Vaclav Vavrycuk

• RNDr., DrSc.
• The Czech Academy of Sciences

In this study, we assess the state of the stress field in eastern Türkiye and discuss whether the stress field in the region has changed over time. To assess the governing stress field, we applied stress tensor inversion techniques using focal mechanisms from earthquake catalogs. The focal mechanisms were grouped into subregions based on spatial an...

We investigate the influence of fault roughness on physical damage prior to large laboratory rock failure and the evolution of the local stress field surrounding the fault zone as macroscopic shear slip approaches. To achieve this, we analyze acoustic emission (AE) data from displacement‐driven rock friction experiments conducted on porous sandston...

This study explores the relationship between the Schwarzschild metric and alternative metrics used to describe the gravitational field of a black hole in free space. While it is well-established that an infinite number of coordinate systems can be employed in general relativity, we demonstrate that the black hole solution is unique when expressed i...

We present arguments supported by several examples showing that the relativistic time dilation observed in frames affected by gravitational and non-gravitational forces are different being thus inconsistent with the Equivalence Principle. This inconsistency questions validity of the standard interpretations of the Equivalence Principle or of the tw...

In this paper, we re-evaluate the estimates of dust mass in galaxies and demonstrate that current dust models are incomplete and based on a priori assumptions. These models suffer from a circularity problem and account for only a small portion of dust, specifically submicron-sized grains. They overlook larger dust particles and other macroscopic bo...

The common opinion that the Lorentz transformation distorts the Minkowski spacetime arises from a mathematically incorrect neglect of its non-diagonal terms. When the non-diagonal Lorentz transformation is properly treated, the time dilation and the space distortion disappear. Consequently, the Lorentz metric produced by the Lorentz transformation...

Tonga is a convergent plate boundary between the Pacific and Australian plates and is the fastest and the most seismically active deep subduction system in the world. We focused on southern Tonga (south of latitude 22°S) and the mantle transition zone (depths of 410–670 km), where seismic activity forms two subparallel bands of events in the east a...

Tonga is a part of Tonga-Kermadec, the 2,550 km long subduction system in SW Pacific. It represents a convergent plate boundary and the outcome of the Pacific plate submerging underneath the Australian plate. The Tonga slab subducts steeply into the mantle and is the fastest converging and the most seismically active deep subduction system in the w...

In this paper, we study the tectonic stress around the South Caspian Basin (SCB), which includes the Kopeh Dagh, Alborz, Talesh, eastern Greater Caucasus mountain belts, the Apsheron sill, and the Balkhan-Ashkabad fault zone. We apply the stress inversion to focal mechanisms of 410 mainshocks that have occurred over the last 69 years. These mechani...

In this study, we determine the stress release from the 2003 Bam earthquake (Mw 6.6) by applying the stress inversion technique to focal mechanisms of 199 aftershocks. There is no evidence of significant surface faulting that can be used to study the faulting pattern of the Bam fault zone. Therefore, we applied two independent methods for identifyi...

We study the relation between the Schwarzschild solution and other coordinate-dependent solutions of the gravitational field produced by a point mass in the free space. We demonstrate that, although an infinite number of different coordinate systems can be used for solving this problem in general relativity, the physical solution is unique and unam...

As an alternative to the moment tensor (MT) model for earthquake sources, the shear-tensile-compressive (STC) model offers a kinematic description of the source mechanism and leads to a more robust inversion problem. However, the premise of the source inversion based on STC is to ensure the accuracy of parameter $\kappa $ defined as the ratio of th...

We present the elastic anisotropy of two rock samples from two underground research laboratories (URL) that are focused mainly on the investigation of functionality of deep repositories: (1) BUK sample – migmatized paragneiss, typical for the test site of the URL Bukov, Czech Republic; (2) GRM sample - Central Aare granite, a predominant host rock...

Modified Newtonian equations for gravitational orbits in the expanding Universe indicate that local gravitationally bounded systems like galaxies and planetary systems are unaffected by the expansion of the Universe. This result is derived for the space expansion described by the standard FLRW metric. In this paper, the modified Newtonian equations...

