Geoscience Reference
In-Depth Information
1.0
normalised
amplitude
0.5
T3
time: ms
T
2
T0
0.0
0
0.5
1
1.
5
2
T1
−
0.5
Fig. 6.5. Characteristic points on received signal for estimation ofarrival time
(Arroyoet al.,2006)
received signal
input signal
arrival of shear wave
arrival of compression wave
Fig. 6.6. Experimental observation of motion at bender element receiver for wave
propagation through sandincubical cell (Sadek, 2006)
The resulting velocities are shown in Figure 6.7 (normalised with the actual shear wave
velocity) for different distances along the axis of the sample. (Velocity estimates made
using a cross-correlation technique
V
cc
, which seeks the optimum match between the
shapes of the input and received waveforms, and a frequency domain cross-spectrum
technique
V
cs
which analyses the dependence of the phase of the received signal on fre-
quencyforacontinuousharmonicinputsignalarealsoincluded.)Thefurtherthereceiver
from the source the closer all the velocity estimates approach the compression wave
velocity
V
p
/
V
s
=
.
1
5.
