Engineers Learn from Powerful Quakes

This article originally appeared in UCLA Today.

BY JUDY LIN-EFTEKHAR
UCLA Today

The devastation left behind after three massive earthquakes in the last three months have hit Turkey and Taiwan is being closely scrutinized by faculty members of the Department of Civil and Environmental Engineering who have traveled halfway around the world to better prepare for "the big one" in California.

While Assistant Professor Jonathan P. Stewart is currently in Turkey to study the tragic aftermath of the magnitude 7.2 temblor that struck Nov. 12, he and two others from UCLA, Professor Jiann-Wen (Woody) Ju and Associate Professor John W. Wallace, served on international reconnaissance teams immediately following the Aug. 17 Izmit earthquake in Turkey, magnitude 7.4, and the Taiwanese Ji-Ji earthqua Jiann-Wen (Woody) Ju, stands in a Taiwanese rice paddy that once was level.

ke, magnitude 7.6, on Sept. 21. All three faculty members are with the Pacific Earthquake Engineering Research Center.

In Turkey, team members saw densely packed high-rise buildings that had completely collapsed and bridges that had been destroyed. A landslide in Taiwan cut power to the entire country when it severely damaged the Junglian power plant, which had been built right on the fault line.

They also saw the aftermath of a Taiwanese landslide that completely demolished a village; only two people miraculously survived when their homes were propelled a distance of two kilometers in two minutes by the slide.

The information collected on these violent, powerful earthquakes will add immensely to knowledge about the nature of earthquakes and their effect on the built environment, team members said. Their findings should prove particularly useful in understanding seismic hazards in California.

All three temblors were larger than any earthquake recorded in Southern California since 1952. By comparison, the 1994 Northridge earthquake had a magnitude of 6.7. A larger earthquake could easily occur in Southern California, said Ju. Scientists visited this running track in Taiwan that dropped 1.7 meters during the earthquake.

"We think the San Andreas fault is capable of producing an earthquake with a magnitude as large as 8.0," Ju said. "Even if it were a 7.6 like Ji-Ji, it would release 22 times more energy than the Northridge quake," spanning a larger area and inflicting more damage.

"We'd like to know how we'd fare were this to occur," said Ju. "Will our buildings, bridges and freeways be able to survive?" Computer simulations will help scientists see how Southern California terrain and structures could be impacted.

Parallels can be drawn between the ground-shaking recorded during the quakes and the expected level of shaking in future California quakes, the engineers said. And data on surface fault ruptures will prove very useful in future construction, they said.

"Before these events, earthquake engineers had very little information on the effect of a fault rupture in densely populated, built-up areas," said Stewart. "This new data will have a great impact on how we view things from now on."

In Taiwan, for example, investigators repeatedly noted that damage was much more severe on the "hanging wall" side of the fault, the side that was pushed up, in contrast to the "foot wall."

"This tells us how far back from the mapped trace of a fault you have to be to safely build," Stewart said.

The massive landslides that occurred in Taiwan's mountains near the fault caught the experts by surprise.

"I don't think any of us fully appreciated the ability of an earthquake to cause giant, deep-seated landslides," Stewart said. "It would be like a big chunk of the Santa Monica Mountains suddenly sliding down into Santa Monica. We need to understand how these happened and assess whether they could happen here."

[Ed.: The UCLA Center for East Asian Studies, a precursor to the Asia Institute, sponsored a forum on Nov. 4, 1999 on the Taiwan quake. Professors Ju, Wallace, and Stewart were among those addressing a crowd of 200, which included officials in charge of Los Angeles disaster preparedness.]