A method of forecasting naturally-occurring phenomena, such as seismic activity, includes taking localized measurements of the Earth's gravitational force change using MEM inertial motion units. Trends in the measurements are interpreted and related to a phenomenon of interest, a likelihood of occurrence is predicted based on the relationship, and the likelihood is reported to interested parties, preferably automatically to emergency bulletin sources. Measurements can be taken from above the Earth's atmosphere. The trends can be interpreted by determining blind source separation information directed to the region underneath the Earth's mantle crust to determine composition and/or movement.