Changes

[[file:marine-seismic-data-acquisition_fig2.png|300px|thumb|{{figure number|2}}Air gun array strength.]]

[[file:marine-seismic-data-acquisition_fig2.png|300px|thumb|{{figure number|2}}Air gun array strength.]]

The output of an air gun array is typically illustrated by a normalized pressure time sequence called a ''signature''. The signature of a 1000-in.³ air gun subarray is shown in [[:file:marine-seismic-data-acquisition_fig1.png|Figure 1]]. One measure of the strength of the source is the ''peak-to-peak pressure'', which is often quoted in pressure units of bars at [[length::1 m]] (bar meters). Another measure of the performance of the array is the ''peak-to-bubble ratio'', which is the peak-to-peak magnitude of the initial pulses divided by the magnitude of the residual bubble oscillations. These simplistic measures of performance can be used to compare different sources provided the signatures have been recorded using the same techniques, especially the same field filters<ref name=pt07r24>Johnston, R. C., D. H. Reed, and J. F. Desler, 1988, SEG standards for specifying marine seismic energy sources: Geophysics, v. 53, p. 566–575., 10., 1190/1., 1442492</ref>.

The output of an air gun array is typically illustrated by a normalized pressure time sequence called a ''signature''. The signature of a 1000-in.³ air gun subarray is shown in [[:file:marine-seismic-data-acquisition_fig1.png|Figure 1]]. One measure of the strength of the source is the ''peak-to-peak pressure'', which is often quoted in pressure units of bars at [[length::1 m]] (bar meters). Another measure of the performance of the array is the ''peak-to-bubble ratio'', which is the peak-to-peak magnitude of the initial pulses divided by the magnitude of the residual bubble oscillations. These simplistic measures of performance can be used to compare different sources provided the signatures have been recorded using the same techniques, especially the same field filters<ref name=pt07r24>Johnston, R. C., D. H. Reed, and J. F. Desler, 1988, SEG standards for specifying marine seismic energy sources: Geophysics, v. 53, p. 566–575</ref>.

The strength of marine seismic sources has increased at a steady pace over the past 20 years, as shown in [[:file:marine-seismic-data-acquisition_fig2.png|Figure 2]]. Stronger sources produce detectable signals from deeper reflectors. Very large air compressors are necessary to charge the air guns, which typically fire every 10 sec. In addition to increased strength, air gun arrays consisting of six, eight, or ten subarrays (''strings'') are deployed in various geometries to improve directivity and/or to reduce shot generated noise. The simple wide array is common and very effective<ref name=pt07r35>Lynn, W., and K. Larner, 1989, Effectiveness of wide marine seismic source arrays: Geophysical Prospecting, v. 37, p. 181–207., 10., 1111/gpr., 1989., 37., issue-2</ref>.

The strength of marine seismic sources has increased at a steady pace over the past 20 years, as shown in [[:file:marine-seismic-data-acquisition_fig2.png|Figure 2]]. Stronger sources produce detectable signals from deeper reflectors. Very large air compressors are necessary to charge the air guns, which typically fire every 10 sec. In addition to increased strength, air gun arrays consisting of six, eight, or ten subarrays (''strings'') are deployed in various geometries to improve directivity and/or to reduce shot generated noise. The simple wide array is common and very effective<ref name=pt07r35>Lynn, W., and K. Larner, 1989, Effectiveness of wide marine seismic source arrays: Geophysical Prospecting, v. 37, p. 181–207.</ref>.

==Receiver==

==Receiver==