Method of determining the travel time of a seismic signal

Claim 1

A METHOD OF DETERMINING THE TRAVEL TIMES BETWEEN SPACED FIRST AND SECOND POINTS IN A MEDIUM, OF MULTIPLE SIGNALS EACH ORIGINATING SIMULTANEOUSLY AT SAID FIRST POINT AND DERIVED FROM A FIRST SINGLE SOURCE SIGNAL AND EACH HAVING A DIFFERENT TRAVEL TIME BETWEEN SAID FIRST AND SAID SECOND POINTS, SAID SOURCE SIGNAL HAVING A LINEARLY INCREASING FREQUENCY WITH TIME OVER ITS PERIOD OF DURATION, COMPRISING: (A) A ORIGINATING SAID SOURCE SIGNAL IN SAID MEDIUM AT SAID FIRST POINT, (B) DETERMINING THE FREQUENCY VARIATION OF THE ATTENUATION BY SAID MEDIUM OF SIGNALS ORIGINATED THEREIN AND AMPLITUDE MODULATING SAID SOURCE SIGNAL TO HAVE INCREASED AMPLITUDE AT FREQUENCIES SUBJECT TO INCREASED ATTENUATION BY SAID MEDIUM, (C) RECEIVING SAID MULTIPLE SIGNALS AT SAID SECOND POINT, (D) AMPLIFYING SAID RECEIVED MULTIPLE SIGNALS, (E) PROVIDING A SECOND SIGNAL ANITIATED SIMULTANEOUSLY WITH SAID SOURCE SIGNAL, THE FREQUENCY AS A FUNCTION OF TIME OF WHICH IS IDENTICAL TO SAID SOURCE SIGNAL AND THE PERIOD OF DURATION OF WHICH IS AT LEAST AS LONG AS THAT OF SAID SOURCE SIGNAL PLUS THE LONGEST TRAVEL TIME OF SAID MULTIPLE SIGNALS, (F) HETERODYNING SAID AMPLIFIED SIGNALS WITH SAID SECOND SIGNAL TO PROVIDE A COMPLEX SIGNAL COMPRISED OF AN UPPER SIDEBAND AND A LOWER SIDEBAND, THE LOWER SIDEBAND OF WHICH IS COMPRISED TO A DISTINCT AND SUBSTANTIALLY CONSTANT FREQUENCY COMPONENT FOR EACH OF SAID RECEIVED SIGNALS, (G) FILTERING SAID COMPLEX SIGNAL TO REMOVE SAID UPPER SIDEBAND AND LEAVE IMPACT SAID LOWER SIDEBAND, (H) PREEMPHASIZING SAID FILTERED SIGNAL TO PROVIDE LOW DYNAMIC AMPLITUDE RANGE OF SAID COMPONENTS, (I) AMPLIFYING AND PREEMPHASIZED SIGNAL, AND (J) TRANSFORMING SAID PREEMPHASIED LOWER SIDEBAND TO PROVIDE A FREQUENCY SPECTRUM THEREOF INCLUDING AN AMPLITUDE SPECTRUM AND A PHASE SPECTRUM, (K) WHEREBY RESPONSE MAXIMA OF SAID AMPLITUDE SPECTRUM ARE INDICATIVE OF THE RESPECTIVE TRAVEL TIMES OF SAID MULTIPLE SIGNALS AND THE VALUES IN SAID PHASE SPECTRUM CORRESPONDING TO SAID MAXIMA INDICATE SIGNAL FORMING CHARACTERISTICS OF THE STRUCTURE GIVING RISE TO SAID MULTIPLE SIGNALS IN SAID MEDIUM.

Claim 2

A METHOD OF DETERMINING THE TRAVEL TIMES BETWEEN SPACED FIRST AND SECOND POINTS IN A MEDIUM, OF MULTIPLE SIGNALS EACH ORIGINATING SIMULTANEOUSLY AT SAID FIRST POINT AND DERIVED FROM A FIRST SINGLE SOURCE SIGNAL AND EACH HAVING A DIFFERENT TRAVEL TIME BETWEEN SAID FIRST AND SAID SECOND POINTS, SAID SOURCE SIGNAL HAVING A LINEARLY INCREASING FREQUENCY WITH TIME OVER ITS PERIOD OF DURATION, COMPRISING: (A) A ORIGINATING SAID SOURCE SIGNAL IN SAID MEDIUM AT SAID FIRST POINT, (B) DETERMINING THE FREQUENCY VARIATION OF THE ATTENUATION BY SAID MEDIUM OF SIGNALS ORIGINATED THEREIN AND AMPLITUDE MODULATING SAID SOURCE SIGNAL TO HAVE INCREASED AMPLITUDE AT FREQUENCIES SUBJECT TO INCREASED ATTENUATION BY SAID MEDIUM, (C) RECEIVING SAID MULTIPLE SIGNALS AT SAID SECOND POINT, (D) AMPLIFYING SAID RECEIVED MULTIPLE SIGNALS, (E) PROVIDING A SECOND SIGNAL ANITIATED SIMULTANEOUSLY WITH SAID SOURCE SIGNAL, THE FREQUENCY AS A FUNCTION OF TIME OF WHICH IS IDENTICAL TO SAID SOURCE SIGNAL AND THE PERIOD OF DURATION OF WHICH IS AT LEAST AS LONG AS THAT OF SAID SOURCE SIGNAL PLUS THE LONGEST TRAVEL TIME OF SAID MULTIPLE SIGNALS, (F) HETERODYNING SAID AMPLIFIED SIGNALS WITH SAID SECOND SIGNAL TO PROVIDE A COMPLEX SIGNAL COMPRISED OF AN UPPER SIDEBAND AND A LOWER SIDEBAND, THE LOWER SIDEBAND OF WHICH IS COMPRISED TO A DISTINCT AND SUBSTANTIALLY CONSTANT FREQUENCY COMPONENT FOR EACH OF SAID RECEIVED SIGNALS, (G) FILTERING SAID COMPLEX SIGNAL TO REMOVE SAID UPPER SIDEBAND AND LEAVE IMPACT SAID LOWER SIDEBAND, (H) PREEMPHASIZING SAID FILTERED SIGNAL TO PROVIDE LOW DYNAMIC AMPLITUDE RANGE OF SAID COMPONENTS, (I) AMPLIFYING AND PREEMPHASIZED SIGNAL, AND (J) TRANSFORMING SAID PREEMPHASIED LOWER SIDEBAND TO PROVIDE A FREQUENCY SPECTRUM THEREOF INCLUDING AN AMPLITUDE SPECTRUM AND A PHASE SPECTRUM, (K) WHEREBY RESPONSE MAXIMA OF SAID AMPLITUDE SPECTRUM ARE INDICATIVE OF THE RESPECTIVE TRAVEL TIMES OF SAID MULTIPLE SIGNALS AND THE VALUES IN SAID PHASE SPECTRUM CORRESPONDING TO SAID MAXIMA INDICATE SIGNAL FORMING CHARACTERISTICS OF THE STRUCTURE GIVING RISE TO SAID MULTIPLE SIGNALS IN SAID MEDIUM.