We suggest a model of elastic rebound for the M = 7.3-7.5 Chuya earthquake of 27 September 2003 based on 3D deformation data from the Gorny Altai. We report processed data from yearly resurveyed Altai GPS stations through 2000-2004. The geodynamic network of the Institute of Geophysics (Novosibirsk) consists of 21 stations, including the Klyuchi reference station (world network code IGS-NVSK DOMES N12319 M001); it covers the structural elements of Gorny Altai and extends into the southern West Siberian plate and the West Sayan mountains. Displacement of the NVSK station in the system of permanent stations of Asia and displacement of Central Asian stations were processed to obtain a map of GPS velocities for the Gorny Altai. The velocities are in a range from 0.2 to 11 mm/yr. The velocity field shows signature of a preseismic process before the Chuya event in the southern Gorny Altai. Measurements through 2003-2004 give a pattern of postseismic deformation indicating a right-lateral strike slip in the epicentral area. The amount of displacement decreases away from the nodal plane from 300 mm at 15 km to 25 mm at 90 km far from the main shock. This regularity is explained in terms of elastic rebound in a 2D dislocation model. Modeling with the use of experimental data showed a 4MPa stress release and a 2 m displacement along the fault in the epicenter, at an average fault depth of 8 km. The shear strain related to the earthquake was estimated to be 10(-6) within 100 km away from the rupture.

Tidal gravity observations had been performed during more than 2 years (April 2001-September 2003) in Eastern Siberia with the LCR402. Simultaneously the gravimeter LCR1006 was recording in Chize Observatory, not far from La Rochelle, in France. In France the station Chize is the third of a network extending from "Aquitaine" (Menesplet) to Brittany (Mordelles).All stations are located far enough from the sea to avoid very local effects in ocean tide loading. The main goal of the project was to compare the observed tidal parameters with the modelled ones, using different ocean models, i.e.: SCW80, CSR3, FES95, ORI96, CSR4, FES02, GOT00 and NAO99.A general conclusion is that the predictions using all the ocean tide models are in agreement within 0.2% for the area of Khabarovsk (Eastern Siberia). We may thus consider that a mean of all the oceanic models will have a precision better than 0. 1 %. It would thus be very difficult to improve the models using tidal gravity observations in this area.However, for the Atlantic coast of France the tidal parameters derived from different ocean tide models can disagree at the level of 3%. The observed results are close to the predictions derived from CSR3, CSR4 and FES02 models. (c) 2005 Elsevier Ltd. All rights reserved.

We report results from a GPS network installed following special criteria in the framework of an international project and implications for recent crustal movements in the western Altai-Sayan region. The network includes one permanent (NVSK, near Novosibirsk) and 17 campaign sites resurveyed yearly in the Altai mountains and their northern surroundings. The sites were operated with three Trimble 4700 GPS receivers and hard-mounted antennas at geodetic marks, in 2-3 day sessions at each site. The experience of seasonal and permanent monitoring along the similar to76 km Talaya-Irkutsk baseline was used to analyze some methodological issues of GPS measurements.

Water level monitoring in a deep borehole 300 km far from the Pacific coast (Bychikha site, Khabarovsk Territory) was used to study the response of elastic parameters (shear modulus) and porosity of a deep water-saturated layer to tidal and atmospheric effects. Numerical values of elastic constants were obtained using static models. Water level measurements make it possible to record time-dependent changes in elastic constants to an accuracy of 1% and to monitor the tectonic component of deep pressure. The results are applied to investigate the causes of water level anomalies associated with earthquake.

Measurements performed by means of tiltmeters and expansometers in special-purpose underground observatories are important part of the research of the crustal kinematic parameters in the northern Tien Shan. Long runs of tilts and deformations observed at the Ala-Archa underground station (42.63 degrees N, 74.50 degrees E) have been analyzed. Results of tidal analysis are reported. Slow variations in tilts and deformations reveal seasonal changes and slope effects caused by seismic activity of the region. The annual average rate of meridional compression was 3 . 10(-7) for the period 1985-97 and 7 . 10(-7) for 1989-97.