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4.Environmental Analysis — • MRZ-1: Areas where adequate information indicates that no significant mineral — deposits are present or where it is judged that little likelihood exists for their presence. • MRZ-2: Areas where adequate information indicates significant mineral deposits are present, or where it is judged that a high likelihood exists for their presence. • MRZ-3: Areas containing mineral deposits the significance of which cannot be evaluated from available data. • MRZ-4: Areas where available information is inadequate for assignment to any other MRZ. The CDMG's Special Report 91-03,Mineral Land Classification: Aggregate Minerals of the South Tracy Site, San Joaquin County (CDMG, 199 1) indicates that different areas of the project site have various mineral land classifications. The eastern area of the project site has been — classified as MRZ-3, the southwest section has been classified as MRZ-2, with the remaining portions of the site being classified as MRZ-1. However,the applicant has indicated that it implemented a subsurface drilling program to determine whether the "Triana/Bames Property" contained suitable aggregate resources for mining. From the subsurface drilling,it was determined that the parcel contains significant,concrete grade aggregate, and satisfies San Joaquin County's Development Title Section 9-854.2(2) in that it"contains significant deposits of — mineral resources." Aggregate resources at the proposed project site consist primarily of coarse- grained alluvial fan deposits composed of gravel, sand, silt,and clay. — Seismicity The Central Valley, similar to a majority of California, is a seismically active region and is susceptible to ground shaking from one of many fault systems including those within the San Francisco Bay Area. The U.S. Geological Survey(USGS) 2002 Working Group on California _ Earthquake Probabilities (WG02)evaluated the likelihood of one or more earthquakes of moment magnitude 6.7 or higher occurring in the San Francisco Bay Area.3 The result of the evaluation indicated a 62 percent likelihood that such an earthquake event will occur in the Bay Area before — 2032(USGS WG02, 2003). While the moment and Richter magnitudes are a measure of the energy released in an earthquake, _ intensity is a measure of the earthquake ground shaking effects at a particular location. Intensity will vary depending on the overall magnitude,distance to the fault, focus of earthquake energy, and type of geologic material underlying an area. The Modified Mercalli Intensity (MMI) scale — (Table 4.7-2)is commonly used to express the earthquake intensity and damage severity caused by earthquakes because it expresses ground shaking relative to actual physical effects observed by people and therefore is a useful scale for comparing different seismic events. MMI values 3 Moment magnitude is related to the physical size of a fault rupture and movement across a fault.The Richter — magnitude scale reflects the maximum amplitude of a particular type of seismic wave.Moment magnitude provides a physically meaningful measure of the size of a faulting event(California Geological Survey(CGS)(formerly the California Division of Mines and Geology[CDMG]), 1997). RMC Pacific Vernalis Quarry Mining and Reclamation Project 4.7-4 ESA/203015 Draft Environmental Impact Report May 2006