In preparation for the next earthquake, a geological survey team has been drilling in various locations around west Berkeley to determine which areas will experience the most violent shaking.
Since June, Geologist Tom Noce of the U.S. Geological Survey, has been leading the USGS Earthquake Hazards Team around west Berkeley in a 22-ton truck boring 1.5 inch-wide holes deep into the ground to assess which parts of the city will shake more than others. There will be a total of 40 borings and the tests are expected to go on until mid August.
The study is focused on west Berkeley because the ground is less dense and more prone to intense shaking during an earthquake compared to the hills areas, which is mostly comprised of bedrock and therefore more stable.
The city manager’s chief of staff, Arrietta Chakos, said the survey data will be compiled in the Comprehensive Earthquake Hazard Map, which city planners will use to develop structural requirements for building and remodeling projects. In addition, emergency response teams will be able to use the maps immediately after an earthquake to determine which sections of the city are most likely to suffer significant injuries and damages.
Chakos said the survey is mandatory under the State Hazards Mapping Act of 1990, which requires cities and counties across the state to map out high-risk areas and take whatever damage-prevention measures possible.
Chakos said the project is being paid for through the federal Project Impact Program, which works with communities throughout the nation to better prepare families, businesses and local governments for natural disasters.
Chakos said the hazard maps should be complete in about a year. Once completed, city planners and Berkeley’s Seismic Technical Advisory Group will analyze the data and make suggestions about building and structural retrofitting in the high-risk areas.
“The maps will basically give us some guidance for building and zoning,” Chakos said. “For example, a developer building in a high-risk area may be required to have a soil engineer study the site and assess potential risks.”
The Seismic Technical Group, is comprised of seismic experts at UC Berkeley. The group has been advising the city for the last six years on earthquake preparedness in city buildings.
“They’ve advised us on the Civic Center, the Public Safety Building and the new library building,” Chakos said. “We’re really quite fortunate to have them.”
Tom Noce, who has conducted similar surveys in Oakland, Alameda and Santa Clara County, said the drilling process so far has been mostly carried out at the Berkeley Marina, which is landfill and more likely to experience intense shaking and ground failure during an earthquake.
He said the USGS Earthquake Hazards Team uses equipment housed in a 22-ton, three-axle truck. A 1.5 inch drill bores a hole approximately 100 feet below the surface. As the drill is driven into the ground, it collects electronic data about the characteristics of the soil at various levels.
The drill does not bring soil the surface to be analyzed.
Once the ground conditions have been measured, Noce creates a mini earthquake by striking the surface with a sledge hammer. The reaction, which is called a sheer wave, is measured. Then Noce estimates the intensity of shaking during a quake by comparing the sheer wave measurement to the characteristics of the soil.
The public is invited to witness the process Friday at 10:30 a.m. behind the Martin Luther King, Jr. Civic Center.
For more information about emergency preparedness in Berkeley you can visit the city’s web site at www.ci.berkeley.ca.us/projectimpact or call the Office of Emergency Service at 644-8736.