...Seismic Hazard Cover Page Historical Examples...
Scenario Earthquakes for Urban Areas Along the Atlantic Seaboard of the United States
Seismic Risk Factors
- Age and Fragility of the Built Inventory
. There exists a large stock of often aged eastern structures originally not designed to resist earthquakes (e.g. old bridges, unreinforced masonry, only lightly reinforced concrete). This built inventory is believed to be more vulnerable to earthquakes than most of the western inventory that tends to be younger and is more likely designed to resist earthquake forces.- Lack of Seismic Performance Record
. As a corollary to the large uncertainty in the seismic hazard, there exists a similar uncertainty about the seismic performance characteristics and fragility of ordinary eastern structures because during the structures’ lifetimes few have so far actually experienced significant seismic shaking. Unsuitable structures in the west have been identified, and even eliminated by past events. Such weeding out by earthquakes has not occurred in the east in recent times.- Asset Concentration in Large Vulnerable Metropolitan Corridors
. The eastern U.S. contains metropolitan corridors with the highest population densities in the U.S., especially along the Washington – New York – Boston corridor of the Atlantic coast. Significant portions of the corridor are seismically active. A single moderate earthquake can cause damage that amounts to a few percent of the value of the built assets in the area of highest intensities. How large these losses actually could become strongly depends on the spatial concentration and seismic performance of the buildings and critical infrastructure systems.These few remarks may serve as a warning that the relatively low level of seismicity of eastern regions can translate into a relatively high seismic risk potential. It is in this low seismicity/high-risk environment that one needs to develop and implement risk-sensitive strategies for seismic design and preparedness.
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Last modified: 5/7/2001 3:39:51 PM
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