Alignment silkworms as seismic animal anomalous behavior (SAAB) and electromagnetic model of a fault: a theory and laboratory experiment

Abstract

Alignment of silkworms and fish, observed as seismic anomalous animal behavior (SAAB) prior to the Kobe earthquake, were duplicated in a laboratory by applying a pulsed electric field assuming SAAB as electrophysiological responses to the stimuli of seismic electric signals (SES). The animals became aligned perpendicularly to the field direction since their skeletal muscle had a higher resistivity perpendicular to the field direction than parallel to it. An electromagnetic model of a fault is proposed in which dipolar charges, ±q are generated due to the change of seismic stress, σ(t). From a mathematical model, dq/dt=−α(dσ/dt) − q/ɛρ, where α is the charge generation constant like a piezoelectric coefficient, ɛ, the dielectric constant and ρ, the resistivity of bedrock granite. A fault having a length 2a and a displacement or rock rupture time τ, during which the stress is changed, gives pulsed dipolar charge surface densities, +q(t, x) and −q(t, x+2a), or an apparent electric dipole moment of P(t)=2aQ(t)=2aAq(t)=aM 0[eρ/(τ-eρ)](e-1/τ-e-1/σρ) using the earthquake moment M 0. The fault displacement, D, its initial velocity, D′ and the stress drop, Δσ give τ=D/D′=(Δσ/σ 0)(α/β). The field fintensity, F, and seismic current density at a fault zone, J were calculated as F=q/ɛ and J=F/ρ′ using ρ′ of water as to give J=0.1-1 A/m2 sufficient to cause SAAB experimentally. The near-field ultra low frequency (ULF) waves generated by P(t) give SES reciprocally proportional to the distance R.