UCSD Professor Examines Earthquake in Chile

Jose Restrepo, Engineering professor

Six months back, UCSD structural engineering professor Jose Restrepo was in Chile, ironically working on preventive earthquake measures.

Cue the 8.8-magnitude earthquake that hit Chile Feb. 27, a quake so strong it moved the entire city of Concepción more than 10 feet to the west.

According to Restrepo, Chile’s earthquake-proof construction codes — which he addressed while in Chile — helped the country avoid the total devastation that Haiti experienced several weeks earlier.

Restrepo worked with structural engineers and architects in Chile to advise a committee of city officials drafting new codes to make buildings earthquake-proof.

“We were deciding if the buildings had to be demolished or had to be repaired for people to be able to safely inhabit them,” he said. Following his recommendations, city officials had a better idea of how to draft strong building codes.

City officials throughout the country enforce design codes, or standards that control how quickly buildings can respond to earthquakes. Restrepo said the latest earthquake — the fifth largest ever recorded, according to the U.S. Geological Survey — caused remarkably little damage considering its scale.

“I don’t recall any earthquakes of this magnitude causing such little damage, actually,” he said. “Less than 1,000 people died due to this earthquake of magnitude 8.8. If you look at the recent earthquake in Haiti and compare the catastrophe, you see the importance of the structures and codes.”

In the aftermath of the earthquake, architects and engineers observed the most substantial damage to older buildings that lacked load-bearing walls — a common fate for buildings constructed before seismic design codes were increased.

“The overall performance in Chile is very good,” Restrepo said. “They have very good engineering, good codes and good practices. The architects are well-trained, too. Their practice is very similar to the U.S.”

However, Chile’s second-largest city, Concepción, was still strongly affected by the earthquake due to its location near the coast. The city was also hit by a resulting tsunami — caused by a slip in tectonic plates during the earthquake — that reportedly reached as far as Antarctica.

“The city of Concepción was hit very hard. The whole city was on shaky ground,” Restrepo said. “They are addressing the damaged and fallen buildings, but Concepción may have significant problems with sewage — and the piping will need to be opened and inspected.”

Following the disaster, scientists from the Scripps Institution of Oceanography explored the quake’s rupture site to investigate the theory that it had been caused by changes in sea floor movements.

“Scripps decided to take on this expedition because of a series of opportune events,” graduate student in geophysics and geology Ashlee Henig said in a statement. “Such a rapid response to an event like the large earthquake allows scientists to get excellent data on the direct effects of the earthquake.”

According to Henig, the Scripps research vessel Melville was near the epicenter of the earthquake at the time it struck, allowing it to examine ruptures and landslides.

Using a sea floor imaging system, the team of scientists worked with Chilean and German researchers to compare the images with those captured before the earthquake. In addition, four GPS receivers were deployed to measure any small sea floor changes that occur as the earthquake rupture settles.

“These receivers will be collected on a return cruise after several months of recording the sea floor,” said Henig. “The GPS receivers will provide insight into the post-seismic movements of the floor, so we can learn about the earthquake rupture and movement of the plates.”

Another part of the expedition will include searching for landslides that may have triggered the tsunamis following the earthquake.

The expedition was completed last Thursday. They are now processing and analyzing the data they collected.

“The data will hopefully provide us with insight into subduction related earthquakes and related co-seismic and post-seismic deformation,” Henig said.

According to Restrepo, if an earthquake were to hit California, buildings would be expected to perform better than, or at the same level as, Chile.

Restrepo said that most of California would be safe in the case of an earthquake.

“California is well-prepared. But if an earthquake hit the West Coast, I don’t think Oregon and Washington are nearly as ready as us, or, as a matter of fact, as Chile,” he said.

Readers can contact Kashi Khorasani at [email protected].

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