ALBERT

Description: Central and Northern Asia is a key natural laboratory for the study of active intra-continental deformation in response to the ongoing far-field collision of India and Eurasia. The induced tectonic processes strongly depend on the thermo-mechanical and compositional (density and thickness) structure of the lithosphere. In particularly, density anomalies within the crust and upper mantle are important factors that control Earth deformations at shallow and deep levels. Moreover, the inherited heterogeneity is responsible also for the local and regional stress field. The main aim of this collaborative research project is to construct new high-resolution 3-D models of the compositional, thermal and rheological structure of the lithosphere of the study area. These models will be constructed by combining and jointly analysing satellite gravity data with terrestrial data (seismic velocity distributions, seismic tomography, GPS derived surface deformations, heat flow measurements and terrestrial gravity). These models will be the basis for subsequent 3-D numerical modelling of the intra-plate stress and strain fields in Central and Northern Asia. Here we present a new crustal model including Moho and seismic velocity distribution for Central and Northern Asia. This model is primarily based on seismic data. Where data coverage is insufficient additional data such as topography and outline of the main tectonic provinces is used to obtain homogeneous models. The new crustal model will be used for the construction of the gravity, thermal, compositional and rheological models of the lithosphere. In the next phase of the project, the new model, combined with a thermal model of the crust and upper mantle, will be used to assess the 3D rheological strength (in)homogeneity of the lithosphere. Probing possible rheological strength variations is essential for a successful quantitative assessment of the present-day intra-plate deformation of the study area.

Description: Central and Northern Asia is a key natural laboratory for the study of active intra-continental deformation in response to the ongoing far-field collision of India and Eurasia. The induced tectonic processes strongly depend on the thermo-mechanical and compositional (density and thickness) structure of the lithosphere. Density heterogeneities within the crust and upper mantle are important factors in the control of the dynamics of Earth deformation at shallow and deep levels. The main aim of this research project is to construct new high-resolution 3D models of the compositional, thermal and rheological structure of the intra-continental lithosphere of the study area. The 3D models will be constructed by combining and jointly analysing satellite gravity data with terrestrial data (seismic velocity distributions, seismic tomography, GPS derived surface deformations, heat flow measurements and terrestrial gravity). Here we present a first new 3D thermal and lithospheric thickness model for Central and Northern Asia. This new thermal model is constructed using an improved version of the methodology presented by Goes et al (2000) and Tesauro et al (2009), and is based on a recent seismic tomographic model of Central Asia (Koulakov, personal communication) and a global Moho model. We also present a new estimate for the lithospheric thickness in the study area, based on the analysis of the spatial distribution of the 1100, 1200, and 1300C isotherms. The new higher resolution models show significant lateral variations in thermal structure across the study area, in particular across main structural boundaries. Central Asia is characterized by more heterogeneous thermal structure of the lithosphere compared to the adjacent cratonic areas in Northern and Western Asia. The observed thermal heterogeneity of Central Asia will result in an anomalous thermo-mechanical structure of the continental lithosphere, which in turn may control the development of the contemporary compressional intra-plate deformation caused by the ongoing far-field collision of India into Eurasia. The new thermal and lithospheric thickness models are compared with the most recent available work in Central Asia. Furthermore possible relationships between the temperature distribution at different depth and the intra-plate deformation are discussed. References Goes, S., Rovers, R., vacher, P., 2000. Shallow mantle temperatures under Europe from P and S wave tomography. J. Geophys. Rec., 105 (B5), 11,153-11,169 Tesauro M., Kaban M., Cloetingh S., 2009. A new thermal and rheological model of the European lithosphere. Tectonophysics, v. 476, p. 478-495.

Description: Asia is a key natural laboratory for the study of active intra-continental deformation in response to the ongoing collision of India and Eurasia. The induced tectonic processes strongly depend on the thermo-mechanical and compositional (density and thickness) structure of the lithosphere. In particularly, density anomalies within the crust and upper mantle are important factors that control Earth deformations at shallow and deep levels. Moreover, the inherited heterogeneity is responsible also for the local and regional stress field. The main aim of this collaborative research project is to construct new high-resolution 3-D models of the compositional, thermal and rheological structure of the lithosphere of the study area. These models will be constructed by combining and jointly analysing satellite gravity data with terrestrial data (seismic velocity distributions, seismic tomography, GPS derived surface deformations, heat flow measurements and terrestrial gravity). These models will be the basis for subsequent 3-D numerical modelling of the intraplate stress and strain fields in Central and Northern Asia. Here we present an improved estimate of the Moho depth as well as a new model of seismic velocity distribution for Asia. This model is primarily based on seismological and seismic data (amongst others: refraction, reflection, split). Knowledge about the outline of the main tectonic provinces in Asia is used a priori. Since data coverage of the primary data is insufficient, secondary data such as topography and distribution of sediments is used to obtain homogeneous models. By combining the primary and secondary data sets using co-kriging, and without assuming isostatic balance a priori, statistically optimal results are ensured.

