Cancelling seismic multiple reflections by transmitting only the down-travelling seismic signals detected from the original transmitted signal

Claim 1

A METHOD OF SEISMIC GEOPHYSICAL SURVEYING WHEREIN CERTAIN MULTIPLE REFLECTIONS ARE AT LEAST PARTIALLY CANCELLED, WHICH METHOD COMPRISES THE STEPS OF GENERATING IN THE EARTH AT A GIVEN INPUT LOCATION AN INITIAL SEISMIC-WAVE SIGNAL, DETECTING AT A DETECTION POINT ABOUT VERTICALLY BELOW SAID INPUT LOCATION, AT A DEPTH BENEATH AT LEAST ONE DOWN-REFLECTING INTERFACE, THE RESULTING DOWN-TRAVELLING SEISMIC WAVES INCLUDING A FIRST ARRIVAL OF SAID INITIAL SIGNAL AND SUBSEQUENT ARRIVALS REPRESENTING DOWN REFLECTIONS OF SEISMIC WAVES FROM AT LEAST SAID INTERFACE, REPRODUCIBLY RECORDING SAID DOWN-TRAVELLING SEISMIC WAVES, REPRODUCING SAID RECORDED DOWN-TRAVELLING WAVES AS A SECOND SEISMIC-WACE INPUT SIGNAL, UTILIZING SAID SECOND INPUT SIGNAL ALONE TO GENERATE CORRESPONDING SEISMIC WAVES IN THE EARTH AT SAID LOCATION, DETECTING AT SAID DETECTION POINT SECOND UP-TRAVELLING SEISMIC WAVES RESULTING FROM SAID SECOND INPUT SIGNAL WHEREIN THE WAVES CORRESPONDING TO SAID SUBSEQUENT ARRIVALS HAVE ALTERED THE RATIO OF PRIMARY TO MULTIPLEREFLECTION AMPLITUDES AS COMPARED WITH ITS VALUE FOR SAID INITIAL SIGNAL, AND DISPLAYING SAID UP-TRAVELLING WAVES IN SUCH A WAY AS TO UTILIZE SAID ALTERED REFLECTION-AMPLITUDE RATIO TO PRODUCE A SUBSTANTIAL DEGREE OF MULTIPLE-REFLECTION CANCELLATION.

Claim 2

A METHOD OF SEISMIC GEOPHYSICAL SURVEYING WHEREIN CERTAIN MULTIPLE REFLECTIONS ARE AT LEAST PARTIALLY CANCELLED, WHICH METHOD COMPRISES THE STEPS OF GENERATING IN THE EARTH AT A GIVEN INPUT LOCATION AN INITIAL SEISMIC-WAVE SIGNAL, DETECTING AT A DETECTION POINT ABOUT VERTICALLY BELOW SAID INPUT LOCATION, AT A DEPTH BENEATH AT LEAST ONE DOWN-REFLECTING INTERFACE, THE RESULTING DOWN-TRAVELLING SEISMIC WAVES INCLUDING A FIRST ARRIVAL OF SAID INITIAL SIGNAL AND SUBSEQUENT ARRIVALS REPRESENTING DOWN REFLECTIONS OF SEISMIC WAVES FROM AT LEAST SAID INTERFACE, REPRODUCIBLY RECORDING SAID DOWN-TRAVELLING SEISMIC WAVES, REPRODUCING SAID RECORDED DOWN-TRAVELLING WAVES AS A SECOND SEISMIC-WACE INPUT SIGNAL, UTILIZING SAID SECOND INPUT SIGNAL ALONE TO GENERATE CORRESPONDING SEISMIC WAVES IN THE EARTH AT SAID LOCATION, DETECTING AT SAID DETECTION POINT SECOND UP-TRAVELLING SEISMIC WAVES RESULTING FROM SAID SECOND INPUT SIGNAL WHEREIN THE WAVES CORRESPONDING TO SAID SUBSEQUENT ARRIVALS HAVE ALTERED THE RATIO OF PRIMARY TO MULTIPLEREFLECTION AMPLITUDES AS COMPARED WITH ITS VALUE FOR SAID INITIAL SIGNAL, AND DISPLAYING SAID UP-TRAVELLING WAVES IN SUCH A WAY AS TO UTILIZE SAID ALTERED REFLECTION-AMPLITUDE RATIO TO PRODUCE A SUBSTANTIAL DEGREE OF MULTIPLE-REFLECTION CANCELLATION.