89-3 Assessing Segment Boundary Controls on Earthquake Rupture in the Eastern Precordillera, Argentina: New Paleoseismic Evidence from the Marquesado Fault

Session: Advancing Earthquake Geology and Surficial Deformation from Geologic Provinces to Political Entities through Multidisciplinary High-Resolution Data

Presenting Author:

Shreya Arora

Authors:

Arora, Shreya¹, Cochran, Drew², Klinger, Yann³, Ortiz, Gustavo Federico⁴, Rimando, Jeremy⁵, Brown, Nathan D.⁶, Villalobos, Melina⁷, Gomez, Raul⁸

(1) Bates College, Department of Earth and Climate Sciences, Lewiston, ME, USA, (2) Department of Earth Sciences, Bates College, Lewiston, Maine, USA, (3) Tectonics and Mechanics of the Lithosphere, Institute de Physique du Globe de Paris, IPGP, Paris, France, (4) Departamento de Geofísica y Astronomía, Universidad Nacional de San Juan, San Juan, Argentina, (5) Canadian Nuclear Safety Commission, Ottawa, Canada, (6) University of Texas at Arlington, Arlington, TX, USA, (7) Departamento de Geología, Universidad Nacional de San Juan, San Juan, Argentina, (8) Departamento de Geología, Universidad Nacional de San Juan, San Juan, Argentina,

Abstract:

Why do some earthquakes repeatedly rupture discrete fault segments, while others rupture entire faults? Answering this remains fundamental to improving seismic hazard analysis and, in turn, to hazard preparedness and mitigation efforts. Over the past two decades, several mechanisms for rupture termination and propagation have been proposed, including variation in geometric, structural, and geologic characteristics of faults (Aki, 1979; King and Nabelek, 1985). In this study, we investigated the Eastern Precordillera (EPC) of the Andes Mountains in Argentina, which is classified into three segments: Villicum, Las Tapias, and Zonda–Pedernal (Siame et al., 2002) to determine whether the historical surface ruptures associated with major earthquakes crossed the segment boundaries, or whether rupture propagation was arrested by structural asperities, indicating an asperity-controlled behavior. In this study, we focused on three major faults within the Eastern Precordillera (EPC): the La Laja Fault within the Villicum segment, the Marquesado Fault in the Las Tapias segment, and the La Rinconada Fault within the Zonda–Pedernal segment. Each of these faults has at least one existing paleoseismic record that provides insights into past surface-rupturing earthquakes. However, a gap in data remained along a NNE-SSW-striking Marquesado Fault. To address this, we conducted a new paleoseismic investigation at this site to complement and integrate with the preexisting dataset to evaluate the extent of past surface ruptures in relation to fault geometry and structural segmentation. We have compiled the earthquake timing of nine earthquakes. Preliminary results suggest that, of the nine identified events, only one earthquake appears to have ruptured across an ~18 km-long segment gap, including a ~4 km stepover and notable lithologic variation evidence consistent with a multi-segment rupture event.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5443

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