Probing the upper end of intracontinental earthquake magnitude: A prehistoric example from the Dzhungarian and Lepsy faults of Kazakhstan

Tectonics
By: , and 

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Abstract

The study of surface ruptures is key to understanding the earthquake occurrence of faults especially in the absence of historical events. We present a detailed analysis of geomorphic displacements along the Dzhungarian Fault, which straddles the border of China and Kazakhstan. We use digital elevation models derived from structure-from-motion analysis of Pléiades satellite imagery and drone imagery from specific field sites to measure surface offsets. We provide direct age constraints from alluvial terraces displaced by faulting and indirect dating from morphological analysis of the scarps. We find that the southern 250 km of the fault likely ruptured in a single event in the last 4000 years, with displacements of 10-15 m, and potentially up to 20 m at one site. We infer that this Dzhungarian rupture is likely linked with a previously identified paleo-earthquake rupture on the Lepsy Fault through a system of splays in the intervening highlands. Though there are remaining uncertainties regarding consistency in age constraints between the two fault ruptures, the majority of sites along the two faults are consistent with a most recent event 2000-4000 years ago. Rupture on the Dzhungarian fault alone is likely to have exceeded Mw 8, and the combined Lepsy-Dzhungarian rupture may have been up to Mw 8.4. Despite being at the upper end of known or inferred continental earthquake magnitudes, our proposed scenario combining the 375 km of the Dzhungarian and Lepsy ruptures yields a slip-to-length ratio consistent with global averages and so do other historical intra-continental earthquakes in Central Asia.

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Publication type Article
Publication Subtype Journal Article
Title Probing the upper end of intracontinental earthquake magnitude: A prehistoric example from the Dzhungarian and Lepsy faults of Kazakhstan
Series title Tectonics
DOI 10.1029/2022TC007300
Volume 41
Issue 10
Year Published 2022
Language English
Publisher American Geophysical Union
Contributing office(s) Earthquake Science Center
Description e2022TC007300, 33 p.
Country China, Kazakhstan
Other Geospatial Dzhungarian fault, Lepsy fault, Tien Shan
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