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Static vertical pendulums or other deformometry apparatus were used for indirect measurement of stress in the upper crust. The first static vertical pendulums were installed in Prokop mine in Příbram and in cave No. 13C in Moravian karsts since 2007. One pendulum was installed in a productive potassium mine in Lubeník (Slovakia) in 2008. The two ye...
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... length of measuring a base between points A and B and their geometry in the chamber determines what reaction of massif on the external stress field will be. If the length of the measuring base will be longer than the results of deformation will be less sensitive to the geometry in the surrounding of points A and B. On a short-time scale, we can observe semidiurnal variations of tilt, caused by earth tides (see Figure 4). The amplitude of tilt varies in time and it is different on both directions (NS and EW) compared each other or compared with theoretical values of tilt according to the semielastic model of the Earth's lithosphere by Wahr-Dehant-Zschau (Skalský 1991). ...
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Static vertical pendulums apparatus were used for indirect measurement of stress in the upper crust. The first static vertical pendulums have been installed in Prokop mine in Příbram and in cave No. 13C in Moravian karsts since 2007. Another pendulum was installed in a productive potassium mine in Lubeník (Slovakia) in 2008. The two years experienc...
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... During the period, when at least one pendulum was in operation in Europe (1.9.2007 -31. 12.2017), the global seismic network registered 182 seismic events of magnitude 7 and greater, including 62 events of magnitude 7.5 and greater, as well as 10 seismic events of magnitude 8 and greater. A retrospective analysis demonstrates that tilt precursors preceded 7 events (70%) in the group of M8+, 39 events (62.9%) in the group of M7.5+, but only 49 events (26.9%) in the group of M7+ (Fig. 10). ...
... We analysed the observed nucleation periods of rock samples [2], of samples of sandstones from the Ostrava-Karviná Coal Basin (OKD) with various matrix grain size (Janaspers. comm.), of rock bursts at OKD (coal + sandstone), of rock bursts at Jelšava (potassium mine) [11], and in the observed earthquakes [23], [7], [12]. The results show that a detectable nucleation period is much shorter than according to theory for the strongest earthquakes and can be approximately described by relationship (1) (Fig. 13). ...
A network of vertical static pendulums (tiltmeters) has been in operation in Central Europe since July 2007. Hundred and eighty three seismic events of magnitude 7 and greater have occurred worldwide (EMSC) during the ten-year period. Several kinds of tilt anomalies were recognised within days up to months before the mainshocks. The most typical anomaly was a sudden tilting, parallel with the geologic structure, where the pendulum was installed. Based on the observations, we are proposing an asperity model, explaining the generation of so called “stress waves” before the mainshocks. Such stress waves of very low frequency (i.e. periods of days up to the first months) could be detected anywhere on the globe, especially on active geological structures, parallel with the fault, where a mainshock can happen. The observations suggest that we could estimate that part of the global fault system, which generates the detected stress wave, and which reaches the critical state. The estimation can be performed according to the amplitude of the stress wave, compared with stress waves detected on other structures of different orientations. According to the length of the stress wave (its period) and the tilt amplitude, it could be possible to estimate the magnitude of the mainshock.
... Both of these methods, however, do not enable us to estimate the stress tensor or the direction of its principal component. That is the reason why we used a completely new apparatus – the vertical static pendulum (Neumann 2007, Kalenda et al. 2009), which allows measuring the microdeformation of the massif in the horizontal plane and the tilt of the plumb line in the frequency range of periods longer than 10 seconds up to the infinity. ...
... The scientific goal of this study was to specify some likely new sources of secondary microseisms, which were revealed during the detailed analysis of our experimental measurements. According to our measurement of microseisms (Holub et al. 2008Holub et al. , 2009 ) and massif deformations (Kalenda and Neumann 2010; Kalenda et al. 2009), we deduced that there are at least three other mechanisms capable of microseism generation in addition to the widely accepted mechanism of generation by ocean waves. The first mechanism can be connected with atmospheric pressure variations; the second is associated with thermoelastic waves in rock mass (Hvoždara and Brimich 1988; Brimich 2006); and, third the relationship is associated with large earthquakes (Kalenda et al. 2011Kalenda et al. , 2013). ...
