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GPS Measurements of Crustal Deformation in the Baikal-Mongolia Area (1994-2002) : Implications for Current Kinematics of Asia E

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GPS Measurements of Crustal Deformation in the Baikal-Mongolia Area (1994-2002) : Implications for Current Kinematics of Asia E GPS measurements of crustal deformation in the Baikal-Mongolia area (1994-2002) : Implications for current kinematics of Asia E. Calais, M. Vergnolle, V. San’Kov, A. Lukhnev, A. Miroshnitchenko, S. Amarjargal, Jacques Déverchère To cite this version: E. Calais, M. Vergnolle, V. San’Kov, A. Lukhnev, A. Miroshnitchenko, et al.. GPS measurements of crustal deformation in the Baikal-Mongolia area (1994-2002) : Implications for current kinematics of Asia. Journal of Geophysical Research, American Geophysical Union, 2003, 108 (B10), pp.ETG 14-1. 10.1029/2002JB002373. hal-00406988 HAL Id: hal-00406988 https://hal.archives-ouvertes.fr/hal-00406988 Submitted on 29 Jan 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. B10, 2501, doi:10.1029/2002JB002373, 2003 GPS measurements of crustal deformation in the Baikal-Mongolia area (1994–2002): Implications for current kinematics of Asia Eric Calais,1 Mathilde Vergnolle,2 Vladimir San’kov,3 Andrei Lukhnev,3 Andrei Miroshnitchenko,3 Sharavyn Amarjargal,4 and Jacques De´verche`re5 Received 27 December 2002; revised 5 May 2003; accepted 14 May 2003; published 25 October 2003. [1] We present new geodetic results of crustal velocities over a large part of northern Asia based on GPS measurements in the Baikal rift zone and Mongolia spanning the 1994– 2002 period. We combine our results with the GPS velocity field for China of Wang et al. [2001] and derive a consistent velocity field for most of Asia. We find contrasted kinematic and strain regimes in Mongolia, with northward velocities and N-S shortening in westernmost Mongolia but eastward to southeastward motion and left-lateral shear for central and eastern Mongolia. This eastward to southeastward motion of central and eastern Mongolia is accommodated by left-lateral slip on the E-W trending Tunka, Bolnay, and Gobi Altay faults (2 ± 1.2 mm yrÀ1, 2.6 ± 1.0 mm yrÀ1, and 1.2 mm yrÀ1, respectively) and by about 4 mm yrÀ1 of extension across the Baikal rift zone. Consequently, 15% of the India-Eurasia convergence is accommodated north of the Tien Shan, by N-S shortening combined with dextral shear in the Mongolian Altay and by eastward displacements along major left-lateral strike-slip faults in central and eastern Mongolia. We find a counterclockwise rotation of north and south China as a quasi-rigid block around a pole north of the Stanovoy belt, which rules out the existence of an Amurian plate as previously defined and implies <2 mm yrÀ1 of left-lateral slip on the Qinling Shan fault zone. INDEX TERMS: 1208 Geodesy and Gravity: Crustal movements—intraplate (8110); 1244 Geodesy and Gravity: Standards and absolute measurements; 8107 Tectonophysics: Continental neotectonics; 9320 Information Related to Geographic Region: Asia; KEYWORDS: continental deformation, active faults, GPS, Mongolia, Baikal, Asia Citation: Calais, E., M. Vergnolle, V. San’kov, A. Lukhnev, A. Miroshnitchenko, S. Amarjargal, and J. De´verche`re, GPS measurements of crustal deformation in the Baikal-Mongolia area (1994–2002): Implications for current kinematics of Asia, J. Geophys. Res., 108(B10), 2501, doi:10.1029/2002JB002373, 2003. 1. Introduction [3] Asia is the major example of present-day deformation of a large continental domain (Figure 1). Current deformation [2] The ability of plate tectonics concepts to describe in Asia is distributed over a broad area extending from the deformation of large continental areas like Asia or the Himalayas in the south to the Baikal rift zone in the north, western United States is subject to much debate. End-mem- with a number of rigid blocks such as the Tarim basin, south ber models assume that continents deform either by rigid China, north China, and the Sunda block, embedded in the motion of lithospheric blocks along narrow fault zones or by deforming zone. The analysis of Landsat imagery in the late viscous flow as continuously deforming solids. Discriminat- 1970s [Tapponnier and Molnar, 1977, 1979] together with ing these end-member models requires spatially dense mea- geologic and seismological data [e.g., Molnar and Deng, surements of surface strain rates covering the whole 1984; Molnar et al., 1987] led to the identification of a deforming area, including areas outside the obvious active limited number of large strike-slip faults straddling Asia, faults and plate boundary zones. accommodating lateral displacements of these rigid litho- spheric blocks. Some of the India-Eurasia convergence is 1 Department of Earth and Atmospheric Sciences, Purdue University, also accommodated by thrusting and crustal shortening in West Lafayette, Indiana, USA. 