Seismic Swarm PS20151207.1 Near Murghob, Tajikistan

On 7 December 2015, a seismic swarm designated PS20151207.1 was recorded 72 km west-northwest of Murghob in eastern Tajikistan. The sequence began at 07:50:05 UTC and concluded at 10:04:58 UTC, encompassing six earthquakes within a span of two hours and fourteen minutes. The events occurred in the tectonically active Pamir region, where the ongoing convergence of the Indian and Eurasian plates generates frequent seismic activity along thrust and strike-slip fault systems.

The swarm initiated with a magnitude 7.2 earthquake at a depth of 22 km. Subsequent events included a magnitude 5.3 shock at 17 km depth, followed by a magnitude 5.2 event at 10 km. Two closely timed earthquakes occurred near 09:24 UTC: a magnitude 4.9 at 10 km depth and a magnitude 5.0 at 30 km depth. The sequence ended with a magnitude 5.4 event at 19 km depth. Depths ranged from 10 km to 30 km, consistent with crustal deformation in the Pamir orogen.

This swarm represents the third such cluster recorded in the region since 1 January 2000. Earlier swarms took place in 2004, comprising one event, and in 2008, comprising two events. The 2015 activity aligns with the broader pattern of clustered seismicity in the area, where moderate aftershocks often accompany larger mainshocks.

A magnitude 7.2 earthquake located 104 km west of Murghob on the same date, approximately 60 km from the swarm centroid, underscores the persistent seismic hazard. The Pamir Mountains lie within the Alpine-Himalayan collision zone, where crustal shortening and uplift produce complex fault networks capable of generating both isolated large events and swarm-like sequences.

Seismic monitoring in this remote, high-elevation terrain remains essential for understanding stress transfer and improving hazard assessment in Tajikistan.

References: SeismoSight internal classification records for swarm PS20151207.1. USGS Earthquake Catalog for regional events since 2000.