A methodology for obtaining the stiffness tensor of an elastic material in its most general form (with 21 independent parameters) using ultrasonic measurements is presented. The methodology is used to define the anisotropic properties of two spherical rock samples: a migmatized gneiss from Bukov (Czech Republic) and a granite from Grimsel (Switzerl...

In modelling the cosmic expansion, the conformal cosmology (CC) has several advantages over the standard cosmological model based on the FLRW metric: it is Lorentz invariant, it leaves the Maxwell’s equations unchanged from their form in the Minkowski spacetime, it properly predicts the cosmological redshift and cosmic time dilation, and it fits th...

We determine the stress field of the Zagros fold-and-thrust belt (ZFTB) in the collisional zone between the Arabian and Iranian plates. Using 898 mainshock focal mechanisms, which occurred along the belt between 1956 and 2021, we calculate stress at 32 locations. The results reveal that the crustal stress in the Zagros belt is heterogeneous with va...

We present an approach of identifying anisotropy axes and the type of symmetry from ultrasonic measurements of 21 elastic constants of the complete stiffness tensor characterizing anisotropic materials. The approach is applied to examine anisotropic elasticity of two crystalline rock samples from two underground research laboratories: (1) the migma...

Identification of the fault plane from two nodal planes of the focal mechanism is, in general, ambiguous. This problem is commonly solved using other constraints provided by tectonic, geological or seismic studies. In this paper, we evaluate the probability of identifying the fault plane using knowledge of stress field. We employ two alternative me...

We study the sensor layouts of surface monitoring systems for injection areas in hydraulic fracturing experiments, which maximize the accuracy of retrieved moment tensors. The moment tensors (MTs) are determined using noisy synthetic P-wave amplitudes of microearthquakes with varying mechanisms. An optimum sensor layout is searched by minimizing a...

Modified Newtonian equations for gravitational orbits in the expanding universe indicate that local gravitationally bounded systems like galaxies and planetary systems are unaffected by the expansion of the Universe. This result is derived under the assumption of the space expansion described by the standard FLRW metric. In this paper, an alternati...

Twenty-four astronomers and physicists from ten countries have signed a petition protesting the censorship of papers that are critical of the Big Bang Hypothesis by the open pre-print website arXiv.

Introduction Recent observations indicate that the Universe is not transparent but partially opaque due to absorption of light by ambient cosmic dust. This implies that the current cosmological model valid for the transparent universe must be modified for the opaque universe. Objectives The paper studies a scenario of the evolution of the Universe...

We present a unique catalogue of full moment tensors (MTs) of earthquakes with ML between 0.5 and 4.4 that occurred in West Bohemia, Czech Republic, in the period from 2008 to 2018 (Vavryčuk et al., 2022a, b). The MTs were calculated from vertical components of P-wave amplitudes. The MT inversion was based on principal component analysis applied to...

Recent observations indicate that the Universe is not transparent but partially opaque due to absorption of light by ambient cosmic dust. This implies that the Friedmann equations valid for the transparent universe must be modified for the opaque universe. This paper studies a scenario in which the opacity rises with redshift. In this case, the lig...

The paper shows that the commonly used Friedmann-Lemaitre-Robertson-Walker (FLRW) metric describing the expanding Universe must be modified to properly predict the cosmological redshift. It is proved that the change in the frequency of redshifted photons is always connected with time dilation, similarly as for the gravitational redshift. Therefore,...

The re-examination of light propagation in space described by the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric reveals surprisingly that this metric does not predict the cosmological redshift as so far incorrectly supposed. It is shown that the change in the frequency of light is always connected with time dilation, similarly as for the gravit...

The Tonga subduction zone in the south-west Pacific is the fastest convergent plate boundary in the world with the most active mantle seismicity. This zone shows unique tectonic features including Samoan volcanic lineament of plume-driven origin near the northern rim of the Tonga subducting slab. The proximity of the Samoa hotspot to the slab is en...

