SFB267
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SFB267
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Deformation and forces at convergent plate margins control the petrophysics and morphology of the subduction channel, fault systems and lithological heterogeneities of convergence zones. Through seismic and seismological imaging and characterization of these features in the Andean Zone, we hope to contribute to the understanding of stress coupling and force transmission across convergent plate boundaries and to the modelling of the material flux in the convergent zones as well as to the modelling of properties of convergent plates. In this way a better understanding of the geophysical signatures of active geodynamic processes at Andean type margins will be achieved. The present seismic and seismological image of the Andean convergence zone is mainly based on the data acquired by the SFB 267 group, DEKORP and the oil industry. The nature and origin of a number of remarkably high reflectivity zones as well as zones of very high seismic attenuation in different tectonic positions is still not yet fully understood. Further, it is not clear which of these anomalies are typical for which specific convergence zone enviroments. Seismic depth slices generally show reflection bands with laterally varying reflection strengths and thicknesses of up to 10 kilometers. We will employ true-amplitude, prestack depth imaging in conjunction with waveform modelling for statistically heterogeneous media in the Central and Southern Andes, in order to investigate the nature of the observed reflectors. Moreover, we propose to study statistical properties of small scale heterogeneities of the lithosphere and their contribution to the seismic attenuation, using the techniques of wave propagation in random media applied to local and regional seismic events. Finally, we want to compare the seismic images with the fine scale seismicity structure in the seismogenic contact zone, determined by high precision earthquake locations using relative relocation techniques. Closely linked to this issue is the question of the existence of a double seismic zone in this region. The comparison of results from the Central and Southern Andes will yield similarities and differences between an accretionary and an erosive continental margin.
References:
Here are two examples of the obtained results:
- ANCORP Working Group, Seismic imaging of a convergent continental margin and plateau in the central Andes (Andean Continental Research Project 1996 (ANCORP'96)). J. Geophys. Res., Vol. 108, No. B7, 2328, 10.1029/2002JB001771, 2003.
- Buske, S., Lüth, S., Meyer, H., Patzig, R., Reichert, C., Shapiro, S., Wigger, P. and Yoon, M., Broad depth range seismic imaging of the subducted Nazca Slab, North Chile. Tectonophysics, 350(4), 273-282, 2002.
- Patzig, R., Shapiro, S.A., Asch, G., Giese, P. and Wigger, P., Seismogenic plane of the northern Andean Subduction Zone from aftershocks of the Antofagasta (Chile) 1995 earthquake. Geophysical Research Letters, 29(8), 10.1029/2001GL013244, 2002.
- Patzig, R., Local earthquake tomography in the Antofagasta region (northern Chile) and a view on the magnitude-frequency parameters in that region. PhD thesis (in german), Institute of Geology, Geophysics and Geoinformatics, Free University of Berlin, Berliner Geowissenschaftliche Abhandlungen, Band 36, Reihe B, 2000.
- Yoon, M., Buske, S., Lüth, S., Schulze, A., Shapiro, S.A., Stiller, M. and Wigger, P., Along-strike variations of crustal reflectivity related to the Andean subduction process . Geophysical Research Letters, vol. 30, No. 4, 10.1029/2002GL015848, 2003.
- Yoon, M., Application of True Amplitude Prestack Migration to a deep seismic dataset (ANCORP, Chile & Bolivia). Master thesis, Institute of Geology, Geophysics and Geoinformatics, Free University of Berlin, 2001.
The CINCA line SO104-13 processed by Christof Sick:
The ANCORP line processed by Mi-Kyung Yoon:
For more information please contact Serge Shapiro, Stefan Buske, Christof Sick, Peter Wigger or Mi-Kyung Yoon.
