APPLICATION OF REFLECTION SEISMOGRAPH 39 
tion, the absence of the reflection in this instance can hardly be called 
conclusive evidence of the presence of the fault. 
Due to the absence of the Pecan Gap reflection, record F.P.58 is of 
special interest. As the amplitude of the Austin reflection on this 
record is larger than on any of the other records, the Pecan Gap re- 
flection under normal conditions should be very large indeed. There 
can be little doubt that this must be the result of very abnormal sub- 
surface conditions. It is seen from the cross section and contour maps 
that the normal reflection point for the Pecan Gap lies in the fault 
plane of the Pecan Gap. This fault, it should be noted, has been lo- 
cated by several other determinations. In many cases it is impossible 
to get any reflections very close to a fault, due probably to minor 
fracturing in the proximity of the fault plane. The presence of the 
Austin reflection in this case would indicate that the fault must be a 
fairly clean break without much minor fracturing. 
CONCLUSION 
It is thought that the reflection seismograph may economically 
justify its use in many cases by permitting the location of a test well 
in the most advantageous position structurally and thus save the cost 
of many unnecessary wells. 
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