Chapter1: Low-resistivity structures in the seismically active lithosphere zones and observations of EM signals of seismic origination -- Chapter2: Theory of magnetic location of the epicentre area of a possible earthquake -- Chapter3: Tsunami precursors: mathematical model and applications -- Chapter4: Space Weather -- Chapter5: Structure of a Brain -- Chapter6: Space weather influence on bioelectric activity of a human brain -- Chapter7: Elements of cardiac anatomy and physiology -- Chapter8: The measured results of magnetic storms’ influence on heart -- Chapter9: String-diffusion systems of equations -- Chapter10: Numerical stability of the discretized initial-boundary value problems of the string-diffusion systems of equations (SDSE) -- Chapter11: A model description of running waves (rw) on water -- Chapter12: Conclusion.This book develops the theory of electromagnetic (EM) precursors to seaquakes (i.e. underwater earthquakes) and tsunamis, including the sequential stages of the transformation of a weak seismic mechanical excitation of the sea bottom into EM signals in the atmosphere. It further examines the relationship between geophysics and biophysics, using appropriate mathematical support. Also described is a new model for the magnetic location of the epicenter of a possible land earthquake, as well as a block-scheme of a multidisciplinary multilevel seaquake monitoring complex. Finally, there is a detailed investigation into measured changes of brain bioelectric activity and heart functioning under the influence of moderate geomagnetic storms.