Author : Gabriel Andrés Bernal Granados
Publisher :
ISBN 13 :
Total Pages : 228 pages
Book Rating : 4.:/5 (112 download)
Book Synopsis Metodología para la modelación, cálculo y calibración de parámetros de la amenaza sísmica para la evaluación probabilista del riesgo by : Gabriel Andrés Bernal Granados
Download or read book Metodología para la modelación, cálculo y calibración de parámetros de la amenaza sísmica para la evaluación probabilista del riesgo written by Gabriel Andrés Bernal Granados and published by . This book was released on 2015 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the assessment of seismic risk, hazard is one of its main components, given that, from a probabilistic perspective, provides the annual rates of exceedance of the intensities of strong motion in the site or region of analysis, or alternatively, provides a set of stochastically generated events that fully represent the hazard of the site or region of analysis. This thesis provides methodological elements of two major components of the assessment of seismic hazard: the attenuation of strong motion and site effects. A numerical procedure for the calibration of a source spectrum model to find the optimal combination of seismological parameters and derive unbiased ground motion prediction equations is presented, using available accelerogram recordings as calibration target. The source spectrum model is used to compute the radiated spectra of SH-waves for different seismic moments and hypocentral distances, combining point (far field) and finite (near field) source models. The expected value of the peak ground acceleration is computed from the radiated spectra using random vibrations theory. A genetic algorithm is used to search for the source spectrum parameters that best fit the available strong motion recordings. The procedure can be applied to any region with statistically significant accelerogram records. The proposed methodology is followed to derive spectral ground motion prediction equations compatible with the seismo-tectonic environment of Colombia, using 206 strong motion recordings as the calibration target. The obtained ground motion prediction equations are compared with those used in the latest national seismic hazard assessment study of Colombia. The comparison shows that the strong ground motion prediction equations obtained using the proposed methodology have lower residual bias, showing reasonable matching between them and the real strong motion recordings. Furthermore, in this thesis a methodology for assessing site effects in cities was developed, which is based on the geometry of the prevailing geological formations and their relation to soft soil deposits. The methodology allows to calculate the soil dynamic response at any location within a city, using a geotechnical seismic response model, which is based on the generation of synthetic stratigraphies from the definition of depth profiles of geotechnical properties relevant in assessing the seismic amplification. These geotechnical properties are modeled as random variables, in order to include in the model, in a consistent way, the uncertainty associated with the lack of the exact value of these properties in depth. This site effects model can be applied with three main objectives: i) obtaining transfer functions of the response spectrum for risk assessment, ii) generating Shake-Maps for emergency response purposes, and iii) the seismic microzonation of a city and obtaining elastic seismic-resistant design spectra. The methodologies presented here are a first step towards the construction of more detailed models of seismic hazard, which adequately reflect the specific conditions of the region where they are applied. This leads to the definition of more accurate models of seismic risk, to reduce the uncertainties associated with the assessment of the hazard and, therefore, to obtain tighter estimates of losses in order to provide decision makers with reliable information for the proper management of seismic risk.
