Non-seismological indications of recent tectonic activity in the West Bohemia earthquake swarm region

Mrlina, J.; Špičák, Aleš; Skalský, Lumír

doi:10.1016/s0264-3707(02)00064-9

Cited by 17 publications

(17 citation statements)

References 9 publications

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“…In 1994, the Geophysical Institute, Academy of Sciences of the Czech Republic, started to carry out the repeated GPS measurements in West Bohemia (the Czech part of the studied area) in a network covering an area of about 1000 km 2 (Mrlina, 1997(Mrlina, , 2000Mrlina et al, 2003;Špičák et al, 1997. Unfortunately, the applied system of GPS measurements (only few hours of registrations, no identical antenna applications in one site during GPS campaigns, etc.)…”

Section: Gps Data In West Bohemia Regionmentioning

confidence: 99%

Geodynamic pattern of the West Bohemia region based on permanent GPS measurements

2009

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In West Bohemia in the period of 2003−2005 five permanent GPS stations were established to detect local movement trends. Their mutual position changes were determined from time series of GPS observations and were associated with seismic, gravity, and geo-scientific data related to the geodynamics of the West Bohemian region. Knowledge of local physical processes based on spatial and time earthquake occurrences, focal mechanisms of main events, stress and strain fields set up a tool for recent seismotectonic analyses. The permanent GPS measurements bring independent effective phenomenon, direct monitoring of site movements. The movements detected by our GPS stations evidenced WSW-ENE extension with subsiding trends in the western part of the Cheb Basin and the Smrčiny Mts. Besides, there were monitored dextral movements along the Mariánské Lázně tectonic fault zone (MLF). A comparison of results with previous data formed a presumption that an antithetic stress pattern has to exist inside the inner part of the MLF tectonic zone. This antithetic stress can explain the coexistence of dextral and sinistral movements on individual tectonic elements in the West Bohemian area.

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Section: Gps Data In West Bohemia Regionmentioning

confidence: 99%

Geodynamic pattern of the West Bohemia region based on permanent GPS measurements

2009

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“…The division line (separating negative from positive movements) is parallel rather to the direction of MLF (Mariánské Lázně fault) than to the axis of elliptical focal zone of Nový Kostel. This is slightly different from the earthquake swarm periods 19961997 and 2000, when the division lines were almost identical with the focal zone axis (Mrlina, 2000;Mrlina et al, 2003). This change may be related to the change of the character of earthquake activity after 2001, as a number of micro-swarms have occurred with partially different parameters (depth, distribution) according to Fischer and Michálek (2008).…”

Section: Figmentioning

confidence: 69%

“…A n n u a l G P S C a m p a i g n s Relatively significant reversible horizontal displacements were determined from GPS data in the period 19982000 (presented by Mrlina et al, 2003). Considering the data accuracy mentioned above, it was evident that the displacements in this period could be realistic, contrary to the previous and latter campaigns (compare Figs.…”

Section: 1 G P S N E T W O R Kmentioning

confidence: 92%

“…However, even before these results were available, we decided to establish GPS and precise levelling networks in the West Bohemia seismoactive region. As well, we started some other observations at that time, as groundwater level monitoring and repeated measurements of gravity (Mrlina et al, 2003) that showed notable correlation with earthquake activity. Recently, we have established also tiltmeters recording in an underground observatory (Boušková et al, unpublished results) in order to contribute to the surface kinematics studies.…”

Section: Introductionmentioning

confidence: 91%

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Relation of surface movements in West Bohemia to earthquake swarms

