Generation of the 2022 earthquake swarm in intersection of four geological units in the seismic experimental Site, southwest China

Abstract

Three adjacent and successive earthquakes with magnitude over 6.0 in the seismic experimental site, southwest China in 2022 were investigated mainly based on multi-disciplinary observation data combined with regional geology. The abnormal variations of GPS horizontal velocity field and cross-fault baselines, seismic activity, and also fluids geochemistry presented strong cascade and pre-, post-, and co-seismic consistency, suggesting these events could belong to one sequence of earthquakes motivated by a lateral expansion of the Tibetan Plateau. Based on comprehensive analysis, the progressive regional localization of deformation and strain in the intersection of the four geological units, subjected to the lateral expansion of the Tibetan Plateau due to the remote action of the India-Eurasia collision, was unveiled to be the tectonic driver controlling the earthquake swarm, and a “south-north–south cascade” model was proposed for the generation process of the earthquake sequence. According to this model, the possible southward stain transfer in the southeastern margin of the Tibetan Plateau should be considered for potential strong earthquakes in the future. Although this study is special for the seismic experimental site, China, it could be inferred that similar processes might be probable elsewhere, thus, prospective transfer direction forecasting for coming seismic activity could be envisaged in some intersections of multiple geological units.