|Institution:||University of Auckland|
|Full text PDF:||http://hdl.handle.net/2292/2535|
It is generally accepted that some areas of the earth's surface are more prone to earthquake occurrence than others. Furthermore, within these earthquake-prone area the distribution of earthquake epicentres is non-uniform. Ttis has led to a system of regional zoning for earthquake resistant design in most countries. Observations of localised damage resulting from earthquakes has only recently led to the general acceptance of the fact that the degree of damage may be influenced by the characteristics of the soils in the affected area. Where the damage is related to gross instability of the soil resulting in large permanent deformations, association of the damage with local soil conditions is readily apparent. A somewhat less obvious effect of soil conditions on building damage is that subsurface soil layering can influence the intensity of ground shaking, and the frequency content of the surface motion, even though the soils underlying structures may remain perfectly stable during an earthquake. The frequency characteristics of the surface motion are important as the existence of a predominant ground frequency may lead to resonance of structures during prolonged shaking. In Chapter 2 a brief resume of existing knowledge of the occurrence, origin and nature of earthquakes is presented. Basic wave models and wave types are outlined.