are developed in terms of the sequential order of various events, time needed 

 to complete each event, the optimum season for field work in the exploration 

 area, and availability of necessary personnel and equipment. 



128. In past exploration programs, geophysical and coring operations 

 were usually carried out in sequence with the geophysical survey, followed by 

 coring operations either later in the same season or during the following 

 year. Although this sequence of events provides more time to analyze the geo- 

 physical data before selecting core locations, there are advantages in carry- 

 ing out both operations at approximately the same time. In this procedure, 

 the coring operation lags a few days behind the geophysical survey so that 

 enough data are collected on each area to permit effective core site selec- 

 tion. This permits preliminary field analysis of cores and geophysical data 

 for the purpose of making advantageous or needed changes in the survey and 

 coring coverage as work proceeds. When concurrent operations are used, one 

 member of the field party should be skilled in interpretation of geophysical 

 and core data, and have the primary duty of processing the records and cores 

 on a day-to-day basis as they become available, and recommending alterations 

 or additions to the basic preplanned coverage. 



129. Basic time elements considered in preparing a schedule are mobili- 

 zation and demobilization, field operations, and contingency time due to 

 weather or equipment malfunction. Mobilization and demobilization of needed 

 equipment can usually be performed in two or three days; however, mobilization 

 may be extended if the vessels used must travel some distance to reach the 

 mobilization site. 



130. Operational schedules are basically derived from a consideration 

 of (a) the number of miles to be traversed to obtain the desired geophysical 

 coverage and the boat speed when running survey tracklines; and (b) the 

 approximate distance between core sites, speed of the coring vessel, and 

 on-site time needed for mooring and taking the core. Time must also be 

 allowed for daily travel to and from the part of the exploration areas cur- 

 rently being covered. Distance values for calculating operational time can be 

 obtained from the trackline and core site plots. Boat speeds for running 

 seismic reflection lines with surface- towed source and receiver combinations 

 must be kept at about 4 knots or less to obtain good quality records. How- 

 ever, seismic reflection equipment in which the acoustic source and the 

 receivers are towed beneath the surface are said to more than double the 



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