Abstract:
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.
