Abstract
It is 15, 000 years or more since Yokoo Landslide came into action. Thick debris was piled up in stratification.
Groundwater divides in to unconfined and artesian ones. Both of them gather at the toe of a moving mass. We cannot find each head of aquifers but a combined piezometric level in the borehole which combines shallow and deep aquifers. The former supplies the latter with groundwater. Its quantity grows according to rainfall.
