Long term measurements from the Mátra Gravitational and Geophysical Laboratory

Abstract

of the long term data taking, related to one of the proposed next generation ground-based gravitational detector's location is presented here. Results of seismic and infrasound noise, electromagnetic attenuation and cosmic muon radiation measurements are reported in the underground Matra Gravitational and Geophysical Laboratory near Gyöngyösoroszi, Hungary. The collected seismic data of more than two years is evaluated from the point of view of the Einstein Telescope, a proposed third generation underground gravitational wave observatory. Applying our results for the site selection will significantly improve the signal to nose ratio of the multi-messenger astrophysics era, especially at the low frequency regime.

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.…”

“…Namely, when measuring Young's modulus (or, in 3D, the two elasticity coefficients) of a solid, the speed of uniaxial loading, or the frequency of sound in a wave-based measurement, may influence the outcome and a sufficient interpretation may come in terms of a PTZ model. Indeed, in rock mechanics, dynamic elastic moduli are known to be larger than their static counterparts [13][14][15], in accord with the thermodynamics-originated inequality in Eq. (32b) (or its 3D version).…”

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

“…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.…”