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A new conceptual approach has been proposed and substantiated for solving the problem of earthquake prediction and organization of monitoring on the South Baikal geodynamic testing ground. The new concept takes into account first of all general geodynamic factors leading to the appearance of foci of metastable state in the Earth's crust. It has been shown that of great importance are regional variations in the stress state caused by the processes of redistribution of crustal stresses during seismic activity in the region as well as by more distant seismogeodynamic processes on interplate boundaries. It is supposed that with time the physics of a focus should give way to the physics of sufficiently large focal zones. One of the main factors determining the seismic properties of a medium is its block structure. Hence, both experimental and theoretical studies are necessary to clear up the behavior of dynamic processes in such block geosystems.

P-wave delays recorded by two linear arrays of seismographs across the Southern Alps of New Zealand require a high-speed zone in the upper mantle beneath the Alps. The pattern of residuals does not match that predicted for subduction of one plate of mantle lithosphere beneath the other. Instead, the high-speed zone seems to mark a blob of cold lithospheric mantle sinking beneath the eastern part of the Southern Alps, directly beneath the thickest crust, and hence where mantle lithosphere has thickened by pure shear. Calculations of Rayleigh-Taylor instability for a thickening heavy layer buoyed up by a lighter layer show that the form of the sinking blobs of dense material depends strongly on the ratio of effective viscosities of crust and mantle. Where the effective viscosity of the buoyant upper layer (crust) is large, a single blob sinks beneath the area of maximum thickening of the upper layer. In New Zealand, where a single sinking blob is inferred, large-strike-slip shear of the region may have lowered the viscosity of the mantle. Elsewhere, if the viscosity of the upper layer is small, however, two sinking blobs can form adjacent to the area where the more buoyant layer (crust) is shortened horizontally. Between the blobs, the unstable layer (lithospheric mantle) thins. Such a process may occur within the Tien Shan.

This paper present results of a comprehensive analysis of the geophysical fields in High Asia, which show the peculiarites of the tectonic structure of the region and geodynamic processes occurring there. Comparison of maps of geophysical fields, namely, geoidal undulations, anomalous magnetic and gravity fields, heat flow, shear-wave attenuation, distributions of group velocities of Rayleigh waves for periods of 10-70 s, and distribution of Pn-wave velocities in the upper mantle of High Asia, shows that they are all caused by an anomalous body which might consist of deconsolidated and hot material and is called by us as the Tibetan plume. We suggest its III-level structure. Comparison of seismicity and geophysical fields shows a particular correlation between the occurrence of earthquakes and the structure of geophysical fields. Gradients of geophysical fields have been found to be indicators of possible zones of strong earthquakes. Dynamic processes in High Asia are governed by combination of collision between the Indostan and Euroasian litospheric plates and the ongoing development of the Tibet plume.

The Tien Shan is the best example of active intracontinental mountain building in the world. In order to determine how strain has accumulated in the range, a 28 station network was deployed in the Tien Shan during 1998

Normalized bimodal interpretation of magnetotelluric sounding in the Kyrgyz Tien Shan mountains provides a reliable geoelectric model for this seismic region. The model contains a conductive layer in the lower crust and subvertical conductive zones in the upper crust. High overall conductivity of crustal zones clearly correlates with low-density zones.

The paper presents results of microseismic and electromagnetic studies of a landslide in the Suusamyr River valley (northern Tien Shan, Kyrgyzstan) and laboratory pulse transmission experiments on ground samples from the landslide. Spectral and polarization patterns of microseisms on the slope show that the main portion of seismic energy in the frequency range of 120 to 210 Hz is related to microfaulting in zones of stress concentration. The high-resolution image of the landslide obtained by the applied techniques of areal TEM soundings and the high sensitivity of seismic parameters to the stress-strain state of the ground demonstrated in the pulse transmission experiments confirm the efficiency of geophysical methods in investigation of landslides and slope stability.

