Mechanism of the 2017 M-w 6.3 Pasni earthquake and its significance for future major earthquakes in the eastern Makran

Author Posting. © The Author(s), 2022. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 231(2),(2022): 1434–1445, https://doi.org/10.1093/gji/ggac257.Makran subduction zone is very active with ∼38 mm yr−1 convergence rate and has experienced great earthquakes in the past. The latest great earthquake of 1945 Mw 8.1 event also triggered a large tsunami and led to ∼4000 casualties. However, due to incomplete historical seismicity records and poor modern instrumentation, earthquake mechanism, co-seismic slip and tsunami characteristics in Makran remain unclear. On 2017 February 17, an Mw 6.3 earthquake rattled offshore Pasni of Pakistan in the eastern Makran, marking the largest event after the 1945 Mw 8.1 earthquake with good geodetic and geophysical data coverage. We use a combination of seismicity, multibeam bathymetry, seismic profile, InSAR measurements and tide-gauge observation to investigate the seismogenic structure, co-seismic deformation, tsunami characteristics of this event and its implication for future major earthquakes. Our results indicate that (1) the earthquake occurred on the shallow-dipping (3°–4°) megathrust; (2) the megathrust co-seismically slipped 15 cm and caused ∼2–4 cm ground subsidence and uplift at Pasni; (3) our tsunami modelling reproduces the observed 5-cm-high small tsunami waveforms. The Pasni earthquake rupture largely overlaps the 1945 slip patch and disturbs the west and east megathrust segments that have not ruptured yet at least since 1765. With such stress perturbation and possible stress evolution effect from the 1945 earthquake, the unruptured patches may fail in the future. This study calls for more preparedness in mitigating earthquake and associated hazards in the eastern Makran.his study is financially supported by the National Natural Science Foundation of China (Nos. 42076059, 41890813, 41976066 and 41976064), the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (No. GML2019ZD0205), Chinese Academy of Sciences (Nos. Y4SL021001, QYZDY-SSW-DQC005, 131551KYSB20200021, ISEE2021PY03, 133244KYSB20180029 and E1SL3C02), Guangdong Basic and Applied Basic Research Foundation (No. 2021B1515020098) and China–Pakistan Joint Research Centre on Earth Sciences