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Start Over Creator Valenta, Jan Rights http://creativecommons.org/licenses/by-nc-sa/4.0/ Type article Type model:article

2. Groundwater level variations in the seismically active region of Western Bohemia in the years 2005-2010

Creator:
Gaždová, Renata, Oldřich Novotný, Málek, Jiří, Valenta, Jan, Brož, Milan, and Kolínský, Petr
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, zemětřesení, seizmicita, earthquake, seismicity, Čechy západní (Česko), Bohemia, Western (Czechia), earthquake swarm, groundwater level, 7, and 551
Language:
English
Description:
The western part of the Bohemian Massif (Vogtland/West-Bohemia region at the Czech-German border) is characterized by relatively frequent intraplate earthquake swarms and by other manifestations of current geodynamic activity, such as mofettes, mineral and thermal springs. In this study we analyze variations of groundwater level in four hydrological wells in the region during the years 2005-2010. Monitoring during the previous time interval of 2000-2004 is also mentioned and used for comparison. Two of the wells are located in the epicentral region of Nový Kostel, and the other wells are more distant. The time interval includes the 2008 earthquake swarm when all the wells displayed a noticeable drop in the water level. This effect was observed up to epicentral distances of nearly 30 km, which exceeds the distances of hydrological changes observed during previous earthquake swarms. Moreover, it seems that a small rise in the water level preceded the intervals of increased seismic activity, which could represent a certain precursory phenomenon. On the other hand, the hydrological changes in the Nový Kostel area were relatively small, indicating that this epicentral area is not hydrologically linked with the seismically active fault at depth. Consequently, more suitable localities for hydrological monitoring should be sought in a broader vicinity of Nový Kostel., Renata Gaždová, Oldřich Novotný, Jiří Málek, Jan Valenta, Milan Brož and Petr Kolínský., and Obsahuje bibliografii
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http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Seismicity, groundwater level variations and earth tides in the Hronov-Poříčí Fault Zone, Czech Republic

Creator:
Kolínský, Petr, Valenta, Jan, and Gaždová, Renata
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print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, seizmicita, tlak vzduchu, seismicity, air pressure, Eastern Bohemian Massif, groundwater level, earth tides, 7, and 551
Language:
English
Description:
Local seismicity of the Hronov-Poříčí Fault Zone is studied using two-year continuous seismic data from four seismic stations in the area. Newly developed software for automatic seismic events detection is introduced - it is based on the method used at the Icelandic seismic network. Twelve major local earthquakes are detected, localized and their magnitudes are estimated. Simultaneously, groundwater levels are continuously monitored in three wells in the area. Multiple-filtering method, originally used for processing of broadband and dispersed seismic signals, is modified and used for the frequency-time analysis of the water level data. Dominant tidal influence on the groundwater level variations is shown. Theoretical tidal potential for all three well locations is computed. Groundwater data and tidal potential are bandpass filtered to focus on the semidiurnal periods. Mutual amplitude ratio and phase shift between both quantities are computed. Each of the three wells exhibits different pattern of the groundwater level variations with respect to tides. A distinct change in the phase shift is observed at the VS-3 well in the second half of 2009. In the same time span, increased seismic activity is also observed. However, other two wells do not exhibit any evidence of such phase shift. Detailed groundwater level data analysis does not prove any significant rises or drops of the groundwater levels in 28 day intervals around the detected local events. In contras t, unexplained groundwater level drop in the V-34 well is obser ved 18 hours before the teleseismic Tohoku earthquake, Japan, March 11, 2011, Mw = 9.0., Petr Kolínský, Jan Valenta and Renata Gaždová., and Obsahuje bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4. Tectonic pattern of the Hronov-Poříčí trough as seen from pole-dipole geoelectrical measurements

Creator:
Valenta, Jan, Vladimír Stejskal, and Štěpančíková, Petra
Format:
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Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, geomorfologie, geomorphology, Hronov (Česko : oblast), Hronov Region (Czechia), Hronov-Poříčí Trough, Hronov-Poříčí Fault Zone, electric resistivity measurements, normal faulting, 7, and 551
Language:
English
Description:
The Hronov-Poříčí Trough represents the easternmost part of the Trutnov-Náchod Depression. The NW-SE striking structure was formed due to the post-Cretaceous flexural folding and is filled with the Upper Cretaceous sediments. Both the NE and SW margins of the trough are bounded by flexures with the Upper Cretaceous strata dipping 40-60° towards the axis of the trough. The NE flexure is situated close to the parallel Hronov-Poříčí Fault Zone. Up to now, it is not fully known, in what extent the normal faulting was involved in the evolution of the structure. From the geomorphological point of view, the normal fault constraints of the trough seem to be acceptable, as the surface topography of its present margins exhibit many signs typical for fault scarps. However, the existence of a fault system bounding all round the Hronov-Poříčí Trough has not b een proved by any geological research. Hence the geophysical research was carried out on both sides of the NW part of the trough to support one of these hypothesis. Five geoelectrical profiles were measured in the area and the fault system was proved on the NE side of the trough. On the SW boundary the fault system was not found. Thus it seems, that the NE boundary is controlled by fault tectonics, whereas the SW boundary is rather formed by a simple flexure., Jan Valenta, Vladimír Stejskal and Petra Štěpančíková., and Obsahuje bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. The identification of faults using morphostructural and geophysical methods: a case study from Strašín Cave site

Creator:
Hartvich, Filip and Valenta, Jan
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Geologie. Meteorologie. Klimatologie, jeskyně, caves, Šumava (pohoří : oblast), Šumava Mountains Region, geophysical profiling, morphostructural analysis, faults, 7, and 551
Language:
English
Description:
This paper combines morphostructural analysis and geophysical methods in order to link the faults monitored inside Strašín Cave with faults and lineaments in the vicinity of the cave. The studied site is situated in SW Bohemia, at the foothills of the Bohemian Forest Mts. Main goal is to combine the morphostructural, morphometrical and geophysical methods in order to identify the fault system, monitored inside the cave. This will allow relevant interpretation of the observed movements in the frame of the local tectonic environment. The results show that the monitored faults are observable in the geophysical profiles and, using our knowledge of the structural setting, we have been able to link them with mapped tectonic structures in the vicinity of the cave. Thus, it has been demonstrated that even where outcrops are absent, the faults can be traced and that the monitored faults are significant enough to yield relevant data on tectonic movements. In addition, the combined resistivity and gravimetry profiles reveal a possible new, presently unknown, cave located 20 m below the surface about 200 m northnortheast of Strašín Cave., Filip Hartvich and Jan Valenta., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public