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be achieved by moving particularly noisy geophones a few inches. Placement is also important. It may not be easy to push a spike fully home in hard ground but a geophone an inch above the ground vibrates in the wind. 3.5 Seismic cables Seismic signals are carried from geophones to recorders as varying electric currents, in cables which must contain twice as many individual wires as there are geophones. Wires are necessarily packed very closely and not only can external current carriers such as power and telephone cables induce currents, but a very strong signal in one wire can be passed inductively to all the others.
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