Moho Topography Estimation using Interactive Forward Modeling of Gravity Data

Document Type : Research Article

Authors

1 Ph.D. Student, Department of Earth Physics, Institute of Geophysics, University of Tehran, Tehran, Iran

2 Professor, Department of Earth Physics, Institute of Geophysics, University of Tehran, Tehran, Iran

3 Professor, Institute of Geophysics, University of Hamburg, Hamburg, Germany

Abstract

The Moho discontinuity is a boundary between the crust and upper mantle that reveals the difference between them with changes in seismic velocity, density, chemical structure, and constituents. Estimating the Moho depth and studying its lateral changes is one of the important goals of geophysical studies. The current study aims to estimate the depth and topography of the Moho discontinuity in the southwestern part of the Baltic Sea, including parts of the central European system, the Trans-European Suture Zone, Caledonian Crustal Suture, and the Ringkobing-Fyn High. This area has been one of the most attractive regions for Geoscientists in the last decades due to its complicated geological structures caused by different tectonic events. For this purpose, a three-dimensional model of the crustal structures based on gravity data forward modeling in the study area has been presented. Previous seismic / non-seismic results have been used to constrain the model and reduce its degree of freedom. This model includes sedimentary sequences, crustal thickness, Moho topography, and high-velocity lower crust expansion in the region and shows the tectonic structures of the study area. This study used a combination of marine, land, and EGM2008 gravity data and modeled them with IGMAS+, Interactive Gravity and Magnetic Application System. The interactive modeling program allows the user to change the geometry as well as the density and susceptibility of the primary model and observe results quickly during the processing. In the software, the model structure could be be more user friendly by eliminating additional details and dividing the whole model into vertical sections. Our primary model consists of three main layers of sediments, crust and upper mantle. The sedimentary layer is divided into two major parts, pre-Permian and post-Carboniferous. Also, the crustal layer is divided into the upper crust and the high-density lower crust. Besides, the upper crust is composed of the upper crust of the Baltica and the upper crust of Avalonia. The last layer of the model is a part of the upper mantle. The model space consists of 16 vertical planes stretching 385 kilometers east-west with an equal distance of 15 kilometers, covering the entire study area. The initial model was developed based on seismic sections and previous models, and it has been improved using interactive forward modeling of gravity data. The result shows a good agreement between the measured and modeled Bouguer anomaly, and the Root Mean Square Error of the model is 1.12 mGal. The model correlates clearly with major tectonic units. It indicates that the Caledonian collision resulted in the amalgamation of Baltica and Avalonia is the most prominent tectonic event in the area, and the Caledonian crustal suture between them is interpreted from changes in physical parameters at crustal levels. There is a relatively thick crystalline crust in the area, and the depth of Moho discontinuity varies from 26 to 42 km. The results also indicate that the transition from the Paleozoic crust of the Central European Basin to the Precambrian crust of the Eastern European Craton occurs within the Tornquist Zone.

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Andersen, O. B., Knudsen, P., Kenyon, S. and Holmes, S., 2014, Global and arctic marine gravity field from recent satellite altimetry (DTU13). In: 76th EAGE Conference and Exhibition 2014, Extended Abstracts, Amsterdam.
Aichroth, B., Prodehl, C. and Thybo, H., 1992, Crustal structure along the central segment of the EGT from seismic-refraction studies: Tectonophysics, 207(1-2), 43-64.
Artemieva, I. M. and Thybo, H. 2013, EUNAseis: a seismic model for Moho and crustal structure in Europe, Greenland, and the North Atlantic region, Tectonophysics, 609, 97–153.
Ashena, Z., E. Ardestani, V., G. Camacho, A., Dehghani, A. and Fernández, J., 2018, Moho depth determination beneath the Zagros Mountains from 3D inversion of gravity data: Arabian Journal of Geosciences, 11(3), 52.