Description: Central Asia is a classical example for intracontinental lithospheric folding. In particular, the Altay-Sayan belt in South-Siberia and the Kyrgyz Tien Shan display a special mode of lithospheric deformation, involving both lithospheric folding and crustal faulting. This area has a contrasting crust with a long history of accretion and collision and has been reactivated during the Indian-Eurasian collision. Thanks to the youthfulness of the tectonic deformation in this region (peak deformation in late Pliocene – early Pleistocene), the surface expression of lithospheric deformation is well documented by the surface topography and superficial structures. The first-order topographic wavelengths (from 150-175 km, up to 400 km) likely reflect first-order lithospheric deformation. Secondary wavelengths ranging between 35 and 70 km is evidenced for the Altai range by regularly spaced E-W trending mountain ranges, alternating with tectonic depressions containing Cenozoic sediments. The folding wavelengths and location appear strongly influenced by the crustal structure and in particular by the juxtaposition of terranes of markedly different thermotectonic age. A review of the tectono-stratigraphic evolution of the Kurai - Chuya basin in the Siberian Altai and the Issyk-Kul basin in the Kyrgyz Tian Shan suggests that they were initiated in an extensional context and inverted by a combination of fault-controlled deformation and flexural folding. In both basin systems, fault-controlled deformation alone appears largely insufficient to explain their architecture and lithospheric buckling inducing surface tilting, uplift and subsidence also played an important role. In the southern margin of these two basins, recent deformation occurs by reverse or transpressional fautling along basinward dipping faults, raising the basin sediments relative to the basement rocks of the adjacent mountain ranges. The characteristics of these basins are examined in reference to other basins in similar context.

Description: TOPO-EUROPE addresses the 4-D topographic evolution of the orogens and intra-plate regions of Europe through a multidisciplinary approach linking geology, geophysics, geodesy and geotechnology. TOPO-EUROPE integrates monitoring, imaging, reconstruction and modelling of the interplay between processes controlling continental topography and related natural hazards. Until now, research on neotectonics and related topography development of orogens and intra-plate regions has received little attention. TOPO-EUROPE initiates a number of novel studies on the quantification of rates of vertical motions, related tectonically controlled river evolution and land subsidence in carefully selected natural laboratories in Europe. From orogen through platform to continental margin, these natural laboratories include the Alps/Carpathians–Pannonian Basin System, the West and Central European Platform, the Apennines–Aegean–Anatolian region, the Iberian Peninsula, the Scandinavian Continental Margin, the East-European Platform, and the Caucasus–Levant area. TOPO-EUROPE integrates European research facilities and know-how essential to advance the understanding of the role of topography in Environmental Earth System Dynamics. The principal objective of the network is twofold. Namely, to integrate national research programs into a common European network and, furthermore, to integrate activities among TOPO-EUROPE institutes and participants. Key objectives are to provide an interdisciplinary forum to share knowledge and information in the field of the neotectonic and topographic evolution of Europe, to promote and encourage multidisciplinary research on a truly European scale, to increase mobility of scientists and to train young scientists. This paper provides an overview of the state-of-the-art of continental topography research, and of the challenges to TOPO-EUROPE researchers in the targeted natural laboratories.

Description: We propose a new methodology to obtain crustal models in areas where data is sparse and data spreading is heterogeneous. This new method involves both interpolating the depth to the Moho discontinuity between observations and estimating a velocity–depth curve for the crust at each interpolation location. The Moho observations are interpolated using a remove–compute–restore technique, used in for instance geodesy. Observations are corrected first for Airy type isostasy. The residual observations show less variation than the original observations, making interpolation more reliable. After interpolation, the applied correction is restored to the solution, leading to the final estimate of Moho depth. The crustal velocities have been estimated by fitting a velocity–depth curve through available data at each interpolation location. Uncertainty of the model is assessed, both for the Moho and the velocity model. The method has been applied successfully to Asia. The resulting crustal model is provided in digital form and can be used in various geophysical applications, for instance in assessing rheological properties and strength profiles of the lithosphere, the correcting gravity for the crustal effects, seismic tomography and geothermal modelling.