Widespread Aseismic Slip Along the Makran Megathrust Triggered by the 2013 Mw 7.7 Balochistan Earthquake. Issue 6 (28th March 2022)

• Record Type: Journal Article
• Authors: Lv, Xiaoran; Amelung, Falk; Shao, Yun
• Is Part Of: Geophysical research letters. Volume 49:Issue 6(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-28
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL097411
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: InSAR time series data for the 2014–2021 period reveal up to 20 cm of radar line‐of‐sight displacements in the area of the 2013 Mw 7.7 Balochistan earthquake northwest of the Hoshab Fault in the eastern Makran subduction zone in southwest Pakistan. We show that surface displacements were caused by ∼80 cm of aseismic slip along a 5, 500‐km 2 ‐wide subhorizontal patch of the megathrust fault. The corresponding moment is Mw 7.3. The percentage of slip in plate‐perpendicular direction ranges from ∼65% in the northwest to 96% in the southeast. Slip is consistent with shear stress imparted by the 2013 earthquake. The triggered aseismic slip suggests that this section of the megathrust is decoupled. The implication for the seismic potential of the subduction zone is that the megathrust is fully locked to at most 220 km distance from the trench, consistent with the lack of M ≥ 9 earthquakes in the historic record. Plain Language Summary: The 2013 Mw 7.7 Balochistan earthquake was one of the worldwide largest earthquakes that occurred in the upper plate of a subduction zone within an accretionary prism. Using 2014–2021 InSAR data, we explore the post‐seismic deformation mechanism. We find that post‐seismic deformation is caused by widespread aseismic slip along the megathrust, induced by the static stress change imparted by the Balochistan earthquake. The detection of aseismic slip has implications for the seismic potential of the megathrust. Key Points: The 2013 Mw 7.7 earthquake caused widespread aseismic slip along the megathrust Moment released by aseismic slip along megathrust corresponds to an Mw 7.3 earthquake Eastern Makran megathrust fault is locked to at most 220 km distance from the trench but not along the entire seismogenic width