ABSTRACT
Earthquakes represent the largest potential source of casualties and damage for
inhabited areas due to natural hazard. Although the location varies, the pattern is
the same: an earthquake strikes without warning, leaving cities in rubble and
killing tens to hundreds of thousands of people. Worldwide during the 20
Century, there were ten earthquakes killing more than 50,000 people and over 100
earthquakes killing more than 1000 people (FEMA 383, 2003). Every year,
something like five thousand to ten thousand people die during earthquakes
worldwide. The 1976 Tangshan-China (magnitude M 8.0), the worst earthquake in
recent times, killed over 600,000. Among these terrifying data, the moderate 1994
Northridge in Los Angeles (magnitude M 6.7), which killed 60 people, and 1995
Kobe in Japan (magnitude M 6.9), which killed 5600 people, seemed to be
relatively insignificant. Nevertheless, these two earthquakes have changed the
direction of earthquake engineering research throughout the World (Blakeborough,
2002). Two main reasons produced this crucial change.