Laboratory Manual for Introductory Geology 4e

EXERCISE 11.7
Locating Liquefaction Potential
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Liquefaction has the greatest impact when all pore spaces between loose grains are filled with water. The water table
separates zones below ground where all the pores are saturated with water from higher zones where some pores are dry.
The water table and its importance in our ability to use underground water are discussed in Chapter 14. Here, we examine
its possible role in predicting damage due to liquefaction.
The figure below shows data from a study of liquefaction potential for San Francisco County. It distinguishes areas
where bedrock is exposed at the surface from those underlain by unconsolidated sediment, and it shows the depth to the
water table in the sediment. Examine the map carefully to locate places where liquefaction has occurred in the past and
for clues to why it happened in those locations.
(a) Briefly describe how the water table relates to past episodes and locations of liquefaction in San Francisco. Why does
it seem important to study the water table when considering the possibility of liquefaction?
Liquefaction history in San Francisco related to bedrock and water table height.
(continued)
11.5 PREDICTING EARTHQUAKE HAZARDS: LIQUEFACTION
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