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42. Period and Q-factor of Free Core Nutation, based on different geophysical excitations and VLBI solutions

Creator:
Jan Vondrák and Cyril Ron
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
geofyzika, geophysics, rotation of the Earth, geophysical excitations, geomagnetic jerks, VLBI, celestial pole offsets, free core nutation, 7, and 551
Language:
English
Description:
Three variants of geophysical excitations and seven different VLBI solutions of celestial pole offsets (CPO) are used to determine period and Q-factor of Free Core Nutation (FCN). Brzeziński’s broad-band Liouville equations (Brzeziński, 1994) are numerically integrated to derive geophysical effects in nutation in time domain. Possible effect of geomagnetic jerks (GMJ) is also considered. Best-fitting values of FCN parameters are estimated by least-squares fit to observed CPO, corrected for the differences between the FCN parameters used in IAU 2000 model of nutation and newly estimated ones; MHB transfer function is used to compute these corrections. It is demonstrated that different VLBI solutions lead to FCN parameters that agree on the level of their formal uncertainties, but different models of geophysical excitations change the results more significantly. Using GMJ excitations always brings improvement of the fit between integrated and observed CPO. The obtained results show that the best fit is achieved when only GMJ excitations are used. Our conclusion is that GMJ are very probably more important for exciting FCN than the atmosphere and oceans. Empirical Sun-synchronous correction, introduced in the present IAU 2000 nutation model, cannot be explained by diurnal atmospheric tidal effects., Jan Vondrák and Cyril Ron., and Obsahuje bibliografii
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

43. Present-day stress orientation and tectonic pulses registered in the caves of the Slovensky kras mts. (South-eastern Slovakia)

Creator:
Briestenský, Miloš, Zdenko Hochmuth, Littva, Juraj, Hók, Jozef, Dobrovič, Roman, Stemberk, Josef, Ľubomír Petro, and Pavel Bella
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
geodynamika, geomechanika, geofyzika, geologie, geodynamics, geomechanics, geophysics, geology, Slovenský kras (Slovensko), Slovak Karst (Slovakia), recent geodynamics, neotectonics, microdisplacement monitoring, cavitonics, 7, and 551
Language:
English
Description:
The fault displacement monitoring network EU-TecNet was established to define microdisplacements across faults in the territory of Central Europe (www.tecnet.cz) using three-dimensional optical-mechanical extensometers. The results of long-term neotectonic activity obtained from two caves localized in the eastern part of the Slovenský kras Mts. (SE Slovakia) show generally NE-SW oriented dilatation. This orientation is in a good accordance with the orogen-parallel extension monitored in the Western Carpathians. Differing short-lasting trends were distinguished in 2011-2012 and 2013-2015, which supports the significance of the tectonic pulse at the end of 2012 and the beginning of 2013. Moreover, simultaneous short-lasting faulting occurred at both sites under the transtensional tectonic regime, where the principal maximum compressional axis operated in a NW-SE direction (σ1). The observed results were compared to data from monitoring points in distant areas of the European plate. and Briestenský Miloš, Hochmuth Zdenko, Littva Juraj, Hók Jozef, Dobrovič Roman, Stemberk Josef, Petro Ľubomír, Bella Pavel.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

44. Přírodní hrozby kolem nás - svahové deformace

Creator:
Jana Olivová
Format:
print, bez média, and svazek
Type:
article, články, journal articles, model:article, and TEXT
Subject:
Věda. Všeobecnosti. Základy vědy a kultury. Vědecká práce, Ústav struktury a mechaniky hornin (Akademie věd ČR), geofyzika, sesuvy půdy, ohrožení životního prostředí, geophysics, landslides, threats to environment, 12, and 00
Language:
Czech
Description:
Jana Olivová.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

