Crustal structure of the northern Andean Precordillera, Argentina, based on seismological and gravity data

Lower and Upper Plate Controls on Crustal Seismicity in the Southern Central and Patagonian Andes

“…Also, the number of earthquakes in the interplate and near‐trench regions (3913 out of 4445) of the NG is much larger than those in the areas to the south [CG: 1893 out of 2029 and SG: 150 out of 243]. The upper‐plate seismicity in this region has been mostly linked to an active compressional regime supported by reverse, and minor strike‐slip, focal mechanisms for larger middle‐upper crustal seismicity over the last 30 years (Alvarado & Beck, 2006; Alvarado & Ramos, 2011; Alvarado et al., 2005, 2009, Farías et al., 2010; Monsalvo et al., 2014; Nacif et al., 2017; Pardo et al., 2002; Richardson et al., 2012; Rivas et al., 2019, 2021; Smalley & Isacks, 1990; Smalley et al., 1993; Venerdini et al., 2020). This is consistent with mapped reverse neotectonic structures from the Andean region to the Pampean broken foreland 600 km away from the trench (e.g., Costa et al., 2018, 2020; Perucca et al., 2015) (Figure 1b).…”

“…Andean orogeny in this segment was achieved through a discontinuous tectonic process that began in the Late Cretaceous‐Paleogene associated with the subduction of the Farallon plate and the subsequent Nazca plate (e.g., Lossada et al., 2017; Martínez et al., 2016). Tectonic activity is still ongoing as suggested by detected within‐plate seismicity (Alvarado et al., 2009; Gutscher et al., 2000; Rivas et al., 2021; Venerdini et al., 2020) and widespread neotectonic structures (Costa et al., 2018, 2020; Perucca et al., 2015). The main shortening stage took place during the flattening of the Nazca plate from 18 to 5‐2 Ma (Cahill & Isacks, 1992; Kay & Mpodozis, 2002; Ramos et al., 2002).…”

“…27.5° and 33.5°S (Barazangi & Isacks, 1976;Cahill & Isacks, 1992), commonly referred to as the Pampean/ Chilean flat-slab (Ramos et al, 2002), and a progressively steeper Nazca slab to the south (Figure 1a). Previous studies of plate-margin seismic activity in the study area have focused on the interplate seismicity (e.g., Comte et al, 2019;Moreno et al, 2009Moreno et al, , 2010Moreno et al, , 2014Ruíz et al, 2017) and earthquakes occurring within the continental plate (Alvarado & Beck, 2006;Alvarado & Ramos, 2011;Alvarado et al, 2005Alvarado et al, , 2009Ammirati et al, 2019;Cembrano & Lara, 2009;Farías et al, 2010;Lange et al, 2007Lange et al, , 2008Monsalvo et al, 2014;Nacif et al, 2017;Olivar et al, 2018;Pardo et al, 2002;Richardson et al, 2012;Rivas et al, 2019Rivas et al, , 2021Sielfeld et al, 2019;Smalley & Isacks, 1990;Smalley et al, 1993;Suárez et al, 2021;Venerdini et al, 2020). By analyzing combined seismic tomography studies and earthquake locations catalogs, Gutscher et al (2000) suggested that areas of flat subduction in the Andean margin release more seismic energy, thus suggesting a first-order control of lower plate geometry on upper-plate seismicity.…”