62 L. D. LEET AND W. M. EWING 
V. Quincy REsULTS 
Specimen records from Quincy are reproduced in Fig. 2. The traces 
marked “7”, “V”, and “L” are the transverse, vertical, and longitudinal 
components respectively. Each record is identified by figures indicating the 
distance, shot position, recording position, and weight assigned it in the 
least square solution. For example, the first record in Fig. 2 is for a distance 
of 1050 feet. The figures 58—64—4 indicate that the shot was fired at position 
58 (see map, Fig. 1), recorded at position 64, and accorded a weight of 4 in 
the least square solution. Weights were assigned on the basis of amplitude 
of trace and general photographic quality, which determined the accuracy 
with which the time could be read. 
The interval between the instant of the explosion and the “0” timing line, 
the travel-time of the longitudinal wave on the vertical component, and the 
travel-time of the transverse wave on the transverse component are shown 
on each record. 
The time-distance graph for Quincy is shown in Fig. 3. The fact that it is 
a straight line through the origin indicates that the waves did not penetrate 
deeply. It is probable that the penetration was not more than twenty meters, 
and certain that it did not exceed 200 meters.* The lines drawn through the 
points were determined by least square solutions. Their reciprocal slopes 
give: 
Vi_=16,260+70 ft./sec. or 4.96+0.02 km/sec. 
Vr= 8,150+90 ft./sec. or 2.48+0.03 km/sec. 
where V, and Vr are the velocities of longitudinal and transverse Waves 
respectively. 
The density of specimens taken from the shooting location was 2.65 
+0.02 grams/cm.® 
The elastic constants of the granite can be obtained by substituting these 
values in the following equations. 

_ (X+ 2 ae 
me ( ; ) (f) 
Vr = (u/p)¥* (2) 
k=dX+ 2/3u (3) 
B = 1/k (4) 
_ B(3d + 2p) 
E= moe a (5) 
x 
7" 20H ~ 
where k is the bulk modulus, 8 the cubical compressibility, u the rigidity, E 
Young’s modulus, ¢ Poisson’s ratio, and p the density. 
* This point is being investigated further. 
206 
