Transient Electromagnetics, Passive Seismic, and Borehole Electromagnetics, Gamma, and Nuclear Magnetic Resonance Methods to Characterize Glacial Sediments in East Falmouth, Massachusetts, Near Nantucket Sound

On June 5, 2015, transient electromagnetic (TEM) data were acquired on the baseball field at the East Falmouth, Massachusetts Elementary School approximately 30 m north the well MA-FWS-750. Transient electromagnetic induction (TEM) surveys provide resistivity soundings of the subsurface, which can be related to lithology and hydrogeology. Electrical current is cycled through a wire placed on the land surface in a transmitter loop (Tx), which in turn produces a static magnetic field. When the current is abruptly terminated, an instantaneous current is induced in the earth, and it moves downward and outward as the induced current decays with time. The decay is controlled by the resistivity of the earth. One or more receivers (Rx) at the center of the Tx loop measure the secondary magnetic field as a function of time (dB/dt). Voltage that is induced in a coil in the receiver is proportional to the rate of change of the magnetic field (dB/dt). Decaying voltage measurements at the receiver are converted to apparent resistivity, which can be inverted to recover the depth-dependent resistivity structure of the earth.