Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

226 PATA Days 2024 the stresses and, consequently, load intraplate crustal faults, depending on their kinematics and preferential orientation (Farías et al., 2011; Aron et al., 2013; Cortés- Aranda et al., 2015). Under favorable conditions, these faults may be reactivated following a major subduction earthquake. Additionally, long-term vertical deformation processes of the crust would influence the activity levels of these faults over geological timescales (González-Alfaro, 2021). The Puerto Aldea Fault, located at the southern edge of the Challenger tectonic segment in the CoquimboRegion (Figure 1), is a structure that exhibits neotectonic activity and has been accommodating part of the deformation undergone by the upper crust during the Quaternary (Heinze, 2003; Emparán Y Pineda, 2006; Saillard et al., 2009).Althoughthefaultpresentsatracewithanextension that could be up to approximately 60-70 km in length (Figure 1), this geological feature has been poorly studied. Vertical displacements within the Pliocene- Pleistocene cover reach up to 2-5 m, implying that crustal earthquakes with a magnitude of Mw ~7.0 would have caused rupture in the study area during the recent geological past (Heinze, 2003). The most recent deformation associated with the Puerto Aldea Fault has been corroborated through studies of fault scarp degradation (Figure 2), which reveal faulting during the Late Pleistocene-Holocene (Heinze, 2003). Field observations (Figure 2) support the findings reported by these studies (Heinze, 2003; Emparán and Pineda, 2006; Saillard et al., 2009). On the other hand, seismic evidence from the crust (<33 km depth) during the years 1969, 1990–2001, and 2016– 2018 reveals normal fault focal mechanisms in the study area and its surroundings, as well as reverse and strike-slip kinematics (Heinze, 2003; Carrasco et al., 2019). Following the Mw 8.3 Illapel earthquake in 2015, an increase in crustal seismic activity in the study area was observed (Carrasco et al., 2019). Crustal earthquakes have also been reported in neighboring areas such as Ovalle and La Serena (Carrasco et al., 2019; Mendez, 2019). One of the primary objectives of this research is to ascertain whether upper crustal seismicity is related to the Puerto Aldea Fault and Quaternary structures. Thus, we will analyze upper crustal microseismic data and describe surface deformation and Quaternary geomorphic features. This will allow us to determine the seismic activity and kinematics of the Puerto Aldea Fault and related faults and their relationship with the surface geology in the study area. These results will be integrated to generate three-dimensional structural models and propose peak ground acceleration maps for seismic hazard assessment. M E T H O D S In this research, we will characterize subaerial and submarine geomorphological features that denote the Quaternary activity of crustal faults; identify the presence and geometry of seismically active faults by analyzing the microseismicity in the upper crust; and propose models of seismic ground acceleration for events triggered by the Puerto Aldea Fault and neighboring faults through various proposed scenarios. To achieve these specific objectives, the primary methodology encompassed installing seismological stations along the Puerto Aldea Fault, and then the analyses of the collected data. Between July 19 and 21, 2022, a field campaign was conducted during which 10 seismic stations (digital broadband receivers) were installed along the Puerto Aldea Fault within the study area (Fig. 1). The