Research Activities- NAGAHAMA Hiroyuki -

Research interests
(1) Studies on the rheology of rocks and lithosphere. Rheology denotes the study of deformation and flow of matter. Our efforts are directed towards a better understanding of the mechanical behavior of rocks and to the formulation of more precise mathematical models for their dominant mechanical properties or electromagnetic radiations, radon emanation, mainly friction and wear during slip-sliding, frictional discharge plasma, viscoelastic behavior and hydrolytic weakening of rocks and lithosphere. Subsequent efforts are focused on analyses of the rheology of lithosphere, which is of first-class significance in earth science.
(2) Studies on random fluctuations and pattern formations in earth science. Randomness is an essential ingredient of most natural phenomena. Therefore we are studying mathematically random fluctuations and pattern formations of most geological phenomena: earthquakes, geomagnetic reversals, fracture and fold patterns and so on. These studies are the source of a renewed interest in the field of earth science.
(3) Studies on fractal geometries, differential geometries and chaos on dislocations, faults, earthquakes and geomagnetic reversals. Especially we are studying differential geometries or gauge theory on seismic ray path, electromagnetic phenomena associated with earthquakes and micromorphic continuum of earthquakes.

Recent products
Electric dipoles perpendicular to a stick-slip plane; Frictional discharge plasma from natural semiconductor/insulator junctions: Origin of seismo-electromagnetic radiation; Implication for fractal seismo-electromagnetic radiation; Surface resetting of thermoluminescence in milled quartz grains; Cumulative Benioff strain-release, modified Omori's law and transient behaviour of rocks; Irreversible thermodynamic and viscoelastic model for power-law relaxation and attenuation of rocks; Micromorhic continuum with defects and Taylor-Bishop-Hill theory for polycrystals: Anisotropic propagation of seismic waves and Golebiewska gauge; Seismic Finsler geometry and Kawaguchi space; From non-local to asymmetrical deformation field; Radon emanation before a large earthquake.
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