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 M_n ∼ 3–4. It culminated on 9 June 2020 with a pair of M_w 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 (M_n ≥ 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 M_w 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.

中文翻译：

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2019-2020 年哈利利（伊朗）地震序列——扎格罗斯简单折叠带的人为地震活动？

我们调查了与主要的 Shanul 天然气田位于同一地点的 Zagros 简单折叠带的 Fars 弧中一个长寿命地震群的起源。该集群于 2019 年 1 月出现，最初由M _n ∼ 3-4 的小事件组成。它于 2020 年 6 月 9 日以一对M _{w 告终}5.4 和 5.7 级地震，随后发生 >100 次余震。我们使用多事件震源重定位、波形反演和 Sentinel-1 干涉合成孔径雷达 (InSAR) 测量和模型来评估地震序列的时空演变。我们发现序列的早期部分在空间上与 2020 年 6 月 9 日的地震及其余震不同。15 个最大 ( M _n ≥ 4.0) 事件的矩张量、质心深度和源参数不确定性 表明，该层序以沉积盖层内浅层深度（大部分≤4 km）的反向断层为主。InSAR 建模表明，M _w5.7 级主震发生在 2-8 km 深度，破裂长度和最大滑移分别为 ∼20 km 和 ∼0.5 m。我们的研究结果表明，2019-2020 年的哈利利地震序列可能受到 Shanul 油田的影响，尽管扎格罗斯的自然地震活动升高使得这种关联难以证明。了解如何区分人为和自然地震有助于灾害和风险评估，特别是在地震活跃且油气储量丰富的扎格罗斯地区。