Kinematics of active deformation and possible segmentation of seismic slip along the foothills of the Western Kunlun (China).
Résumé
The Tibetan Plateau stands as a prominent topographic feature at the Earth’s surface, characterized by intense seismic activity, in particular along its bounding mountain ranges. To the northwest, the Western Kunlun Range has received increasing attention since the 2015 Pishan earthquake but its kinematics of deformation remain to be properly documented. Here, we analyse the terrace record of active deformation along the Karakash River, where it crosses the Hotan anticline. We date terraces using in-situ produced cosmogenic isotopes, and show that terrace incision and uplift are spatially correlated with blind duplex ramps beneath the anticline. From there, we quantify the slip rate of the overall duplex to be 1.2-2.8 mm/yr over the last ~250 kyr. Our data are not able to resolve the detailed kinematics on each blind ramp and we cannot exclude that several of them are active at places along the anticline. By comparing to available data, we propose that the system of blind structures all along the foothills of the Western Kunlun has an overall slip rate of ~2 mm/yr. However, the way this slip rate is partitioned on the various blind ramps is expected to vary along strike. The structural segmentation of the foothills may therefore explain the moderate recorded seismicity in this region. Because this slip is transmitted upward and forward onto the Mazar Tagh wide and geometrically simple frontal thrust sheet, we question the possibility of large – but rare – earthquakes rupturing this structure.
Domaines
Planète et Univers [physics]Origine | Fichiers produits par l'(les) auteur(s) |
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