Spatial Distribution of Volcanic Ash Soil Layers by Cokriging Interpolation Method in Mashiki Town, Kumamoto

Abstract

In Mashiki town, Kumamoto, Japan, the earthquakes, of magnitude 6.5 and 7.3, struck on April 14 and 16, 2016. The earthquakes inflicted severe damage to residential areas because of liquefaction, sand boiling, and retaining wall collapse. Many residential land construct on volcanic ash soil ground. The soil is extremely sensitive and have a very low N-value. For future countermeasures to protect residences, it is important to clarify the volcanic ash soil layer distributions. The study revealed a relation to each distribution investigated for distribution characteristics of surface ground in Mashiki town and investigated Cokriging applied to distribution characteristic. The main conclusions are the following. (1) Show that correlation of the ground surface and the elevation values of volcanic ash soil layer is high. (2) The borehole logs of Kuroboku, Akaboku in Mashiki town, and Haido show few results. However, objective spatial distribution estimation is possible when applying Cokriging.