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<br />L J~ <br />Source Geometry <br />i In the probabilistic analyses, it is assumed that earthquakes of a certain magnitude may occur <br /> randomly along the length of a given fault or segment. The distance from an earthquake to <br />1 the site is dependent on the source geometry, the size and shape of the rupture on the fault <br /> plane, and the likelihood of the earthquake occurring at different points along the fault length. <br /> The distance to the fault is defined to be consistent with the specific attenuation relationship <br /> used to calculate the ground motions. The distance, therefore, is dependent on both the dip <br />' and depth of the fault plane, and a sepazate distance function is calculated for each geometry <br /> and each attenuation relationship. The size and shape of the rupture on the fault plane aze <br /> dependent on the magnitude of the earthquake, with larger events rupturing longer and wider <br /> portions of the fault plane. We modeled the rupture dimensions following the magnitude- <br /> rupture area and magnitude-rupture length relationships of Wells and Coppersmdth (1994). <br /> <br /> Recurrence <br /> <br /> The recurrence relationships for the faults are modeled using both the exponentiallly truncated <br /> Gutenberg-Richter relationship and the characteristic earthquake recurrence model. For the <br /> source zones, only an exponential recurrence relationship is assumed appropriate. We have <br /> used the general approach of Molnar (1979) and Anderson (1979) to arrive at the recurrence <br />l <br />d <br />d i <br />th <br />d <br />l <br />ti <br />ll <br />t <br />t <br />d <br />d <br />l <br />A 70% <br />b <br />bili <br />h <br />b <br />i <br />f <br />th <br /> nc <br />u <br />e <br />n <br />e mo <br />e <br />or <br />e exponen <br />a <br />y <br />runca <br />e <br />mo <br />e <br />. <br />pro <br />a <br />ty <br />as <br />een <br /> that the faults rupture with a "characteristic" magnitude on specific segments. This model <br /> is described by Aki (1983) and Schwartz and Coppersmith (1984). We have used the <br /> numerical model of Youngs and Coppersmith (1985) for the chazacteristic model. These <br />' exponential and characteristic models are weighted to represent our judgmE:nt on their <br /> applicability to the sources (Figure 1). The number of events exceeding a given magnitude, <br /> N(m), for the truncated exponential relationship is <br /> N(m)_n(m,)10"a'"-"'~-10'btm~-"'9 (4) <br />1-10'bt'" ~"°' <br />H:1CON7RACI1234561.DUP3 5 M0309951609 <br />