Why do you need to study the structure of the earth and how to do it?

The structure of the Earth must be studied to prevent natural disasters (volcanic eruptions, earthquakes, tsunamis, etc.), to discover minerals and other mineral resources (oil, gas, coal, gold, etc.).
Methods for studying the structure of the Earth:
1) direct study (well drilling, mine methods)
2) geochemical methods (laws of distribution of chemical elements)
3) remote sensing method (aerial photographs, space photographs)
4) geophysical methods (assessment of seismic vibrations, study of the distribution of gravity, study of the effect of magnetic and electric and thermal fields)