The amplitude of an electromagnetic wave propagating between the radar transmitter and receiver that intersects a region containing iron will decrease with respect to background radar-pulse amplitudes. The scans below 40 m were used to determine the mean background amplitude because these scans are several meters below the expected bottom of the wall. Model configuration to determine the extent of the wall. After normalization, all of the field data were combined into contoured cross-section plots. Normalized amplitudes below the value of 84 percent, which is the median value of the normalized amplitude data, outline an irregularly shaped zone about 9 m wide and 12 m high.
Horizontal bands extend outward from the main zone.
These stringers could be a result of the presence of salt water, suspension gel used in the hydraulic-fracturing process, or iron particles moving into higher permeability zones within the saturated sediments. Cross-section plot of the normalized transmission amplitude data collected over the south iron filing wall, MMR, Cape Cod, Massachusetts. The 0.84 contour represents the median value of the normalized amplitude data. The outline of the south wall using the results of the edge model simulations are superimposed in figure 10 . The wall edge is defined as the 43-percent normalized wave amplitude contour.