Preserved collisional crustal structure of the southern urals revealed by vibroseis profiling

Science

Volumn 274, Issue 5285, 1996, Pages 224-226

  Echtler, H P ^a   Stiller, M ^a   Steinhoff, F ^a   Krawczyk, C ^a   Suleimanov, A ^b   Spiridonov, V ^b   Knapp, J H ^c   Menshikov, Y ^d   Alvarez Marron J ^e   Yunusov, N ^f  

^a GFZ GERMAN RESEARCH CENTRE FOR GEOSCIENCES   (Germany)

^b Spetsgeofisika   (Russian Federation)

^c Department of Obstetrics Gynecology   (United States)

^d Bazhenov Geophysical Expedition   (Russian Federation)

^e INSTITUTE OF EARTH SCIENCES JAUME ALMERA   (Spain)

^f Bashneftegeofizika   (Russian Federation)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; EARTHQUAKE; GEOGRAPHY; GEOLOGY; GEOMETRY; PRIORITY JOURNAL; SEA; VOLCANO;

COLLISION; CRUSTAL ROOT; CRUSTAL STRUCTURE; SEISMIC EXPERIMENT; TECTONICS;

RUSSIAN FEDERATION, URALS;

EID: 0029663990     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.274.5285.224     Document Type: Article

References (16)

1. K. S. Ivanov, V. N. Puchkov, S. N. Ivanov, Formation of the Earth's Crust of the Urals (Nauka, Moscow, 1986); V. N. Puchkov, Geotectonics 27, 184 (1993).
2. K. S. Ivanov, V. N. Puchkov, S. N. Ivanov, Formation of the Earth's Crust of the Urals (Nauka, Moscow, 1986); V. N. Puchkov, Geotectonics 27, 184 (1993).
3. H. Echtler et al., Sci. Tech. Rep. STR95/01 (GeoForschungsZentrum, Potsdam, Germany, 1995).
4. The geological strip map is based on geologic field work and compilation of existing maps and data sets at a scale of 1:100,000 in cooperation with K. Ivanov and colleagues (Institute of Geology and Geochemistry, Russian Academy of Sciences, Ekaterinburg).
5. The energy source used for the experiment consisted of a five-truck vibrator group (each with a peak force of 10 tons) in the center of an 18-km geophone spread with a 50-m group spacing. Vibrator recording points were spaced 100 to 150 m apart, using a 30-s sweep (10 to 64 Hz), a 10-fold vertical stacking rate, and a 25-s recording time with a sampling rate of 4 ms, resulting in a nominal common depth-point fold of 60 to 90. This section represents processing of the eastern 420 km (out of 465 km) to 18-s TWT (two-way travel time) (∼60 km depth). Processing steps (prestack): trace-individual static time corrections (topography and weathering layer effects), dynamic time corrections (source-receiver distance and subsurface velocity), amplitude corrections (surface condition, spherbal divergence, and absorption), and noise wave elimination (refracted and shear wave energy). Final seismic displays were converted at 400 m above sea level. Depth-conversion of the time section after migration with a spatially variant time-velocity field was derived from the applied migration velocity functions. The uncertainty in the depth calculations caused by velocity inaccuracies is estimated to be ∼3 to 5 km at a depth of 50 km. The high resolution of the seismic sections (>18,500 traces, 25-m spacing, 6400 samples per trace) was simplified for display purposes by building the envelope of each trace and summing each four adjacent traces.
6. A. M. C. Sengör, B. A. Natalyn, V. S. Burtman, Nature 364, 299 (1993).
7. The Rb-Sr whole rock age of the Chebik granite is 267 ± 16 million years [K. S. Ivanov, S. N. Ivanov, Y. L. Ronkin, Yearb. Ekaterinburg 1994, 171 (1995)].
8. M. A. Kamaletdinov, The Nappe Structures of the Urals (Nauka, Moscow, 1974).
9. D. Brown, V. N. Puchkov, J. Alvarez-Marron, A. Perez-Estaun, Earth. Sci. Rev. 40, 125 (1996).
10. The Uraltau anticline comprises subduction-related high-pressure assemblages (eclogites and blueschists) [V. I. Lennykh, in Pre-Ordovician History of the Urals, S. N. Juanova, Ed. (Uralian Scientific Centre, Sverdlovsk, Russia, 1980), pp. 3-40], The Kraka klippe (Fig. 1A) comprises westward-obducted ultramafic, oceanic assemblages rooted in the MUF [G. N. Savelieva, Gabbro-Ultramatic Complexes of Ophiolites of the Urals and their Analogues in the Modern Oceanic Crust (Nauka, Moscow, 1987); (7)].
11. The Uraltau anticline comprises subduction-related high-pressure assemblages (eclogites and blueschists) [V. I. Lennykh, in Pre-Ordovician History of the Urals, S. N. Juanova, Ed. (Uralian Scientific Centre, Sverdlovsk, Russia, 1980), pp. 3-40], The Kraka klippe (Fig. 1A) comprises westward-obducted ultramafic, oceanic assemblages rooted in the MUF [G. N. Savelieva, Gabbro-Ultramatic Complexes of Ophiolites of the Urals and their Analogues in the Modern Oceanic Crust (Nauka, Moscow, 1987); (7)].
12. J. H. Knapp et al., Science 274, 226 (1996).
13. J. H. Knapp et al., EOS 76, 549 (1995)
14. Special volume, Tectonophysics 238 (1994), and numerous references within.
15. R. Berzin et al., Science 274, 220 (1996).
16. Data acquisition in the southern Urals from June to November 1995 involved more than 100 scientists and technicians, not all of whom are named here, but whose contributions are gratefully acknowledged. The German part of URSEIS was funded through the program DEKORP 2000 (grant 03GT94101) by the German Federal Ministry of Science and Technology and was supported by the GeoForschungsZentrum Potsdam; the project also benefited from funding by the German Science Foundation, ROSCOMNEDRA (Committee on Geology and Use of Mineral Resources of the Russian Federation), the Continental Dynamics Program (NSF grant EAR-9418251 to Cornell University), Comision Interministerial de Ciencia y Tecnología, Spain (grant AMB 95-0987E), and International Association for the Cooperation with Scientists from the Former Soviet Union grant 94-1857. This project forms part of EUROPROBE, whose members of the Urals Project have contributed significantly to this work.