KOPETDAG

Abstract

In 2013, the seismic process in the Kopetdag region was monitored by a stationary network of nineteen ana-log and two digital stations supported by eleven mobile digital stations. From September to December, eight GEOSIG-type digital sets of equipment were installed at eight analog stations – “Danata”, “Krasnovodsk”, “Nebitdag”, “Kenekesir”, “Kara-Kala”, “Gaurdak”, “Serniy” and “Serakhs” – with the prospect of further replacement of analog equipment. In total, 158 earthquakes with КР≥8.6 were recorded by Turkmenistan seismic stations during the year, and focal mechanisms were determined for 41 events. The installation of highly sensitive equipment did not lead to an increase in the number of registered earthquakes, since in 2013, the released seismic energy (ΣE=7.051012, J compared to ΣE=17.621012, J in 2012) and seismic activity decreased in the region’s territory (A10=0.032 compared to A10=0.038 in 2012). Despite the decrease of seismic activity in the region as a whole, in some areas (Balkhan-Caspian, the northern part of the Turkmen-Khorasan area), on the contrary, it increased. Particularly noticeable is the intensification of seismicity in the area of Magtymguly town, which began in 2012 in the form of swarms of earthquakes with increasing total energy, and on December 9, 2013, was manifested by an earthquake with КР=12.4, felt in the towns of Ser-dar and Magtymguly with an intensity of 2 on the MSK-64 scale and accompanied by a large number of aftershocks. The chain of aftershocks of the earthquake on December 9 was lined up in the northeast direction from the epicenter of the main shock, marking the western border of the earth's crust block activated in 2012–2013. The sublatitudinal segment of a line, passing through the epicenters of the main shock, after-shock on December 10, previous event of August 28 and ending with the location of the swarm No.1 of 2012, defined its southern boundary. Such an assumption about the configuration of the mobile block of the earth’s crust is supported by the northeastern and sublatitudinal orientation of the nodal planes of most focal mechanisms of 2012–2013 earthquakes in this area, and the presence of both reverse and normal fault components of a slip indicates an alternating pattern of movement on the block boundaries. Another major seismic event in Turkmenistan with КР=12.0 occurred on February 28 at 11h05m, 20 km West of the Germab seismic station, at the site of the intersection of the Germab fault and the Main Kopetdag fault. The earth-quake was felt with intensity I=3 in the village of Baharly, I=2–3 in Ashgabat. The movement in the source was a right-lateral strike-slip with a normal fault component along the north–north-west plane coinciding with the Hermab fault orientation