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Another structural risk factor for death
and severe injury in earthquakes is the building height. In the 1988
Armenian earthquake, people inside buildings with five or more floors were
3.65 times more likely to be injured compared to those inside buildings less
than five floors in height (95% CI, 2.12-6.33) (65), and in the 1990
Philippine earthquake, people inside buildings with seven or more floors
were 34.7 times more likely to be injured (95% CI, 8.1-306.9) (66). In a
high-rise building, escape from upper floors is unlikely before the building
collapses, and if it collapses completely, perhaps 70% of the building's
occupants are likely to be trapped inside (64). On the other hand, in a
low-rise building that takes perhaps 20 or 30 seconds to collapse, more than
three-quarters of the building's occupants may be able to escape before the
collapse (64).
Damage to other human-engineered structures such as transportation networks
(e.g., bridges, roads, and railways) can also pose serious threats to life
in earthquakes. For example, in the 1989 Loma Prieta earthquake, 42 of the
62 total deaths resulted from the collapse of the upper section of the
Cypress Viaduct of Interstate 880 in Oakland, which trapped motorists
driving on the lower section (77). |