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Mr. Jonathan Scharfman Silver Stone Communities 10 June 2005 Page 3 Tread\YelI&RoIIo Figure 2 also shows the earthquake epicenters for events with magnitude greater than 5.0 from January 1800 through January 1996. Since 1800, four major earthquakes have been recorded on the San Andreas Fault. In 1836 an earthquake with an estimated maximum intensity ofVil on the Modified Mercalli (MM) scale (Figure 3) occurred east of Monterey Bay on the San Andreas Fault (Toppozada and Borchardt 1998). The estimated Moment magnitude, Mw. for this earthquake is about 6.25. In 1838, an earthquake occurred with an estimated intensity of about VID-IX (MM). corresponding to a Mw of about 7.5. The San Francisco Earthquake of 1906 caused the most significant damage in the history ofthe Bay Area in terms ofloss oflives and property damage. This earthquake created a surface rupture along the San Andreas Fault from Shelter Cove to San Juan Bautista approximately 470 kilometers .in length. It had a maximum intensity of XI (MM), a Mw of about 7.9. and was felt 560 kilometers away in Oregon, Nevada, and Los Angeles. The most recent earthquake to affect the Bay Area was the Loma Prieta Earthquake of 17 October 1989, in the Santa Cruz Mountains with a Mw of 6.9. approximately 70 Ian from the site. In 1868 an earthquake with an estimated maximum intensity of X on the MM scale occurred on the southern segment (between San Leandro and Fremont) of the Hayward Fault. The estimated Mw for the earthquake is 7.0. In 1861, an earthquake of unknown magnitude (probably aMw of about 6.5) was reported on the Calaveras Fault. The most recent significant earthquake on this fault was the 1984 Morgan Hill earthquake (Mw = 6.2). In 2002 the Working Group on California Earthquake Probabilities (WGCEP 2003) at the U.S. Geologic Survey (USGS) predicted a 62 percent probability of a magnitude 6.7 or greater earthquake occurring in the San Francisco Bay Area by the year 2031. More specific estimates of the probabilities for different faults in the Bay Area are presented in Table 2. TABLE 2 WGCEP (2003) Estimates of30-Year Probability (2002 to 2031) of a Magnitude 6.7 or Greater Earthquake ..,.......-...... .. .. '" h_" .. ..-. ....- .,...-......"...,.. .. .. om .......} .. ..... '---"," .. I'l"obabil#Y:<' ... . ... . .. ... ... .. - "-..', .....- , :::,',Fiiult' .. .' ."(p~p@O:ii .:,.. .. .... ....... -. .. , ... ,.....,...:.': ... Hayward-Rodgers Creek . 27 San Andreas 21 Calaveras 1 1 San Gregorio 1 0 Concord-Green Valley 4 Greenville 3