The 2019 Mw 7.1 mainshock of the Ridgecrest earthquake sequence, which was the first event exceeding Mw 7.0 in California since the 1999 Hector Mine earthquake, caused near‐fault ground motions exceeding 0.5g and 70 cm/s⁠. In this study, the rupture process and the generation mechanism of strong ground motions of the mainshock were investigated through waveform inversions of strong‐motion data in the frequency range of 0.2–2.0 Hz using empirical Green’s functions (EGFs). The results suggest that the mainshock involved two large slip regions: the primary one with a maximum slip of approximately 4.4 m was centered ∼3 km northwest of the hypocenter, which was slightly shallower than the hypocenter, and the secondary one was centered ∼25 km southeast of the hypocenter. Outside these regions, the slip was rather small and restricted to deeper parts of the fault. A relatively small rupture velocity of 2.1 km/s was identified. The robustness of the slip model was examined by conducting additional inversion analyses with different combinations of EGF events and near‐fault stations. In addition, using the preferred slip model, we synthesized strong motions at stations that were not used in the inversion analyses. The synthetic waveforms captured the timing of the main phases of observed waveforms, indicating the validity of the major spatiotemporal characteristics of the slip model. Our large slip regions are also generally visible in the models proposed by other researchers based on different datasets and focusing on lower frequency ranges (generally lower than 0.5 Hz). In particular, two large slip regions in our model are very consistent with two of the four subevents identified by Ross et al. (2019), which may indicate that part of the large slip regions that generated low‐frequency ground motions also generated high‐frequency ground motions up to 2.0 Hz during the Ridgecrest mainshock.

中文翻译：

---

基于经验格林函数的波形反演2019年里奇克里斯特地震序列主震的破裂过程

自1999年赫克托矿山地震以来，加利福尼亚州里奇克雷斯特地震序列的2019年兆瓦级7.1级地震是自1999年赫克托矿山地震以来加州首次超过7.0兆瓦级地震，造成近断层地震动超过0.5g和70 cm /s⁠。在这项研究中，通过经验格林函数（EGF），通过在0.2–2.0 Hz频率范围内的强运动数据的波形反演，研究了主冲击的破裂过程和强地面运动的产生机理。结果表明，主震涉及两个大的滑移区：最大的滑移区大约在4.4 m处，位于震中区西北约3 km，比震中区浅，而次震区位于约25 km。震源东南。在这些区域之外，滑移很小，只限于断层较深的部分。确认到相对较小的破裂速度为2.1 km / s。通过对EGF事件和近断层站的不同组合进行额外的反演分析，检验了滑动模型的鲁棒性。此外，使用首选滑移模型，我们在反演分析中未使用的站点上合成了强运动。合成波形捕获了观测波形主要相位的时序，表明滑移模型的主要时空特征是正确的。在其他研究人员根据不同数据集提出的模型中，我们的大滑移区域通常也可见，并且着眼于较低的频率范围（通常低于0.5 Hz）。尤其是，我们模型中的两个较大的滑动区域与Ross等人确定的四个子事件中的两个非常一致。（2019），这可能表明在Ridgecrest主震期间产生低频地面运动的部分大滑移区域也产生了高达2.0 Hz的高频地面运动。