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Appendix C SEISMICITY STUDY The maximum probable earthquake (MPE) evaluation for the San Joaquin County Landfill Development site was conducted to develop estimates of design ground accelerations that may occur at the site due to earth- quakes occurring on potential seismic sources (i.e., faults) within 100 kilometers (km) of the site. Because the San Joaquin County Landfill Development site is a proposed Class III landfill, the study included a determination of peak ground accelerations expected in association with MPEs, as required by Subchapter 15 regulations. The MPE is defined in Subchapter 15 as the maximum earthquake that is likely to occur during a 100 -year interval. Identifying faults capable of generating earthquakes that may affect the site in a 100 -year period was the initial step in developing MPE estimates. To accomplish this, faults which are considered to have been active in Late Quaternary time (i.e., the last 300,000 to 500,000 years) and are within 100 km of the site were evaluated based on a review of publications pertaining to the geology and tectonics of the region (Jennings, 1975; Woodward -Clyde Consultants, 1977 and 1986; and Clark, et al., 1984). The geographic relationships between the site and significant Late Quaternary faults are depicted on the Regional Fault Map (see Plate C-1). Relevant characteristics, and the spatial relationship between faults nearest the site are summarized in Table C-1. Pertinent seismic sources include faults of both the Sierra Nevada and Northern Coast Ranges geomorphic provinces (see Plate C-1). The nearest known faults are the Bear Mountains fault zone and the Melones fault zone, located 28 and 38 km east of the site, respectively. Both of these faults are considered part of the Sierran Foothills fault system. All other significant faults are located at least 57 km from U