EW9103 Seismic Acquisition Parameters - South East Pacific Rise ********************************************************** Number of Channels 160 Group Spacing 25 meters Source to Near Channel meters 358 Antenna to Source (Ewing) 95 meters Antenna to Source (Washington) 42 meters Near Channel Number 160 Cable Depth Unknown meters Acquisition System Name DSS240 Source Pressure 2000 psi Source Type Bolt 1500C Source Depth Unknown meters Acquisition Sample Interval 4000 microseconds Shot Control Time Compass No Active Tail Buoy No Recording Delay No Acquisition System Digital 2 or more ships Yes Lines 1081-1090, 1111,1114.1126,1137 Source Number 10 Source Volume 4193 cu. in. Shot Interval (10 sec interval for ~ 25 meters) Record Length 8.8 secs Line 1149, 1152 Source Number 10 Source Volume 4193 cu. in. Shot Interval (10 sec interval for ~ 25 meters) Record Length 8.7 secs Line 1091, 1106-1110, 1112-1113, 1115-1125. 1136,1139-1144 Source Number 20 Source Volume 8385 cu. in. Shot Interval (20 sec interval for ~ 50 meters) Record Length 18.75 secs Lines 1145-1148, 1150, 1152 Source Number 20 Source Volume 8385 cu. in. Shot Interval (20 sec interval for ~ 50 meters) Record Length 18 secs Lines 1092-1105 (ESPs , 1127-1135 ESP lines In general for the ESP lines the WASHINGTON (TW) shots were on the minute and the EWING shots (for a reflection profile) at 40 secs after the minute. For EWING shots the 'THISSHOTFLAG'was set to 1. The WASHINGTON shots on the minute were flagged as 2 and the second 20 sec recordings of the WASHINGTON shots were flagged as 3. In some cases we found that the shot pattern was different for a period of time and so changed the shot flags appropriately. The fields in the ts.n files for the ESP lines are as follows; Time, shot Lat, Lon, Line, Depth (N/A), FFID, Ship-to-Ship range (meters x 10), shot flag, TW shot (not used), Ewing heading (deg x 100), TW heading (deg x 100), Bearing TW to Ewing (deg x 100), Recording delay (msecs) for that record. NOTE: The SEG-Y files show a recording delay of zero for all records. The delay for all flag 1 records is in fact zero. For the ESP records the recording delay (or timing correction) is a result of the difference between the time of the TW shot and the start of recording on the Ewing. The TW navigation files for the ESPs are included in the nav bundle (ESPxx.TW.nav). Source Number (Ewing Shots) 20 Source Volume (Ewing Shots) 8385 cu. in. Shot Interval (60 sec interval for ~ 150 meters) Record Length 18.75 secs Source Number (Washington Shots) 6 Source Volume (Washington Shots) 2850 cu. in. Shot Interval 60 sec interval Record Length 2 X 18.75 sec Line 1138 (WAP line) For this Wide Aperture line Ewing and Washington alternated shots every 20 secs so Each ship was shooting every 40 secs. The Ewing was the Lead ship and the shot flag was set to 1, The Washington followed the Ewing at about 7.5 km and its shot flag was 2. The The ts.n file for the WAP line contains the ship-to-ship range but no headings or bearing. The recording delay for both Ewing and TW shots was zero. Source Number (Ewing Shots) 6 Source Volume (Ewing Shots) 2620 cu. in. Shot Interval (40 sec interval for ~ 100 meters) Record Length 18.75 secs Source Number (Washington Shots) 6 Source Volume (Washington Shots) 2850 cu. in. Shot Interval 40 sec interval Record Length 18.75 sec Line numbers corresponding to the cruise report line names: 1081 SEPR-1 1117 SEPR-37 1082 SEPR-2 1118 SEPR-38 1083 SEPR-3 1119 SEPR-39 1084 SEPR-4 1120 SEPR-40 1085 SEPR-5 1121 SEPR-41 1086 SEPR-6 1122 SEPR-42 1087 SEPR-7 1123 SEPR-43 1088 SEPR-8 1124 SEPR-44 1089 SEPR-9 1125 SEPR-45 1090 SEPR-10 1126 SEPR-46 1091 SEPR-11 1127 SEPR-47, ESP-15 1092 SEPR-12, ESP-1 1128 SEPR-48, ESP-16 1093 SEPR 13, ESP-2 1129 SEPR-49, ESP-17 1094 SEPR-14, ESP-3 1130 SEPR-50, ESP-18 1095 SEPR-15, ESP-5 1131 SEPR-51, ESP-20 1096 SEPR-16, ESP-6 1132 SEPR-52, ESP-19 1097 SEPR-17, ESP-4 1133 SEPR-53. ESP-21 1098 SEPR-18, ESP-7 1134 SEPR-54. ESP-22 1099 SEPR-19, ESP-8 1135 SEPR-55, ESP-23 1100 SEPR-20, ESP-9 1136 SEPR-56 1101 SEPR-21, ESP-10 1137 SEPR-57 1102 SEPR-22, ESP-11 1138 SEPR-58. WAP-1 1103 SEPR-23, ESP-12 1139 SEPR-59 1104 SEPR-24, ESP-13 1140 SEPR-60 1105 SEPR-25, ESP-14 1141 SEPR_61 1106 SEPR-26 1142 SEPR-62 1107 SEPR-27 1143 SEPR-63 1108 SEPR-28 1144 SEPR-64 1109 SEPR-29 1145 SEPR 65 1110 SEPR-30 1146 SEPR 66 1111 SEPR-31 1147 SEPR 67 1112 SEPR-32 1148 SEPR 68 1113 SEPR-33 1149 SEPR-69 1114 SEPR-34 1150 SEPR-70 1115 SEPR-35 1151 SEPR-71 1116 SEPR_36 1152 SEPR-72 ********************************************************** ********************************************************** **********************************************************