Cyclic Fault Slip Under the Magnifier: Co‐ and Postseismic Response of the Pamir Front to the 2015 Mw7.2 Sarez, Central Pamir, Earthquake.

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. Plain Language Summary: The 2015 Mw7.2 Sarez earthquake, occurred in the Central Pamir, caused m‐scale displacement of the Earth's surface. This earthquake also affected another system near the northern Pamir front at 120–170 km distance from the epicenter where the Pamir thrust system separates the Pamir from the Alay valley (a testimony of an ancient ocean) and the adjacent Tien Shan mountain range to the North. Time‐series analysis of accurate positioning data (GPS) showed 10–20 mm displacements of the Alai crust surface toward the earthquake epicenter with an increased level of deformation near the western segment of the system—in the zone of the Aramkungey right strike‐slip fault. As a result of the earthquake, this fault was unlocked, but then gradually began to be relocked, accelerating the strain accumulation in the following 4.5 years. Key Points: The 2015 Sarez earthquake unlocked the Aramkungey fault at 150 km distance but in the following 0.5–2.5 years the locking began again10–20 mm Alai coseismic displacements toward the Sarez earthquake epicenter led to a slight decrease in the load state of this areaThe Sarez сoseismic deformations attenuated faster in the decompaction strip around the Aramkungey fault with a width of at least 7.5 km [ABSTRACT FROM AUTHOR]