GEOPH424 Midterm: GEOPHYS 424 UofA midterm Exams 424Midterm 2008
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Note the number of points allocated for each part. Notes and textbooks may not be used during the exam. Please hand in this exam, with your name and student number listed above. Question 1 ( total = 10 points) (1a) name the two main sources of magnetotelluric signals. State the frequency band at which each occurs. (4 points) (1b) how does the presence of clay change the resistivity of a rock? (1c) state two assumptions that are made when archie"s law is used to estimate the. What is the physical basis for this? (4 points) resistivity of a water saturated rock? (2 points) Question 2 resistivity of rocks ( total = 10 points) A fractured rock has a porosity, and is saturated with brine. The brine has a resistivity of 0 = 1 ohm-m and the rock matrix has a resistivity of 1 = 1000 ohm-m.