The basic scientific question of this study was: do other mechanisms exist for excitation of secondary microseisms aside from the widely accepted mechanism by non-linear interactions of respective ocean waves. Here we use continuous broad-band data from secondary microseisms recorded at the Ostrava-Krásné Pole, Czech Republic (OKC) seismic station to create a massive seismological database. Except for seismological data, various meteorological features and their mutual relations were analysed: temperature, the so called “shifted” temperature, air density, changes of atmospheric pressure, and synoptic situations. These analyses prove that maximum amplitudes of microseisms were observed during winter, while minimum amplitudes occured in summer months. The annual variations of microseisms amplitudes could not be explained by annual variations of storm activity above the North Atlantic. In addition, current analyses also aim at quantitative and quantitative evaluation of synoptic situations for triggering individual microseismic anomalies. Some of the meteorological features, namely the distribution of low pressures above northern Europe and high-pressure areas in Central Europe make it easy to explain most of the microseismic extremes. Here we pay special attention to the influence of large earthquakes, which usually induce slow deformation waves. We conclude that at least three mechanisms of microseism generation are possible: (1) the function of atmospheric pressure at sea level in the North Atlantic, (2) the effects of spreading of thermoelastic waves in the rock mass and (3) deformation waves induced by large earthquakes.
... Because the tectonic stress in the rock mass is mostly horizontal (Staš & Souček 2002), the common deforma tions will be in vertical directions (Fig. 1). we suggested a quite new apparatus for indirect stress measurement, based on the vertical static pendulum (Neumann 2007, Kalenda et al. 2009). A vertical static pendulum consists of a concrete mass, which is hung on the rod. ...
... The raw data are sent to the trans mitting PC, which is connected with a data server via GSM modem (). The vertical static pendulum is able to measure the displacement ds in the horizontal plane with a preci sion of hundreds of nanometers or the tilt of plumb line α with a precision of tens of nanoradians, depending on the length of the pendulum (Fig. 1) (Kalenda et al. 2009). Such measurement is advantageous as it excludes errors due to friction. ...
... 9 ture earthquakes, we suppose that one of the best meth ods for earthquake prediction is to measure the stress in rocks continuously using direct or indirect methods (Crampin & Gao 2009, Shi et al. 2009). we recognize that the anomalous tilt is visible be fore large earthquakes (Kalenda et al. 2009). The greatest changes in stress orientation and in stress state were observed before the biggest earthquakes on the Eurasian lithosphere plate. ...
Vertical static pendulums have been installed in mines or caves in Central Europe since 2007. Two-dimensional optical measurement of the tilt of a rock mass and continuous fully digital on-line evaluation of results makes possible the detection of a small tilt of the surroundings with a resolution of tens of nanoradians or the deformation of the surroundings in the horizontal plane with resolution of hundreds of nanometres. The paper describes the measurement device and the first results of the measurements in Magdalena Jama, which is part of the Postojna Cave System (Slovenia). The correlation of deformation between distant stations shows the existence of stress variations that are not only of local origin (high floods, local seismicity, and aseismic deformations). The stress field has a wider, and not only regional, character with effects that can be observed very far from the origin.
... The tilt and " noise " has been measured in Bohemia since February 2007 by a quite new apparatus – vertical static pendulum (Kalenda et al., 2009). The precision of tilt measurement is in the order of 10-100 nRad depending on the length of pendulum and local conditions. ...
... Blue – tilt in the X direction (perpendicular to the camera), red – tilt in the Y direction (parallel with the camera and perpendicular to the wall). A) diurnal variations of tilt due to thermal expansion of rocks mass and penetration of the thermoelastic wave into depth; B) typical creep registered at the depth of 96 m below the surface (Kalenda et al., 2009). We analysed the noise parameter on all of our pendulums (11) apparatus were in operation at the end of 2011). ...
