14 



EXPLORATION GEOPHYSICS 



the continental United States, seismograph operations accounted for some 

 $90,000,000. Crews working in this country increased in number from four 

 in 1929 to about 450 in 1947, as shown in Figure 3. It is interesting to note 

 that about three-fourths of the seismograph work during the latter year 

 was done in Texas, Louisiana, and Oklahoma, which states are credited 

 with five-sixths of all the new oil pool reserves discovered in the United 

 States in 1947, (Figure 4). Ofif-shore seismograph work accounted for one- 

 sixth of the total for coastal Texas, and one-third for coastal Louisiana. f 

 A great majority of all fields discovered during the past 15 years are 

 wholly or in part due to seismic work. 



Fig. 4. Geographical distribution of seismograph activity in the United States, 

 1947. (E. A. Eckhardt, ibid.) 



Today, successful seismic prospecting, is being carried to depths of 

 15,000 feet as routine procedure, and some surveys are being conducted to 

 depths exceeding 25,000 feet. 



CONTEMPORARY WORKERS AND PRESENT 

 DEVELOPMENTS 



Time and achievement must evaluate the improved methods being 

 advocated and utilized today. This chapter, covering only the early history 

 of development, is followed in later chapters by a record of current devel- 



t E. A. Eckhardt, Geophysics, XIII, 4, Oct. 1948. 



