Geophysical research: article

Аnnotation: The results of complex geophysical observations conducted at the Bishkek geodynamic test site, the Tien Shan, are presented. The seismic network KNET operating at the test site enables the recording of earthquake with the minimum energetic class K=7 and determining their focal mechanisms. The observations of deformations of the Earth’s crust were carried out for many years at the Tien-Shan territory and adjacent regions using the methods of satellite geodesy. The weekly measurements were organized at three sites with linear sizes up to 3 km in 2012; their first results are discussed. The special attention is drawn to strain recording in the fault zones, which allows the estimation of variations observed in tectonic stresses. Variations in several parameters: distances between different observation points, surface strains using GPS data, and electrical resistivity at various depths were studied and compared with the seismicity and focal mechanisms of earthquakes. The analysis of the data provided the possibility to estimate the geodynamic situation during the local earthquake of 12.02.2013, energetic class K=10. The depression of the Bishkek geodynamic test site at ~20 mm was revealed several days before the earthquake. The width of the nearby tectonic fault increased up to 8 mm, which corresponds to the variation in effective tectonic stress by about 7 MPa. It is concluded that the changes in geodynamic conditions contribute to the occurrence of the local earthquake.