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Main Results

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In 2017, the staff of GPS laboratory has fulfilled the planned scope of field geodetic observations except for some cases when weather conditions or other objective conditions made it impossible to conduct measurements.

From May to August 2017, we conducted 2 campaigns to measure regional sites at the territory of Kyrgyzstan (fig.1). The regional GPS campaigns involved four field teams including the operator and the driver of ZIL-131 truck. During one month, each team can measure up to 14-15 sites (36 hours for one site). The trucks have travelled 1466-2836 km, ~ 1860 on average.

Fig-1 2017-RegMes KGS 1

Figure 1 – Regional sites served in 2017. Yellow triangles – installed previously and measured in 2017 (112); green stars – new sites (6); red circles – not measured GPS sites due to bad roads and bridges, bad weather conditions etc. (14); red crosses – sites and marks destroyed by vandals (3).

Since 1997, GPS laboratory staff has been conducting GPS measurements at the sites of Bishkek local network several times a year. These observations are aimed at studying modern movements of the Earth’s crust in the junction zone of Kyrgyz Range and Chui Depression (fig.2). Since 2012, the local GPS network surveying campaign involves 36 sites of local network and 10 fundamental sites of geodetic grounds POLIGON and KENTOR.

Fig-2 2017-LNW P K 1

Figure 2 – sites of local GPS network: blue triangles – previously installed sites (32); green stars – sites installed in 2017 (4); red crosses – sites destroyed in 2016-2017 (2); yellow squares – sites transferred to the regional category in 2017. Fundamental posts: lilac diamonds - POLIGON (IP*, 6); lilac circles - KENTOR (IK*, 4).

In 2017, we have conducted 4 full circles of 36-hour measurements at each previously installed site of local network. New sites were measured one time. We have also carried out 10 local campaigns up to 13 days long involving 3-4 teams (fig.3). Next year, to provide a more informative coverage of researched area, we plan to continue reconfiguring the Bishkek local GPS network.

Fig-3 20171221 164002(1)

Figure 3 – Measurement of IV21 site of Bishkek local GPS network in December 2017.

Since 2012 to present, we conduct linear-angular measurements of deformation mode at POLIGON, KENTOR and ALMALY geodetic grounds (fig.4) every week. The grounds are 6-14 km away from each other along the line of Shamsi active fault. Each ground is equipped with fundamental benchmarks dispersed at distances from 150 m to 2.5 km. The purpose of these works is to observe the level, character and mode of deformations near active faults.

Fig-4 2016 Overview GA 1

Figure 4 – Geodetic grounds of Bishkek test site, red lines – active faults. The basic lines for linear-angular measurements are highlighted in green. Points and numbers show fundamental benchmarks and their numbers.

In 2017, we conducted from 31 to 36 cycles of measurements at these grounds. At every ground, the measurements were conducted with fixation of slant distance for the baseline, vertical angle and horizontal angle between 2 lines with one common benchmark. Within one cycle, each line was measured in two directions with difference from 5-10 minutes (with 2 operating tachymeters) to 2-3 hours (with 1 operating tachymeter). As a result of unidirectional measurement of baseline in tachymeter memory (depending on its type), on average 5 records with automatic averaging of 10 readings, or 20 records with single measurement of parameters were obtained.  

 

 

The Research Station RAS has been studying the modern movements of the Earth's crust by GPS technology since 1992. We have created one of the largest observation networks in the world - the regional Central Asian GPS network. According to the density and number of observation sites, the network ranks as the third in the world, following Japan and the USA. By 2009, the number of observation sites has reached > 550. The network covers the territories of Kyrgyzstan, Kazakhstan, Uzbekistan, Tadjikistan and China. In 2000, we were awarded the certificates of the International GPS Service and NASA, which evidence the high level of works carried out by the staff of the Research Station RAS.

certificate

certificate

 

Our collaboration with organizations in neighboring countries made it possible to combine data on the adjacent regions and broaden the investigated territory. Particularly, the Agreement between the Earthquake Administration of Xinjiang Uygur Autonomous Region of China and the Research Station RAS made it possible to exchange information on the territories of Tien Shan and Tarim Depression.
The dense network of observation sites has helped us to chart the detailed maps to show the allocation of vectors of rates of modern movements and deformations all along the Central Asia.

Горизонтальные векторы скорости

Horizontal velocity vectors for the sites of Central Asian GPS network

calculated for the period 1994-2008 in the EURA 2005 reference frame.

The Tien Shan undergoes basically meridian contraction, which is consistent with geological data on Indo-Eurasian collision. By analyzing the received data we revealed a significant nonuniformity in distribution of intensity of modern movements in the researched territory. By developing methods of structuring horizontal field of velocity vectors we received a more detailed conception about the nature of modern movements of the region. Particularly, by singling out the quasi-hard blocks (domains) on statistical base for a discrete set of data on horizontal vectors we revealed important features of the modern kinematics of movement of the near-surface part of the Earth’s crust.

Парные относительных смещения

Pairs of relative displacements of quasi-hard domains for Tien Shan region.

The dashed line joins sites which move in the direction of arrows relative to each other.

Arrow lengths are proportional to values of linear velocities (mm per year)

calculated for movements of hard domain.

 

Modern deformation of the Earth’s crust in the India-Eurasia convergence zone can be presented in the form of movements of the least deformable blocks of different sizes separated by the zones with high rate of displacements. In the territory of Central Asian GPS network, the kinematics of movements in intrablock zones depends on their spatial orientation.

 

Относительные смещения бортов

Relative displacements of sides of neighboring domains projected at midlines of interdomain zones (IDZ).
The small box shows average directions for different kinematic modes of IDZ .

 

Interdomain zones (IDZ) of the northeastern direction (average azimuth ~54°) have domination of left-side component of displacement, sub-latitudinal (~88°) IDZ - lateral contraction, southeast (~116°) IDZ – right displacement, and submeridional (~165°) IDZ – lateral extension. Orientation of zones of lateral shortening and extension after correction for orthogonality (~82° and ~172° accordingly) give the actual average estimate of directions of main axes of horizontal deformation velocity tensor. The nature of deformation of the Earth’s crust within the interdomain zones is a subject of further investigations in detail.

On average the signs of displacement and directions of such zones coincide (up to first degrees) with average directions of main axes of horizontal field of deformation rate and deformation determined by mechanisms of earthquake sources.

 

Оценки средних направлений

Estimate of average directions of main axes of horizontal deformation: by domain-kinematic constructions, on the base of GPS velocity field and by solutions of focal mechanisms of seismic events.

 

Modern interblock zones and neotectonic faults in the investigated area have no significant spatial correlation, and their territories and displacement signs coincide only in individual cases.

 

Photogallery

Geographic location

40 km. from Bishkek