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E. Brückl, M. Behm, W. Chwatal:
"The application of signal detection and stacking techniques to refraction seismic data.";
Talk: AGU Fall Meeting San Francisco, San Francisco; 2003-12-08 - 2003-12-12; in: "AGU 2003 Fall Meeting", Vol.84, No.46 (2003), ISSN: 0096-3941.

From 1997 to 2003 large refraction seismic experiments were carried out in order to study the lithosphere of Central Europe and the Alpine area (Guterch et al., 2003). These experiments are characterized by a net of intersecting lines with a total about 1000 seismic recorders. Shots are recorded on all lines deployed contemporaneously. Generally, the seismic records show a high signal to noise ratio and picking the Pn-phase or crustal arrivals can be done accurately. However, in some mountainous areas like the Alps and the Carpathians the quality of the seismic records is severely decreased by poor seismic energy transmission. The application of signal detection and stacking methods can enhance the seismic signal and provide a reliable interpretation even in these areas. Stacking of seismic waveforms makes only sense if constructive interference can be achieved. In refraction studies of the lithosphere we usually do not have the information to establish coherency by appropriate traveltime corrections. Therefore, we apply the STA/LTA (short time average / long time average) signal detection algorithm to the records. The output of the STA/LTA algorithm displays only positive amplitudes and stacking of these traces is very robust (Astiz et al., 1996). The next step is sorting the processed traces to common cell gathers, which cover the investigation area. We use two sorting keys, CMP and SRC\&RCV. The CMP sorting generates trace gathers with midpoints in common cells, the SRC\&RCV generates sorting gathers with the source or the receiver locations in the common cells. Finally, traces within a common cell are stacked in offset bins building one offset stack for each cell. CMP-sorted offset stacks enhance either diving waves like Pg- or Sg-phases, or refracted waves like the Pn-phase in order to extract refractor velocity. SRC\&RCV-sorted offset stacks concentrate on delay times of refractors like the crystalline basement of sedimentary basins or the Moho. The inversion of the data extracted from the stacks is based on tomography and delay time decomposition. The capability of the techniques will be demonstrated by a synthetic data set and real data from the Alpine area. Guterch, A., M. Grad, A. Spicak, E. Brueckl, E. Hegedues, G. R. Keller, H. Thybo and CELEBRATION 2000, ALP 2002, SUDETES 2003 Working Groups (2003). An overview of recent seismic refraction experiments in Central Europe. Stud.Geophys.Geod., in press Astiz, L., P. Earle and P. Shearer (1996). Global stacking of broadband seismograms. Seismological Research Letters, 67, 4, 8-18.

Project Head Ewald Brückl:
ALP 2002 - Ein seismisches 3D-Modell der Ostalpen