Two earthquakes of magnitudes 5.1 and 4.1, both centered north of Brea, Calif., struck Los Angeles on March 28 and March 29, respectively. Neither earthquake caused damage to Occidental’s campus, but they provided new data on how campus facilities withstand such tremors, according to Director of Facilities Thomas Polansky.
The March 28 5.1 earthquake was felt as far south as San Diego and as far north as Ventura County, according to citizen responses collected online by the United States Geological Survey. The first earthquake occurred at 9:11 p.m. on March 28 night. The second earthquake occurred around 2:30 p.m. the following day with a 4.1 magnitude on the Ritcher scale.
Brea, Calif., is approximately 20 miles from campus. Because the earthquakes were not larger, the impact to Eagle Rock was small and no assessment of the campus by Facilities Management was necessary, according to Director of Communications Jim Tranquada.
“In earthquakes of greater magnitude, such as the 1994 Northridge quake (6.7 on the Richter scale), Facilities would conduct an assessment of campus buildings, relying in part on reports of damage from students, faculty and staff,” Tranquada said via email.
According to associate professor of geology Brandon Browne, if the earthquakes had been of greater magnitudes or centered on a closer fault line, the school would have felt the effects of these seismic activities much more.
Browne noted that, for an earthquake of 6.0 magnitude or greater, there would have been considerable damage such as broken windows, chemistry lab problems and books falling off of shelves.
“If there was a large earthquake, of the same magnitude, like a 5.1 earthquake on the Raymond fault [to the south of campus near York Boulevard], [it] doesn’t matter if you are on bedrock or what, you would definitely be experiencing significant damage here,” Browne said. “It would be very high amplification of seismic waves.”
When an earthquake goes up one whole number in magnitude — from 5.1 to 6.1 for example — its amplitude increases tenfold while its energy increases by a factor of 31. Browne recalled an earthquake from 1987 that occurred around the same area as the earthquakes last week. The earthquake was a 5.9 and caused substantially more damage to buildings in the area around Pasadena.
Not small enough to go unnoticed and not large enough to cause any damage to any buildings, recent earthquakes could be beneficial to Occidental’s undertakings to prepare for larger earthquakes in the future, according Polansky.
The college hired the structural engineering firm John A. Martin & Associates, Inc. in February to do a preliminary assessment of buildings to determine if any way have seismic issues. The employees working for the firm will be able to retrieve data from the earthquakes that recently hit Los Angeles, contributing to the firm’s survey.
“Each quake gives structural engineers a new opportunity to study how structures behave in seismic events, based upon different design, construction materials and location geology,” Polansky said via email. “The building standards for southern California are some of the strictest in the country, because of our proximity to a seismically active area.”