String a wire back and forth across / along a fault line to measure very small displacements in the earth's surface. If the resistance and/or tensile strength needs to be higher than a common single alloy wire then structural steel cable could be wrapped around a insulated wire with a higher resistivity. It could be temperature compensated as usual, with another wire of the same length loosely supported nearby in another leg of the bridge.
An abandoned power line may be good to go if it is properly located.
Good info sometimes comes in small displacements.