The Tohoku earthquake, which struck the northeast coast of Honshu, Japan on March 11 and triggered a 23-foot tsunami, is not only a tragedy in and of itself, but a grim reminder for seismologists and scientists that earthquakes are one of the most dangerous natural disasters out there, according to Stanford researchers.
Based on geological records and written historical accounts, Japanese seismologists anticipated earthquake magnitudes from 7.0 to 8.0 from the Japan Trench. The resulting 9.0 earthquake reveals that despite the wealth of seismic data that has been collected over the years, earthquakes are capricious events.
“Earthquakes don’t happen on a schedule,” said geophysics professor Greg Beroza. “They’re not only unpredictable, the onset is extremely rapid.”
Stanford is not invulnerable to these quakes. The two nearest faults that pose the greatest threat to Stanford are the San Andreas and Hayward faults. Although the San Andreas Fault is closer to Stanford, Stanford seismologists are more concerned about the Hayward fault, which, according to geophysics professor Paul Segall, is reaching the end of its average fault slip cycle of 140 years.
Segall is currently tackling the difficulty of measuring earthquake occurrence by studying crustal deformation and fault mechanics by using precise GPS measurements to measure distortions created by the accumulated stress of faults locking together due to friction. Earthquakes occur when the stress of the faults overcomes the friction of the locked plates.
“Take the Hayward fault, the fault that runs directly under Berkeley,” Segall said. “The average distance the fault should move is about one centimeter per year. The Hayward fault hasn’t slipped since 1868, so about 140 years. If you multiply 140 years times one centimeter, you need over a meter’s worth of slip.”
These measurements, however precise, need to be taken with a grain of salt. Segall cautioned against viewing the average cycle calculations as rigid, accurate predictions of seismic activity.
“Just because the average is 140 years doesn’t mean it’s going to happen exactly at that average time,” Segall said. “There is a range of variability, which makes prediction rather difficult. However, what geological studies can give us is information that lets us know that there is a higher possibility of an earthquake happening.”
According to Segall, an earthquake of a magnitude comparable to that of Japan’s is highly unlikely for the San Andreas Fault.
“Even the San Andreas cannot produce a 9.0 earthquake, but a 7.0 to 8.0 at most,” Segall said. “But the Cascadia subduction zone — which extends from Canada to northern California — can potentially reach a magnitude of nine.”
This news bodes well for Stanford, which, over the years, has undergone a rigorous seismic retrofitting for vulnerable buildings. All new buildings, including the Knight Management Center, have been carefully constructed to withstand earthquakes.
“The Knight building uses a buckling restrain brace, a new type of system developed 10 to 15 years ago,” said Greg Deierlein, a civil and environmental engineering professor. “The brace structure helps the building during compression to resist buckling. The new Bio-E building will also have this brace.”
The department of Environmental Health & Safety (EHS) works with Stanford’s seismologists to develop measures to ensure campus safety.
“What Stanford has done over many years is to really try to combine preparedness with what we know about the possibility of seismic activity in the area and attempt to mitigate as many risks as possible,” wrote Lawrence Gibbs, EHS associate vice provost, in an email to The Daily.
“These include seismic retrofitting of many of our buildings, adding emergency generators to many buildings to ensure power availability [and] ensuring emergency food and water supplies are available,” he said.
Other measures that the department has taken include the installation of fire sprinkler systems in all undergraduate housing residences and most laboratories, automatic seismic gas shutoffs and emergency warning and communication systems. It also ensured that data backup systems are available to protect critical information. More recently, a program to provide for non-structural restraints on high value research equipment has been proposed.
“People’s perceptions of earthquakes are often of buildings falling or collapsing completely,” said Mary-Lou Zoback, vice president of Earthquake Risk Applications at Risk Management Solutions, a local risk assessment consulting group.
“However, most of the damage that people don’t generally think about is the shaking and disruption of the building’s contents,” she added. “Lab materials and equipment can be damaged, data can be lost.”
While the proactive measures implemented can sufficiently help Stanford withstand up to a 7.5 quake from the San Andreas Fault, earthquake researchers and staff emphasize the importance of maintaining vigilance in building inspections and earthquake safety education.
“Stanford’s preparedness is based on the probability that an earthquake would impact the whole region,” Gibbs said. “Stanford needs to be able to be self sufficient in the immediate aftermath of an earthquake. Therefore, our programs are focused on attempting to ensure all individuals understand how to prepare and react in event of an earthquake.”