It is relatively easy to get a good 2-D view of earth’s materials and structure as exposed at earth’s surface. Sometimes steep topography (as we have here in the mountains), vertical cuts into a hillside, or drill holes (such as those poked in the ground for water or oil exploration) provide us with some perspective on the third dimension. Geologists use surface observations, 3-D clues such as drill holes, and knowledge of material properties and behaviors to predict the character of the subsurface.
Geophysics provides us with tools to better constrain our understanding of what is down beneath our feet, but out of sight. Geophysics is not a magic wand, but it can be a powerful tool when wielded with a proper respect for the known (observations). Waves and forces that are in the realm of measurement by physicists behave in predictable ways when they encounter contrasts in the physical properties of materials.
For instance:
- Variations in the magnetic character of earth materials (referred to as susceptibility) can add to or subtract from the earth’s magnetic field as measured at the surface.\
- Variations in density of materials can very measurably modify the local pull of earth’s gravity.
- The way that different materials conduct or resist the flow of electrical current is variable.
- The density and elastic properties of materials modify the velocity and path of seismic waves passing through.
For more information, visit: