Abstract Nearly 20 years after the Mw = 6.0 Athens (Greece) earthquake of 7 September 1999, a significant Mw = 5.1 event struck on 19 July 2019 in roughly the same epicentral region, south of Mt Parnitha, ∼20 km NW of the Athens metropolitan area. In this work, we present a seismotectonic study of the 2019 sequence and investigate its relation with the 1999 aftershock zone and fault geometry. We also take advantage of this opportunity to re-examine the 1999 sequence, using modern cross-correlation and double-difference relocation tools. Waveforms recorded by stations of temporary local networks that were installed at a common site in both case studies are taken into account to identify strongly correlated earthquakes, in terms of waveform similarity, that may indicate a significant degree of resemblance in their source parameters. Our results indicate that the 2019 sequence partially overlaps the western segment of the 1999 aftershock zone. A spatial gap in the middle of that zone, attributed to a high coseismic slip patch during the 1999 mainshock, is still present in 2019, while an isolated cluster of the eastern segment was also reactivated. The relocated hypocenters of both sequences are distributed on nearly coinciding planes that strike ∼N113°-118 °E and dip 48−55° towards SSW, apparently offset by 1−2 km at seismogenic depths, though this difference is attributed to location biases. Their updip extensions outcrop at Mt Parnitha, 1−3 km north of the mapped Fili fault segments or their westwards extension. The 2019 sequence is considered to have occurred at the same structure as the western group of the 1999 aftershocks, which is likely a blind fault.

中文翻译：

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2019 年 7 月 19 日希腊雅典地震：1999 年 Mw = 6.0 事件的延迟主要余震，还是不同结构的激活？

摘要 1999 年 9 月 7 日发生 Mw = 6.0 雅典（希腊）地震近 20 年后，2019 年 7 月 19 日在大致相同的震中区域发生了重大 Mw = 5.1 事件，位于帕尼萨山以南，雅典大都会西北约 20 公里区域。在这项工作中，我们对 2019 年序列进行了地震构造研究，并调查了其与 1999 年余震带和断层几何形状的关系。我们还利用这个机会，使用现代互相关和双差重定位工具重新检查 1999 年的序列。在这两个案例研究中，安装在公共站点的临时本地网络台站记录的波形被考虑在内，以识别强相关地震，就波形相似性而言，这可能表明它们的震源参数有很大程度的相似性。我们的结果表明，2019 年的序列与 1999 年余震区的西段部分重叠。该区域中部的空间缺口归因于 1999 年主震期间的高同震滑动斑块，2019 年仍然存在，而东段的一个孤立集群也被重新激活。两个层序的重新定位的震源分布在几乎重合的平面上，这些平面的走向为~N113°-118°E，向 SSW 倾斜 48-55°，在发震深度明显偏移 1-2 公里，尽管这种差异归因于位置偏差。它们的上倾延伸在 Mt Parnitha 露头，位于映射的 Fili 断层段或它们向西延伸以北 1-3 公里处。2019 年的序列被认为与 1999 年余震的西部组发生在同一结构上，这可能是一个盲断层。