We present a unique catalogue of full moment tensors (MTs) of microearthquakes that occurred in West Bohemia, Czech Republic, in the period from 2008 to 2018. The catalogue is exceptional in several aspects: (1) it represents an extraordinary extensive dataset of more than 5.000 MTs, (2) it covers a long period of seismicity in the studied area, du...

The analysis of the 2017 earthquake swarm along the obliquely divergent Reykjanes Peninsula plate boundary revealed the most frequent focal mechanisms corresponding to main activated fault, which relates to transform faulting of the North Atlantic Rift in Iceland. Detailed double-difference locations, focal mechanisms and non-double-couple (non-DC)...

The efficiency of three inversions for accurate moment tensors: (1) the standard least-squares inversion, (2) the weighted least-squares inversion, and (3) the shear-tensile-compressive (STC) source inversion, is tested on acoustic emissions (AEs) produced during the Brazilian splitting test. A comparison of plots of the P/T axes of the focal mecha...

Fluids on faults facilitate triggering of earthquakes and affect seismic energy release. Their detection in the focal zone is, however, difficult. Here, we present mapping of stress changes and fluid flow based on determining seismic moment tensors (MTs), which describe focal mechanisms and shear/tensile/compressive fracturing modes of earthquake s...

The distance-duality relation (DDR) between the luminosity distance DL and the angular diameter distance DA is viewed as a powerful tool for testing for the opacity of the Universe, being independent of any cosmological model. It was applied by many authors, who mostly confirm its validity and report a negligible opacity of the Universe. Neverthele...

This paper presents a fast sweeping method (FSM) to calculate the first‐arrival traveltimes of the qP, qSV, and qSH waves in two‐dimensional (2D) transversely isotropic media, whose symmetry axis may have an arbitrary orientation (tilted transverse isotropy [TTI]). The method discretizes the anisotropic eikonal equation with finite difference appro...

The distance-duality relation (DDR) between the luminosity distance $D_L$ and the angular diameter distance $D_A$ is viewed as a powerful tool for testing for the opacity of the Universe, being independent of any cosmological model. It was applied by many authors, who mostly confirm its validity and report a negligible opacity of the Universe. Neve...

Surface arrays became an important tool for monitoring the induced seismicity in hydraulic fracturing experiments and for assessing the impact of fluid injection on the fracturing process of microearthquakes. The layout of sensors plays a key role in this task, because it controls the accuracy of event locations and retrieved seismic moment tensors...

The Friedmann equations valid for the transparent universe are modified for the universe with opacity caused by absorption of light by ambient cosmic dust in intergalactic space. The modified equations lead to a cosmological model, in which cosmic opacity produces radiation pressure that counterbalances gravitational forces. The proposed model pred...

We present a joint inversion for empirical Green’s functions (EGFs) and high‐resolution non‐double‐couple (non‐DC) moment tensors. First, the EGFs are constructed using known moment tensors of earthquakes occurring in a small focal zone. Second, the estimated EGFs are applied to refine the original moment tensors used for constructing the EGFs. Bec...

In this paper, I revoke a debate about an origin of Type Ia supernova (SN Ia) dimming. I argue that except for a commonly accepted accelerating expansion of the Universe, a cIn this paper, I revoke a debate about an origin of Type Ia supernova (SN Ia) dimming. I argue that except for a commonly accepted accelerating expansion of the Universe, a con...

In this paper, I revoke a debate about an origin of Type Ia supernova (SN Ia) dimming. I argue that except for a commonly accepted accelerating expansion of the Universe, a conceivable alternative for explaining this observation is universe opacity caused by light extinction by intergalactic dust, even though it is commonly assumed that this effect...

Plain Language Summary Moment tensor (MT) describes shear and tensile motions in the earthquake source. The components of MT are usually assumed to be independent of the frequency. However, this assumption may not satisfy the complex rupture process of induced microearthquakes. We use a novel approach to investigate 984 induced microearthquakes fro...

