Seismological observatory activity
Basic research objectives
Research into natural seismicity in the eastern part of the Bohemian Massif. Long-term seismological observations on the territory of northern Moravia and Silesia proved the existence of natural seismic events (microearthquakes) in this region. However, the overall level of seismic activity can be estimated as low, especially as for their number, but also in regard of their intensity classification according to the magnitude scale. If particular events have a sufficient magnitude, they are detected at regional seismic stations, while the less intensive ones are recorded locally at the seismic station OKC and at stations operated by IPE MU, which are distributed in northern and southern Moravia. Except for weak microearthquakes, these events are also recorded at the seismic stations ZLHC, RADC and KLOK. The seismic station OKC is connected online with the interpretation centre of GIAS, and with the Laboratory of geophysics of IGAS. On the other hand, the IPE seismic stations, e.g., MORC, VRAC, KRUC, MUTC, and JAVC, are connected with the Prague centre by their own computing centre.
The automation applied in the process of transmission of all available seismic data and evaluated results significantly contributes to the primary determination of earthquake foci almost in real time; arrival times of P- and S-waves and data describing position of microearthquake foci are part of a seismic bulletin, which is being completed by the GIAS. Data from the seismic stations RADC, ZLHC and KLOK that is not directly included in the regional seismic bulletin is also processed and added with a certain delay. This data can serve for the refinement of already localized focal regions. The purpose of IGAS seismic station network is exactly the detection of weak microearthquakes, which are expected in the immediate vicinity of the known focal regions. At present, a mutual exchange of data observed at the seismic stations included into IGAS and IPE MU networks is considered a purposeful approach. On this basis, it is possible to determine foci positions in the region under investigation more precisely by extending the data set.
Investigation of technical seismicity manifestations. A very important group of observed seismic events encompasses events denoted as technical seismicity. This group includes, first of all, events induced by mining and quarry blasts fired in quarries situated on the territory of northern Moravia and Silesia.
Mining induced events are recorded mainly in the Ostrava-Karvina coal mine district, but also in Polish coal mines near Katowice and Rybnik, as well as copper mines situated in the Legnice-Glogow region (LGOM). Rockbursts and mining shocks from the LGOM, and very intensive events occurring in Polish coal mines are reliably detected by the stations of the Czech Regional Seismological Network (CRSN). Events from the technical seismicity category, which are not included in the regional bulletin, represent a complementary source of information for the IGAS network local bulletin.
As for research objectives relating to the technical seismicity, observations of quarry blasts are considered very purposeful and useful. This has several reasons. First, the knowledge of a quarry position and the firing time of explosions makes the unambiguous discrimination between an explosion and a tectonic microearthquake easier. Second, the knowledge of the exact time of a quarry blast also enables to test and operate a precise current velocity model in order to check the accuracy of the quarry localization. Moreover, records from a quarry blast can be used in research of the properties of seismic waves generated by the explosion. Overall available information will, therefore, be continuously put into the local bulletin, which will serve for seismological data interpretation by other institutions.
Seismic stations
φ = 50,2232ºN, λ = 17,4063ºE, h = 517 m
Three-component short-period system
seismometers: SM-3, T0 = 2 s, D ≈ 0,7
data acquisition: apparatus PCM-EPC (IGAS)
triggered registration, sampling frequency f = 100 Hz
GSM data transmission to the laboratory of IGAS
data format ESSTF ½
φ = 49,8931ºN, λ = 17,9412ºE, h = 295 m
Three-component short-period system
seismometers: S5S, T0 = 5 s, D ≈ 0,7
data acquisition: apparatus PCM-EPC (IGAS)
triggered registration, sampling frequency f = 100 Hz
GSM data transmission to the laboratory of IGAS
data format ESSTF ½
φ = 49,93433ºN, λ = 17,77217ºE, h =377 m
Three-component short-period system
seismometers: Le3D, T0 = 1 s, D ≈ 0,7
data acquisition: apparatus GAIA 2
continuous record, sampling frquency f = 100 Hz
data record used flash card 2x 1 GB
data gathering approx. once a month
data format MiniSEED
φ = 49,7563ºN, λ = 17,7193ºE, h = 598 m
Three-component short-period system
seismometers: Le3D, T0 = 1 s, D ≈ 0,7
data acquisition: apparatus GAIA 2
continuous record, sampling frquency f = 100 Hz
data record used flash card 2x 1 GB
data gathering approx. once a month
data format MiniSEED
Coordinates
φ = 49,8353ºN, λ = 18,1423ºE, h = 250 m
Three-component broadband system
seismometers: Guralp CMG-3ESP, T0 = 30 s, D ≈ 0,7
digitizer: EarthData
data acquisition: SeisComp
continuous record, sampling frequency f = 20 Hz
on-line data transmission to GIAS and to IGAS
Three-component short-period system
seismometers: SM-3, T0 = 1,4 s, D ≈ 0,7
continuous record, sampling frequency f = 20 Hz
data format MiniSEED