Analysis and Evaluation of Recent Deformation on the Huaytapallana Fault (Central Region of Peru) Based on Data Obtained from a Local Seismic Network

Abstract

In the central region of Peru, two earthquakes with magnitudes of M ₛ 5.6 and 6.2 occurred in 1969, originating from the Huaytapallana fault. As a result, two fault scarps formed on the surface: the first measuring 4 km and the second one 9.5 km in length, separated by a 4 km section without a surface scarp. A three‐year seismic campaign (2015–2018) conducted around the Huaytapallana fault has provided insights into its current dynamics. The 172 microearthquakes recorded, with magnitudes ranging from M w 0.6 to 3.1, are distributed along the northeastern flank of the fault and extend over 40 km, including segments without visible surface scarps. The Huaytapallana fault is estimated to have a depth of around 15 km with a dip of 60° toward the northeast. The composite focal mechanisms indicate a deformation process due to compression, with a fault plane oriented in the north‐northwest–south‐southeast direction and dipping toward the northeast at angles between 55° and 60°. The M w 4.7 earthquake in 2022 and its series of aftershocks exhibit a similar deformation pattern associated with the Huaytapallana fault. These results are consistent with the regional tectonics, which control the deformation processes in the Mantaro basin, originating from the convergence of the Nazca and South American plates. We consider that the significant microseismic activity occurring in areas without visible surface scarps suggests the accumulation of substantial deformation, which could lead to future earthquakes of greater magnitude that may cause significant surface displacements.