Harvard Earthquake Experts Evaluate L.A.

The fact that Cambridge doesn't lie on the San Andreas fault doesn't stop Harvard seismologists from contributing significantly to the study of earthquakes around the world.

While Cal Tech scientists got the lion's share of the press attention following the magnitude 6.6 earthquake in southern California last Monday, Harvard scientists are leaders in the study of global earthquakes.

The department of Earth and Planetary Sciences is the world center for data on large earthquakes, according to James R. Rice, McKay professor of engineering sciences and geophysics.

"From a global point of view," said Rice, "it doesn't help to live in L.A."

Although there is a significant minority of Harvard scientists interested in the actual physics of earthquakes, the department's research focus is on "using earthquakes as signals to understand the three dimensional structure of the Earth," Rice said.

Professor of Geology Adam M. Dziewonski was quick to say that seismologists aren't glad when earthquakes occur, although he did point out that many earthquakes do not cause the kind of damage sustained in California.

When the California quake hit, Dziewonski was at a conference of seismologists in New Zealand. He immediately put together a presentation for the scientists there, using information retrieved from a computer network.

The development of the network, which includes about 100 seismographic stations around the world, facilitates the work of seismologists who are in low-risk areas such as Cambridge.

Harvard uses a rapid earthquake analysis system developed here to collect world-wide earthquake data automatically.

Within hours of the California quake, Harvard scientists had analyzed the earthquake and sent out preliminary results to other scientists to give them an idea of what sort of fault to look for following the quake.

The most interesting aspect of the recent California quake from a seismic point of view is that it was not caused by the infamous San Andreas fault, or any other known, visible fault.

Rather, the quake was caused by what is termed a blind thrust, or more commonly, ahidden fault. This is a fault which has not risento the surface.

Goran A. Ekstrom, assistant professor ofgeophysics, is studying the hidden faults in theSan Joaquin Valley in California. The faults foundthere are analogous to the one that caused lastweek's earthquake.

According to Ekstrom, the fact that thisearthquake is one of several in the last few yearsto be caused by such hidden faults will promptmore research on them.

This earthquake "will further make peoplerealize that the focus shouldn't be exclusively onthe San Andreas fault," said Ekstrom.

The cumulative damage resulting from thesehidden fault-based earthquakes may surpass that ofa major earthquake on the San Andreas fault,according to Dziewonski.

The most recent quake, which follows a seriesof smaller, hidden-fault based earthquakes inCalifornia, is causing a re-evaluation in thedebate about what type of earthquake would causethe greatest urban damage.

"If anyone had talked about this five or 10years ago," said Ekstrom, "no one would have takenit very seriously."

"We had no idea of the complexities of thefaults in L.A. until recently," Rice said.

Until the 1987 earthquake in Whittier,California, the state had had little seismicactivity for 30 or 40 years. Since 1987 severalearthquakes have shaken the region.

"This earthquake was not a particularly largeearthquake," said Ekstrom. Seismologists generallyconsider earthquakes of magnitude seven or more asmajor quakes.

The damage caused by this medium-sizedearthquake in such a populated urban area mayprompt more research in the prediction ofearthquakes as a means to evacuate at-risk areas.

"Some earthquakes are more predictable thanothers," said Rice.

Rice cited the 1975 earthquake in China whichwas predicted by scientists and resulted in theevacuation of the area. Scientists were able tomake their accurate prediction based onforeshocks, which increased in frequency to thepoint of being "massive signals," according toRice.

But Rice said such quakes were rare. Thefollowing year, in another region of China, anearthquake resulted in a quarter of a milliondeaths. The signs prior to this quake were not asobvious as the first, and thus the region was notevacuated.

"It looks right now that there was nothing tolet us know that this earthquake was coming," saidRice about the California quake. "We don't seeanything that could have been a signal."

"You can only predict that a type of earthquakewill occur in your area," said Ekstrom.

The kind of prediction that is most likely inthe future is a better ability to determine thelikelihood of the type and frequency ofearthquakes in a given area, thus determining thestructure and sites of buildings.

Wood-frame houses are traditionally consideredearthquake safe, according to Ekstrom, but many ofthe buildings that fell in the California quakewere wood-frame.

The research conducted by most Harvardscientists does not encompass such localizedproblems.

"We try to uniformly study the effect of earthquakes on a planetary scale," said Dziewonski.

But the societal impact of earth quakes is notignored in Harvard classrooms. Ekstrom says thathe plans to use the California earth quake "as avery topical example" in his class to discussquake-related topics, such as the costs andresponsibilities associated with clean-up.CrimsonEdward H. WuA seismograph on the first floor of theScience Center shows the L.A. quake.

Goran A. Ekstrom, assistant professor ofgeophysics, is studying the hidden faults in theSan Joaquin Valley in California. The faults foundthere are analogous to the one that caused lastweek's earthquake.

According to Ekstrom, the fact that thisearthquake is one of several in the last few yearsto be caused by such hidden faults will promptmore research on them.

This earthquake "will further make peoplerealize that the focus shouldn't be exclusively onthe San Andreas fault," said Ekstrom.

The cumulative damage resulting from thesehidden fault-based earthquakes may surpass that ofa major earthquake on the San Andreas fault,according to Dziewonski.

The most recent quake, which follows a seriesof smaller, hidden-fault based earthquakes inCalifornia, is causing a re-evaluation in thedebate about what type of earthquake would causethe greatest urban damage.

"If anyone had talked about this five or 10years ago," said Ekstrom, "no one would have takenit very seriously."

"We had no idea of the complexities of thefaults in L.A. until recently," Rice said.

Until the 1987 earthquake in Whittier,California, the state had had little seismicactivity for 30 or 40 years. Since 1987 severalearthquakes have shaken the region.

"This earthquake was not a particularly largeearthquake," said Ekstrom. Seismologists generallyconsider earthquakes of magnitude seven or more asmajor quakes.

The damage caused by this medium-sizedearthquake in such a populated urban area mayprompt more research in the prediction ofearthquakes as a means to evacuate at-risk areas.

"Some earthquakes are more predictable thanothers," said Rice.

Rice cited the 1975 earthquake in China whichwas predicted by scientists and resulted in theevacuation of the area. Scientists were able tomake their accurate prediction based onforeshocks, which increased in frequency to thepoint of being "massive signals," according toRice.

But Rice said such quakes were rare. Thefollowing year, in another region of China, anearthquake resulted in a quarter of a milliondeaths. The signs prior to this quake were not asobvious as the first, and thus the region was notevacuated.

"It looks right now that there was nothing tolet us know that this earthquake was coming," saidRice about the California quake. "We don't seeanything that could have been a signal."

"You can only predict that a type of earthquakewill occur in your area," said Ekstrom.

The kind of prediction that is most likely inthe future is a better ability to determine thelikelihood of the type and frequency ofearthquakes in a given area, thus determining thestructure and sites of buildings.

Wood-frame houses are traditionally consideredearthquake safe, according to Ekstrom, but many ofthe buildings that fell in the California quakewere wood-frame.

The research conducted by most Harvardscientists does not encompass such localizedproblems.

"We try to uniformly study the effect of earthquakes on a planetary scale," said Dziewonski.

But the societal impact of earth quakes is notignored in Harvard classrooms. Ekstrom says thathe plans to use the California earth quake "as avery topical example" in his class to discussquake-related topics, such as the costs andresponsibilities associated with clean-up.CrimsonEdward H. WuA seismograph on the first floor of theScience Center shows the L.A. quake.