Kenekesir Earthquake of October 12, 2015 (MW = 5.2) in the Western Kopet Dag: Aftershock Series and Strong Ground Motions

Abstract

The article presents the results of studying the source of the 2015 Kenekesir earthquake and its aftershock sequence. The earthquake occurred in the Archman–Nokhur tectonic node zone, where the northwest orientation of the Central Kopet Dag faults changes to the northeast orientation of the Western Kopet Dag faults. The actual rupture plane at the Kenekesir earthquake was determined from the dataset of the focal mechanism, three-dimensional orientation of the aftershock cluster, orientation of the nearest faults, and first isoseismals of previous earthquakes. The rupture plane strikes southwest and dips to the northwest. The displacement type is oblique slip with equal normal-fault and left-lateral strike-slip components. The aftershock series lasted 186 days and consisted of 1249 aftershocks of the representative level (K_R ≥ 5.6). At its initial stage, the 11-day period of regular development of the aftershock process is identified, when the Omori law is fulfilled with the highest correlation coefficient and aftershock attenuation parameter p = 1.35. Then, the aftershock process assumes a pulsating character, passing to the stage of stress relaxation in the medium. Accelerograms and velocigrams of the Kenekesir earthquake and its aftershocks are of undoubted interest for assessing the seismic hazard in this area. It was found that the instrumental intensities determined from the velocity (I_PGV) and seismic wave power (I_{PGA ⋅ PGV}) agree the best with the regional macroseismic field equation.