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Project No. 9929.G Geotechnical Investigation/Vineyard Avenue, Pleasanton 8 August 2003 <br />observed on the western portion of the property, some of which toed into an adjoining gully. The <br />swales appeared to be filled with colluvium and may represent dormant or old landslides. The <br />location of the mapped colluvium and landslides are shown on Figure 2, Site Plan. <br />Seismic Considerations <br />Damage to structures related to fault movement maybe divided into two categories: <br />a) Primary deformation such as displacement of a structure located <br />directly on a fault and violent ground shaking; and <br />b) Secondary failure such as lurch cracking, landsliding, liquefaction, <br />and differential compaction. <br />Surface faulting or ground rupture tends to occur along lines of previous faulting. Since previously <br />identified fault lines are not within the site or project toward the site, the possibility of surface fault <br />rupture is negligible within the subject property. <br />Ground shaking is a complex concept related to velocity, amplitude, and duration of earthquake <br />vibrations. Damage from ground shaking is caused by the transmission of earthquake vibrations <br />from the ground to the structure. The most destructive effects of an earthquake are usually seen <br />where the ground is unstable and structures are poorly designed and constructed. Maximum <br />accelerations in rock and soil are based on the attenuation relationships formulated by Sadigh and <br />Chang (1997) and Abrahamson and Silva (1997). FRISKSP computer program by Blake (2001) <br />was used to calculate site-specific probabilistic peak ground accelerations (PGA) for the site. <br />FRISKSP is a computer program for the probabilistic estimation of seismic hazard using three- <br />dimensional faults as earthquake sources. Using a 10% probability of exceedance within 50 <br />years with maximum-horizontal ground acceleration was calculated for the site at 0.67g. This <br />calculation considered all active earthquake fault zones within a 50-kilometer radius of the site <br />and a return period of 475 years. <br />TERRASEARCH, inG Page 9 of 53 <br />