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Section 3.0 Data Analysis <br />3.1 Preparation of Seismic Data Files for Analysis <br />3.1. l Measuring the Source lime time Break) <br />The goal of directly recording the actual shot time for each source (time <br />break) was not accomplished as originally planned. However, analysis of <br />the seismic records has shown that the injection and production steel <br />pipes combined provided a very reliable waveguide. This waveguide <br />carried seismic energy from each shot in the injection hole with nearly a <br />constant velocity of 16,700 ffls, both up and down both pipes (figure Ab). <br />This velocity was higher than the velocity of seismic waves in the <br />surrounding ground. The velocity measurement was confirmed by seismic <br />records acquired from sledge hammer strikes at the ground surface near <br />the surveyed well and from hydrophones in the production hole at depths <br />ranging from 1,537 to 1,717 feet below the surface. See Appendix D for <br />defiails. <br />The stable velocity of seismic signals traveling along the pipes was used to <br />calculate the source time for each shot location. Each record was then <br />shiffed back so the source time was at the origin of that record. Thus, all <br />records were made compatible with respect to the timing of their sources. <br />3.1.2 Deffning Velocity Model <br />The seismic records were dominated by waves traveling along the steel <br />pipes (velocity 16,700 ff/s) and the tube waves in water (velocity 4750 <br />ff/s), as shown in figures A6 and A7. No seismic velocity numbers <br />measured in the ground were available for the site. Therefore, the <br />average velocity values for the mine zone were derived from Young's <br />modulus = 1,402,000 psi, and Poisson's ratio = 0.41, which were provided <br />by the Agapito and Associates. The resulting velocity numbers of 10,500 <br />ff/s for P-waves and 4,100 ff/s for S-waves were used to generate two <br />average velocity models within the orthogonal block selected for seismic <br />data processing. The square base of the block was 400 by 400 feet, and <br />the vertical dimension was set in the depth range from 2,190 to 1,240 feet. <br />The block was centered with respect to Well 28-21. <br />3.2 Data Processing <br />Seismic data for each set of sources and receivers were processed <br />separately, once for S-wave reflections using an S-wave velocity model, <br />and once for P-wave reflections using a P-wave velocity model. The <br />