Laserfiche WebLink
10-b(m-m°)-10-b(m°-m <br /> N(m)=a(m°) (4) <br /> 1-10-b(m`-m O) <br /> where a(m) is the annual frequency of occurrence of earthquakes greater than the minimum <br /> magnitude, m°; b is the Gutenberg-Richter parameter defining the slope of the recurrence <br /> curve; and W is the maximum magnitude event that can occur on the source. A m° 5 was <br /> used for the hazard calculations because smaller events are not considered likely to produce <br /> ground motions with sufficient energy to damage well designed structures. <br /> For the characteristic model, the number of events exceeding a given magnitude is the sum <br /> of the characteristic events and the non-characteristic events. The characteristic events are <br /> distributed uniformly over ± 0.3 magnitude unit around the characteristic magnitude <br /> (Figure 1) and the remainder of the moment rate is distributed exponentially using the above <br /> equation with a maximum magnitude one unit lower than the characteristic magnitude. <br /> The recurrence rates for the fault sources are defined by the slip rate for the maximum or <br /> characteristic event and the recurrence b-value. The slip rate is used to calculate the moment <br /> rate on the fault using the following equation defining the seismic moment. <br /> Mo = it A D (5) <br /> where Ma is the seismic moment, It is the shear modulus, A is the area of the rupture plane, <br /> and D is the slip on the plane. Dividing both sides of the equation by time results in the <br /> moment rate as a function of slip rate: <br /> M = µ A S (6) <br /> where M is the moment rate and S is the slip rate. M. has been related to Ma, by Hanks and <br /> Kanamori (1979): <br /> M, = 2/3 log M. - 10.7 (7) <br /> H:\CONTRACT\TENMII.E\6 6 M0412951500 <br />