THE CHARACTER AND EXTENT OF SEISMIC DEFORMATION IN THE FOCAL ZONE OF GAZLI EARTHQUAKES OF 1976 AND 1984, MGREATER-THAN7.0

With objective of investigating the peculiarities of seismic process d evelopment and seismotectonic deformation character in the focal area of the Gazli earthquakes of 1976 (7.0 < M < 7.3) and 1984 (M = 7.2), a local seismic network was installed. For the field observation period (May to June, 1991) more than 400 events with magnitudes -0.2 < M < 4 .5 were recorded by at least 6 stations.Isometric presentation of eart hquake hypocenters distribution allows us to define the depth and dipp ing planes orientation of seismoactive faults of the region. The focal mechanisms of 35 earthquakes for the period 1979-1988, M > 2.8, conne cted to a gas extraction regime period, and 75 events 1 < M < 4.3 for the 1991 period (gas storage regime) are used to analyze the dynamics of seismotectonic deformation processes (SDP) in this region. It has b een ascertained, that the earth's crust in the Gazli region is subject to complicated deformation processes, particularly below 4 km depth. The predominant kind of deformation is compression. Vertical velocitie s of deformation show uplift of most of the region during the period o f field work. The maximum velocity of vertical deformations for the Ga zli structure is V = 0.41 mm/year. The comparison of the vertical velo cities' displacements due to seismic flow with recent tectonic movemen ts of the earth's crust has revealed their direct relation and high pe rcentage of seismic flow contribution to the tectonic movement. The re sults obtained testify that the active seismic processes in the Gazli region are connected not as much as the residual stress release in the focal zone of the earthquakes 05. 1976 and 1984, M > 7.0 but rather w ith the influence of the gas reservoir exploitational regime on the ro cks with different theologic properties.