In this study we derive the stress tensor and its local variations throughout the Marmara region, Turkey. Based on a recently compiled 10-year earthquake catalogue, we directly invert first-motion polarity data and quantify confidence intervals for the principal stress orientations. We find a combined strike-slip and normal faulting stress field fo...

With the author(s)’ decision to opt for Open Choice the copyright of the article changed on.

Equations of cosmic dynamics for a model of the opaque Universe are derived and tested on supernovae (SNe) Ia observations. The model predicts a cyclic expansion/contraction evolution of the Universe within a limited range of scale factors. The maximum scale factor is controlled by the overcritical density of the Universe, the minimum scale factor...

Due to an unfortunate technical error this article has not been published as Open Access.

Observations of the 2008–2014 seismic activity in West Bohemia, Czech Republic, provide evidence of interaction of compressive fault steps that created local stress anomaly and triggered a seismic sequence with exceptional properties. The West Bohemia is a geothermal area, characterized by persistent fluid-driven seismicity in the form of earthquak...

Full moment tensors of 1,421 microearthquakes in The Geysers geothermal field were calculated using waveform data from a field-wide broadband network and the approach based on the principal component analysis. Spatial characteristics of faulting regime, stress tensor and the isotropic component (ISO) of moment tensors were investigated. The studied...

A cosmological model, in which the cosmic microwave background (CMB) is a thermal radiation of intergalactic dust instead of a relic radiation of the big bang, is revived and revisited. The model suggests that a virtually transparent local Universe becomes considerably opaque at redshifts z > 2-3. Such opacity is hardly to be detected in the Type I...

We study two earthquake swarms that occurred in the Ubaye Valley, French Alps within the past decade: the 2003–2004 earthquake swarm with the strongest shock of magnitude ML = 2.7, and the 2012–2015 earthquake swarm with the strongest shock of magnitude ML = 4.8. The 2003–2004 seismic activity clustered along a 9-km-long rupture zone at depth betwe...

Seismic moment tensors of earthquakes in anisotropic media have more complicated properties than in isotropic media. For example. planar shear faulting produces pure double-couple mechanism in isotropy, but generally non-double-couple mechanism in anisotropy. The effects of anisotropy on moment tensors are numerically modelled and exemplified on ac...

A cosmological model, in which the cosmic microwave background (CMB) is a thermal radiation of intergalactic dust instead of a relic radiation of the Big Bang, is revived and revisited. The model suggests that a virtually transparent local Universe becomes considerably opaque at redshifts $z > 2-3$. Such opacity is hardly to be detected in the Type...

The main drawback of ranking of researchers by the number of papers, citations or by the Hirsch index is ignoring the problem of distributing authorship among authors in multi-author publications. So far, the single-author or multi-author publications contribute to the publication record of a researcher equally. This full counting scheme is apparen...

We analyze waveforms of local earthquakes occurring before, between, and after the two consecutive 1999 Mw > 7 İzmit and Düzce earthquakes in NW Turkey. The waveforms were recorded at three seismic stations DOK, EKI, and GOK located around the Mudurnu segment of the North Anatolian Fault Zone. We focus on the interpretation of a distinct secondary...

The Eger Rift is an active element of the European Cenozoic Rift System associated with intense Cenozoic intraplate alkaline volcanism and system of sedimentary basins. The intracontinental Cheb Basin at its western part displays geodynamic activity with fluid emanations, persistent seismicity, Cenozoic volcanism, and neotectonic crustal movements...

We develop and test a new hybrid approach of the amplitude and waveform moment tensor inversions, which utilizes the principal component analysis of seismograms. The proposed inversion is less sensitive to noise in data, being thus more accurate and more robust than the amplitude inversion. It also suppresses other unmodeled phenomena, like a direc...

I examine a possible spectral distortion of the Cosmic Microwave Background (CMB) due to its absorption by galactic and intergalactic dust. I show that even subtle intergalactic opacity of 1 × 10⁻⁷ mag h Gpc⁻¹ at the CMB wavelengths in the local Universe causes non-negligible CMB absorption and decline of the CMB intensity because the opacity steep...

