Passage VI

Figure 1 shows the relative ground elevation at Sites A-D in an earthquake-prone area, measured over 30 yr. Relative ground elevation is the vertical distance above or below the nearest benchmark (location of known, fixed elevation). Figure 2 shows the resistivity (which is directly proportion to the resistance to the flow of electrical current) of the bedrock in the same area, measured over 8 months (mo) in 1996. Figure 3 shows the level of the radon (a radioactive gas) emissions from well water in the same area, measured over 8 yr. The time at which an earthquake occurred in the area is indicated in all 3 figures.