Details zur Publikation
|Titel (primär)||Geochemical fluid-monitoring results in relation to the NW Bohemian earthquake swarm period 2000|
|Titel (sekundär)||27th EGS General Assembly, Nice, France, 21-26 April 2002|
|Autor||Bräuer, K.; Kämpf, H.; Faber, E.; Heinicke, J.; Koch, U.; Strauch, G.; Weise, S.M.|
|Journal / Serie||Geophysical Research Abstracts|
|Abstract||The monitoring of the isotope distribution from escaping gases of active continental rifts is a useful tool for the understanding of concealed upper mantle-crust interaction processes. Mantle derived fluid exhalations are known in the earthquake swarm re- gion Vogtland/ NW Bohemia, the western part of the Eger rift in Central Europe. At four locations, gas and isotope composition (C, He, N) were monitored weekly and monthly, respectively, since May 2000: two mofettes (Bublak, Soos) located in the centre of the CO2 plume and two mineral springs (Plesna, Wettinquelle/Bad Bram- bach) located at its periphery. The proportion of MORB-type helium decreases from the centre of the CO2 plume (up to 80%) in the south to the periphery (about 30%) in the north. Besides the periodic gas sampling, a seismohydrological online monitoring started at the same locations likewise since May 2000. From the end of August to the end of December 2000 a period of swarm quake seismicity occurred at what several phases of seismicity could be distinguished.
Here, we present results of the first year of our monitoring study (May 2000 to April 2001). Peaks in the CO2 gas flow rate, the gas composition (helium, methane) as well as in the isotope distribution (3He/4He,15N, 13C) were found. Shifts in the gas and isotope composition are interpreted in connection with seasonal, seismohydrological and magmatic processes. The mineral springs show a seasonal induced correlation be- tween water temperature and CO2 content in the free gas phase. Peaks of 3He/4He ratios at the Wettinquelle and the Plesna mineral spring point out crustal contribu- tions several weeks after the beginning of the period of seismicity. Such a trend we have already found after the 12/1994 earthquake swarm. Each monitoring location is characterized by an isotope 'baseline' signature that reflects the balance of upper mantle-crust interaction. The isotope signature of the 'baseline' flux can change dur- ing opening of crustal reservoir. Long-term trends in Bublak and Plesna (1993 to 2000) of 3He/4He show an all-over increase of MORB-type He which point to active mag- matic processes.
|Bräuer, K., Kämpf, H., Faber, E., Heinicke, J., Koch, U., Strauch, G., Weise, S.M. (2002):
Geochemical fluid-monitoring results in relation to the NW Bohemian earthquake swarm period 2000
27th EGS General Assembly, Nice, France, 21-26 April 2002
Geophysical Research Abstracts 4
European Geosciences Union (EGU), p. EGS02 - EGS0A