Seismology and site effects

This chapter reviews seismology and site effects to provide background for understanding ground motion characteristics and their influence on the behavior of structures. It discusses earthquake sources, magnitude, and magnitude-recurrence relationships. The chapter also discusses the propagation of ground motion to a site, near-source effects, site amplification, and shaking intensity and its representation using response spectra. Seismology is the field of science that studies earthquakes and the propagation of waves through the earth. A number of signal processing techniques are applied to remove noise and sensor artifacts in order to generate the processed acceleration time histories. Because high-frequency waves attenuate faster with distance, most such far-field recordings will have a lower amplitude vertical component. Duration is a scalar measure of interest, especially when discussing the behavior of cyclically degrading structures.