Development of earthquake ground motion relations for Puerto Rico

Empirical ground motion relations are a key input to seismic hazard analysis. Ground motion relations describe the peak ground amplitudes and frequency response characteristics of seismic waves as a function of magnitude and distance. This thesis provides the first region-specific ground motion relations for Puerto Rico. This work is important because Puerto Rico is a region of high seismic hazard and dense population.; Due to a paucity of data at small distances and large magnitudes, there are insufficient Puerto Rico ground motion data to directly obtain ground motion relations for magnitudes and distances of most engineering interest. However data from moderate events can be used in conjunction with a seismological model to develop the relations. Fourier amplitudes and response spectra of Puerto Rico earthquakes of magnitude 3 to 5.5 have been analyzed to determine underlying regional model parameters. The regional data were used to determine key attenuation parameters, such as the quality factor Q, the duration of ground motion and generic site amplifications.; To overcome the incompleteness of the data set, stochastic finite fault modeling was applied to generate a set of generic artificial waveforms for different magnitudes and distances. In stochastic finite fault modeling a large fault is divided into N subfaults and each subfault is considered as a small point source. Ground motions of subfaults, each of which are calculated by the stochastic point-source method, are summed with a proper delay time in the time domain to obtain the ground motion from the entire fault. The input parameters for the simulations are based on the attenuation parameters obtained from the real recorded waveforms from small to moderate events.; Finite-fault simulations based on the stochastic method can be made using the computer program FINSIM. FINSIM has been validated in other regions, such as California, for which more data are available. FINSIM provides results that are comparable to the empirical attenuation relationships that can be obtained by regression analysis of a large strong motion database. Nevertheless, there are some conceptual aspects of FINSIM that should be improved, as described in this thesis.; A new approach has been introduced in the stochastic finite fault modeling based on the concept of the "dynamic corner frequency" (where the comer frequency is a parameter that controls spectral shape). In this approach, the comer frequency is a function of time, and the rupture history controls the frequency content of the simulated time series of each subfault. (Abstract shortened by UMI.)...