Coda waves from local earthquakes in the southern part of the Netherlands and just across the border in Belgium and Germany are used to estimate the seismic attenuation of that area. Two different models are applied, the single back-scattering model of Aki and Chouet (1975) and the multiple scattering model of Zeng (1991). The goal is to achive attenuation as a function offrequency. The results from the single scattering model show a singnificant difference in coda Q between smaller and larger epicentral distances. Therefore the results are divided into three different models, one for epicentral distances from 0 to 25 km, one for 25 to 75 km and one for distances larger than 75 km. The value of Q0 for smaller distances is about 100 and for the larger distances about 200. The value of n is for all distances nearly the same, namely about 0.8. In the time of this research it was not possible to do the inversion of the multiple lapse time analysis, the analysis of the multiple scattering model. Therefore no exact coda Q values are obtained from this model, but only an estimation based on figures of an article of Hoshiba, Sato and Fehler (1991(. The estimated values are slightly different from those of other studies that applied this model. When the coda Q values of the single scattering model are compared with attenuation values obtained from the local magnitude, they fall within each others error bars. This is the same when the coda Q is inserted in an approximation of peak ground acceleration of McGuire and Hanks (1980) and then compared to an empirical attenuation relation of Ambraseys (1990).
FH Goutbeek. Coda Q in the Southern Part of the Netherlands
Journal: Master Thesis University of Utrecht, Year: 2000