In general, the "Method for screw weight sounding" is used for geotechnical investigation when building a single-family wooden house, in which a steel rod is penetrated into the ground and the ground condition is measured continuously.
It used to be called "Swedish sounding test". This method is relatively inexpensive.
Even if the building itself is built to withstand earthquakes, the weak ground may cause the house to lean. If the results of the ground investigation show that the ground is soft, it may be necessary to improve the ground at a cost of around 1 million yen.