Environmental Geology GGE322 Name______________________________
Test 2 Spring 2000
1. (8) The city of Royal Rivers is searching for a new landfill site. At a recent meeting, the following statements were made that will be used in making the final decision:
a. "The Tyvestad site is perfect; the water table is deep, the soils have very low permeability, the site is cheap and close to the city. All of the other potential sites have negative aspects".
b. "The Green Valley site is too far away. Running the trucks that long distance just plain won’t work".
c. "The soils at the Sandafoot site are too sandy for use as daily refuse cover. The cost of designing around that problem is more than we can afford."
d. "Regardless of the other possible sites, we have to select a site that has a subsoil permeability of 5 x 10-3 feet per day. That’s a state regulation."
Associate each of these decision-making statements with one of the following terms: dominance, feasibility range, lexicography, or effectiveness measure. (Choose the best term for each statement).
a_______________________________ b____________________________________
c_______________________________ d____________________________________
2. (24) Compared to many other Californian cities, there are not many recently active faults in the vicinity of San Diego (see map). Donovan (1973) suggested that the following equation be used to predict the seismic acceleration (as % of gravitational acceleration) from earthquakes of magnitude m:
110 e (0.5 m)
% acceleration = ---------------
(D + 25) 1.32
where D is the distance to the focus of the earthquake (in kilometers) and e (or exp) is Euler’s number = 2.72.
a. Use this empirical relationship to determine if there would be greater acceleration in San Diego from a small earthquake 40 km off-shore (m = 4.8) or from a larger quake (m = 7.1) about 3 times farther away (120 km), with a focus beneath the south end of the Salton Sea. (Show all your work)
b. What would be the maximum % acceleration of the larger earthquake in the vicinity of the Salton Sea (set D = 0 km)?
c. Explain how information like this might be helpful in siting sensitive structures (such as nuclear power generation stations). Would there be any benefit to locating these structures in seismically "quiet" areas of the state? Or doesn’t it really matter where you put the structure in California when we’re dealing with accelerations related to really big earthquakes (m = 7 to 8)?
3. (20) Match the following earthquake precursor phenomena (U.S. model) with the typical change prior to an earthquake.
_____geological electrical resistivity a. drops and then rises
_____P-wave velocity b. rises early on, then may stabilize
_____radon concentration in groundwater c. rises early, then may slowly fall
_____topographic changes and tilt d. drops continuously
e. does not change
f. increases in irregularity
4. (15) The U.S. seems to have moved toward tighter construction standards and structural retrofitting as the best way to mitigate earthquake hazards.
a. Do you think this is wise? Why?
b. Think of and list some possible problems with implementing this approach in seismically-active areas of the U.S. outside of California (such as Memphis TN, Boston MA, and Charleston, SC) where the recurrence interval between great quakes may be very large.
c. What are the problems with techniques of prediction and fault manipulation?
5. (15) In your assigned reading, Smith and Jol describe some work they did in characterizing the Wasatch Fault.
a. Where is the Wasatch Fault?
b. What method did they use to investigate the fault?
c. What did they find?
d. In what way was their method better than the old-fashioned "trenching" method for characterizing faults?
6. (18) a. Sketch the molecular structure of smectite. Label the elements and show the "t" and "o" sheets.
b. Describe some of the physical properties of smectite
c. Where geographically and geologically are you likely to fine abundant smectite in soil?