46. Rock anisotropy and brittleness from laboratory ultrasonic measurements in the service of hydraulic fracturing

Creator:
Moska, Rafal, Kasza, Piotr, and Maslowski, Mateusz
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
geodynamika, geomechanika, geofyzika, geologie, ultrasonografie, měření, geodynamics, geomechanics, geophysics, geology, index lámavosti, ultrasonic laboratory measurements, elastic anisotropy, brittleness index, 7, and 551
Language:
English
Description:
Ultrasonic velocity anisotropy in the rock provides information of variability of the dynamic elastic moduli. Young’s modulus and Poisson’s ratio calculated from waves velocities can be used to determine brittleness index, which is usually used to predict rock susceptibility for hydraulic fracturing. This paper describes laboratory ultrasonic measurements carried out in order to improve hydraulic fracturing designing. The research was conducted over two types of rock: shale and limestone. The samples were cut out perpendicularly and parallel to the bedding planes. Next they were tested for effective porosity and mineral composition using XRD method. Directionally depended seismic velocities revealed noticeable anisotropy of laminated shale, caused by orientation of the bedding planes and weak anisotropy of limestone. Based on the velocities, dynamic elastic moduli and its anisotropy coefficients were determined. Calculations of brittleness index based on Young’s modulus to Poisson’s ratio relation and three types of mineral composition brittleness indexes, revealed strong variability in brittleness for both kind of tested formations. These results show, that different types of brittleness indexes should be used complementary, to better describe fracability of the rock. and Moska Rafal, Kasza Piotr, Maslowski Mateusz.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

47. San Francisco zničeno zemětřesením - uplynulo sto let

Creator:
Kozák, Jan T.
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
geofyzika, zemětřesení, geophysics, earthquake, San Francisco (Kalifornie), San Francisco (California), 6, and 53
Language:
Czech
Description:
Před necelým půl rokem - 1. listopadu 2005 - vzpomněli přírodovědci na celém světě dvěstěpadesátého výročí nejsilnějšího evropského, tzv. velkého Lisabonského zemětřesení, při kterém na Iberském poloostrově zahynuly desítky tisíc lidí. V těchto dnech si připomínáme sté výročí jiné seismické katastrofy - nejničivější v historii celé Severní Ameriky -, zemětřesení, které dne 18. dubna 1906 devastovalo nejen město San Francisco v Kalifornii, ale i další sídliště v rozsáhlé přilehlé oblasti. and Jan T. Kozák.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

48. Seismické profilování ve střední Evropě a jeho přínos ke studiu litosféry

Creator:
Hrubcová, Pavla, Novotný, Miroslav, Růžek, Bohuslav, and Špičák, Aleš
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
geofyzika, geologický výzkum, seizmologie, geophysics, geological research, seismology, Evropa střední, Europe, Central, 6, and 53
Language:
Czech
Description:
Mezinárodní seismické experimenty uskutečněné v posledních letech ve střední Evropě studují stavbu zemské kůry a svrchního pláště pod touto oblastí. Pro studium hlubinné stavby se využívá seismická refrakční metoda, kdy se registrují seismické vlny generované odpaly a následně je zjišťována rychlost šíření vln v horninovém prostředí. Tyto údaje umožňují zpřesnit naše znalosti o vlastnostech svrchních partií litosféry do hloubek 50-60 km., Pavla Hrubcová, Miroslav Novotný, Bohuslav Růžek, Aleš Špičák., and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

49. Seismologické předpovědi: skutečnost a sen

Creator:
Burjánek, Jan, Gallovič, František, and Zahradník, Jiří
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
geofyzika, seizmologie, předpověď zemětřesení, geophysics, seismology, earthquake prediction, 6, and 53
Language:
Czech
Description:
Jan Burjánek, František Gallovič, Jiří Zahradník. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

50. Seismotectonics of Bosnia: overview

Creator:
Omerbashich, Mensur and Sijarić, Galiba
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, tektonika, geodynamika, geofyzika, geodezie, geotectonics, geodynamics, geophysics, geodesy, Bosna, Bosnia and Hercegovina, seismic hazard, 7, and 551
Language:
English
Description:
Bosnia’s seismotectonics seems to follow the Mediterranean marine regime. Earthquakes occur mostly in the outer Dinaric Alps (southern Bosnia), while the strongest earthquakes occur within the Sarajevo Fault system in southern and northwestern Bosnia. In addition to active tectonics being strong, crustal earthquakes occur often as well. Due to Bosnia’s rich hydrogeology, crustal loading such as by snow and rain, or reservoir inundation, represents the most important secondary seismogenic source in the region. Despite its exquisite and active geomorphology no comprehensive and reliable geodynamical studies exist on the region. Seismic sensors coverage is extremely poor also. One centenary analogue, and a few recently installed digital seismometers are insufficient for a region that exhibits mild-to-high seismic activity. Significant investments are needed in order for GPS, seismic and other sensor-instrumented networks to be put in place or enhanced. Technical personnel needs to be educated to enable support provide for studies that are done within broader scientific activities. Such efforts that presently seek to include Bosnia under their scope are ESF-COST Action 625, NATO Stability Pact DPPI program, and EUREF/CERGOP geophysics projects., Mensur Omerbashich and Galiba Sijarić., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public