The Hayward Fault, which extends for 74 miles through a densely populated East Bay and connects with the Calaveras Fault near San Jose, one of the most dangerous faults in Northern California, was last active in 1868. That quake, now estimated at a 7.1 magnitude, leads scientists to believe that the fault is overdue for another major quake, reports the SFGate. They anticipate the Hayward Fault will be twice as likely to rupture over the next 30 years than the San Andreas, prompting this seismic study to help explore the fault zone.
Last week, Geologists began drilling narrow, 30-foot deep holes in which a series of small explosives will be placed. Over the next few weeks, these charges will detonate late at night when no other vibrations from passing vehicles or other cultural noise are present to shake the ground and skew readings from the seismographs. These detonations will not be felt by residents, but will create a series of small, controlled tremors. The seismic waves will be collected by the seismographs and the data processed to create a three dimensional map of the rock layers and formations which lie beneath the surface along the faults.
This imagery will then allow scientists to better predict how the region will respond to future earthquakes, helping local communities better prepare for potential earthquakes in the East Bay area. “Understanding that fault structure – and how the energy will move along that fault – is important,” The Mercury News quotes Rufus Catchings, USGS geophysicist, saying. “We can improve our “Shake Maps,’ which helps first responders. It helps homeowners, who may want to retrofit their houses.”
Luther Strayer, Cal State East Bay professor of geology, explains, “We’re trying to keep people alive. We’re trying to assess the hazard so we understand what’s going on underground – and then inform people what to do about it.”
Follow the Oakland Geology blog on the East Bay Seismic investigation for updates on the study. Similar research has been done in the south Santa Clara valley, on the Peninsula and in Napa.