Learning from Earthquakes - Earthquake Engineering for Structural Design - page 75

possible. The earthquake hazard is typically determined using a
combination of seismological, morphological, geological and geotechnical
investigations, combined with the history of earthquakes in the region. It
depends not only on the seismicity, but also on collateral hazards:
liquefaction, landslide, etc.
- Vulnerability is the degree of loss resulting from the occurrence of an
earthquake of a given magnitude. The vulnerability refers to foundations,
structural elements and non-structural elements of all built environment,
including buildings and different facilities, roads, bridges, dams,
population density, preparedness, building and lifeline damage, fire
following, etc.
- Losses refer to the direct losses (failure of buildings and lifelines), indirect
losses (interruption of activities), usually specified as a monetary value (in
US $), and secondary losses (short and long-term impacts on the overall
economy and socio-economic conditions).
If the earthquakes in some areas are inevitable, being out of human control, the
vulnerability must be supervised and this should be the main objective of
earthquake preparedness programs . Trends in mitigation of seismic risk refer to
improving the Seismic hazard knowledge and to using new design methodologies
aiming to reduce the vulnerability and losses. These trends differ in function of the
degree of the economical development in the examined region.
Development in computer technologies, including Geographic Information
System (GIS), Data Base Management System (DBMS), and Knowledge-Based
Expert System (KBES), have made it possible to develop innovative methods for
earthquake damage and loss estimation.

3.2LESSONSFOR EARTHQUAKEHAZARD

A representative listing of topics involved in the earthquake hazard examination
might consider the seismological, geotechnical and engineering aspects.
A better understanding of the seismological aspects of the earthquake
phenomena results from the cooperation between geophysicists and seismologists.
In spite of the complexity of an earthquake manifestation, real progress was
marked in the classification of earthquakes. Nowadays it is very clear that there are
some basic earthquake types with very different characteristics (Burkhard, 2001,
Gioncu and Mazzolani, 2003) (Fig. 3.2).
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Earthquakes tend to recur where they have occurred in the past, especially
along the boundary of tectonic plates (i.e. the Californian earthquakes) but
major devastating earthquakes can occur also in areas where no previous
events have been recorded (see New-Madrid, USA, or Bluj, India,
earthquakes). There are very few areas in the world that are immune from
the earthquake danger.