First report of long term measurements of the MGGL laboratory in the Mátra mountain range

Abstract

Matra Gravitational and Geophysical Laboratory (MGGL) has been established near Gyöngyösoroszi, Hungary in 2015, in the cavern system of an unused ore mine. The Laboratory is located at 88 m below the surface, with the aim to measure and analyse the advantages of the underground installation of third generation gravitational wave detectors. Specialized instruments have been installed to measure seismic, infrasound, electromagnetic noise, and the variation of the cosmic muon flux. In the preliminary (RUN-0) test period, March-August 2016, data collection has been accomplished. In this paper we describe the research potential of the MGGL, list the installed equipments and summarize the experimental results of RUN-0. Here we report RUN-0 data, that prepares systematic and synchronized data collection of the next run period.

Wave Propagation in Rocks – Investigating the Effect of Rheology

“…A consequence of the second law of thermodynamics is that dynamic values must be larger than static ones. This prediction has been confirmed recently for many various types of rock [12][13][14]. For the Hooke model with the force equilibrium assumption (i.e., neglecting the material time derivative of velocity in the Cauchy momentum equation), analytical calculations are also available for simple yet relevant -symmetric enough -geometries and boundary conditions.…”

“…(5), proves to be (11) where σ̂ denotes the rheology-originated addition in stress with respect to the previous, elastic, stress σ̅ , i.e., σ = σ̅ + σ̂. The Onsagerian way to ensure the non-negativeness of this entropy production is to consider linear equations (12)…”

Investigation of the relationship between dynamic and static deformation moduli of rocks

“…It is worth mentioning that more detailed material models beyond ideal elasticity give an exact relationship between the elastic and static moduli. Notably, the observed relations can be explained in a universal thermodynamic framework where internal variables (Barnaföldi et al 2017;Ván et al 2019) These constitutive models are based only on universal principles of thermodynamics, are independent of particular mechanisms and are successful in characterizing rheological phenomena in rocks including and beyond simple creep and relaxation. This is in accordance with the difficulty for finding a very detailed quantitative mesoscopic mechanism for the dynamics of dissipative phenomena in rocks as well.…”

Four Spacetime Dimensional Simulation of Rheological Waves in Solids and the Merits of Thermodynamics

“…Accordingly, the wave propagation speeds follow. This, on one side, illustrates how the PTZ model can interpret that the dynamic elasticity coefficients of rocks are larger than their static counterpart [ 1 , 2 , 3 , 4 ]. On the other side, the nontrivial—frequency dependent, therefore, dispersive—wave propagation indicates that the numerical solution of PTZ wave propagation problems should contain the minimal possible amount of dispersion error, in order to give account of the dispersive property of the continuum model itself.…”

“…This viscoelastic/rheological reaction may not be simply explained by a viscosity-related additional stress (the Kelvin–Voigt model of rheology), but the time derivative of stress may also be needed in the description, with the simplest such model being the so-called standard or Poynting–Thomson–Zener (PTZ) one [see its details below]. Namely, the PTZ model is the simplest model that enables describing both creep (declining increase of strain during constant stress) and relaxation (declining decrease of stress during constant strain), as well as the simplest one, via which it is possible to interpret that the dynamic elasticity coefficients of rocks are different from, and larger than, their static counterpart [ 1 , 2 , 3 , 4 ]. Related to the latter aspect, high-frequency waves have a larger propagation speed in PTZ media than low-frequency ones [ 4 ], which makes this model relevant for, e.g., seismic phenomena and acoustic rock mechanical measurement methods.…”