Method and apparatus for 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 APART FIRST AND SECOND POINTS ON THE EARTH OF A VIBRATORY SIGNAL WHICH IS NON-RESPECTIVE DURING A TIME INTERVAL 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, AND WHEREIN IS PRODUCED AN ELECTRICAL REPLICA OF THE TRANSMITTED VIBRATORY SIGNAL AND AN ELECTRICAL SIGNAL REPRESENTATIVE OF THE VIBRATORY SIGNAL AS RECEIVED AT SAID SECOND POINT, AND WHEREIN THE ELECTRICAL REPLICA OF THE TRANSMITTED VIBRATORY SIGNAL AND THE ELECTRICAL SIGNAL REPRESENTATIVE OF THE VIBRATORY SIGNAL AS RECEIVED AT SAID SECOND POINT ARE CROSS CORELATED WITH A MULTIPLICITY OF TIME-PHASE RELATIONSHIPS THEREBETWEEN, THE IMPROBEMENT WHICH COMPRISES: PRODUCING A BINARY CODE OF MAXIMAL LENGTH WHEREIN A CODE GROUP OF N BINARY BITS IS NOT REPEATED FOR (2N-1) BITS; FORMING AN ELECTRICAL ANALOG OF BINARY BIT HAVING A WAVEFORM WITH SUBSTANTIALLY ZERO SLOPE AT ZERO AMPLITUDE AT THE BEGINNING AND END THEREOF AND COMPLETELY CONTINUOUS THEREBETWEEN; FORMING AN ELECTRICAL ANALOG OF SAID BINARY CODE OF MAXIMAL LENGTH BY VARYING A CHARACTERISTIC OF THE ELECTRICAL ANALOG OF SAID BINARY BIT BETWEEN TWO STATES THEREOF IN ACCORDANCE WITH SAID BINARY CODE OF MAXIMAL LENGTH; AND FORMING SAID VIBRATORY SEISMIC SIGNAL BY DRIVING AN ELECTROACOUSTIC TRANSDUCER WITH SAID ELECTRICAL ANALOG OF SAID BINARY CODE OF MAXIMAL LENGTH