Depth-Recursive Tomography of the Bohemian Massif at the CEL09 Transect—Part A: Resolution Estimates and Deblurring Aspects
- 101 Downloads
The refraction CEL09 profile from the CELEBRATION 2000 project intersects the main terranes of the Bohemian Massif in the NW–SE direction: the Saxothuringian, the Teplá-Barrandian, the Moldanubian and the Moravo-Silesian. In its easternmost part, it crosses the Western Outer Carpathians overthrust westward onto the Bohemian Massif. Only the first 450 km were surveyed with the densest deployment of shot points providing data suitable for a reliable geological interpretation. The first-arrival depth-recursive tomography was applied here to derive a P-wave velocity image of the upper and middle crust (Part A). The proper interpretation of the obtained velocity features is the subject of the accompanying paper (Part B). The attained resolution in the velocity image is shown to be superior as compared with the previous CEL09 models based also on the more uncertain later arrivals of reflection waves. The applied DRTG (depth-recursive tomography on grid) method is based on a regular network of refraction grid rays generated for iteratively updated starting models. Only the distinct first arrivals with minimum uncertainty are used for the DRTG inversions to yield the maximum resolution. Thanks to the full control of the data fit by the grid rays used, the statistical lateral resolution could be determined at single grid depths for the chosen confidence levels. Thus, the lateral sizes of the anomalies that can be yet resolved are determined in dependence on their depths and their velocity excesses. The defocusing of the imaged features is studied on the basis of the spatial responses to spike excitation. The calculated spatial responses also allowed the edge smearing of the velocity anomalies to be assessed. Special attention is paid to the imaging of low-velocity zones that are usually suppressed by the smoothing measures used in standard tomographic methods. An improvement was achieved if the smoothing was suggested with regard to the occurrence of the low-velocity zones repeatedly appearing in higher iterations. The gained deblurring effect concerns both the negative and positive anomalies as documented on the velocity features interpreted in the accompanying paper.
KeywordsRefraction tomography Depth-recursive tomography Lateral resolution Impulse response Two-point resolution Deblurring of velocity image CEL09 refraction profile Bohemian Massif
This study was supported by Project LA08036 of the Program INGO of the Ministry of Education of the Czech Republic. The CELEBRATION 2000 data on Czech territory were acquired thanks to the Research Project No. 630/3/00 granted by the Ministry of the Environment of the Czech Republic and wide international cooperation, mainly with the Polish State Committee for Scientific Research, Ministry of the Environment and the Association for Deep Geological Investigations in Poland. Most of the instrumentation for the CELEBRATION 2000 seismic experiment was provided through grants to the University of Texas at El Paso, USA. The author is grateful to all reviewers whose careful reviews contributed to improvement of this paper.
- Aki K, Richards PG (1980) Quantitative seismology, volume II. W. H. Freeman and Company, San FranciscoGoogle Scholar
- Grad M, Guterch A, Mazur S, Keller GR, Špičák A, Hrubcová P, Geissler WH (2008) Lithospheric structure of the Bohemian Massif and adjacent Variscan belt in central Europe based on profile S01 from the SUDETES 2003 experiment. J Geophys Res 113:B10304. doi: 10.1029/2007JB005497
- Novotný M (1981) Two methods of solving the linearized two-dimensional inverse seismic kinematic problems. J Geophys 50:7–15Google Scholar
- Novotný M (2012) Depth-recursive tomography of Bohemian Massif at Cel09 transect—Part B: interpretation. Surv Geophys (in preparation)Google Scholar
- Novotný M, Skácelová Z, Mrlina J, Mlčoch B, Růžek B (2009) Depth-recursive tomography along the Eger Rift using the S01 profile refraction data: tested at the KTB super drilling hole, structural interpretation supported by magnetic, gravity and petrophysical data. Surv Geophys 30:561–600. doi: 10.1007/s10712-009-9068-0 CrossRefGoogle Scholar
- Novotný M, Špičák A, Weinlich FH (2011) Depth-recursive tomography reveals the focal zones of West Bohemian earthquake swarms and their sealing caps as distinct low and high-velocity anomalies. The IUGG 2011 Abstract Proceedings, Abstract ID 2429, Melbourne, AustraliaGoogle Scholar
- Švancara J, Chlupáčová M (1997) Density model of geological structure along the profile 9HR. In: Vrána S, Štědrá V (eds) Geological model of western Bohemia related to the KTB borehole in Germany. J Geol Sci 47:32–36 (Prague)Google Scholar
- Švancara J, Špaček P, Hubatka F (2005) Chap. 3 in Novotný M et al. SLICE-seismic lithospheric investigation of Central Europe (in Czech). Final report, Czech Geological Survey—Geofond, PragueGoogle Scholar
- Tomek Č, Dvořáková V, Vrána S (1997) Geological interpretation of the 9HR and 503M seismic profiles in western Bohemia. J Geol Sci 47:43–51 PragueGoogle Scholar
- Zelt CA (1994) Software package ZPLOT. Bullard Laboratories, University of Cambridge, CambridgeGoogle Scholar