# US 2019/0170889 A1 · Method for determining notional seismic source signatures and their ghosts from near field measurements and its application to determining far field source signatures > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0170889 A1 - Document ID: US20190170889A1 - Status: Published application - Kind: A1 - Application number: 16/266,379 - Filed: 2019-02-04 - Published: 2019-06-06 - Earliest claimed: 2016-08-05 - Assignees: DownUnder GeoSolutions Pty Ltd. - Applicants: DownUnder GeoSolutions Pty Ltd - Inventors: Gary Hampson - Web page: https://patentgrep.com/patent/US20190170889A1 ## CPC - G01V 1/3835: {measuring position, e.g. by GPS or acoustically} - G01V 1/364: {Seismic filtering (G01V1/37 takes precedence)} - G01V 1/38: specially adapted for water-covered areas (G01V1/28 takes precedence) - G01V 1/3861: {control of source arrays, e.g. for far field control} - G01V 2210/1212: Shot - G01V 2210/1293: Sea - G01V 2210/1423: Sea - G01V 2210/56: De-ghosting; Reverberation compensation - G01V 2210/59: Other corrections - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) ## Abstract A method for estimating a far field seismic energy source signature includes using detected near field seismic signals corresponding to actuation of each one of a plurality of seismic energy sources in an array of seismic energy sources. The near field seismic signals are detected at two spaced apart locations in the near field of each seismic energy source, the at least two spaced apart locations being arranged such that a direction of propagation of the detected near field seismic signals is determinable from the detected near field signals. A notional source signature for each seismic energy source and a notional ghost for each seismic energy source using the detected near field seismic signals. A far field signature is determined for the plurality of seismic energy sources using the determined notional source signature and notional ghost signature from each seismic energy source. ## Claims ### Claim 1 A method for determining seismic sensor depths below a free-surface, comprising: accepting as input to a computer measurements of seismic signals made by a plurality of seismic sensors disposed at selected depths below the free-surface, the seismic signals resulting from actuation of a seismic energy source disposed at a selected depth with reference to the free-surface; defining a depth increment and a range of sensor depths for correlation of signals from each of the plurality of seismic sensors; in the computer, extrapolating the input seismic measurements to each depth increment in the range; and in the computer, determining a depth of each seismic sensor by correlating the seismic signal measurements with depth-extrapolated measurements of the seismic signal measurements. ### Claim 2 (depends on 1) The method of claim 1 wherein the range of sensor depths is defined using an initial estimate of sensor depths. ### Claim 3 (depends on 2) The method of claim 2 wherein the initial estimate is derived from measurements of a depth of each sensor in a body of water. ### Claim 4 (depends on 3) The method of claim 3 wherein the measurements of depth of each sensor comprises measurement of water pressure at each sensor. ### Claim 5 (depends on 3) The method of claim 3 further comprising quality checking the measured depths using the determined depths. ### Claim 6 (depends on 1) The method of claim 1 wherein the depth increment is selected to be consistent with a digital sample interval of the input seismic signal measurements. ### Claim 7 (depends on 1) The method of claim 1 wherein the extrapolating comprises delaying a measured up-going wavefield so that the measured up-going wavefield aligns with a ghost component of a wavefield of the seismic signal measurements. ### Claim 8 (depends on 7) The method of claim 7 wherein the delaying is performed with respect to seismic sensor depth. ### Claim 9 (depends on 1) The method of claim 1 wherein the correlating comprises a wave equation equivalent of autocorrelation. ### Claim 10 (depends on 1) The method of claim 1 wherein measurements of depths of each of the plurality of seismic sensors is made using measurements of water pressure. ### Claim 11 (depends on 1) The method of claim 1 further comprising, in the computer, determining at least one source depth using the depth-extrapolated measurements of the seismic signal measurements. ### Claim 12 (depends on 1) The method of claim 1 further comprising, in the computer, determining a water depth of each seismic sensor at a horizontal position thereof by correlating primary reflections and water layer multiple reflections. ### Claim 13 (depends on 1) The method of claim 1 further comprising, in the computer, using the determined depths to deghost the measurements of seismic signals. ### Claim 14 (depends on 1) The method of claim 1 wherein the depth extrapolated seismic measurements and the input seismic measurements comprise unseparated upgoing and downgoing components. ### Claim 15 A method for seismic surveying, comprising: towing a seismic energy source and a plurality of spaced apart seismic sensors in a body of water; actuating the seismic energy source and detecting seismic signals at each of the plurality of seismic sensors; communicating the detected seismic signals as input to a computer; defining a depth increment and a range of sensor depths for correlation of the detected seismic signals from each of the plurality of seismic sensors; in the computer, extrapolating the detected seismic signals to each depth increment in the range; and in the computer, determining a depth of each of the plurality of seismic sensors by correlating the detected seismic signals with depth-extrapolated detected seismic signals. ### Claim 16 (depends on 15) The method of claim 15 wherein the depth increment is selected to be consistent with a digital sample interval of the detected seismic signals. ### Claim 17 (depends on 15) The method of claim 15 wherein the extrapolating comprises delaying a measured up-going wavefield so that the measured up-going wavefield aligns with a ghost component of a wavefield of the detected seismic signals. ### Claim 18 (depends on 17) The method of claim 17 wherein the delaying is performed with respect to seismic sensor depth. ### Claim 19 (depends on 15) The method of claim 15 wherein the correlating comprises a wave equation equivalent of autocorrelation. ### Claim 20 (depends on 15) The method of claim 15 wherein the range of sensor depths is defined using an initial estimate of sensor depths. ### Claim 21 (depends on 20) The method of claim 20 wherein the initial estimate is derived from measurements of a depth of each sensor in the body of water. ### Claim 22 (depends on 21) The method of claim 21 wherein the measurements of depth of each sensor comprises measurement of water pressure at each sensor. ### Claim 23 (depends on 21) The method of claim 21 further comprising using the determined depths to quality check the measured depths. ### Claim 24 (depends on 15) The method of claim 15 further comprising, in the computer, determining at least one source depth using the depth-extrapolated measurements of the seismic signal measurements. ### Claim 25 (depends on 15) The method of claim 15 further comprising, in the computer, determining a water depth of each seismic sensor at a horizontal position thereof by correlating primary reflections and water layer multiple reflections. ### Claim 26 (depends on 15) The method of claim 15 further comprising, in the computer, using the determined depths to deghost the detected seismic signals. ### Claim 27 (depends on 15) The method of claim 15 wherein the depth extrapolated seismic measurements and the input seismic measurements comprise unseparated upgoing and downgoing components.