We present a detailed study on the pressure dependence of P-wave velocities and amplitudes on a spherical sample of antigorite serpentinite from Val Malenco, Northern Italy. Measurements were done at room temperature and hydrostatic pressures up to 400 MPa in a pressure vessel with oil as a pressure medium. The transducer/sample assembly allows sim...

The occurrence and specific properties of earthquake swarms in geothermal areas are usually attributed to a highly fractured rock and/or heterogeneous stress within the rock mass being triggered by magmatic or hydrothermal fluid intrusion. The increase of fluid pressure destabilizes fractures and causes their opening and subsequent shear-tensile ru...

Anisotropic attenuation affects seismic observations and complicates their interpretations. Its accurate determination is, however, difficult and needs extensive measurements of wawefields in many directions. So far, the travel time and amplitude decay of waves are usually measured along a sparse grid of propagation directions, and methods for inve...

The observed extragalactic background light (EBL) is affected by light attenuation due to absorption of light by galactic and intergalactic dust in the Universe. Even galactic opacity of 10-20 percent and minute universe intergalactic opacity of $0.01\,\mathrm{mag}\,h\,\mathrm{Gpc}^{-1}$ at the local Universe have a significant impact on the EBL be...

The observed extragalactic background light (EBL) is affected by light attenuation due to absorption of light by galactic and intergalactic dust in the Universe. Even galactic opacity of 10-20 percent and minute universe intergalactic opacity of $0.01\,\mathrm{mag}\,h\,\mathrm{Gpc}^{-1}$ at the local Universe have a significant impact on the EBL be...

Microseismic data acquired in a single observation well parallel to the axis of rotational symmetry of surrounding rocks - typically, in a vertical well drilled through a horizontally layered isotropic or vertically transversely isotropic formation - cannot be uniquely inverted for six independent components comprising the full seismic moment tenso...

We investigate the sensitivity of stress inversion from focal mechanisms to pore pressure changes. Synthetic tests reveal that pore pressure variations can cause apparent changes in the retrieved stress ratio R relating the magnitude of the intermediate principal stress with respect to the maximum and minimum principal stresses. Pore pressure and r...

Current theories assume that the low intensity of the stellar extragalactic background light (stellar EBL) is caused primarily by finite age of the Universe because the finite age limits the number of photons pumped into the space by galaxies and thus the sky is dark in the night. We oppose this opinion and show that two main factors are responsibl...

Current theories assume that the low intensity of the stellar extragalactic background light (stellar EBL) is caused primarily by finite age of the Universe because the finite age limits the number of photons pumped into the space by galaxies and thus the sky is dark in the night. We oppose this opinion and show that two main factors are responsibl...

Seismic moment tensors can provide information on the size and orientation of fractures producing acoustic emissions (AEs) and on the stress conditions in the sample. The moment tensor inversion of AEs is, however, a demanding procedure requiring carefully calibrated sensors and accurate knowledge of the velocity model. In field observations, the v...

The waveforms of microearthquakes are of high frequency and complicated. They contain many phases secondarily generated at crustal interfaces and at small-scale inhomogeneities. They are highly sensitive to focal mechanisms and thus very different for each station of local networks. However, with a large number of microearthquakes, the scattered wa...

We have developed and numerically tested a method for determining parameters of homogeneous viscoelastic anisotropy from measurements of wavefields generated by point sources. The method is based on complex algebra and consists of several steps. First, a complex energy velocity surface is constructed from the directionally dependent velocity and at...

The stress field and fracture processes in the Earth’s crust are closely related phenomena. Fracturing is controlled by shear stress on the fault, pore-fluid pressure, cohesion and fault friction. In addition, the orientation of the fault with respect to the principal stress directions governs susceptibility of the fault to be ruptured.An essential...

The moment tensor represents equivalent body forces of a seismic source. The forces described by the moment tensor are not the actual forces acting at the source because the moment tensor description assumes elastic behavior of the medium and ignores nonlinear rheology at the focal area. Nevertheless, the moment tensor proved to be a useful quantit...

