Method and apparatus for determining the density characteristics of underground earth formations

A plurality of detectors are disposed within a bore hole for ascertaining the frequency and trajectory of high energy muons which penetrate through the earth. This information is converted by data processor into an integrated density value of the earth for incremental angular lines of sight extending through spaced apart elevations along the detectors. The data processor uses a tomographic analysis process to combine together all of these integrated density values for all of the elevations of interest to calculate the densities of discrete spatial volumes composing the underground region being investigated. Detectors produce electrical signals indicative of the trajectory of the passing muon. The signals are recorded by time-to-digital convertor (''TDC'') units. If the signals appear to have possibly originated from a high energy muon, a microprocessor retrieves the information collected by TDC units and transmits it to a data logger located at the earth's surface. The data processor then utilizes tomographic analysis to make the localized density determinations discussed above