ORIGINAL PAPER Flow instabilities in two-phase or supercritical crust fluids and its possible relevance to seismo- electromagnetic disturbances Nadezda V. Yagova 1 • Viktor V. Yagov 2 • Ashwini K. Sinha 3 • Masashi Hayakawa 4 • Evgeny N. Fedorov 1 • Geeta Vichare 3 Received: 12 April 2016 / Accepted: 1 February 2018 Ó Springer Science+Business Media B.V., part of Springer Nature 2018 Abstract Flow pulsations in two-phase and single-phase near-critical fluids are considered as a possible source of ultra-low-frequency seismo-electromagnetic variations. The con- ditions for generation and suppression of density wave instability in the crust are analyzed and the surface electromagnetic effect due to streaming potential generation is estimated. The upper limit of amplitude of magnetic field variations due to density wave instability is about 0.1 nT for single-phase supercritical and 1 nT for two-phase flow oscillations in the frequency range 10 4 10 2 Hz for the temperature gradients and spatial scales possible during strike slip events. The signal is characterized by a decaying amplitude with typical relaxation time of about several quasi-periods. The possibility of generation of very low- frequency flow pulsations in two-phase fluids via individual bubble evolution and inter- action with external acoustic waves is discussed. Keywords Seismo-electromagnetics  Two-phase fluid  Electrokinetic effect 1 Introduction A role of rock pore water in processes of rock fracturing and the associated generation of electromagnetic signals has been recognized many years ago (Lachenbruch 1980; Roeloffs 1988). Transient variations of pore pressure and heat flux in rocks related with seismic slip are considered as an important element of the seismic process (Lee and Delaney 1987; Lee & Nadezda V. Yagova nyagova@yandex.ru 1 Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences, Moscow, Russia 2 National Research University MPEI (Moscow Power-Engineering Institute), Moscow, Russia 3 Indian Institute of Geomagnetism, Navi Mumbai, India 4 Hayakawa Institute of Seismo Electromagnetics, Co. Ltd., UEC Alliance Center 521, 1-1-1 Kojima-cho, Chofu Tokyo, Japan 123 Nat Hazards https://doi.org/10.1007/s11069-018-3203-5