The composite moment tensor is defined in analogy to the composite focal mechanism as the averaged representative seismic moment tensor characteristic for a focal area under study. In contrast to the composite focal mechanism, which provides information on shear faulting, the composite moment tensor can provide additional information on nonshear ru...

On February 12, 2013, North Korea conducted an underground nuclear test in the north-eastern mountainous part of the country. The explosion reached magnitude mb = 5.1 being recorded at most of seismic stations around the world and becoming one of the best ever recorded nuclear explosions in history. Similarly as other nuclear explosions buried in N...

The decomposition of moment tensors into isotropic (ISO), double-couple (DC) and compensated linear vector dipole (CLVD) components is a tool for classifying and physically interpreting seismic sources. Since an increasing quantity and quality of seismic data allow inverting for accurate moment tensors and interpreting details of the source process...

The increasing amount of seismic data and their quality allow resolving details of source processes of natural as well as induced earthquakes. Accurately determined moment tensors reveal that induced earthquakes frequently deviate from shear faulting and contain significant non-double-couple (non-DC) components (Julian et al. 1998). One of the mode...

The most common type of waves used for probing anisotropy of rocks in laboratory is the direct P wave. Information potential of the measured P-wave velocity, however, is limited. In rocks displaying weak triclinic anisotropy, the P-wave velocity depends just on 15 linear combinations of 21 elastic parameters, called the weak-anisotropy parameters....

In this study, we apply the double-difference tomography to investigate the detailed 3-D structure within and around the Nový Kostel Seismic Zone, an area in the Czech Republic known for frequent occurrences of earthquake swarms. We use data from the 2008 swarm since it has already been analysed in terms of earthquake focal mechanisms, principal fa...

Stress inversions from focal mechanisms require knowledge of which nodal plane is the fault. If such information is missing, and faults and auxiliary nodal planes are interchanged, the stress inversions can produce inaccurate results. It is shown that the linear inversion method developed by Michael (1984) is reasonably accurate when retrieving the...

We study potential non-double-couple (non-DC) components in aftershocks of the 1999 Izmit earthquake. The Izmit earthquake ruptured a ̃140-km-long segment of the North Anatolian Fault Zone in northwestern Turkey and was followed by the Mw = 7.1 Düzce earthquake that extended the rupture further to the east. Focal mechanisms of Izmit aftershocks cle...

We perform a detailed synthetic study on the resolution of non-double-couple (non-DC) components in the seismic moment tensors from short-period data observed at regional networks designed typically for monitoring aftershock sequences of large earthquakes. In addition, we test two different inversion approaches—a linear full moment tensor inversion...

In this study, we apply the double-difference tomography method to investigate the detailed 3-D structure within and around the Nový Kostel seismic zone, an area in the Czech Republic known for frequent occurrences of earthquake swarms. We use data from the extensively analyzed 2008 swarm, which has known focal mechanisms, principal faults, tectoni...

Acoustic axes are directions in anisotropic elastic media, in which phase velocities of two or three plane waves (P, S1 or S2 waves) coincide. Acoustic axes are important, because they can cause singularities in the field of polarization vectors and anomalies in the shape of the slowness surface. The maximum number of acoustic axes in triclinic ani...

We apply a method for retrieving accurate moment tensors in the acoustic emission (AE) experiments based on the joint inversion of a family of AE events for their moment tensors and for the sensor amplifications including coupling effects between sensors and a specimen. The accuracy and efficiency of the method is tested on Aes recorded during thre...

The relative locations of earthquake hypocentres determined with the master-event (ME) or the double-difference (DD) methods are more accurate and less dispersive compared to the absolute locations. In this paper, we conduct synthetic tests to assess the accuracy of the ME and DD location methods, to study the effects of the control parameters on t...

The moment tensors are unique and describe the body force equivalents of rupture processes in any medium including faulting at a material interface, defined as the contact of two media with non-zero velocity or density contrasts. From a practical point of view, however, the moment tensor inversion of sources near or at a material interface is more...