Environmental Engineering Reference
In-Depth Information
Surface Damage Relationships
Factors
Earthquake destruction is related to a number of factors including magnitude, proximity
to populated areas, duration of the event, the local geologic and topographic conditions,
and the local construction practices.
Example
The effects of some of these factors are illustrated by a comparison of damage to two cities
during earthquakes of similar magnitude: Managua, Nicaragua (1972),
M
6.2, and San
Fernando, California (1971),
M
6.6. Both events affected an area with about 400,000
inhabitants. The Managua quake resulted in 6000 deaths compared with 60 in San
Fernando; the difference is related to soil conditions and local building practices. Managua
is located over relatively weak lacustrine soils, and relatively few structures have been
constructed with consideration for seismic forces. The San Fernando valley is filled with
relatively compact soils and most major structures have been constructed according to
modern practices. Even with “modern” practices, however, a number of new structures
were severely damaged as shown in Figure 11.39 and
Figure 11.40.
FIGURE 11.39
Modern freeway structures at the interchange of Highways 5 and 210, San Fernando, California, damaged by
the earthquake of February 9, 1971. (Photograph courtesy of the U.S. Geological Survey.)