BABEL Working Group, 1993, Deep Seismic Reflection/Refraction Interpretation of Crustal Structure along Babel Profiles A and B in the Southern Baltic Sea: Geophysical Journal International, 112(3), 325-343.
Baldschuhn, R., Best, G. and Kockel, F., 1991, Inversion tectonics in the North-west German Basin, In: Spencer, A.M. (Ed.), Generation, Accumulation and Production of Europe's Hydrocarbons. Special Publication of the European Association of Petroleum Geoscientists. Vol. 1, 149–159.
Bayer, U., Scheck, M., Rabbel, W., Krawczyk, C. M., Götze, H. J., Stiller, M., Beilecke, T., Marotta, A. M., Barrio-Alvers, L. and Kuder, J., 1999, An integrated study of the NE German Basin: Tectonophysics, 314(1), 285-307.
Berthelsen, A., 1980, Towards a palinspastic tectonic analysis of the Baltic Shield.
Berthelsen, A., 1998, The Tornquist Zone northwest of the Carpathians: an intraplate pseudosuture: Gff, 120(2), 223-230.
Birch, F., 1961, The velocity of compressional waves in rocks to 10 kilobars: 2: Journal of Geophysical Research, 66(7), 2199-2224.
Björck, S., 1995, A review of the history of the Baltic Sea, 13.0-8.0 ka BP: Quaternary international, 27, 19-40.
Blakely, R. J., 1995, Potential theory in gravity and magnetic applications, Cambridge university press, 61-63.
Bleibinhaus, F., Beilecke, T., Bram, K. and Gebrande, H., 1999, A seismic velocity model for the SW Baltic Sea derived from BASIN'96 refraction seismic data: Tectonophysics, 314(1-3), 269-283.
Carlson, R. and Raskin, G., 1984, density of the ocean crust: Nature, 311(5986), 555-558.
Cartwright, J., 1992, The structural evolution of the Ringkobing-Fyn High, in Proceedings Tectonic evolution of the North Sea rifts1992, 200-216.
Christensen, N. I. and Mooney, W. D., 1995, Seismic velocity structure and composition of the continental crust: A global view: Journal of Geophysical Research: Solid Earth, 100(B6), 9761-9788.
Clausen, O. R. and Pedersen, P. K., 1999, Late Triassic structural evolution of the southern margin of the Ringkøbing-Fyn High, Denmark: Marine and Petroleum Geology, 16(7), 653-665.
DEKORP-BASINResearch Group, 1999, Deep crustal structure of the Northeast German basin: New DEKORP-BASIN'96 deep-profiling results: Geology, 27(1), 55-58.
Dragoi‐Stavar, D. and Hall, S., 2009, Gravity modeling of the ocean‐continent transition along the South Atlantic margins: Journal of Geophysical Research: Solid Earth, 114(B9).
Ebbing, J., Braitenberg, C. and Wienecke, S., 2007, Insights into the lithospheric structure and tectonic setting of the Barents Sea region from isostatic considerations, Geophys. J. Int., 171(3), 1390–1403.
Erlström, M., Thomas, S., Deeks, N. and Sivhed, U., 1997, structure and tectonic evolution of the Tornquist Zone and adjacent sedimentary basins in Scania and the southern Baltic Sea area: Tectonophysics, 271(3-4), 191-215.
EUGENO-S Working Group, 1988, Crustal structure and tectonic evolution european of the transition between the Baltic Shield and the North German Caledonides (the EUGENO-S Project): Tectonophysics, 150(3), 253-348.
Gardner, G. F., Gardner, L. and Gregory, A., 1985, Formation velocity and density: the diagnostic basics for stratigraphic traps: Geophysics, 50(11), 2085-2095.
Godfrey, N., Beaudoin, B. and Klemperer, S., 1997, Ophiolitic basement to the Great Valley forearc basin, California, from seismic and gravity data: Implications for crustal growth at the North American continental margin: Geological Society of America Bulletin, 109(12), 1536-1562.