... The noise of tilt on the pendulums on the surface or at small depths shows diurnal variations, which depends on the sunshine (Neumann, 2007). The pendulums situated at deeper horizon show mostly the annual cycles of tilt and noise too, with the maximum noise during the winter period (Kalenda et al., 2009). This is in accordance with the measurement of deformation velocity or deformation noise in the Gallery of St. Padua in Vyhne, Slovakia, by horizontal in wells in Police Basin (Stejskal et al strainmeters (Brimich, 2006), which exactly detected the annual thermoelastic waves even at depths of hundreds meters below the surface (Hvoždara et al., 1988), with water level measurement (2007) (Fig. 2) and with measurement of movement of active faults (Briestenský et al., 2010).Figure 2. Water level in the well VS3 in Police Basin, Bohemia (acc. to Stejskal et al. 2007) and strain in Vyhne, Slovakia, (Brimich personal info) in 2007. ...
The noise data obtained from new apparatus for indirect stress measurement, i.e., vertical static pendulum was compared with microseisms recorded at the seismic station OKC (Czech Republic). It was documented that results of both methods of measurement were comparable, being estimated by a high value of correlation coefficient. The microseismic anomalies after strong earthquakes in 2009 (Samoa M=8.1) and 2010 (Chile M=8.8 and Mentawai M=7.7) were analysed and "deformation waves" were recognised. The microseismic and deformation noise were triggered on the crest of "deformation waves". The velocity of these waves were in the order of hundreds km/h, i.e. such waves can circulate around the globe in one to three weeks. Three circumvolutions of deformation wave were recognised after the Chile earthquake, which could probably cause the triggering of many earthquakes and volcano activity. The theory dealing with the problem of microseisms generation is based on the influence of deformation and/or stress waves as well.
In contrast to unsuccessful searching (lasting over 150 years) for
correlation of earthquakes with biweekly tides, the author found
correlation of earthquakes with sidereal 13.66 days Earth's rotation
variations expressed as length of a day (LOD) measured daily by
International Earth's Rotation Service. After short mention about
earthquakes M 8.8 Denali Fault Alaska 3 November 2002 triggered on LOD
maximum and M 9.1 Great Sumatra earthquake 26 December 2004 triggered on
LOD minimum and the full Moon, the main object of this paper are
earthquakes of period 2010-June 2011: M 7.0 Haiti (12 January 2010 on
LOD minimum, M 8.8 Maule Chile 12 February 2010 on LOD maximum, map
constructed on the Indian plate revealing 6 earthquakes from 7 on LOD
minimum in Sumatra and Andaman Sea region, M 7.1 New Zealand
Christchurch 9 September 2010 on LOD minimum and M 6.3 Christchurch 21
February 2011 on LOD maximum, and M 9.1 Japan near coast of Honshu 11
March 2011 on LOD minimum. It was found that LOD minimums coincide with
full or new Moon only twice in a year in solstices. To prove that
determined coincidences of earthquakes and LOD extremes stated above are
not accidental events, histograms were constructed of earthquake
occurrences and their position on LOD graph deeply in the past, in some
cases from the time the IERS (International Earth's Rotation Service)
started to measure the Earth's rotation variations in 1962. Evaluations
of histograms and the Schuster's test have proven that majority of
earthquakes are triggered in both Earth's rotation deceleration and
acceleration. Because during these coincidences evident movements of
lithosphere occur, among others measured by GPS, it is concluded that
Earth's rotation variations effectively contribute to the lithospheric
plates movement. Retrospective overview of past earthquakes revealed
that the Great Sumatra earthquake 26 December 2004 had its equivalent in
the shape of LOD graph, full Moon position, and character of aftershocks
19 years earlier in difference only one day to 27 December 1985
earthquake, proving that not only sidereal 13.66 days variations but
also that the 19 years Metons cycle is the period of the earthquakes
occurrence. Histograms show the regular change of earthquake positions
on branches of LOD graph and also the shape of histogram and number of
earthquakes on LOD branches from the mid-ocean ridge can show which side
of the ridge moves quicker.
