During routine processing of selected events of an active KTB experiment it has appeared doubts concerning data reliability and consequently the reliability of results based on them. In the paper 3 events are studied in detail, full seismic moment tensors, as well as their errors, are determined (by non-linear inversion of P/SH waves ratios). It is shown that for the processed low constrained data moment tensor (MT) can be determined, however the relative error is of order of first tens of percent; the results also considerably depend on the way of data picking, used medium model, way of Cost function construction, etc. Any subsequent geophysical interpretation therefore should takes into account this uncertainty. MTs are finally decomposed into DC and non-DC parts, MTs errors are also transformed., Petr Kolář., and Obsahuje bibliografii
A quantitatively new analog-to-digital converter (ADC) module has been developed during 2010, in co-operation with Tedia Ltd. The module has a 28-bit final resolution and uses 32-bit arithmetic. There are two versions, with four and twelve analog inputs. The 4-input module replaces the original 21-bit version, produced until 2009. The 12-input module is intended to be deployed in small-aperture seismic arrays. The whole set consists of four 3-channel detached modules that can be interconnected with the main module using a cable of up to 100 m in length. This design increases signal-to-noise ratio (SNR) by placing the A/D part as close to the seismograph as possible in order to transmit digital data for storage. All channels are sampled coherently so that all four sensors are automatically synchronised. It allows the detection of local events even though the sync-signal is absent. In other words, the 12-input module is suitable for ad-hoc field measurements even in places where there is no GPS signal. All arrays operated by the Institute of Rock Structure and Mechanics (IRSM) are going to be upgraded to use these modules and some new sites will also be set-up with this innovative equipment (e.g. Lazy in Western Bohemia and Dobrá Voda in Slovakia)., Milan Brož and Jaroslav Štrunc., and Obsahuje bibliografii
Analyzing the earthquake catalogue of the Upper Egypt area since 1982 revealed some char acteristics of the seismic activity in the area. Construction of a seismicity map according to the seismicity level in the Upper Egypt showed 14 seismic zones and that the seismic activity is intense around the stra it of the Gulf of Suez, along the Red Sea axis, Abu Dabbab and Aswan area. While the detailed study of Aswan zone showed 8 distinct sub-seismic zones and that the activity is concentrated in and around Gable Marawa area. The b-value was calculated for each seismic zone; it is found that the highest value is in Abu Dabbab area followed by Aswan area. A seismic energy rele ased map of the Upper Egypt was constructed for the period from 1982 to 2006; the map reveals the main active zones with high energy values. The study gives new insight for a better understanding of the seismic activity in the Upper Egypt and helps in the seismic hazard assessment., Haggag Hamed Mohamed, Gaber Hassan Hassib, Sayed Abdalah Dahy and Ezzat Mohamed El-Amin., and Obsahuje bibliografické odkazy
Fractures commonly existing in rocks flow on their elastic properties and hence on velocity of seismic waves propagating in the rock mass. This relation allows to use seismic methods to determine the fracture density and the orientation of fracture sets. This paper presents results of the research which concern directional changes of dynamic elastic moduli in sedimentary and igneous rocks from south part of Poland. These moduli depend on density of the rock matrix as well as density and orientation of cracks and flow on seismic wave velocity. The seismic equipment Terraloc MK6 (ABEM) was used for the measurements of seismic wave velocity in the surface layers of rock mass. The research was made along precise oriented radial seismic profiles. P-waves and S-waves ve locities were established from recorded seism ograms. The values of P and S waves velocity allowed to calculate values of dynamic elastic moduli for all profiles. The results were presented on diagrams of azimuth distribution of elastic moduli, and diagrams of dynamic elastic moduli versus P - wave velocity. The diagrams showed an anisotropy of elastic properties of the investigated rocks. The maximal values of moduli agree with maximal values of velocity and also with orientation of main crack sets or potential directions of weakening of rock mass. Obtained results point that the seismic methods allow to assign the directions of weakening of rocks what can be for example use during preliminary designing, constructing and exploitation of tunnels., Iwona Stan - Kleczek and Adam F. Idziak., and Obsahuje bibliografické odkazy
Classical Russian pendulum seismometer S-5-S was modified for recording of the rotational components of ground motion around the vertical or horizontal axes; the modified sensor is denoted here as S-5-SR. Experimental field testing of the S-5-SR sensor started in December 2010 in the Karvina coal region that is known as an area of intensive mining induced seismicity. First seismic station was installed in Doubrava village characterized by thick sedimentary layers. Next seismic station was installed in Orlova village, in different local geological conditions, i.e. in region without sedimentary layers. More than 200 mining induced seismic events were recorded on each seismic station during the period of six months of seismic monitoring. The recorded wave patterns confirm the existence of rotational ground motion components in this region; the strongest recorded value of this component exceeded 1 mrad.s-1. Analysis of the obtained records is presented in this paper., Zdeněk Kaláb, Jaromír Knejzlík and Markéta Lednická., and Obsahuje bibliografii
