Scholarly record

GEODETIC MEASUREMENTS OF MODERN MOVEMENTS OF THE EARTH SURFACE ON ALMATY GEODYNAMIC POLYGON

Omirzhanova Zh., Kuralay Kartbayeva, A. Aimenov, A. Jazbayev

Abstract

Surveying methods are precursors of strong earthquakes and play a big role to study current movements of the earth's surface. For this reason, the prognostic geodynamic polygons have been set. Almaty geodynamic polygon (GDP) was created in the years between 1967 and 1971. The area is located in the zone of 5 deep faults and it refers to Almaty seismic areas with magnitude of 9. Since 1971 in Almaty geodynamic polygon have been hold about 52 cycles of high-precision leveling classes I and II. Leveling network consists of 5 sections that laid in the area of 200 km2. Since 1974 the linear measurements were carried out with light range finder and radio range finder. The length of the 35 parties was measured in the 1st class triangulation network with the number of 172 programs. Depending on the distances, the measurements of lines lengths are made of two and four programs. Each program consists of two series, and each series consists of ten tricks. Precision GNSS measurements have been performed since 2004. The GNSS network includes 17 points of the network. The accuracy of GNSS measurements at 5-15 km distance is 1-2пїЅ10 -7m. SELE is taken as a basis point during the GNSS measurements. Planned coordinates obtained in the WGS-84 system, and a conversion of coordinates into a flat rectangular system was also produced. The paper analyzed the results of high-precision observations of leveling. The graphs of changes in the nature of vertical movements were built. According to the results of light range finder and GPS measurements, the tables, graphs and analysis on the comparative results are shown, and the values of horizontal displacements on the GDP were evaluated. The following parameters of deformations were calculated: shift, dilation, rotation, maximum and minimum tension, compression and azimuth. The maps of dilation and the planned network shift were built for the past period. The measurement results show that they are confined to the preceding or following moments of seismic events in the Northern Tien Shan, however they still do not have explicit anomalous character that come before the strong earthquakes.

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DOI resolver: doi.org/10.5593/sgem2017/22/s09.042

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