Seismotectonic analysis of the 2021 Damasi-Tyrnavos (Thessaly, Central Greece) earthquake sequence and implications on the stress field rotations

IF 2.1 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Ioannis Kassaras , Vasilis Kapetanidis , Athanassios Ganas , Andreas Karakonstantis , Panayotis Papadimitriou , George Kaviris , Vasiliki Kouskouna , Nicholas Voulgaris
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引用次数: 11

Abstract

In early March 2021, three shallow earthquakes, two mainshocks with M6.3 and M6.0 and one major aftershock with M5.6 impacted both the mountainous Damasi-Tyrnavos region (northern Thessaly, Greece) and the adjacent Plio-Quaternary basin. Each major event was followed by rich aftershock activity recorded by local and regional seismographs and accelerographs. Herein, we present a comprehensive analysis of the seismic sequence, from its foreshock activity starting on 28 February, 2021 and for a period of two months using new high-resolution catalogues of relocated earthquakes and hundreds of focal mechanisms. The results indicate that the aftershocks form a zone that spans ~50 km NW-SE, while focal depths range between 5 and 15 km. More than 400 focal mechanisms, computed for events with M≥ 2.5, mainly exhibit normal faulting in a NW-SE direction, while WNW-ESE to E-W normal faulting is also evidenced, in particular after the occurrence of the last major event on 12 March. The stress-field was reconstructed on a local and broader scale by inverting focal mechanism data, revealing a rotation of the σ3 axis trend from NNE-SSW, in the Damasi-broader region, to NW-SE northwards, to the region of Kozani-Grevena that hosted an Mw = 6.6 shallow mainshock in 1995. Subcrustal seismicity, present beneath those areas, implies that large-scale tectonics and plate dynamics are likely involved in the deformation of the upper crust. Coulomb stress transfer after the 3 major events of the 2021 Damasi-Tyrnavos sequence reveals that stress-loaded areas include those where most aftershocks were triggered. The analysis provides implications to the seismic hazard of the activated area, as a major NW-SE active normal fault close to Larissa city became stress-loaded, constituting a possible candidate source for significant future earthquakes.

2021年达玛西- tyrnavos(希腊中部色萨利)地震序列的地震构造分析及其对应力场旋转的影响
2021年3月初,三次浅层地震、两次6.3级和6.0级的主震以及一次5.6级的主要余震同时影响了达玛西-蒂尔纳沃斯山区(希腊色萨利北部)和邻近的普利奥-第四纪盆地。每次大地震发生后,当地和区域地震仪和加速度仪都会记录下丰富的余震活动。在此,我们对地震序列进行了全面分析,从2021年2月28日开始的前震活动开始,持续两个月,使用新的高分辨率地震目录和数百个震源机制。结果表明,余震形成了一个横跨西北-东南~50 km的区域,震源深度在5 ~ 15 km之间。在400多个震源机制中,M≥2.5的震源机制主要表现为NW-SE方向的正断层,同时也表现为WNW-ESE到E-W方向的正断层,特别是在3月12日最后一次大地震发生后。通过震源机制数据反演,在局部和更大范围内重建应力场,发现σ3轴的旋转趋势从达玛西-更广地区的北北北北北西-南西向北,到1995年发生Mw = 6.6浅层主震的kozini - grevena地区。这些地区下面的地壳下地震活动表明,大范围的构造和板块动力学可能与上地壳的变形有关。2021年达玛西-蒂尔纳沃斯序列三次大地震后的库仑应力传递表明,应力负荷区包括那些触发余震最多的地区。该分析为活动性区域的地震危险性提供了暗示,因为靠近Larissa市的主要NW-SE活动性正断层成为应力负荷,构成了未来重大地震的可能候选震源。
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来源期刊
Journal of Geodynamics
Journal of Geodynamics 地学-地球化学与地球物理
CiteScore
4.60
自引率
0.00%
发文量
21
审稿时长
6-12 weeks
期刊介绍: The Journal of Geodynamics is an international and interdisciplinary forum for the publication of results and discussions of solid earth research in geodetic, geophysical, geological and geochemical geodynamics, with special emphasis on the large scale processes involved.
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