Mathematical simulation and experimental studies of the shugo mud volcano

Nonhysteretic Nonlinear Losses at Intergrain Contacts in Rocks: Application to Tidal Modulation Phenomena in Seismics

“…Due to the increased compliance (and thus locally increased strain and strain rate), both increased deviations from the linear Hooke's law and increased losses are localized at those defects. This means that the effective compliance parameter 9 characterizing the crack sensitivity may reach values 10 -6 (or even less) for corrugated cracks with much larger average aspect ratio Taking this into account one can readily obtain estimates of the complementary tide-induced variations in the wave velocities decrements, which well agree with observations [7,8] of amplitude and phase (or travel time) variations for radiation of artificial stable seismic sources (see a more detailed discussion in [11]). It was shown in [10] using an instructive 1D model of microinhomogeneous material containing identical quadratically nonlinear viscoelasic defects with compliance parameter 1 9 that in the presence of quasistatic strain 0 H , the macroscopic effective modulus eff E and the decrement T for a weaker oscillation at frequency Z can be written as can close the cracks completely.…”

“…In continuous observations [5,6], high-resolution coherent signal stacking excluded eventual factors with nearly 24-hour and 12-hour periods and singled out noise intensity variations with periodicity of tidal waves O 1 (diurnal principal lunar, period T=25.82h), M 2 (semi-diurnal principal lunar, T=12.42h), and N 2 (major elliptic lunar wave, T=12.66h). Indeed, the increased elastic nonlinearity of rocks can only account for tidal variations in seismic wave velocities with magnitudes 10 -5 ..10 -3 [1,2,7,8], but is not sufficient to explain 2-3 orders of magnitude stronger tidal modulation of the noise intensity. 1).…”

Giant strain-sensitivity of local acoustic dissipation near inner wavy contacts in dry and fluid-saturated cracks

“…Consequently, by analogy with the thermoelastic loss, quite a small portion of cracks with the waists determined by the factor ( h/h) 3 (L/ l) 1 (which can easily be 10 −2 − 10 −4 ) can ensure in the low-frequency range around ω a contribution to the viscous dissipation comparable with and even exceeding the contribution of the majority of other cracks without the waists. Therefore, the same geometrical feature, wavy asperities creating either strip-like contacts or nearly closed waists results in appearance of giant strain sensitivity of thermoelastic loss in dry cracks and viscous loss in liquid-saturated cracks, which suggest an explanation to observations [5,6].…”

“…There are observations indicating that quite pronounced perturbations of elastic-wave dissipation (from a few percents to about ten percents in magnitude) can be caused by even much weaker average strains, in particular, tidal strains in the Earth crust with typical amplitude 10 −8 (see, e.g., [5,6]). The existence of cracks with aspect ratios 10 −8 (and even with ratios on the order of 10 −6 ) seems to be very unrealistic.…”