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The seismoelectrical method (which is different form the electroseismic physical principle) is based on the generation of electromagnetic fields in soils and rocks by seismic waves. This technique is still under development and in the future it may have applications like detecting and characterizing fluids in the underground by their electrical properties, among others, usually related to fluids (porosity, transmisivity, physical properties) ==Operation== When a seismic wave encounters an interface, it creates a charge separation at the interface forming an electric dipole. This dipole radiates an electromagnetic wave that can be detected by antennae on the ground surface. As the seismic (P or compression) waves stress earth materials, four geophysical phenomenon occur: # The resistivity of the earth materials is modulated by the seismic wave; # Electrokinetic effects analogous to streaming potentials are created by the seismic wave; # Piezoelectric effects are created by the seismic wave; and # High-frequency, audio- and high-frequency radio frequency impulsive responses are generated in sulfide minerals (sometimes referred to as RPE). The dominant application of the electroseismic method is to measure the electrokinetic effect or streaming potential (item 2, above). Electrokinetic effects are initiated by sound waves (typically P-waves) passing through a porous rock inducing relative motion of the rock matrix and fluid. Motion of the ionic fluid through the capillaries in the rock occurs with cations (or less commonly, anions) preferentially adhering to the capillary walls, so that applied pressure and resulting fluid flow relative to the rock matrix produces an electric dipole. In a non-homogeneous formation, the seismic wave generates an oscillating flow of fluid and a corresponding oscillating electrical and EM field. The resulting EM wave can be detected by electrode pairs placed on the ground surface. However, P-waves moving through a solid that contains some moisture also generates an electric phenomena called coseismic waves.〔Pride, S., Haartsen, M.W., 1996. Electroseismic wave properties. J. Acoust. Soc. Am. 100, 1301–1315〕 The coseismic waves travel with P-waves and are not sensitive to electrical propierties of the subsurface. The dipole antenna cannot distinguish electrokinetic signal from coseismic signal so it records them both, and coseismic waves must be removed while processing field data to be able to actually interpret electrokinetic effect 〔Zyserman, F., Jouniaux, L., Warden, S., and Garambois, S. (2015). "Borehole seismoelectric logging using a shear-wave source: Possible application to CO2 disposal?." International Journal of Greenhouse Gas Control, 10.1016/j.ijggc.2014.12.009, 89-102.〕 At the moment, there is not a field routine operation method, but in scientific studies an array of several dipole antennas is placed along a straight line to record seismoelectric waves, and an array of geophones placed between dipole antennas to record seismic wave arrivals. Geophones are necessary to be able to suppress coseismic waves from the seismoelectric signal, so that electrokinetic effect can be separated and studied.〔Dupuis, J.C., Butler, K.E., Kepic, A.W., 2007. Seismoelectric imaging of the vadose zone of a sand aquifer. Geophysics 72, A81–A85.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Seismoelectrical method」の詳細全文を読む スポンサード リンク
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