Bay Area sits atop dangerous faults
Strain mounting on Hayward line
Published: Monday, October 28, 2013
Updated: Monday, October 28, 2013 19:10
The Bay Area is at risk of experiencing a 6.7 or greater earthquake within the next 26 years according to the United States Geological Survey (USGS).
Running through Contra Costa College, reports done by the USGS show that the Hayward Fault has a 31 percent chance of hosting a “devastating” earthquake along its cracked line. Labeled by the USGS as the fault “most at risk” of producing a major earthquake, the fault’s presence leaves students on campus at risk.
“The fault is considered dangerous because of how long it’s been since its last big shift,” geography professor Chris Johnson said.
Studies conducted by the USGS estimate that the fault shifts violently every 150 years. “We are due for another one,” Johnson said.
The 74-mile-long Hayward Fault starts in the San Pablo Bay near Point Pinole, just south of where the Rodgers Creek Fault ends. The fault cuts underneath the campus through the Bus Transfer Center, Lot 1 and Lot 10. It brushes along the foot of the East Bay hills until connecting with the Calaveras Fault in San Jose.
USGS official seismic reports say that the fault “creeps,” or steadily moves, about 5 millimeters a year.
There is evidence of movement throughout the campus. Shifts along sidewalk curbs, cracks in paths and warped fences are only a few. An earthquake occurs when energy, stored miles beneath the ground is released. In an abrupt shift, one side of the fault moves to the right, while the other moves left causing the telltale shaking which occurs during an earthquake, Johnson said.
The last time the Hayward Fault released a large amount of energy was in 1868. It was known as the “Great San Francisco Earthquake” until the 1906 quake that devastated an ill prepared city. The 6.7 shockwave started in Fremont and ripped along the fault until reaching Berkeley. Thirty people died and $350,000 worth of damage was done to the sparsely populated Bay Area.
A special 2010 report issued by Risk Management Solutions (RMS), an investigative insurance company, detailed the 1868 Hayward Fault earthquake.
Based on the latest U.S Census data, seven million people live in the Bay Area. At least 2.4 million live within the Alquist-Priolo Zone, a 2,000-foot area running parallel on either side of the active Hayward Fault line.
In 1972, a law was created suggesting retrofits to buildings within the Alquist-Priolo zone. The law prohibited future development without seismic studies by a third party within the zone.
“We rest on the Hayward Fault here on campus. We are at a greater risk,” Buildings and Grounds Manager Bruce King said. “Construction on campus cannot start until we make sure we are not building on a fault.”
Communities that the fault directly cuts through include San Jose, Oakland, Fremont, Richmond, Berkeley, Hayward, San Leandro, San Lorenzo, El Cerrito, Emeryville, Kensington and Milpitas.
UC Berkeley seismology lab Operations Manager Peggy Hallwag said the shaking caused by an earthquake on the Hayward Fault would cause landslides in Bay Area hills and liquefaction in the low-lying cities.
Some parts of Richmond, Berkeley, San Pablo, Oakland and Alameda built on artificial landfill are at risk of sliding.
Johnson said artificial fill is when people dump garbage and other debris (construction debris, or just soil) to fill them in so they can build on them.
“This makes the ground underneath very unstable,” he said. “It turns the soil into quicksand.”
CCC is too far away from the coast to be susceptible to liquefaction. Johnson said, “Landslides are a greater threat to the campus than liquefaction.”
Roughly $255 billion of residential and commercial properties in Contra Costa County are at risk in the event of a major earthquake on the Hayward Fault based on the 2009 RMS U.S. Industry Exposure Database (IED). Within the Bay Area’s eight counties the combined damage cost is estimated to be $1.9 trillion.
“In the best case scenario, it will be very bad,” Hallwag said. “In the worst case, it will be extremely bad.”