The 2019–2020 Khalili (Iran) Earthquake Sequence—Anthropogenic Seismicity in the Zagros Simply Folded Belt?
Date
2021-12
Authors
Jamalreyhani, Mohammadreza
Pousse-Beltran, Léa
Büyükakpınar, Pınar
Cesca, Simone
Nissen, Edwin
Ghods, Abdolreza
López-Comino, José Ángel
Rezapour, Mehdi
Najafi, Mahdi
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Geophysical Research: solid Earth
Abstract
We investigate the origin of a long-lived earthquake cluster in the Fars arc of the Zagros Simply Folded Belt that is colocated with the major Shanul natural gas field. The cluster emerged in January 2019 and initially comprised small events of Mn ∼ 3–4. It culminated on 9 June 2020 with a pair of Mw 5.4 and 5.7 earthquakes, which was followed by >100 aftershocks. We assess the spatiotemporal evolution of the earthquake sequence using multiple event hypocenter relocations, waveform inversions, and Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) measurements and models. We find that the early part of the sequence is spatially distinct from the 9 June 2020 earthquakes and their aftershocks. Moment tensors, centroid depths, and source parameter uncertainties of 15 of the largest (Mn ≥ 4.0) events show that the sequence is dominated by reverse faulting at shallow depths (mostly ≤4 km) within the sedimentary cover. InSAR modeling shows that the Mw 5.7 mainshock occurred at depths of 2–8 km with a rupture length and maximum slip of ∼20 km and ∼0.5 m, respectively. Our results suggest that the 2019–2020 Khalili earthquake sequence was likely influenced by operation of the Shanul field, though elevated natural seismicity in the Zagros makes the association difficult to prove. Understanding how to distinguish man-made from natural seismicity is helpful for hazard and risk assessment, notably in the Zagros, which is both seismically active and rich in oil and gas reserves.
Description
. We are thankful to Gudrun Richter,
Christian Heberland, Sebastian Hainzl,
Torsten Dahm, and Mir Ali Hassanzadeh
for constructive comments on this work.
M. Jamalreyhani and P. Büyükakpınar
are very grateful to Claus Milkereit
and Dorina Kroll for supporting them,
during their visit to the GFZ Potsdam.
Furthermore, we are grateful to Editor
Rachel Abercrombie, the associate editor,
and four anonymous reviewers for their
valuable comments and suggestions that
helped us to improve the manuscript.
Keywords
Zagros, anthropogenic earthquakes, Shanul gas field, gas extraction, InSAR, Khalili earthquakes
Citation
Jamalreyhani, M., Pousse-Beltran, L., Büyükakpınar, P., Cesca, S., Nissen, E., et al. (2021). The 2019–2020 Khalili (Iran) earthquake sequence—anthropogenic seismicity in the Zagros simply folded belt? Journal of Geophysical Research: Solid Earth, 126(12). https://doi.org/10.1029/2021JB022797