The MW5.5 earthquake on August 6, 2023, in Pingyuan, Shandong, China: A rupture on a buried fault

IF 1.2 4区地球科学 Q3 Earth and Planetary Sciences

Earthquake Science Pub Date : 2024-02-01 DOI:10.1016/j.eqs.2023.10.001

Zhe Zhang, Lisheng Xu, Lihua Fang

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引用次数: 0

Abstract

On August 6, 2023, a magnitude M_W5.5 earthquake struck Pingyuan County, Dezhou City, Shandong Province, China. This event was significant as no large earthquakes had been recorded in the region for over a century, and no active fault had been previously identified. This study collects 1309 P-wave arrival times and 866 S-wave arrival times from 74 seismic stations less than 200 km to the epicenter to constrain the spatial distribution of the mainshock and its 125 early aftershocks by the double difference earthquake relocation method, and selects 864 P-waveforms from 288 stations located within 800 km of the epicenter to constrain the focal mechanism solution of the mainshock through centroid moment tensor inversion. The relocation and the inversion indicate, the Pingyuan M_W5.5 earthquake was caused by a rupture on a buried fault, likely an extensive segment of the Gaotang fault. This buried fault exhibited a dip of approximately 75° to the northwest, with a strike of 222°, similar to the Gaotang fault. The rupture initiated at the depth of 18.6 km and propagated upward and northeastward. However, the ground surface was not broken. The total duration of the rupture was ∼6.0 s, releasing the scalar moment of 2.5895 × 10¹⁷ N·m, equivalent to M_W5.54. The moment rate reached the maximum only 1.4 seconds after the rupture initiation, and the 90% scalar moment was released in the first 4.6 s. In the first 1.4 seconds of the rupture process, the rupture velocity was estimated to be 2.6 km/s, slower than the local S-wave velocity. As the rupture neared its end, the rupture velocity decreased significantly. This study provides valuable insights into the seismic characteristics of the Pingyuan M_W5.5 earthquake, shedding light on the previously unidentified buried fault responsible for the seismic activity in the region. Understanding the behavior of such faults is crucial for assessing seismic hazards and enhancing earthquake preparedness in the future.

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2023 年 8 月 6 日，中国山东平原发生 MW5.5 级地震：埋藏断层上的断裂

2023 年 8 月 6 日，中国山东省德州市平原县发生 MW5.5 级地震。此次地震意义重大，因为该地区一个多世纪以来从未发生过大地震，此前也未发现活动断层。本研究收集了距震中不足 200 公里的 74 个地震台站的 1309 个 P 波到达时间和 866 个 S 波到达时间，通过双差分地震重定位方法约束了主震及其 125 个早期余震的空间分布，并从震中 800 公里范围内的 288 个台站中选择了 864 个 P 波形，通过中心点矩张量反演约束了主震的焦点机制解。搬迁和反演结果表明，平远 MW5.5 地震是由一条埋藏断层上的断裂引起的，该断层很可能是高塘断层的一个广泛地段。该埋藏断层向西北倾角约 75°，走向 222°，与高塘断层相似。断裂始于 18.6 千米深处，向上并向东北方向传播。然而，地表并未被破坏。断裂总持续时间为 6.0 秒，释放的标量力矩为 2.5895 × 1017 N-m，相当于 MW5.54。在断裂过程的前 1.4 秒，断裂速度估计为 2.6 km/s，慢于当地的 S 波速度。随着断裂接近尾声，断裂速度明显下降。这项研究为了解平远 MW5.5 地震的地震特征提供了有价值的见解，揭示了导致该地区地震活动的、之前尚未发现的埋藏断层。了解此类断层的行为对评估地震灾害和加强未来地震防备至关重要。

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来源期刊

Earthquake Science GEOCHEMISTRY & GEOPHYSICS-

CiteScore

1.10

自引率

8.30%

发文量

审稿时长

3 months

期刊介绍： Earthquake Science (EQS) aims to publish high-quality, original, peer-reviewed articles on earthquake-related research subjects. It is an English international journal sponsored by the Seismological Society of China and the Institute of Geophysics, China Earthquake Administration. The topics include, but not limited to, the following ● Seismic sources of all kinds. ● Earth structure at all scales. ● Seismotectonics. ● New methods and theoretical seismology. ● Strong ground motion. ● Seismic phenomena of all kinds. ● Seismic hazards, earthquake forecasting and prediction. ● Seismic instrumentation. ● Significant recent or past seismic events. ● Documentation of recent seismic events or important observations. ● Descriptions of field deployments, new methods, and available software tools. The types of manuscripts include the following. There is no length requirement, except for the Short Notes. 【Articles】 Original contributions that have not been published elsewhere. 【Short Notes】 Short papers of recent events or topics that warrant rapid peer reviews and publications. Limited to 4 publication pages. 【Rapid Communications】 Significant contributions that warrant rapid peer reviews and publications. 【Review Articles】Review articles are by invitation only. Please contact the editorial office and editors for possible proposals. 【Toolboxes】 Descriptions of novel numerical methods and associated computer codes. 【Data Products】 Documentation of datasets of various kinds that are interested to the community and available for open access (field data, processed data, synthetic data, or models). 【Opinions】Views on important topics and future directions in earthquake science. 【Comments and Replies】Commentaries on a recently published EQS paper is welcome. The authors of the paper commented will be invited to reply. Both the Comment and the Reply are subject to peer review.