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INVESTIGATION CONCERNING INFLUENCE OF SEISMIC ACTIVITY ON THE REGIME OF HYDROTHERMAL DEPOSIT PCHELINSKI BANI, BULGARIA. BORYANA YORDANOVA DENEVA PhD student University of Mining and Geology "St. Ivan Rilski" Bulgaria. STRUCTURE OF THE PAPER. Introduction
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INVESTIGATION CONCERNING INFLUENCE OF SEISMIC ACTIVITY ON THE REGIME OF HYDROTHERMAL DEPOSIT PCHELINSKI BANI, BULGARIA BORYANA YORDANOVA DENEVA PhD student University of Mining and Geology "St. Ivan Rilski" Bulgaria BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
STRUCTURE OF THE PAPER • Introduction • Geological setting and Hydrogeological background • Information base • ResultsandDiscussion • Conclusions • References BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
GENERAL DESCRIPTION OF THE INVESTIGATED OBJECT • Pchelinski Bani thermal water deposit is a hydrogeological structure of a fissure-vein type. • Basic collectors of thermal water are Upper Cretaceous granodiorites (guγδK2). • The water from the hydrothermal deposit is hyperthermal (72.8 ºC), sulfate sodium by composition with mineralization 0.98 g/l and high content of metasilic acid, fluoride and radon. • The main water source is the captured thermal spring "Pchelin", which drains the whole thermal zone. • The spring has an expressed postseismic reaction – a sharp decrease in its discharge immediately after strong earthquakes, occurring both on the territory of Bulgaria and its neighboring countries. BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
INFORMATION BASE The investigations on the thermal water regime have been carried out empirically - on the basis of an analysis of data obtained from: • The regime observations on the spring discharge for a period of 28 years (1975 - 2003). • The water level observations in a monitoring well for a 20-year period (1983 - 2003). BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
RESULTS AND DISCUSSION Figure 1 Visualization of thermal spring discharge data during 1975-2003 BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
Discharge variations and corresponding seismic activity data BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
Figure 2 Locations of the earthquake epicenters that affected the thermal spring discharge BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
Figure 4 Parallel observations of thermal spring discharge and water level in monitoring borehole during 1983. Figure 3 Visualization of water level data obtained during the period 01.01.1983 - 30.09.1990. As a consequence of earthquake with a magnitude of 6.9 according to the Richter scale, occurred on 06.08.1983 in the territory of Northern Greece, thermal spring discharge had decreased with 7.6 l/s (from 12.3 to 4.6 l/s) and water level had dropped with 7 cm. BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
CONCLUSIONS • The thermal spring discharge is affected by seismic activity occurring in the regions of Aegean Sea, Marmara Sea, FYR Macedonia, Romania and Bulgaria. • Two points of sharp level lowering were registered in the monitoring borehole. Changes have appeared as a result of strong seismic activity in the region of Strazica (Bulgaria, 1986) and Aegean Sea (Greece, 1988). BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
FUTURE INVESTIGATIONS • Implementation of continuous water level monitoring - installation of a continuing device in the monitoring borehole (Borehole N2); • Implementation of parallel measurements of thermal spring discharge and water level in the monitoring borehole (Borehole N2); • Investigations for possible variations in water chemical content and temperature as a result from seismic activity; • Including the hydrothermal deposit in an extensive monitoring set for investigation of seismic impacts on similar hydrogelogical structures on the territory of Bulgaria and its neighboring countries. BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
Control measurement of water level in Borehole N2 – May 2004. BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia
Dear colleagues, thank you for your kind attention! Boryana Deneva BALWOIS Conference - 25, 29 May 2004 - Ohrid, FY Republic of Macedonia