Götze, H. J., 1978, Ein numerisches Verfahren zur Berechnung der gravimetrischen Feldgr aen drei-dimensionaler Modellkörper, Archives for Meteorology Geophysics and Bioclimatology Series A 25, 195–215.
Götze, H.-J. and Lahmeyer, B., 1988, Application of three-dimensional interactive modeling in gravity and magnetics: Geophysics, 53(8), 1096-1108.
Götze, H., 1984, Uber den Einsatz interaktiver Computer graphik im Rahmen 3-dimensionaler Interpretationstechniken in Gravimetrie unt Magnetik: Habilitationsschrift.
Grad, M., Guterch, A. and Lund, C.-E., 1991, Seismic models of the lower lithosphere beneath the southern Baltic Sea between Sweden and Poland, Tectonophysics, 189, 219–227.
Grad, M., Guterch, A. and Mazur, S., 2002, Seismic refraction evidence for crustal structure in the central part of the Trans-European Suture Zone in Poland, in Palaeozoic Amalgamation of Central Europe, Vol. 201, pp. 295–309, eds Winchester, J.A., Pharaoh,
Grad, M., Tiira, T. and Group, E. W., 2009, The Moho depth map of the European Plate: Geophysical Journal International, 176(1), 279-292.
Guterch, A., Grad, M., Thybo, H., Keller, G. and Group, P. W., 1999, POLONAISE'97—an international seismic experiment between Precambrian and Variscan Europe in Poland: Tectonophysics, 314(1-3), 101-121.
Haase, C., Ebbing, J. and Funck, T., 2017, A 3D regional crustal model of the NE Atlantic based on seismic and gravity data: Geological Society, London, Special Publications, 447(1), 233-247.
Habibian, B. D., Brasse, H., Oskooi, B., Ernst, T., Sokolova, E., Varentsov, I. and Group, E. W., 2010, The conductivity structure across the Trans-European Suture Zone from magnetotelluric and magnetovariational data modeling: Physics of the Earth and Planetary Interiors, 183(3-4), 377-386.
Hansen, D., Nielsen, S. and Lykke-Andersen, H., 2000, The post-Triassic evolution of the Sorgenfrei–Tornquist Zone—results from thermo-mechanical modelling: Tectonophysics, 328(3-4), 245-267.
Hansen, M. B., Lykke-Andersen, H., Dehghani, A., Gajewski, D., Hübscher, C., Olesen, M., Reicherter, K., 2005, The Mesozoic–Cenozoic structural framework of the Bay of Kiel area, western Baltic Sea International Journal of Earth Sciences 94:1070-1082.
Hansen, M.B., Scheck-Wenderoth M, Hübscher C, Lykke-Andersen H, Dehghani A, Hell B, Gajewski D (2007) Basin evolution of the northern part of the Northeast German Basin — Insights from a 3D structural model Tectonophysics 437, 1-16.
Harff, J., Björck, S. and Hoth, P., 2011, The Baltic Sea Basin, Springer.
Heinbockel, R. E., 2002, Gravity and magnetic investigations along the Peruvian continental marginDissertation]: Univ. Hamburg. PPN (Catalogue ID): 36154112.I.
Kossow, D., Krawczyk, C., McCann, T., Strecker, M. and Negendank, J. F., 2000, Style and evolution of salt pillows and related structures in the northern part of the Northeast German Basin: International Journal of Earth Sciences, 89(3), 652-664.
Krauss, M., 1994, The tectonic structure below the southern Baltic Sea and its evolution: Zeitschrift für geologische Wissenschaften, Vol. 22, 19-19.
Krawczyk, C., Stiller, M. and Group, D. B. R., 1999, Reflection seismic constraints on Paleozoic crustal structure and Moho beneath the NE German Basin: Tectonophysics, 314(1-3), 241-253.
Larsen, H. C., Saunders, A. D. and Cliff, P. D. (and the Shipboard Scientific Party), 1994, Proceeding of the Drilling Program Initial Report, Ocean Drill. Program, College Station, Tex, 152 pp.
