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SAN LEANDRO SHORELINE DEVELOPMENT DRAFT EIR <br />CITY OF SAN LEANDRO <br />GEOLOGY, SOILS, AND SEISMICITY <br />The most recent significant earthquake in the area was the Loma Pieta earthquake of October 17, 1989. <br />This earthquake had a magnitude of 7.1 and was centered approximately 49 miles southeast of San <br />Leandro. Strong ground shaking occurred in the San Leandro area and property damage in the area was <br />light to moderate. <br />In 2008, The Working Group on California Earthquake Probabilities (WGCEP), in conjunction with the <br />United States Geological Survey (USGS), published an updated report evaluating the probabilities of <br />significant earthquakes occurring in the Bay Area over the next three decades.12 The WGCEP report <br />indicates that there is a 0.63 (63 percent) probability that at least one magnitude 6.7 or greater <br />earthquake will occur in the San Francisco Bay region before 2036. This probability is an aggregate value <br />that considers seven principal Bay Area fault systems and unknown faults (background values). The <br />findings of the WGCEP report are summarized in Table 4.5-3. <br />TABLE 4.5-3 EARTHQUAKE PROBABILITY <br />The WGCEP report indicates that between 2007 and 2036 there is a 14 percent chance that an <br />earthquake with a magnitude of greater than 6.7 may occur in the Bay Area on a fault system not <br />characterized in the study. <br />4.5.2 STANDARDS OF SIGNIFICANCE <br />The Project would result in a significant geology, soils, and seismicity impact if it would: <br />1. Expose people or structures to potential substantial adverse effects, including the risk of loss, injury, <br />or death involving: <br />12 Working Group on California Earthquake Probabilities (WGCEP), 2008. "The Uniform California Earthquake Rupture <br />Forecast, Version 2 (UCERF 2): 2007-2036. U. S. Geological Survey Open File Report 2007-1437. <br />P L A C E W 0 R K S 4.5-9 <br />Probability of <br />at Least One Magnitude 6.7 <br />Fault System <br />or Greater Earthquake in 2007-2036 <br />Hayward — Rodgers Creek <br />0.31 <br />Calaveras <br />0.07 <br />San Andreas <br />0.21 <br />Concord -Green Valley <br />0.03 <br />San Gregorio <br />0.06 <br />Greenville <br />0.03 <br />Mount Diablo Thrust <br />0.01 <br />Background <br />0.14 <br />Source: Working Group on California Earthquake <br />Probabilities (WGCEP), 2008, The Uniform <br />California Rupture Forecast, Version 2 (UCERF <br />2): 2007-2036. U.S. Geological Survey Open <br />File Report 2007-1437. <br />The WGCEP report indicates that between 2007 and 2036 there is a 14 percent chance that an <br />earthquake with a magnitude of greater than 6.7 may occur in the Bay Area on a fault system not <br />characterized in the study. <br />4.5.2 STANDARDS OF SIGNIFICANCE <br />The Project would result in a significant geology, soils, and seismicity impact if it would: <br />1. Expose people or structures to potential substantial adverse effects, including the risk of loss, injury, <br />or death involving: <br />12 Working Group on California Earthquake Probabilities (WGCEP), 2008. "The Uniform California Earthquake Rupture <br />Forecast, Version 2 (UCERF 2): 2007-2036. U. S. Geological Survey Open File Report 2007-1437. <br />P L A C E W 0 R K S 4.5-9 <br />