The study of select physical fields and their manifestations in the rock massif and observatory activities.
The first studies of the given region were initiated in 1997. Monitoring of regional seismic activity, establishment of solitaire stations, identification of records and detailed interpretation of seismic events are basic activities. Obtained data is also used to study the velocity field of seismic waves in the region under study and to determine the character and properties of recorded surface waves generated by quarry blasts. Conduction of the seismic station Ostrava-Krasne Pole (OKC) which is part of the Czech Regional Seismic Network is realized in cooperation with the Geophysical Institute of AS CR, Prague and VSB- Technical University of Ostrava. In the frame of cooperation with the Institute of Physics of the Earth in Brno (IPE) the exchange of seismic data related to local tectonic events has been performed.
The main aim is to explore by experiments and calculations the dynamic behaviour of technological structures and buildings that are under non-stationary dynamic loads. this is caused by technical seismicity, especially by seismicity induced by mining activities in the Karvina region. Measurements at solitaire permanent stations are performed and also some short-term measurements are realized. Surface geodetic measurements for the study of sinking effects during initial periods of underground mining are realized and new methods for the joint interpretation of geodetic and geophysical data are developed.
This topic results from joint research theme with prof. Lyubushin from the Institute of Physics of the Earth, Russian Academy of Sciences, Moscow (e.g. using of wavelet transform for seismological studies) and the use of historical mines as a natural laboratory for research of a new methodology for geomechanical measurements is part of this topic.
The development of special instrumentation for geophysical measurements, measurement and interpretation of technical seismicity, and the operation and interpretation of geodetic and geophysical measurement for shallow depths are other activities of the department.
Natural seismicity since 1993 has been very low. Almost 100 local microearthquakes were detected at solitaire seismic stations of the Institute of Geonics AS CR; some of them were successfully located. In the region under discussion, seismic manifestations generated by mining induced seismicity in Upper Silesian Coal Basin (both Karvina and Polish parts), Legnica-G³ogow Copper District and Lubin Copper Basin are detected. For example, during the year 2007 14 rockbursts from Ostrava-Karvina Coal Basin were recorded having a local magnitude span of ML = 2.0- 2.8 and two were felt on the surface with a macroseismic intensity of I0 = 2.0.
Using data from seismic refraction measurements, a 1D shallow velocity model was established for the first time. For the determination of the velocity-depth function along a short refraction profile, the classical Wiechert-Herglotz method was used. This method seems to be a robust method for computing simple vertically inhomogeneous models of shallow structures, as far as the observed travel-time curve is sufficiently smoothed. The model is characterized by a relatively low superficial velocity vP ~ 4.5 km/s which is followed by a steep increase of velocity vP ~ 5.8 km/s to a depth of about 1.5 km.
The 3D velocity model is based on data collected between the years 2000 and 2009. It was set up by means of seismic tomography and is valid only for the territory of Northern Moravia and Silesia. The research issues are from reinterpretation of data from international and local seismic field experiments and records from permanent and temporary seismic stations. Records of quarry blasts, mining induced seismic events and local microearthquakes are used. For better inspection of the calculated model within the space, special software packages were applied for the purpose of its visualization and animation.
The research is of a mutual link-up with long-period microseisms (T = 4-8 s) and the current meteorological situation in the broad area of the European continent. Observation of the microseisms' amplitude level is based on a long-term series of observations and their changes depending on the season of the year and the position of atmospheric pressure configurations above oceans and continents. The first results are related to two strong windstorms Kyrill and Emma which occurred in mid-January 2007 and at the turn of February and March 2008 have already been published.
The main goal is observing the development of subsidence depressions with a view to the irregularity in processes causing movement and deformations that are evoked first of all by the rock massif pattern. A partial goal is to observe the boundary of subsidence depressions with special emphasis on determining the possible subsequent causes of slight vertical movements.
The partial aims are using a wavelet transform for signal filtrations, determination of optimal wavelet base (according to the minimum optimum entropy) and optimal levels for packet decomposition. Spatial mapping is used to plan the absolute values of wavelet coefficients, it gives a concise presentation of the decomposed signal in time-frequency domain. Analysis of long-term seismological records and multifractal analysis of long-term geomechanical measurements are partial subjects.
Studies use a distributed measurement system for the evaluation of seismic load, changes of mine water level, development of failures in the rock massif, changes of underground spaces (deformation of spaces) and changes of stress tensor in the rock massif which are gradually occurring in a medieval tin mine. Today, almost 20 sensors are used. A single-board PC of seismic apparatus is used as a base for the control system. Transmission via GSM network enables us to control the system and also to transfer measured data to the operating system at the Institute of Geonics. This system provides data for the study of the stability of mine spaces, in which a new museum is planned.
The main goal is to study the seismic effects generated by blasting operations or other manifestations of technical seismicity, which occur in the vicinity of driving of shallow underground constructions. Vibration effects in urban areas in orabove driven constructions or suburban tunnels are very representative examples that illustrate the urgency of research because of structural damage that has occurred.
The Solution of the partial topic of the Research Programme of the AS CR: The study of select physical fields and their manifestations in the rock massif and observatory activity.
Solution of two projects of Czech Grant Foundation:
The solution of the joint research theme was in frame of cooperation of Russian and Czech Academies named Analysis of geophysical data using modern mathematic methods.
Organisation of 19th regional conference of seismologists, engineering geophysicist and geotechnical engineers with international participation (April 2010): New Knowledge and Measurements in Seismology, Engineering Geophysics and Geotechnics OVA'10.
Co-operation with VSB – Technical University of Ostrava: Joint scientific laboratory with Department of geotechnics and underground engineering, Faculty of Civil Engineering, topic Measurement and analysis of technical seismicity.