Summary
It is known that P wave propagated in porous media below water table in shallow subsurface can be very low in velocity and exhibits a strong attenuation because of a buffer effect by contained gas bubbles. It has been pointed out, on the other hand, that the ground vibration caused by traffic was less severe in summer season. We postulate that a seasonal change in the degree of gas-saturation of ground water depending on the temperature fluctuation is responsible for the change in attenuation of causative waves. Based on preliminary laboratory tests of temperature dependence of P-wave velocity and attenuation in submerged sand, we have roughly estimated the seasonal change of P wave propagation in shallow subsurface under the average Japanese condition.
