforts on building foundation response, liquefaction and other ground failures, performance of bridges and other lifelines, performance of port facilities, and slope failures.
The aim of the mission was to collect as much geotechnical engineering data as possible before demolition and reconstruction begins. The team's findings will be published in a post-event report that will be published on the Geo-engineering Extreme Events Reconnaissance (GEER) Association Website.
The team performed the majority of its field work in the suburbs just outside the cordon in the the central city, which remains a highly unstable environment. Christchurch is New Zealand's second largest city.
"As an engineer, I was overwhelmed when I saw the extent of the damage," said Bradshaw, who earned master’s and doctoral degrees from URI. "You look around at the damage and think where do you even begin? The city is going to have to go through a major reconstruction."
Bradshaw was selected for the reconnaissance team because of his experience designing building foundations in the seismically active region of Seattle and his background studying soil liquefaction, a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking.
"It's all about the soil" he says. "One of the major problems is soil liquefaction, and there's a lot of that here."
Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world.
Liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other.
When liquefaction occurs, the strength of the soil decreases and the ability of a soil deposit to support foundations for buildings and bridges is reduced.
"The other problem is that a large percentage of the buildings here don't have unreinforced masonry or steel rebar in them," he said.
Bradshaw said he is impressed by the resilience of the New Zealand people.
"Talking with the people here you sense two things," he said. "On the one hand, they are still very sad and devastated by this tragedy, but at the same time they are positive and focused on rebuilding their city."