2021 年 10 月 12 日,M_W=6.4,克里特岛 Zakros 地震

IF 1.6 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
Konstantinos Lentas, Charikleia Gkarlaouni, Nikos Kalligeris, Nikolaos S. Melis
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引用次数: 0

摘要

我们研究了 2021 年 10 月 12 日克里特岛 Zakros 近海发生的强度为 6.4 的地震及其对地震构造的影响。我们通过综合所有免费提供的本地、区域和远震相位到达(直接和深度相位到达),获得了主震的稳健位置(方位角间隙等于17\(^{\circ }\))。根据我们的位置和余震序列的空间分布,我们将断层区域参数化为一个 30 km \(\times \) 20 km 的平面,并使用三分量强震数据计算两个地震节点平面的滑移模型。我们的首选方案显示,在一个东北-西南走向、西北浅倾的断层面上发生了简单的单次滑移,而不是一个东北-南方向、几乎垂直的节点面。余震空间分布与我们模型的最大滑移(27 厘米)的反相关性进一步证实了这一点,尽管余震次中心位置的准确性可能存在一些问题。两种运动学模型计算出的库仑应力变化并没有显示出实质性的差异,因为主震后前 3 个月内的余震地震活动是沿着应力阴影带和主震诱发的南部断层边缘应力增强区分布的。卡索斯岛验潮仪记录分析显示地震后出现了一个小信号,但由于信噪比较低,难以证明海啸波的存在。对两个结点平面进行的海啸模拟计算并没有得出确切的证据来说明成因断层平面是东北-西南走向、西北浅倾角平面还是东北-西南走向,不过,西北浅倾角结点平面的功率谱分析与 8 秒周期的频谱峰值相吻合,总体上更接近验潮仪记录的频谱。美国地质调查局还制作了一个 Shakemap,其中包含所有可用的当地强运动数据和 EMSC 证书。我们也对此进行了调查,以记录应对此负责的断层。这项研究的总体分析略微表明,该近海断层带偏西,倾角较浅,与主要的 Zakros 几乎垂直的正断层相反,后者塑造了克里特岛东部海岸,并垂直于该地区托勒密海沟的方向。这一结果与地震构造和测深证据相吻合,后者支持克里特岛东部和东北部存在近似 N-S 走向的地堑。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

The 12 October 2021, \(M_W\)=6.4, Zakros, Crete earthquake

The 12 October 2021, \(M_W\)=6.4, Zakros, Crete earthquake

We study the strong 12 October 2021, \(M_W\)=6.4, offshore Zakros, Crete earthquake, and its seismotectonic implications. We obtain a robust location (azimuthal gap equal to 17\(^{\circ }\)) for the mainshock by combining all freely available local, regional and teleseismic phase arrivals (direct and depth phase arrivals). Based on our location and the spatial distribution of the poor aftershock sequence we parameterise the fault area as a 30 km \(\times \) 20 km planar surface, and using three-component strong motion data we calculate slip models for both earthquake nodal planes. Our preferred solution shows a simple, single slip episode on a NE-SW oriented, NW shallow-dipping fault plane, instead of a N-S oriented, almost vertical nodal plane. An anti-correlation of the aftershocks spatial distribution versus the maximum slip (\(\sim \) 27 cm) of our model further supports this, although the accuracy of the aftershock hypocentral locations could be somewhat questionable. Coulomb stress changes calculated for both kinematic models do not show substantial differences, as the aftershock seismicity within the first 3 months after the mainshock is distributed along the stress shadow zone and over the stress enhanced areas developed at the southern fault edge, induced by the mainshock. The Kasos island tide gauge record analysis shows a small signal after the earthquake, but it can hardly demonstrate the existence of tsunami waves due to the low signal-to-noise ratio. Tsunami simulations computed for the two nodal planes do not yield conclusive evidence to highlight whether the causative fault plane is NE-SW oriented, NW shallow-dipping plane, or the N-S oriented plane, nevertheless, the power spectrum analysis of the NW shallow-dipping nodal plane matches the spectral peak at 8 s period and is overall closer to the spectrum of the tide gauge record. A USGS Shakemap was also produced with all available local strong motion data and EMSC testimonies. This was also investigated in an effort to document the responsible fault. The overall analysis in this study, slightly suggests a rather westward, shallow-dipping offshore fault zone, being antithetic to the main Zakros almost vertical normal fault which shapes the coast of eastern Crete and is perpendicular to the direction of Ptolemy Trench in this area. This result agrees with seismotectonic and bathymetric evidence which support the existence of approximately N-S trending grabens, east and northeast of Crete.

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来源期刊
Journal of Seismology
Journal of Seismology 地学-地球化学与地球物理
CiteScore
3.30
自引率
6.20%
发文量
67
审稿时长
3 months
期刊介绍: Journal of Seismology is an international journal specialising in all observational and theoretical aspects related to earthquake occurrence. Research topics may cover: seismotectonics, seismicity, historical seismicity, seismic source physics, strong ground motion studies, seismic hazard or risk, engineering seismology, physics of fault systems, triggered and induced seismicity, mining seismology, volcano seismology, earthquake prediction, structural investigations ranging from local to regional and global studies with a particular focus on passive experiments.
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