Mrlina¹,

Seidl²

2008

Stud Geophys Geod

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GPS observations in the WesternBohemia/Vogtland earthquake swarm region revealed indications of horizontal displacements of low amplitude, and no clear long-term trend in 19932007. On the other hand, in 19982001 there was relatively significant active movement along NNE-SSW oriented line that we called the "Cheb-Kraslice GPS Boundary" (ChKB), identical with an important limitation of earthquake activity. The most impressive were dextral (right-lateral) movements in the 19981999 period followed by reverse sinistral (left-lateral) movements in 19992000 that correlate with prevailing motion defined by fault plane solutions of the Autumn 2000 earthquake swarm. Before the February 2004 micro-swarm, two points located on opposite sides of the Mariánské Lázně fault showed extension in the order of about 7 mm in the same NNE-SSW direction of ChKB. The new NOKO permanent GPS station in Nový Kostel showed the peak-to-peak vertical changes up to 10 mm before and during the February 2007 micro-swarm. Annual precise levelling campaigns in the local network around Nový Kostel revealed regular vertical displacements during the 1994, 1997 and 2000 earthquake swarms. The points around the Nový Kostel seismological station showed uplift during the active periods, including the micro-swarm February 2004. However, no such indication was observed on levelling points in the period of the February 2007 swarm. Long-term vertical displacements depend on the same direction NNE-SSW (ChKB) as the GPS displacements. Both geodetic techniques have revealed oscillating displacements, GPS horizontal, and levelling vertical, rather than any long-term trends in the study period 19932007. The displacements exhibited significant spatial and temporal relation to tectonic activity (earthquake swarms) including their coincidence with the seismologically determined sense of motion along the fault plane during earthquakes.

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“…Such fluid pressure pulses or sudden changes in fault permeability caused by fault movements in the geodynamic active area of NW Bohemia (Mrlina et al . ; Mrlina & Seidl ) are revealed in CO 2 gas flux peaks at a mofette of the Soos mofette field (Fig. ).…”

Section: Magmatic Co2 Gas Ascent In the Cheb Basinmentioning

confidence: 85%

Carbon dioxide controlled earthquake distribution pattern in the NW Bohemian swarm earthquake region, western Eger Rift, Czech Republic – gas migration in the crystalline basement

Weinlich

2013

Geofluids

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The ascent of magmatic carbon dioxide in the western Eger (Ohře) Rift is interlinked with the fault systems of the Variscian basement. In the Cheb Basin, the minimum CO2 flux is about 160 m3 h−1, with a diminishing trend towards the north and ceasing in the main epicentral area of the Northwest Bohemian swarm earthquakes. The ascending CO2 forms Ca‐Mg‐HCO3 type waters by leaching of cations from the fault planes and creates clay minerals, such as kaolinite, as alteration products on affected fault planes. These mineral reactions result in fault weakness and in hydraulically interconnected fault network. This leads to a decrease in the friction coefficient of the Coulomb failure stress (CFS) and to fault creep as stress build‐up cannot occur in the weak segments. At the transition zone in the north of the Cheb Basin, between areas of weak, fluid conductive faults and areas of locked faults with frictional strength, fluid pressure can increase resulting in stress build‐up. This can trigger strike‐slip swarm earthquakes. Fault creep or movements in weak segments may support a stress build‐up in the transition area by transmitting fluid pressure pulses. Additionally to fluid‐driven triggering models, it is important to consider that fluids ascending along faults are CO2‐supersaturated thus intensifying the effect of fluid flow. The enforced flow of CO2‐supersaturated fluids in the transitional zone from high to low permeability segments through narrowings triggers gas exsolution and may generate pressure fluctuations. Phase separation starts according to the phase behaviour of CO2‐H2O systems in the seismically active depths of NW Bohemia and may explain the vertical distribution of the seismicity. Changes in the size of the fluid transport channels in the fault systems caused, or superimposed, by fault movements, can produce fluid pressure increases or pulses, which are the precondition for triggering fluid‐induced swarm earthquakes.

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Non-seismological indications of recent tectonic activity in the West Bohemia earthquake swarm region

Cited by 17 publications

References 9 publications

Geodynamic pattern of the West Bohemia region based on permanent GPS measurements

Geodynamic pattern of the West Bohemia region based on permanent GPS measurements

Relation of surface movements in West Bohemia to earthquake swarms

Carbon dioxide controlled earthquake distribution pattern in the NW Bohemian swarm earthquake region, western Eger Rift, Czech Republic – gas migration in the crystalline basement

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