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LLNL Emergency Plan Rev-23 October 2017 20 of ground shaking of about 1 Hz and above that would be the most damaging to buildings at the sites. For example, a magnitude 5.8 earthquake (followed by a magnitude 5.4 aftershock) on the Greenville Fault in 1980 produced high frequency shaking having an estimated peak acceleration of about 0.3 g (g is the acceleration due to gravity) and some instances of significant structural damage at Site 200. Comparable high frequency shaking would not be experienced from earthquakes on larger faults of the San Andreas system (i.e., San Andreas, Hayward-Rogers Creek, San Gregorio). Rather, these faults would produce relatively large low-frequency ground motions of longer duration. For example, the 1989 Loma Prieta earthquake on the San Andreas Fault produced a peak ground acceleration of 0.1 g at Site 200, but caused no damage. The Carnegie-Corral Hollow Fault system passes through Site 300 and 3 km east of Site 200. Field investigations by LLNL Geosciences in 1991 suggested that the Carnegie-Corral Hollow Fault should be considered potentially active, in which case it makes significant contributions to the hazard at both sites. Apparently, less active and/or shorter faults that make lesser contributions to the overall hazard include the Las Positas and Verona-Williams faults, and the recently discovered Mount Diablo thrust fault under the Livermore and Sycamore valleys. Historical records indicate that about once every 20 years Site 200 is subject to an earthquake that can at least knock books off shelves, overturn furniture, cause lighting fixtures to fall, and the like. No active faults are known to underlie Site 200, and there is no historical record of surface rupturing or faulting at the site. Flooding resulting from seismic events would not occur at LLNL from a failure of the Del Valle Reservoir dam, from loss of water from the Patterson Reservoir, or from a break in the South Bay Aqueduct near LLNL. Wildland Fires Wildland fires are a concern at LLNL. Historically, wildland fires have not been a threat at Site 200. However, wildland fires are a significant concern at Site 300. Precautions are taken to reduce the potential for a wildland fire spreading at Site 300 by reducing/controlling the growth of vegetation within a buffer area inside the perimeter fence. Wildland fire control at Site 300 is also mitigated aggressively by the annual prescribed burn. The prescribed burn confines a potential fire to the property boundaries of Site 300, eliminates the fuel in high fire probability areas (high explosive test areas), and generally breaks the fuel path, thereby limiting the size of potential fires in other areas. The Fire Department has been successfully conducting prescribed burns at Site 300 for over 45 years. Three documents describe and regulate the prescribed burns, the Prescribed Burning/Smoke Management Plan, Site 300 Explosive Test Facility Prescribed Burn/Smoke Management Plan and EMD Procedure 1606, Tactical Plan - Command Procedures: Controlled Burns at Site 300. Because of the prescribed burn process, firefighters assigned to ACFD Station 21 at Site 300 are well trained and experienced with “back-fire” techniques and use that technique extensively as a fire control measure when responding to wildland fires at Site 300.