Survey: Calif.’s Hayward Fault “Ready to Pop”

Time is not on our side, when it comes to suffering damage from an earthquake along Northern California’s Hayward Fault, according to a new map by the U.S. Geological Survey.

The USGS released a new map showing the shaking produced by the 1868 Hayward earthquake, the 12th most deadly earthquake in U.S. history. A repeat of the 1868 earthquake on the Hayward Fault would produce strong shaking throughout the San Francisco Bay Area with shaking ranging from strong to very strong in the cities of Hayward, San Leandro, and Fremont, the agency said.

According to Jack Boatwright, the USGS seismologist who prepared the new map, “the Oct. 21, 1868, earthquake struck Hayward the hardest of any town in the Bay Area. The earthquake rupture clove the town in two, and it threw many frame houses from their foundations. Few places have paid such a steep price for the privilege of naming a fault and an earthquake.”

Sunday, Oct. 21, 2007, marked the 139th anniversary of the 1868 Hayward earthquake. Scientific studies indicate that the average interval between the past five large earthquakes on the Hayward fault has been 140 years. It would not be surprising if another large Hayward Fault earthquake happened tomorrow, USGS said.

“Damaging earthquakes have occurred on the Hayward fault almost like clockwork,” said Jim Lienkaemper, a USGS geologist who has studied the prehistory of earthquakes along the Hayward fault.

“The Hayward fault is the single most dangerous fault in the entire Bay Area,” said Tom Brocher, a USGS seismologist and member of the 1868 Hayward Earthquake Alliance, “because it is ready to pop and because nearly 2 million people live directly on top of it.”

Proactive efforts to reduce the loss of life and property following a large Hayward fault earthquake have been tackled head on by East Bay cities such as Berkeley, Fremont, Hayward and Oakland. The city of Hayward replaced its old City Hall that lay directly over the Hayward fault, with a newly built earthquake resistant City Hall now located off of the fault zone. Oakland recently passed a city ordinance that provides a property tax rebate to encourage homeowners to retrofit their residences. These efforts are necessary to reduce the number of homeless — now estimated at more than 100,000 — which would result from a large Hayward Fault earthquake, USGS said.

The new USGS 1868 ShakeMap can be viewed on the Earthquake Program Web site at http://earthquake.usgs.gov/regional/nca/1868/shakemap/.

Information about the 1868 Hayward earthquake is also available online on the Hayward Fault Earthquake Web page at http://earthquake.usgs.gov/regional/nca/1868/.