The Economic Consequences of a Catastrophic Earthquake Proceedings of a Forum (1992) / Chapter Skim
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1 WHAT IS KNOWN ABOUT SEISMIC RISK NATIONALLY?
1 WHAT IS KNOWN ABOUT SEISMIC RISK NATIONALLY?
Pages 11-34
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From page 11... ...
Although Califorma is the area most frequently associated with earthquake events, other areas of the country are also at risk, notably: the Puget Sound area in Oregon and Washington; the Wasatch fault area in Utah; the New Madrid fault area in the central United States; Charleston, South Carolina; the Boston-New York area; Alaska; Hawaii; and Puerto Rico. This chapter establishes the scientific basis for earthquake risks in these areas as well as Probabilities (where such evidence exists)
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From page 12... ...
As illustrated, the western margin of the United States is part of the boundary of the Pacific plate. The Pacific plate Is drifting toward the northwest relative to California and the North American plate.
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From page 13... ...
The plate boundary lies along the western margin of the continent; a lot of the plate-related activity extends into the western part of the United States as far as the Wasatch front in Utah. The Pacific plate is moving at about 8 cm per year relative to the North American plate, which is moving at about 2.5 cm per year.
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From page 14... ...
Figure 1-6 illustrates the concept that the San Andreas fault system is not just one boundary between the North American plate and the Pacific plate, but rather is a complex zone of blocks. In general, Los Angeles is moving north, but there are other blocks that are moving in different directions.
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From page 15... ...
The 1906 earthquake broke the San Andreas from just north of San Juan Bautista toward Cape Mendocino. That was the last magnitude 8 earthquake in California.
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From page 16... ...
A-E . NORT:H A~:E~CAN: PLATE ~ ~ FIGURE 1~4 The North American plate.
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From page 17... ...
The Loma Prieta earthquake occurred along the San Andreas fault system in the Santa Cruz Mountains (Figure 1-7)
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From page 18... ...
18 ECONOMIC CONSEQUENCES OFANE~THQU~E _ in : .'. FIGURE 1-7 The Loma Prieta earthquake.
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From page 19... ...
These cross sections run from near San Francisco to central California. The top portion of the figure shows earthquake activity that had occurred in the several years before the Loma Prieta earthquake.
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From page 20... ...
In the Marina District in San Francisco, a phenomenon occurred that is very important. It is called liquefaction.
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From page 21... ...
SEISMIC RISK NATIONALLY FIGURE 1-9 Loma Prieta earthquakes (October 17-19, 1989~. 21 FIGURE 1-10 Preliminary probabilities of large San Andreas earthquakes (1988-2018)
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From page 22... ...
W...~. FIGURE 1-12 Multistory building in the Marina Distnct.
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From page 23... ...
Usually unreinforced masonry structures have the most difficulties. The areas of damage in the Loma Prieta earthquake in the San Francisco Bay area were largely predicted.
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From page 24... ...
They are fairly broadly distributed; however, there are concentrations. One of the biggest concentrations is in the central Mississippi Valley area, in the area of the New Madrid seismic zone, which has been -- over the last several hundred years and even recently -- the most active seismic area In the eastern United States.
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From page 25... ...
A,, ..... / FIGURE 1-15 Nimitz Freeway, showing collapsed pilings.
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From page 26... ...
26 ECONOMIC CONSEQUENCES OF AN EARTHQUAKE FIGURE 1-16 Chasms in the Santa Cruz Mountains.
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From page 27... ...
EXPLANATION ~ VIOLENT ~ VERY STRONG ~ S+. PONG ~ ~ : ~W=AK ~: FIGURE 1-18 San Francisco Bay area: predicted maximum earthquake intensity.
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From page 28... ...
As stated at the beginning of this chapter, earthquakes in the East affect a far greater area than earthquakes of corresponding magnitude in the West. Figure 1-20 shows the areas of intensities 6 and 7 for the New Madrid earthquake of 1811, the Charleston earthquake of 1886, the San Francisco earthquake of 1906, and the San Fernando earthquake of 1971.
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From page 29... ...
Figure 1-21 shows the terrain (elevations) in the eastern United States.
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From page 30... ...
30 ECONOMIC CONSEQUENCES OF AN EAR THQUA~ FIGURE 1-21 Terrain map of the eastern United States. FIGURE 1-22 Gravity map of the eastern United States.
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From page 31... ...
At, _ SECOND In,. =~t,,^~_ FIGURE 1-24 Magnetic field in the New Madrid region.
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From page 32... ...
Since then, the stresses that have been caused by the flexing of the North American plate have repeatedly jostled the keystone and created a new geologic structure, but it is basically the reactivation of the keystone that is causing earthquakes now. In 1886, a magnitude approximately 7 earthquake occurred in the Charleston, South Carolina, area and caused significant damage.
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From page 33... ...
An instrument run by a professor at Stanford, which monitored electromagnetic phenomena, had recorded anomalous activity a few hours and days before the earthquake. But, there is no reliable basis for a short-term earthquake prediction.
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From page 34... ...
QUESTION: Figure 1-18 showed the high probability of earthquake likelihood on the east side of the San Francisco Bay. Do those areas also indicate something about damage?
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