## 1 Introduction  
Greece, located at the southeastern end of Europe, has been a witness to significant geological processes, such as the Alpine orogen, which led to the uplift of major mountain ranges like the Dianic Alps and the Pintus mountain range. This orogenic phase was also the driving force behind the formation of complex tectonic structures. The Hellenic Arc, a prime example of this, is a fascinating mix of thrust tectonics, strike-slip faulting, and normal faults in the back-arc region (Figure 1). These tectonic structures are a testament to the ongoing geological activity in the region [1, 2]. This study centers on Attica Prefecture and neighboring areas, which are significant due to their location between two major rifts, the Gulf of Corinth and the Euboekos Gulf. Several studies indicate that the present tectonic system in Central Greece is due to back-arc extension and transtensional tectonic regimes [3, 4, 5, 6, 7]. The morphotectonic structure of the Attica region is intricate, consisting of tectonic horsts and grabens. The primary fault zones are Kifissos, Aegaleo-Parnitha, and Thriassio-Kamatero (Figure S1). The Athens area has been primarily affected by earthquakes located at distances <100 km outside the city, with most of them occurring near the coasts of the Eastern Gulf of Corinth, according to historical evidence. Among the largest recent earthquakes was a sequence of three Mw > 6.0 earthquakes that took place in 1981 in the Eastern Gulf of Corinth [11; 12; 13]. Since 1984, the largest recorded earthquake in the area has been an MS = 4.5 event, lasting for around 15 years [14]. However, on 7 September 1999, an earthquake with a magnitude of 6.0 struck 20 km NW of Athens, on the southern slopes of the Parnitha Mountain [15; 16; 17; 18; 19; 20] (Figure 2; Table S1). This event caused significant damage to the Greek capital, with over 100 buildings collapsing, 143 fatalities, and an estimated cost of over USD 3 billion. In the aftermath of the Athens earthquake in 1999, studies have highlighted a significant horizontal element on the marginal faults of the Athens basin and an uplift of the SE slopes of Mt Parnitha, caused by block rotation [3; 4; 5; 6; 7]. In the following period, seismicity was notably limited in both number and size range (ML < 4.5). Among the few instances, a cluster was observed in Villia near the Eastern Corinth Gulf [21; 22], and some scattered seismic activity was recorded on the southern coasts of Attica. Ref. [23] further highlighted the occurrence of spatial clusters on the Fyli and Thrakomakedones faults, a rare phenomenon. Additionally, a significant portion of the recorded microseismicity was located in the Thriassion basin, in hypocentral depths ~20 km. Nearly twenty years after the Mw = 6.0 earthquake, a seismic event with a moderate magnitude (Mw = 5.1) took place in the NW of the Thriassio basin. The location  
Figure 1: Main tectonic features in Greece and Western Turkey. The purple rectangle contains the study area. Abbreviations—HT: Hellenic Trench; NAT: North Aegean Trough; SAVA: South Aegean Volcanic Arc; CLTFZ: Cephalonia–Lefkas Transform Fault Zone; CG: Corinth Gulf. Fault traces (red lines) derived by [8; 9]. Black and white arrows indicate trend of the major (S1) and minor (S3) principal stress axes; yellow arrows show the strike-slip motion on the projected faults [10]. of the aftershocks was mainly observed near the mainshock's hypocenter, while some other events were clustered at the central part of the Thriassio basin, near the location of the 7 September 1999 mainshock [24]. Severe damages were accounted for in the western outskirts of Athens despite the magnitude of the event [25]. In recent years (2020-today), more than 3000 events have been situated in the following areas:  
* The Perachora peninsula (Eastern Corinth Gulf), where an intense earthquake sequence was initiated during the 2020-2021 time interval, presenting the characteristics of swarm activity [27].