Earthquakes in Hostěradice in June 2014

Southern Moravia – a southeastern part of the Czech Republic at the contact of the Bohemian Massif and the Carpathian Foredeep – is one of the regions with the lowest seismic activity in the Czech Republic. Reports on historical earthquakes in this area are sporadic and poorly evidenced, many of the messages are in fact observations of earthquakes originating mainly in Austria. Instrumental seismic monitoring in southern Moravia commenced in 1995. Thereafter only three local earthquakes were observed – magnitude 2.5 event near Hostěradice in 2000, perhaps induced event near Uhřice in 2003 with magnitude of 0.7 and magnitude 1.4 earthquake near Božice in 2006.A sequence of four weak earthquakes in June 2014 is only the fourth occurrence of earthquakes in southern Moravia since the beginning of instrumental measurements. Events originated near Hostěradice (SE margin of the Bohemian Massif), 40 km southwest of Brno. The strongest event reaching local magnitude of 2.0 occurred on June 1, 2014 at 00:43 UTC. It was felt by people close to the epicentre with a macroseismic intensity 4 European Macroseismic Scale EMS-98. A temporary seismic station was immediately installed in the epicentral area. The station recorded two of four shocks and helped to confi rm a focus position of the sequence: 48.95° N 16.24° E, depth 3 km.In 2014 a review of historical earthquakes in this region was conducted using new catalogues of historical earthquakes in neighboring countries in order to avoid confusion between local and regional phenomena. Some new information sources were found. In any case, historical earthquakes in this region are very rare and most of them are poorly substantiated.Southern Moravia – a southeastern part of the Czech Republic at the contact of the Bohemian Massif and the Carpathian Foredeep – is one of the regions with the lowest seismic activity in the Czech Republic. Reports on historical earthquakes in this area are sporadic and poorly evidenced, many of the messages are in fact observations of earthquakes originating mainly in Austria. Instrumental seismic monitoring in southern Moravia commenced in 1995. Thereafter only three local earthquakes were observed – magnitude 2.5 event near Hostěradice in 2000, perhaps induced event near Uhřice in 2003 with magnitude of 0.7 and magnitude 1.4 earthquake near Božice in 2006.A sequence of four weak earthquakes in June 2014 is only the fourth occurrence of earthquakes in southern Moravia since the beginning of instrumental measurements. Events originated near Hostěradice (SE margin of the Bohemian Massif), 40 km southwest of Brno. The strongest event reaching local magnitude of 2.0 occurred on June 1, 2014 at 00:43 UTC. It was felt by people close to the epicentre with a macroseismic intensity 4 European Macroseismic Scale EMS-98. A temporary seismic station was immediately installed in the epicentral area. The station recorded two of four shocks and helped to confi rm a focus position of the sequence: 48.95° N 16.24° E, depth 3 km.In 2014 a review of historical earthquakes in this region was conducted using new catalogues of historical earthquakes in neighboring countries in order to avoid confusion between local and regional phenomena. Some new information sources were found. In any case, historical earthquakes in this region are very rare and most of them are poorly substantiated

Earthquake in the Hrubý Jeseník Mts. on 14. 6. 2012

A sequence of very weak earthquakes was recorded by local seismic stations in Hrubý Jeseník Mts. (NE part of the Czech Republic) in June and July 2012. The strongest event with local magnitude 2.3 on June 14, 2012 at 21:38 UTC was felt by people to 20 km around the epicentre with a macroseismic intensity 3–4° EMS-98. In spite of the fact that calculated focal mechanisms are still missing, the spatial extent of microearthquake epicentres suggests that the local seismicity is co-determined by the activity of the Klepáčov fault and the Sudetic Marginal – Bělá fault system.A sequence of very weak earthquakes was recorded by local seismic stations in Hrubý Jeseník Mts. (NE part of the Czech Republic) in June and July 2012. The strongest event with local magnitude 2.3 on June 14, 2012 at 21:38 UTC was felt by people to 20 km around the epicentre with a macroseismic intensity 3–4° EMS-98. In spite of the fact that calculated focal mechanisms are still missing, the spatial extent of microearthquake epicentres suggests that the local seismicity is co-determined by the activity of the Klepáčov fault and the Sudetic Marginal – Bělá fault system

MOBILIZACE CHEMICKÝCH SLOŽEK STRUSKOVÉ DEPONIE V NÁRODNÍ PŘÍRODNÍ REZERVACI RUDICKÉ PROPADÁNÍ

The Rudice swallow hole (Rudické propadání) National Nature Monument is a locality affected by occasional mass movements and landslides. During exceptional rainfall events, the slag material from the slopes of a small valley called “Ve struskách” (“In the Slags”) slides into an episodic stream, which enters the local karst system near the swallow hole of the Jedovnice Creek (Jedovnický potok).The slag was dumped in the locality in consequence of the past processing of iron ore in blast furnaces, which had been built near Jedovnice by the princely Salm family in the 19th century. Even though the blast furnaces were closed down a hundred years ago, the slag components leaking into the Rudice stream sink cave system still demonstrably damage the speleothems. This was the majorimpulse for us to have a closer look at the geochemical properties of the slag.The chemical composition was determined by silicate analyses carried out in the Institute of Geological Sciences at the Faculty of Sciences of the Masaryk University in Brno and in the ACME laboratories in Canada. The ACME laboratories determined heavy metal contents by atomic absorption spectroscopy (AAS) and by inductively coupled plasma mass spectrometry (ICP-MS). The petrographic characterization of the slag and its enclosures was conducted based on point analyses by a wavelength dispersive X ray (WDX) electron microprobe. Predictions regarding the geochemical behavior of the slag components in an aqueous environment were made using the sequential extraction analysis (SEA) according to Tessier (1979).We have found the expected spatial variability of the basic chemical composition of the slag dumps, as well as the presence of heavy metals (cadmium and especially zinc are present at high concentrations).The slag material exhibits a glassy amorphous structure containing occasional mineral crystals, droplets of pure or oxidized iron and fragments of other materials (such as charcoal or blast furnace bricks). The ongoing weathering of the slag is accompanied by oxidation of crude iron and formation of limonite. Apart from that, the material is not subject to signifi cant secondary transformations. The results of the sequential extraction analyses of slag and soil samples suggest that Cd and Zn are chemically bound to the “carbonate fraction”, which, in general, tends to dissolve under acidic conditions. Even though the environment of the carbonate rock cave systems is typically alkaline, there is a persisting risk of mobilization of heavy metals by acid soil solutions. From the environmental point of view, the slag deposition primarily represents a source of clastic material, which contaminates the cave system and damages speleothems by mechanical abrasion