Principles of Probabilistic Seismic Hazard Assessment (PSHA) and Site Effect Evaluation and Its Application for the Volcanic Environment in El Salvador

Abstract

This book chapter explains the fundamental concepts of the probabilistic seismic hazard and site effect evaluation. It is divided into four parts: firstly, the theoretical background of the probabilistic seismic hazard methods is explained to compute the earthquake loads used in structural analysis of buildings, namely, the rigid-zone method, the free-zone methods, and the characteristic models. We emphasize the physical meaning of the seismic coefficient prescribed in the seismic code regulations and its association with the return period of ground motion and spectral ordinates. The interconnection of the return period, the recurrence interval, and the lifetime concepts are explained to clarify misconceptions among these terms in connection with the probability of exceedance of motion. Secondly, the seismic hazard methods are applied employing volcanic chain seismicity data, and preliminary seismic hazard maps for rock site are presented for flat topography conditions along El Salvador. Thirdly, the site effects in terms of the amplification of ground motion are studied using soil profiles characterized by the interbedding of lava flows and volcanic ashes. Finally, we present a summary that highlights the most important concepts explained in this book chapter.

Perspective Chapter: Testing the Interoccurrence Times Probability Distributions of Earthquakes

“…For time-independent seismic hazard analysis, the probability that a magnitude will fall within a magnitude m1 and m2 is given by: PM ðÞ ¼ ð m2 m1 fM ðÞ dM (8) where f(M) is the magnitude probability density function based on the constants A and B in Eq. ( 7) [28]. We present in Figure 7b the magnitude probability for the overall subduction zone suitable for time-independent seismic hazard analysis.…”

Seismic And Geomorphic Assessment For Coseismic Landslides Zonation In Tropical Volcanic Contexts

“…We also evaluated the mean recurrence interval (MRI) of magnitudes above 5.0 Mw for the seismic zone C6. This is usually the time to elapse between two subsequent earthquakes of a given magnitude rupturing on a given seismogenic source (e.g., Wang 2007;Salazar 2018). This can be described by the Gutenberg-Richter relationship, if M is solved in terms of the frequency of the events (1/t) based on the estimated a and b-values.…”

Cross-validated Probabilistic Seismic Hazard 

“…for which a person can buy and own property, so the risk transfers to the individuals that acquire old buildings (Salazar, 2018).…”

“…Cornell-McGuire approach and the free-zone Woo (1993). An in-depth discussion of these methods is elsewhere (e.g., Salazar, 2018).…”