Dear Muthu,

The art of interpreting something subsurface without invasion is a tricky business. It applies lot of science and mathematical modelling techniques. The theory of scanning and X-ray as applied in your medical science is applied to the earth as well, however with greater complexities as the unknown factor lies underneath. All these studies and techniques are undertaken in a specialised field of Earth Sciences known as Geophysics. There is lot of literature available for your reference on various techniques applied for different explorations be it minerals, oil or water.

There are a number of tools which support non-destructive methods for investigation:-

In Exploration Geophysics some of the techniques are Ground Penetrating Radar (GPR), Electrical Resistivity Methods, Seismic Methods etc. (Check Attached link.) If you simply search for the keywords, 'non destructive exploration techniques' Geophysics, you will find thousands of results in any search engine like Google.

Satellite, Airbone and UAV based Remote Sensing methods also actively support non destructive exploration techniques and have come a long way. As far as your geological questions are concerned, Remote Sensing Geologists look for certain kinds of rocks, minerals, oil seepages, anomalous surface temperatures etc. both with in Images acquired with sophisticated cameras (Multispectral, Hyperspectral, Panchromatic) as well as by employing Insitu observations which are indicative of (signs of) the presense of sub surface oil, natural gas, geothermal sources, precious minerals and so forth. Usually with Remote Sensing techniques, Geo-physical techniques are combined to provide a better perspective of the object under investigation.

http://www.gbgoz.com.au/pdfs/services/GBGA%20Resource%20Delineation.pdf

I would look to MLA or advanced SEM techniques.

 @James - Thank you for the possibilities. Will explore the link. 

@Michael Hitch - What is MLA?

Thank you very much for your inputs