Process of forming time-variant filters for filtering seismic data

Claim 1

A method of forming a set of time-variant filters from an input set of filters having predetermined start times, for operating on a time series of seismic data, said method being carried out in an automatic computing system, comprising the steps of: determining the center frequency and envelope frequency of adjacent input filters of said input set, determining a number of filters to be interpolated between adjacent input filters, determining the envelope frequencies of the interpolated filters between adjacent input filters, and determining the length of the input filters and interpolated filters as inversely proportional to their envelope frequencies.

Claim 2

A method of forming a set of time-variant filters from an input set of filters having predetermined start times, for operating on a time series of seismic data, said method being carried out in an automatic computing system, comprising the steps of: determining the center frequency and envelope frequency of adjacent input filters of said input set, determining a number of filters to be interpolated between adjacent input filters, determining the envelope frequencies of the interpolated filters between adjacent input filters, and determining the length of the input filters and interpolated filters as inversely proportional to their envelope frequencies.

Claim 3

A method of forming a set of time-variant filters from an input set of filters having predetermined start times, for operating on a time series of seismic data, said method being carried out in an automatic computing system, comprising the steps of: determining the center frequency and envelope frequency of adjacent input filters of said input set, determining the center frequency difference between adjacent input filters, determining a number of filters to be interpolated between adjacent input filters as a function of the difference in center frequencies between adjacent input filters, determining the start times and the envelope frequencies of the interpolated filters, and determining the length of the input filters and interpolated filters as inversely proportional to their envelope frequencies.

Claim 4

A method of forming a set of time-variant filters from an input set of filters having predetermined start times, for operating on a time series of seismic data, said method being carried out in an automatic computing system, comprising the steps of: determining the center frequency and envelope frequency of adjacent input filters of said input set, determining the center frequency difference between adjacent input filters, determining a number of filters to be interpolated between adjacent input filters as a function of the difference in center frequencies between adjacent input filters, determining the start times and the envelope frequencies of the interpolated filters, and determining the length of the input filters and interpolated filters as inversely proportional to their envelope frequencies.

Claim 8

A method of forming a set of time-variant filters from an input set of filters having predetermined start times, for operating on a time series of seismic data, said method being carried out in an automatic computing system, comprising the steps of: determining the center frequency NFZ and envelope frequency FC for the Ith and Ith+1 input filters of said input set, determining a number of filters N to be interpolated between the Ith and Ith+1 inPuts in the following manner: N NFZ(I) -NFZ(I+1)-1 where NFZ(I) is the center frequency of the Ith filter and NFZ (I+1) is the center frequency of the Ith+1 filter, linearly interpolating envelope frequency values FC, N times between FC(I) and FC(I+1), where FC(I) is the envelope frequency of the Ith filter and FC(I+1) is the envelope frequency of the Ith+1 filter, placing said number N of interpolated filters (T(I+1)-T(I))/(N+1) mils apart in time, between the Ith and Ith+1 inputs, where T(I) is the start time of the Ith input and T(I+1) is the start time of the Ith+1 input, determining the length of the input filters and interpolated filters as inversely proportional to their envelope frequencies FC, calculating the time responses of each of said filters to their respective lengths, and truncating the time responses with a truncator having the same length as said time responses and defined in the following manner: cos(( pi t)/T) . ( 1-(0.46t)/T) where T is the filter length in time and t is the time from the center of each filter.

Claim 9

A method of forming a set of time-variant filters from an input set of filters having predetermined start times, for operating on a time series of seismic data, said method being carried out in an automatic computing system, comprising the steps of: determining the center frequency NFZ and envelope frequency FC for the Ith and Ith+1 input filters of said input set, determining a number of filters N to be interpolated between the Ith and Ith+1 inPuts in the following manner: N NFZ(I) -NFZ(I+1)-1 where NFZ(I) is the center frequency of the Ith filter and NFZ (I+1) is the center frequency of the Ith+1 filter, linearly interpolating envelope frequency values FC, N times between FC(I) and FC(I+1), where FC(I) is the envelope frequency of the Ith filter and FC(I+1) is the envelope frequency of the Ith+1 filter, placing said number N of interpolated filters (T(I+1)-T(I))/(N+1) mils apart in time, between the Ith and Ith+1 inputs, where T(I) is the start time of the Ith input and T(I+1) is the start time of the Ith+1 input, determining the length of the input filters and interpolated filters as inversely proportional to their envelope frequencies FC, calculating the time responses of each of said filters to their respective lengths, and truncating the time responses with a truncator having the same length as said time responses and defined in the following manner: cos(( pi t)/T) . ( 1-(0.46t)/T) where T is the filter length in time and t is the time from the center of each filter.

Claim 12

A method of forming a set of time-variant filters from an input set of filters having predetermined start times, for operating on a time series of seismic data, said method being carried out in an automatic computing system, comprising the steps of: determining the center frequency and envelope frequency of adjacent input filters of said input set, determining the center frequency difference between adjacent input filters, filling in intermediate filters between adjacent input filters, determining the number of intermediate filters to be filled in between adjacent input filters as a function of the difference in center frequencies between adjacent input filters, determining the start times and the envelope frequencies of the intermediate filters, and determining the length of the input filters and intermediate filters in accordance with the relationship, K/FC, where K is a constant, and FC is the envelope frequency of the corresponding filters.

Claim 13

A method of forming a set of time-variant filters from an input set of filters having predetermined start times, for operating on a time series of seismic data, said method being carried out in an automatic computing system, comprising the steps of: determining the center frequency and envelope frequency of adjacent input filters of said input set, determining the center frequency difference between adjacent input filters, filling in intermediate filters between adjacent input filters, determining the number of intermediate filters to be filled in between adjacent input filters as a function of the difference in center frequencies between adjacent input filters, determining the start times and the envelope frequencies of the intermediate filters, and determining the length of the input filters and intermediate filters in accordance with the relationship, K/FC, where K is a constant, and FC is the envelope frequency of the corresponding filters.