DATA PROCESSING

As described in Appendix 3, two channels from the streamer were directly written onto the navigation (NAVLOG) 3480 cartridge tapes during our leg, a near-trace (ch. 150) and a far-trace (ch. 10). After the cruise we plotted constant offset sections for all lines using the near-trace, ch. 150, located 412.5 meters behind the center of the air gun array. Processing of these data included: (1) bandpass filter from 4-8-48-60 Hz, (2) automatic gain control (AGC), using a 500-msec window, (3) a water-bottom mute (to eliminate water column noise), and (4) display.

DESCRIPTION OF THE DATA

The constant offset sections indicate the multichannel seismic-reflection data are of high quality (Figures 7-9). The sections image a number of important deformation structures in the San Pedro, Catalina, and San Nicolas Basins. Folding of the sediments south of Long Beach in San Pedro basin is well-displayed on Line 1. Line 2 imaged a relict fault south of San Clemente ridge. Line 2 also reveals that Catalina Basin is underlain by a buried basement high that trends northwest and appears to bound an active fault. Block tilting of the Santa Catalina Ridge and Pilgrim Banks is clearly shown in these profiles.

Prominent multiples were generated over the hard basement outcrops such as Santa Catalina Ridge. Several orders of multiples, which were not suppressed by any of the processing used here, are evident.

No reflections beneath the sedimentary basins are observed in the constant offset sections, so they have been plotted to a depth of 6 seconds only. No lower crustal reflections were observed in these unstacked data.

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