Rethinking the 1946 Chatkal earthquake: Contributions of Pléiades and UAV images to a surface-rupturing event along the Talas-Fergana Fault

Abstract

This study re-evaluates the paleoseismicity and seismic hazard of the northern Talas-Fergana Fault (TFF), a major strike-slip fault in Central Asia, through geomorphic and paleoseismic investigations in the Chatkal Range. Although active during the late Holocene, the TFF's seismic behavior remains poorly understood. No major earthquakes have been definitively linked to it in instrumental or historical records, and paleoseismic data are scarce. The most significant regional event, the Ms 7.5 Chatkal earthquake of November 2, 1946, generated intense ground shaking, despite its epicenter being located approximately 20 to 70 km away from the Talas-Fergana Fault (TFF). Yet, no clear surface rupture or fresh tectonic scarps have been documented nearby, fueling ongoing debate over the fault source, location, and relation to the TFF. To resolve these uncertainties, we integrate remote sensing, high-resolution topographic analysis, field mapping, and trenching to identify and characterize surface faulting along the TFF. Satellite and drone imagery reveal a well-preserved rupture zone extending 32–55 km, with horizontal displacements of 4.8–6.5 m, values consistent with an earthquake of Mw 6.9–7.3, aligning well with the 1946 event. Trenching results indicate at least three surface-rupturing earthquakes over the past 6500 years and dating of a displaced alluvial fan yields slip rate of 0.9–1.8 mm/yr—substantially lower than values reported further south. These findings confirm that the TFF is capable of generating significant earthquakes. A key finding is that the 1946 rupture may have initiated on a subsidiary ENE-trending thrust fault before propagating onto the TFF—a slip-partitioned rupture model that reconciles surface rupture observations with relocated epicenters and mirrors behavior seen in other complex strike-slip fault systems. Our results point to segmented rupture patterns and the potential for Mw 6.5–7.5 earthquakes along the northern TFF, underscoring its importance for seismic hazard assessments in the region.