Cyclic Fault Slip Under the Magnifier: Co‐ and Postseismic Response of the Pamir Front to the 2015 M_w7.2 Sarez, Central Pamir, Earthquake

Abstract

The constant increase of geodetic instrumentation over the past decades enables us to not only detect ever smaller tectonic signals but also to monitor their evolution in time and space. We present spatial and temporal slip variations observed on a fault affected by a large, intermediate‐field earthquake: the 2015 Mw7.2 Sarez, Central Pamir, earthquake ruptured the sinistral, NE‐trending Sarez‐Karakul fault system. 120–170 km North of the main rupture, the thin‐skinned, E‐trending Pamir thrust system bounding the Pamir to the North was co‐seismically activated. We derived co‐seismic offsets and post‐seismic rates observed by two dense, high‐rate Global Positioning System (GPS) profiles crossing the Pamir thrust system at different longitudes. The continuous GPS observations of the western profile focus on the dextral, NW‐striking Aramkungey fault segment that connects two thrust faults with opposite dip. We compare inter‐, co‐ and post‐seismic displacement rates by complementing the continuous data with survey‐mode GPS data and East rates derived from satellite radar interferometric displacement time‐series. All the GPS stations were shifted toward the epicenter against the direction of the interseismic load with an increased gradient in the Aramkungey fault segment. During the postseismic stage, the fault‐parallel and fault‐perpendicular rates were affected differently, suggesting gradual re‐locking of the Aramkungey fault after its unlocking by right‐lateral co‐seismic slip.

Coseismic Source Model of the February 2023 Mw 6.8 Tajikistan Earthquake from Sentinel-1A InSAR Observations and Its Associated Earthquake Hazard

“…The strain rate of the Tajikistan earthquake epicenter zone is not high before the earthquake, the second invariant strain rate is only 12 nano-strain/yr. Many devastating earthquakes occurred along the junction zone between the South Tian Shan and the Pamir plateau [7], however, the seismicity of the Sarez-Murghab fault zone is less active. The 2015 Mw 7.2 Sarez earthquake is the only strong earthquake that happened during the last 100 years on the Sarez-Karakul fault, the distance between the 2023 earthquake and the 2015 earthquake is only approximately 40 km [8].…”

The 2015–2017 Pamir earthquake sequence: foreshocks, main shocks and aftershocks, seismotectonics, fault interaction and fluid processes

“…The northward-increasing transtensional component in the Sarez aftershocks, the rift appearance of the Karakul segment, the anticlockwise change in strike of the northernmost SKFS segments, and the (little-studied) merger of these strands with the MPTS (Figs 10b and 4) suggest increasingly stronger westward motion of material from the eastern Pamir in the east to the Tajik Depression to the west, and from the Hindu Kush and Karakorum in the south to the front of the Pamir in the north; this is traced by the GNSS velocity vectors (Fig. 1b; Metzger et al 2020;Zubovich et al 2022) and the anticlockwise rotations recorded in the northern Tajik Depression by palaeomagnetic data (Pozzi & Feinberg 1991;Thomas et al 1994). The SKFS at and south of Lake Sarez and the dextral Aksu-Murghab Fault Zone and its western prolongation, the Sarez-Murghab Thrust System, may outline-on first-order-the triangular shape of the tip of the mantle indenter by distributed deformation in the crust (Figs 1 and 3).…”

“…1; e.g. Jade et al 2004;Zubovich et al 2010;Ischuk et al 2013;Schurr et al 2014;Chevalier et al 2015;Zubovich et al 2016;Metzger et al 2020;Zubovich et al 2022). The Karakorum Fault System probably links with the Sarez-Murghab Thrust System via the Aksu-Murghab Fault Zone on the Pamir Plateau (Robinson 2009;Rutte et al 2017).…”