SAN FRANCISCO, Dec. 13 (Xinhua) -- San Jose and Walnut Creek, two Bay Area cities, are facing greater risks of seismic damage if a new earthquake strikes, according to new earthquake hazard maps released by the US Geological Survey (USGS) Thursday.
The maps analyzed the chance of damaging earthquakes shaking across the United States in 100 years.
A new assessment report made public at an annual meeting of the American Geophysical Union in San Francisco showed that San Jose and Walnut Creek are susceptible to the longer wavelength of ground shaking common in sedimentary basins and must address the challenges of earthquake hazards given the existence of tall buildings in both cities.
The geologic basins resulted from the warping of rocks when tectonic plates squeeze each other and strain the earth.
A USGS scientist told the East Bay Times newspaper that San Jose in South Bay saw a growth of 5 percent to 10 percent in estimates of ground motion, while Walnut Creek in East Bay estimates jumping by 10 percent to 25 percent.
San Jose has several tall buildings, such as the 27-story San Jose Marriott and the 22-story Fairmont Hotel, in addition to the 18-story San Jose City Halls, said the newspaper.
In Walnut Creek, most buildings stand at 10 stories or shorter. Concord city north of Walnut Creek has some building that are taller than 13 stories, it added.
Northern California has two of the most hazardous faults -- the Hayward-Rodgers Creek fault system and the San Andreas fault, which are most likely to have a damaging earthquake, according to the website of the USGS.
East Bay has a higher earthquake hazard than other regions given its greater number of faults that traverse the area, said the USGS.