P-wave velocity anisotropy of rocks is often investigated by laboratory methods. The extrapolation of the laboratory results to larger rock units requires comparison with direct field measurements. Physical properties of deep-originated rocks were performed on mantle-derived peridotite from the Ivrea zone (N orthwestern Italy). These rock s were exhumed by tectonic processes during collision orogeny up to the Earth’s surface. The direct surface seismic measurements of elastic waves velocity were realized by means of shallow seismic refraction method on the outcrop of peridotite. The measuring base was about 10 m long. Laboratory seismic anisotropy measurement was realized on rock samples from the same outcrop. The geographically oriented spherical samples with diameter 50 mm were radiated by elastic waves in 132 directions under confining stress from atmospheric level up to 200 MPa. Laboratory and field values of the anisotropy of seismic wave ve locities were compared and different scales of measurements were evaluated. The field measuremen ts used frequency about 1 kHz whereas the laboratory measur ement used 700 kHz radiation. Field measurements proved relatively high value of anisotropy P-wave propagation - 25%, while laboratory experiments only 1.5%. This difference is caused by different reason of anisotropy. Laboratory samples contain only microcraks, which represents nearly continuum with rega rd to ultrasound wave length (11 mm). Rock massif, however, contains beside mickrocraks also cracks with comparable size of applied seismic wave length (10 m)., Jan Vilhelm, Vladimír Rudajev, Roman Živor, Tomáš Lokajíček and Zdeněk Pros., and Obsahuje bibliografické odkazy
The paper presents selected results of seismological observations in Silesia and northern Moravia between 01/2004 - 08/2008, which are based on interpretation of three-component digital recordings at solitary seismic stations operated by the Institute of Geonics of the ASCR Ostrava (IGN) distributed in the region under investigation. Five seismic stations had recorded local tectonic seismic events in a continuous regime until 12/2005, when the grant project GA CR No. 205/03/0999 terminated. Meanwhile, the Ostrava - Krásné Pole (OKC) seismic station have continued in operation as a part of the Czech regional seismological network since 1983 up to present. Other three stations have been operating in a so-called triggered regime. At the mid-January 2007, seismic station in Klokočov village was re-opened in continuous regime. During 55 months of observation, 90 tectonic events have been detected at one or more seismic stations mentioned above. However, database of the Institute of Physics of the Earth of the MU contains more than 640 microearthquakes during the same time. This discrepancy is caused mainly due to a higher concentration of microearthquake foci distributed all over the western part of the region under investigation where the IPE seismic stations are situated. On the other hand, the IGN seismic stations are spread predominantly within the eastern part of the territory, i.e. relatively far from the recent foci, and moreover, some stations are operated using the triggered regime., Karel Holub, Zdeněk Kaláb, Jaromír Knejzlík and Jana Rušajová., and Obsahuje bibliografii
Experimental geomechanical and seismological measurements are performed in the medieval Jeroným Mine near Čistá (Sokolov district). The main aim of this activity is geomech anical stability evaluation of this monument. Periodical monitoring was started in 2001 whereas quarterly period was applied (measurement of crack development in the mine working, development in changes in convergence cross-sections of linear and spatial workings and fluctuations of water levels in underground spaces). Seismological monitoring was started during reconstruction of partly impassable drainage adit. At present, selected parts of described geomechanical system are newly instrumented to obtain continuous information. Data obtained from periodical and continuous monitoring are presented in this contribution. Interpretation of seismological data on both natural and technical seismicity and fluctuations of water levels is presented in details., Zdeněk Kaláb, Jaromír Knejzlík, Robert Kořínek, Radovan Kukutsch, Markéta Lednická and Petr Žůrek., and Obsahuje bibliografické odkazy
The aim of this paper is to present the results of an investigation of induced seismic events which occurred during mining in the coalfields of Plants Paskov and Staříč of the Paskov Mine which belong to the southern part of the Ostrava-Karviná coal mines. Some results obtained in the time period January 1992 - December 2002 have already been published, and therefore, are mentioned here only briefly. The paper is based on new results of seismological observations at the OKC, KLOK, STEB seismic stations operated by the Institute of Geonics AS CR and stations of the Green Gas DPB, a.s., Paskov. A total of 26 seismic events were monitored from January 2008 to February 2012, most of them were localized into the area under study. As for the energy span of individual events according to the energetic classification of the Geophysical Centre of the Green Gas DPB, a.s., Paskov, all seismic events in Table 1 were estimated within the limits E(J) <5.0 ×102 ÷ 2.0 × 104>., Karel Holub, Jana Rušajová and Josef Holečko., and Obsahuje bibliografii
The essential point for seismological observation in the northern part of Moravia, Czech Republic, is a permanent seismic station Ostrava - Krásné Pole (OKC) that is a part of the Czech regional seismological network (hereafter CRSN). Institute o f Geonics AS CR, v.v.i., has also operated temporary seismic stations in this region since 1997. Current seismological stations are located in an abandoned mine working located in Zlaté Hory and in cellars in Klokočov and castle Raduň near Opava. The natural seismicity is after the swarm of microearthquakes in the vicinity of Opava in 1993 very low now. In region under discussion, seismic manifestations generated by mining induced seismicity in Upper Silesian Coal Basin (both Karviná an d Polish parts) and in Legnica-Głogów Copper District (LGOM) are also detected. Significant part of observations in this region is made by the Institute of Physics of the Earth (hereafter IPE), Masaryk University Brno, and about 1000 microearthquakes have been detected during the last ten years with maximum local magnitude up to 1.9., Zdeněk Kaláb, Jaromír Knejzlík and Karel Holub., and Obsahuje bibliografické odkazy