The present paper describes a method for identification of reflected waves on the seismogr ams from a cluster of quarry blasts. These reflections are used for determination of the Moho depth. Only one seismic station is sufficient, but a cluster of seismic sources is needed. To increase the signal-to-noise ratio of reflected waves, several techniques are applied, such as filtering, polarisation analysis and stacking of seismograms. Th e method was tested on seismic data from the central part of the Ore Mountains region, Czech Republic. Seismic waves were generated by strong quarry blasts at the Tušimice open-pit coal mine, and recorded at the Přísečnice (PRI) temporal seismic station at an epicentral distance of about 16 km. As the station was equipped with a three-component seismograph, also S-wave onsets could be determined. Although Pg, Sg and surface waves dominate the seismograms, weak Moho reflections of P and S waves could also be recognized at travel times of 9.7 s and 17.3 s, respectively. From these times we found the mean ratio of the P- to S-wave ve locities in the crust to be 1.78. Considering P-wave velocity model of Beránek (1971), the observed travel times of the reflections yield a crustal thickness of 29.5 -n31.5 km, which agrees with recent receiver function studies. These agreements indicate that the proposed method of reflected seismic waves, generated by quarry blasts, could represent a simple way for mapping the Moho discontinuity., Hana Kampfová, Jiří Málek and Oldřich Novotný., and Obsahuje bibliografické odkazy
A grant project for the period 2003-2005, supported by the Grant Agency of the Czech Republic, was set up to determine properties of seismic waves and the structure of the uppermost part of the Earth´s crust in the territory of northern Moravia and Silesia. Quarry blasts and mining induced seismic events served as seismic sources. Permanent, temporary and portable seismic stations were used for the monitoring of these seismic events. During the experiments local microearthquakes were also detected and localized. For the complex evaluation of seismic wave features, data of the CELEBRATION 2000 and SUDETES 2003 refraction experiments were incorporated, as well. The velocity-depth dependence of body waves was searched by joint inversions of travel times of Pg/Sg phases. A special feature of the wave trains, generated by quarry blasts, was a pronounced dispersive character of short-period Rayleigh surface waves. These waves enabled us to establish their dispersion curves, on the basis of which the structure of superficial layers was determined down to a depth of several hundreds of meters., Karel Holub, Jaromír Knejzlík, Bohuslav Růžek, Jana Rušajová and Oldřich Novotný., and Obsahuje bibliografii