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JC Isham, PG January 20, 2015 <br />Page 2 of 2 <br />The yield acceleration (ky) is the average horizontal acceleration value within the critical failure mass that <br />results in a pseudo-static factor of safety equal to 1.00. Based on Newmark (1965), if the maximum value <br />of the averaged accelerations induced within the critical stability failure surface exceeds the yield <br />acceleration value (ky), the potential exists for permanent displacement along the critical failure surface. <br />The averaged accelerations induced within the critical slope are often referred to as the seismic <br />coefficient (kmax) or the maximum horizontal equivalent acceleration (MHEA), both which are often lower <br />than the estimated PGA value. In other words, if the ground shaking caused by the design event <br />produces accelerations less than the calculated yield acceleration, seismic slope displacement is very <br />unlikely. <br />The results of the seismic displacement analysis yielded a median displacement value of 0.0275 inch and a <br />16% probability of exceedance value of 0.6523 inch. Both values are deemed negligible and are less than the <br />limit of 12 inches recommended by the U.S. Environmental Protection Agency in their 1995 Seismic Design <br />Guidance for Municipal Solid Waste Landfills. Title 27 California Code of Regulations does not specify an <br />acceptable value for permanent displacement under seismic loading.