We have determined slip rates on the most active reverse faults, reconstructed an extensive preorogenic erosion surface, constructed local and regional cross sections, and dated syntectonic Tertiary sedimentary rocks by magnetostratigraphy along a north-south transect that spans the Kyrgyz portion of the west-central Tien Shan. The cumulative Late Quaternary shortening rate along this transect is ~12 mm/yr. The trabsect consists of five major fault zones, and the most active faults lie in the interior of the range. Using geometric models developed in other regions of basement-involved determination, we estimate shortening during the Late Cenozoic at 40-80 km. Apparent simultaneous onset of sedimentary basins (at least 3 major basins) about 12 Ma BP is interpreted to mark the onset of the current orogeny. Given the current shortening rate of about 10 mm/yr, measured across active faults and by GPS, we infer that the rate increased with time. We assumed accelerated shortening and have shown that it has always been of similar style, dominated by north-south shortening across east-west trending basement-involved reverse faults. Deformations were localized in five zones, which border the largest and deepest Tertiary basins, show the greatest structural relief, and contain the currently most active faults.

Earlier investigations based on seismological data and results of electromagnetic monitoring of a terrain in one of the most active seismic regions of the North Tien Shan (Bishkek prognostic test ground) revealed that regional and local deformations proceed synchronously. It is important to clear up the mechanism of link of these processes. As known, the seismic process depends on distribution of stresses in a volume of rocks. The pattern of distribution of stresses can be statistically mirrored through allocation of earthquakes in the study terrain. Allocation of seismic events permits us to judge about the mechanism that controls the distribution of stresses.
The obtained maps of allocation of earthquake epicenters show a stable maximum in the Hindu Kush area and a gradual decrease in magnitudes at a distance from it. Preliminary solutions to the model problem on distribution of stresses in an elastic medium demonstrate that the stresses from a central source attenuate much faster than it could be inferred from the observed allocation of earthquakes in the region. It is possible to eliminate this discrepancy by assuming that horizontal forces act from below.
The GPS data received from 1993 to 1999 on the Tien Shan regional networks suggest that some tectonic blocks (especially in the eastern part of the study terrain) move at approximately identical velocities predominantly northward. The impression is created that the blocks move over the surface of a certain ductile horizon in the Earth's crust. Magnetotelluric investigations have revealed an electroconductive horizon in the lower crust throughout South Kazakhstan and the Tien Shan. This geological bed can be just that plastic horizon, on the top of which the Earth's crust moves and through which the horizontal forces are transmitted simultaneously to the entire region at the expense of viscosity of current matter.
It is established that local seismogenic zones coincide with subhorizontal areas of elevated conductivity. These areas are tectonic zones of weakening. Their elevated conductivity is, most likely, caused by inflow of hot solutions from lower-crust horizon through subvertical zones connecting these horizons. The subvertical zones are also channels through which seismogenic zones and lower-crust horizon are interacted by force.

We interpret Global Positioning System measurements of interseismic deformation throughout the western Tien Shan in the context of a block model which accounts for important geologic features (faults) and physical processes (elastic strain accumulation.) Through this analysis we are able to quantify the amount of deformation localized on active structures. In the central part of the belt the Dzhuanaryk fault zone appears to be the most important thrust fault, accommodating nearly five millimeters per year of north-south shortening across it. Conversely, the most widely recognized strike-slip fault in the region, the Talas-Fergana, is found to have very little of the previously estimated right lateral motion.

High density of GPS network in the Tien Shan and long period of observations have allowed us to construct a velocity vector field of movement on the Earth's surface and a strain rate field. A compact uniform area of compressing deformations has been detected. Comparison of the strain rate field with the spatial distribution of weak seismicity for the same period of time showed their considerable correlation. The GPS and seismic data were also compared with data of the magnetotelluric sounding and in particular with geometry of the surface of a crustal conductive layer detected beneath the Tien Shan. The area of maximum compressing deformations coincided with the northern slope of the layer surface, and the strain rate intensity is correlated with the slope angle magnitude of that surface. Nearly all seismic events occur above the surface of the crustal conductive layer. The coincidences suggest that the deformation field and the seismicity distribution are connected by a single tectonic process and depend on the geometry of the crustal layer.