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

40 PATA Days 2024 1 2 T H I N T E R N AT I O N A L I N Q U A M E E T I N G O N PA L E O S E I S M O L O G Y , A C T I V E T E C T O N I C S A N D A R C H A E O S E I S M O L O G Y ( PATA ) , O C T O B E R 6 T H - 1 1 T H , 2 0 2 4 , L O S A N D E S , C H I L E K E Y W O R D S Paleoseismology, Marquesado Fault, Seismic Hazard, Andean Backarc, Earthquake Chronology (1) Earth and Climate Science, Bates College, Lewiston Maine, US. (2) University of Toronto (3) Universidad Nacional de San Juan *Email: sarora@bates.edu Shreya Arora (1) Drew Cochran (1) Jeremy Rimando (2) Gustavo Federico Ortiz (3) Raúl Gómez (3) Melina Villalobos (3) PALEOSEISMIC INVESTIGATION OF THE MARQUESADO FAULT IN SAN JUAN (27-33 . 5°S) , EASTERN PRECORDILLERA, ARGENTINA A B S T R A C T The Marquesado Fault, located in the Pampean segment of the Andean backarc in Argentina, presents a complex history of seismic activity, far from the plate boundary. This study aims to establish a chronology of prehistoric earthquakes along the fault, contributing to our understanding of seismic hazards in this region. Through paleoseismic trenching and detailed stratigraphic analysis, we identified at least four paleoearthquakes over the past 19,000 years. The recurrence interval between these events ranges from 2.9 to 4.0 thousand years, with the most recent event occurring approximately 3.6 ± 0.9 thousand years ago. These findings suggest that the Marquesado Fault may be due for another significant seismic event, given the elapsed time since the last rupture. I N T R O D U C T I O N Some of the world’s most significant earthquakes occur along subduction plate boundaries, where broad, gently dipping detachment faults that remain locked, accumulate seismic energy throughout the interseismic period (Bilham, 2019). Some of the classic examples include the 1960 Chile earthquake (Mw 9.5), the 2011 Tohoku earthquake (Mw 9.1), and the 2004 Sumatra and Andaman earthquake (Mw 9.3) (Kanamori, 1977; Simmons et al., 2011; Ishii et al., 2005). However, there are also examples of earthquakes occurring far from the plate boundaries, within the foreland, and resulting in significant devastation, such as the Mw 7.6 1905 Kangra earthquake in the Himalayas, and the Mw 7.4 1944 San Juan earthquake in Argentina (Bilham, 2000; Kadinsky- Cade et al., 1985). The presence of seismic activity within the foreland, provides a unique opportunity and extensive datasets for understanding ongoing deformation and earthquake mechanisms away from the trench boundary.