COMPLIANCE INFO_1978-1992 - Laserfiche WebLink

Home Browse Search

Mr. Robert 0Evans January 3, 1991 Page 3 Pr ' ct 802-02.03 ered inactive. The 1975 Oroville earthquake (magnitude 5.7) occurred along a northern segment of the Sierra Foothills fault system and prompted a re-evalua- tion of the earthquake potential of this system. The results of this evaluation indi- cate that the fault system is capable of generating maximum earthquakes ranging in magnitude from 6.0 to 6.5. To develop MCE estimates, it is necessary to evaluate the earthquake potential of each significant seismic source. For this study, the earthquake potential of the various sources was evaluated using a combination of methods. For many seis- mic sources, previous researchers have applied published empirical relationships (Slemmons, 1977; Slemmons and Chung, 1982; Bonilla et al., 1984; and Wesnousky, 1986) that relate various fault parameters (e.g., fault length, fault type, and seismic moment) to MCE magnitude. When published maximum earth- quake magnitudes are not available, the earthquake potential of a seismic source can be determined by application of the various empirical relationships. Additionally, the historic earthquake record or paleoseismicity data, or both, can be used to evaluate the earthquake potential of a seismic source. MCE estimates (see Table 1) were developed for the French Camp Landfill using CDMG guidelines, the previously discussed empirical relationships, and the his- toric earthquake record (see Figure 2). The MCE for the nearest faults to the French Camp Landfill range from 6.2 to 6.8 magnitude. The Greenville fault was determined to have the highest MCE of 7.0. MCE estimates for the Hayward and Calaveras were determined to have magni- tudes of 7.0 and 6.9, respectively. The Bear Mountain and Melones fault zones have MCE estimates of 6.5 for each fault zone. The San Andreas MCE is esti- mated at 8.3. DILION 4 Il• The level of ground shaking resulting from earthquakes may be estimated from widely accepted, published relationships that relate ground acceleration to earth- quake magnitude and distance from the causative fault or earthquake epicenter. For the French Camp Landfill, relationships developed by Seed and Schnable and published in Seed and Idris (1982) were used to estimate the mean peak horizontal bedrock accelerations that may occur at the site due to MCEs occur- ring in the area (see Figure 3). Estimated bedrock accelerations for the corre- sponding MCEs are summarized in Table 1. pjb\b02\b020203e