Lokhorst, A., Adlam, K., Brugge, J., David, P., Diapari, L., Fermont, W., Geluk, M., Gerling, P., Heckers, J. and Kockel, F., 1998, NW European Gas Atlas–composition and isotope ratios of natural gases: GIS application on CD-ROM by the British Geological Survey, Bundesanstalt für Geowissenschaften und Rohstoffe, Danmarks og Gronlands Geologiske, Undersogelse, Netherlands Instituut voor Toegepaste geowetenschappen, Panstwowy Instytut Geologiczny, European Union.
Ludwig, W., Nafe, J. and Drake, C. L., 1970, Seismic refraction. In: Maxwell, A.E. The Sea. Wiley-Interscience, New York:53-84
Marello, L., Ebbing, J. and Gernigon, L., 2013, Basement inhomogeneities and crustal setting in the Barents Sea from a combined 3D gravity and magnetic model: Geophysical Journal International, v. 193, no. 2, p. 557-584.
Makris, J., Wang, S.-R., 1994, Crustal structure at the Tornquist–Teisseyre zone in the Southern Baltic Sea, Z. Geol. Wiss. 22 1–2, 47–54.
Maystrenko, Y., Bayer, U. and Scheck-Wenderoth, M., 2005, The Glueckstadt Graben, a sedimentary record between the North and Baltic Sea in north Central Europe: Tectonophysics, 397(1-2), 113-126.
Maystrenko, Y. P. and Scheck-Wenderoth, M., 2013, 3D lithosphere-scale density model of the Central European Basin System and adjacent areas: Tectonophysics, Vol. 601, 53-77.
Mazur, S., Mikolajczak, M., Krzywiec, P., Malinowski, M., Buffenmyer, V. and Lewandowski, M., 2015, Is the Teisseyre‐Tornquist Zone an ancient plate boundary of Baltica?: Tectonics, 34(12), 2465-2477.
Meissner, R., Thybo, H. and Abramovitz, T., 2002, Interwedging and inversion structures around the trans-European suture zone in the Baltic Sea, a manifestation of compressive tectonic phases: Tectonophysics, 360(1-4), 265-280.
Molinari, I., Morelli, A., 2011, EPcrust: a reference crustal model for the European Plate, Geophys. J. Int. 185, 352–364.
Nafe, J. E. and Drake, C. L., 1957, Variation with depth in shallow and deep water marine sediments of porosity, density and the velocities of compressional and shear waves: Geophysics, 22(3), 523-552.
Pail, R., Goiginger, H., Schuh, W. D., Höck, E., Brockmann, J. M., Fecher, T., Gruber, T., Mayer‐Gürr, T., Kusche, J. and Jäggi, A., 2010, Combined satellite gravity field model GOCO01S derived from GOCE and GRACE: Geophysical Research Letters, 37(20), L20314.
Pedersen, T. and Gregersen, S., 1999, Project Tor: deep lithospheric variation across the Sorgenfrei-Tornquist Zone, southern Scandinavia: Bulletin of the Geological Society of Denmark, Vol. 46, 13-24.
Pharaoh, T. C., 1999, Palaeozoic terranes and their lithospheric boundaries within the Trans-European Suture Zone (TESZ): a review: Tectonophysics, 314(1-3), 17-41.
Rabbel, W., Förste, K., Schulze, A., Bittner, R., Röhl, J. and Reichert, J., 1995, A high‐velocity layer in the lower crust of the North German Basin: Terra Nova, 7(3), 327-337.
Reicherter, K., Froitzheim, N., Jarosinski, M., Badura, J., Franzke, H., Hansen, M., Hübscher, C., Müller, R., Poprawa, P. and Reinecker, J., 2008, Alpine tectonics north of the Alps: The geology of central Europe, Vol. 2, 1233-1285.
Salem, A., Green, C., Campbell, S., Fairhead, J. D., Cascone, L. and Moorhead, L., 2013, Moho depth and sediment thickness estimation beneath the Red Sea derived from satellite and terrestrial gravity data: Geophysics, 78(5), G89-G101.
