In some of the volcanic sites of the world such as Kilauea (Hawaii, USA), Asama (Japan), Ruapehu (New Zealand) etc., extensive measurements of seismic activity, tilt, strain, gravity and magnetic fields, electrical resistivity, radioactivity, emissions of various gases etc. were made to understand the process of volcanic eruptions and their prediction (Fujinawa et. al., 1992). Long term measurements of some of the above parameters specially at Kilauea and Asama have isolated the precursory changes for prediction of volcanic eruptions. Volcanic seismicity and ground tilt are the two significant parameters associated with volcanic eruptions. Remnant magnetic measurements indicate cooling history of lava. This multitude of physical measurements has been useful in determining the 3-dimensional geometry of volcanic pipes and vents at Kilauea.