New Challenges in Seismic Design - Earthquake Engineering for Structural Design - page 4

the remarkable knowledge development during the last decades in the frame of
Seismology. The main considered task is to transfer the accumulated results from
the academic research works to the design practice, filling the existing gap between
these to activities, disseminating upgrade guidelines and new codes, cooperating
with professional associations, promoting education for practicing professionals.
1.2GLOBALURBANIZATIONANDIMPACT OFEARTHQUAKES
1.2.1 Urban Revolution
The urban revolution is the process which produces the transformation of villages
or small cities into large, socially complex, civilized urban centers, as a result of
the population increasing. The total urbanization of the society is an inevitable
process.
The world population has exploded, and continues to explode, both in number
and global distribution during the past few centuries. Between 100 BC and about
1600 AD global population doubled from perhaps 300 million to more than 600
million. In the following 200 years, improvements in medicine, living conditions
and a dramatic reduction of mortality rates, resulted in a second doubling in the
world population to 1200 million. Between 1800 and 1950 the global population
doubled for the third time, reaching 2500 million. The fourth doubling occurred in
less than 40 years bringing global population in 1990 to more than 5000 million. In
2000 the world population reached 6100 million. Although the rate of population
increase seems now to be reduced, a doubling of population in the next 50 years is
predicted (Bilham, 1995, 2000).
But the most important observation is the global urbanization produced in the
last decades. If in 1800 only 2% of the world's population was urbanized, in 1950,
the percentage increased to 30%, while in 2000, this value reached 47%. In 2008 it
is expected that more than half the population will be living in urban areas, and by
2030, more than 60% will live in these areas (UN-Habitat, 2005). The increase is
not uniform in the world: the population in urban areas in developing countries will
grow from 0.5 billion in 1960 to 4.1 billion in 2020, while in developed countries,
the increase will be lower, from 0.55 billion in 1960 to 1.2 billion in 2020 (Fig.
1.1).
If in 1950 there was only one city with a population over 10 million inhabitants
(New York City), in 2005 there are 24 mega cities. Five of these cities exceed 20
million inhabitants (Brinkhoff, 2005). The most dynamic urbanization occurs in
developing countries of Asia, Latin America and Africa. By 2030 these continents
will have a higher number of urban areas than any other major area in the world. In
the developed countries, with few exceptions, urban populations have grown just a
little.