Schäfer, A., Brasse, H. and Hoffmann, N., 2009, Magnetotelluric investigation of the Sorgenfrei-Tornquist Zone and the NE German Basin, in Proceedings Proceedings of the 23rd Schmucker-Weidelt-Colloquium for Electromagnetic Depth Research, Heimvolkshochschule am Seddiner See 2009, Vol. 28, 252-262.
Scheck-Wenderoth, M. and Lamarche, J., 2005, Crustal memory and basin evolution in the Central European Basin System—new insights from a 3D structural model: Tectonophysics,  397(1-2), 143-165.
Schmidt, S. and Götze, H.-J., 1998, Interactive visualization and modification of 3D-models using GIS-functions: Physics and Chemistry of the Earth, 23(3), 289-295.
Schmidt, S., Plonka, C., Götze, H.-J. and Lahmeyer, B., 2011, Hybrid modeling of gravity, gravity gradients and magnetic fields. Geophysical Prospecting, 59(6), 1046-1051.
Shomali, Z. H., Roberts, R. G., Pedersen, L. B. and Group, T. W., 2006, Lithospheric structure of the Tornquist Zone resolved by nonlinear P and S teleseismic tomography along the TOR array: Tectonophysics, 416(1-4), 133-149.
Sippel, J., Scheck-Wenderoth, M., Lewerenz, B. and Kroeger, K. F., 2013, A crust-scale 3D structural model of the Beaufort-Mackenzie Basin (Arctic Canada): Tectonophysics, Vol. 591, 30-51.
Smirnov, M. Y. and Pedersen, L. B., 2009, Magnetotelluric measurements across the Sorgenfrei-Tornquist Zone in southern Sweden and Denmark: Geophysical Journal International, 176(2), 443-456.
Tesauro, M., Kaban, M. K. and Cloetingh, S. A., 2008, EuCRUST-07: A new reference model for the European crust: Geophysical Research Letters, 35(5).
Thybo, H., A, 1990, seismic velocity model along the EGT profile-from the North German Basin into the Baltic Shield, in Proceedings The European Geotraverse: Integrative studies, Results from the earth science study centre. 5, 99-108.
Thybo, H, 2000, Crustal structure and tectonic evolution of the Tornquist Fan region as revealed by geophysical methods: Bulletin of the Geological Society of Denmark, Vol. 46, 145-160.
Thybo, H, 2001, Crustal structure along the EGT profile across the Tornquist Fan interpreted from seismic, gravity and magnetic data: Tectonophysics, 334(3-4), 155-190.
Thybo, H. and Schönharting, G., 1991, Geophysical evidence for Early Permian igneous activity in a transtensional environment, Denmark: Tectonophysics, 189(1-4), 193-208.
Thybo, H., Kiørboe, L. L., Møller, C., Scho¨nharting, G., Berthelsen, A., 1989, Geophysical and tectonic modelling of EUGENO-S Profiles. In: Freeman, R., Mueller, St. (Eds.), Proceedings of the Sixth Workshop on the European Geotraverse Project. ESF, Strasbourg, 93– 104.
Vejbæk, O. V., 1997, Dybe strukturer i danske sedimentære bassiner, Dansk Geologisk Forening= DGF.
Yegorova, T., Bayer, U., Thybo, H., Maystrenko, Y., Scheck-Wenderoth, M. and Lyngsie, S., 2007, Gravity signals from the lithosphere in the Central European Basin System: Tectonophysics, 429(1-2), 133-163.
Ziegler, P. and Dèzes, P., 2006, Crustal evolution of western and central Europe: Geological Society, London, Memoirs, 32(1), 43-56.
Ziegler, P. A., Geological atlas of western and central Europe1990, Geological Society of London.
Zielhuis, A. and Nolet, G., 1994, Shear-wave velocity variations in the upper mantle beneath central Europe: Geophysical Journal International, 117(3), 695-715.