We examined the relationship between the Absolute Ages and the Compression Strength of the sandstones and the mudstones in the Miyazaki Group. As a result, we prove the compression strength increase rate of the sandstones is larger than that of the mudstones.
 And we can achieve the economically design of engineering works but the according uneconomical design of civil structure by the relationship between the Absolute Ages and the compression strength in the Miyazaki Group.