Seismogenic zones of the trans-caspian region: Characteristics of sources of the largest earthquakes. I. The Ashkhabad earthquake of 1948

摘要

The fault-plane solution of the Ashkhabad earthquake, well known in the seismogeological literature, is revised with invoking of additional data on displacements of P and S waves. A new interpretation of the geological origin of the Ashkhabad earthquake source is proposed on the basis of the revised fault-plane solution, taking into account aftershock manifestations and macroseismic data. The source, about 60 km long, was produced by a steep WNW-striking normal fault with a right-lateral component rather than by a subhorizontal thrust, as was indicated in the majority of seismogeological publications. The normal-strike-slip fault in the Ashkhabad earthquake source is apparently confined to a deep regional fault near the southern border of the Koper Dagh foredeep and is caused by the tectonic process of the present development of the foredeep. The average velocity of tectonic movements on this fault is estimated at V-tect similar to 0.2 cm/yr. This value suggests the recurrence of M similar to 7.2 earthquakes in the Ashkhabad source with a period T similar to 900-1000 yr, which does not contradict the information about destructive earthquakes of the historical past.