Geometric effect on a laboratory-scale wavefield

In the laboratory, the waves transmit through a rock sample is contaminated by reflected and converted waves. Though direct waves of the transmitted waves have been utilized to estimate the internal structure of a rock sample, later part of the waveforms did not utilized because their origin were unclear. Understanding the reflection and conversion effect in a rock sample would help to retrieve more information from whole waveform obtained from a laboratory experiment. It would also help to connect laboratory works with the studies in natural fields. For this purpose, we investigate the origin of wave packets in elastic waves propagate through a rock sample based on a 3D finite difference method simulation.


Velocity waveforms (200-400 kHz) of the same height as the source, observed by (red) the simulation and (black) the laboratory experiment.



Snapshot images of the wavefield obtained from the simulation. Red and green colors indicate the absolute value of the divergence and the curl of the 3D velocity motion, which represent the P and S waves, respectively. The black arrow indicates location of the source. The elapsed times from the force input are 7, 14, and 28 micro-sec with (a) cross-section view perpendicular to the cylindrical axis, and (b) vertical section view parallel to the cylindrical axis.

See Yoshimitsu et al. (2016) for a detailed description.
Geometric effect on a laboratory-scale wavefield inferred from a three-dimensional numerical simulation