2UMR CNRS 6526, University of Nice, Valbonne, France. high topography compressional ranges such as the Hima- 3Institute of the Earth’s Crust, Siberian Branch of the Russian Academy layas, the Pamir-Tien Shan range, the Mongolian Altay, and of Sciences, Irkutsk, Russia. the Gobi Altay. In addition, Asia is characterized by two 4Research Center for Astronomy and Geophysics, Ulan Baatar, broad high elevation plateaus, the Tibetan and Mongolia Mongolia. plateaus, with an average elevation of 5000 and 2500 m and 5UMR CNRS 6538, University Bretagne Occidentale, Plouzane´, France. crustal thicknesses up to 70 and 50 km, respectively. Copyright 2003 by the American Geophysical Union. [4] It was recognized early on that intracontinental defor- 0148-0227/03/2002JB002373$09.00 mation in Asia was the result of the collision between India ETG 14 - 1 ETG 14 - 2 CALAIS ET AL.: GPS MEASUREMENTS IN MONGOLIA Figure 1. Topography, main active faults, and index of the geographical names used in this paper. The box centered on Mongolia shows the study area, shown in more detail on Figure 2. and Eurasia [Argand,1924].Sincethen,anumberof al., 1997; Paul et al., 2001; Calais et al., 1998; Larson et deformation models have been proposed to explain the al., 1999; Heki et al., 1999; Shen et al., 2000; Chen et al., available geological and geophysical data sets. ‘‘Kinematic’’ 2000; Kogan et al., 2000; Calais and Amarjargal, 2000; models propose that continental deformation occurs by Bendick et al., 2000; Wang et al., 2001; Calais et al., 2002]. eastward extrusion of lithospheric blocks of quasi-rigid One of the main motivations for geodetic studies is the hope behavior, bounded by lithospheric-scale strike-slip faults, to discriminate between ‘‘kinematic’’ deformation models, in response to the India-Eurasia collision [Tapponnier that favor the motion of rigid crustal blocks along large et al., 1982; Peltzer and Tapponnier, 1988; Avouac and active faults, and ‘‘dynamic’’ models, that favor deforma- Tapponnier, 1993; Peltzer and Saucier, 1996]. In these tion by lithospheric thickening with a significant role of models, continental deformation is entirely edge-driven, buoyancy forces rather than the extrusion of rigid crustal and continental tectonics does not differ from that of the blocks (see discussion above). For instance, Bendick et al. oceans. Conversely, ‘‘dynamic’’ models assume that the [2000] claim that the 9 mm yrÀ1 GPS-derived slip rate on lithosphere can be treated as a continuous viscous medium. the Altyn Tagh fault, together with N-S shortening of Tibet In these models, India-Eurasia convergence is accommodated at 9mmyrÀ1, supports the idea of pervasive deformation by crustal thickening, inducing lateral variations in gravita- and thickening of the Asian lithosphere better than extrusion tional potential energy that, in turn, drive the present-day models. On the other hand, the eastward velocity of south deformation [Vilotte et al., 1982; England and Houseman, China at 8 to 10 mm yrÀ1 measured by GPS [e.g., Larson et 1986; Cobbold and Davy, 1988; Houseman and England, al., 1999; Wang et al., 2001] fits kinematic and dynamic 1986, 1993; England and Molnar, 1997]. While the advances models equally well. Therefore, even though it is now made in modeling continental deformation in Asia during accepted that only 20–30% of the India-Eurasia conver- the last 20 years are impressive, each of these studies gence is accommodated by lateral extrusion of continental have suffered from limited data quality and quantity. The blocks [e.g., Molnar and Gibson, 1996; Peltzer and Saucier, differences in the conclusions drawn might not only reflect 1996], no consensus has yet been reached on the processes the true complexity of deformation processes and heteroge- and relative importance of the forces that drive present-day neity of the lithosphere but also the limitations of the data sets continental deformation in Asia. used. [6] One of the reasons may reside in the geographical [5] The past few years have seen a rapid increase in distribution of the available geodetic data, mostly concen- the amount of geodetic results available in Asia [e.g., trated in the Himalayas, Tibet, Pamir-Tien Shan, and sur- Abdrakhmatov et al., 1996; Bilham et al., 1997; King et rounding regions (mostly south China). In contrast, the CALAIS ET AL.: GPS MEASUREMENTS IN MONGOLIA ETG 14 - 3 Figure 2. Topography, main active faults, and focal mechanisms of major earthquakes (6 < M <8in grey, M > 8 in black) in the Mongolia-Baikal region (see location map on Figure 1). Triangles, location of campaign GPS sites; black stars, permanent GPS sites. Topography indicates strong elevation changes from the Siberian craton to the north (450 m) to the Hangay dome and Mongolia-Altay belt (4500 m). current level of knowledge is much lower to the north in the available geodetic data sets suffer a number of problems.
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