Method of continuous wave seismic prospecting

Claim 1

IN THE METHOD OF MEASURING THE TRAVEL TIME ALONG AT LEAST ONE PATH OF PROPAGATION THROUGH THE EARTH BETWEEN SPACED FIRST AND SECOND POINTS THEREON OF A VIBRATORY SIGNAL INJECTED INTO THE EARTH AT SAID FIRST POINT WHICH IS SUBSTANTIALLY LONGER THAN THE TRAVEL TIME OF SUCH SIGNAL ALONG ANY OF THOSE PATHS OF ITS PROPAGATION THROUGH THE EARTH BY WHICH IT REACHES SAID SECOND POINT AT USABLE ENERGY LEVELS, THE IMPROVEMENT WHICH COMPRISES; FORMING A SHIFT REGISTER BINARY CODE OF MAXIMAL LENGTH; VARYING A CHARACTERISTIC OF SAID VIBRATORY SIGNAL INJECTED INTO THE EARTH AT SAID FIRST POINT IN ACCORDANCE WITH SAID BINARY CODE OF MAXIMAL LENGTH FOR A TIME INTERVAL WHICH IS SUBSTANTIALLY LONGER THAN THE TRAVEL TIME OF SAID SIGNAL ALONG ANY OF THOSE PATHS OF ITS PROPAGATION THROUGH THE EARTH BY WHICH IT REACHES SAID SECOND POINT AT USABLE ENERGY LEVELS BEFORE REPEATING SAID BINARY CODE; PRODUCING A FIRST ELECTRICAL SIGNAL WHICH IS A REPLICA OF SAID VARIED VIBRATORY SIGNAL AND A SECOND ELECTRICAL SIGNAL REPRESENTATIVE OF THE VARIED VIBRATORY SIGNAL AS RECEIVED AT SAID SECOND POINT; PRODUCING A THIRD ELECTRICAL SIGNAL WHICH IS THE TIME DIFFERENTIAL OF SAID FIRST ELECTRICAL SIGNAL; PRODUCING A FOURTH ELECTRICAL SIGNAL WHICH IS THE TIME DIFFERENTIAL OF SAID SECOND ELECTRICAL SIGNAL; PRODUCING ELECTRICAL PULSES AT SALIENT POINTS IN THE THIRD ELECTRICAL SIGNAL TO FORM A FIRST PULSE TRAIN AND AT SALIENT POINTS IN THE FOURTH ELECTRICAL SIGNAL TO FORM A SECOND PULSE TRAIN; COMPRESSING SAID FIRST AND SECOND PULSE TRAINS IN REAL TIME BY DECREASING THE REAL TIME SPACING BETWEEN INDIVIDUAL PULSES THEREOF WHILE MAINTAINING CONSTANT THE RELATIVE TIME SPACING BETWEEN SAID INDIVIDUAL PULSES; CROSS-CORRELATING SAID FIRST AND SECOND PULSE TRAINS AT A PREDETERMINED NUMBER OF TIME-PHASE RELATIONSHIPS THEREBETWEEN TO PRODUCE A FIRST CORRELATION SIGNAL HAVING AN AMPLITUDE VARYING IN ACCORDANCE WITH THE DEGREE OF CORRELATION BETWEEN SAID PULSE TRAINS AT VARIOUS TIME-PHASE RELATIONSHIPS THEREBETWEEN; RESPONDING TO A MAXIMUM VALUE OF MAGNITUDE OF SAID SECOND CORRELATION SIGNAL.