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- Title
Probing the Upper End of Intracontinental Earthquake Magnitude: A Prehistoric Example From the Dzhungarian and Lepsy Faults of Kazakhstan.
- Authors
Tsai, C.‐H.; Abdrakhmatov, K.; Mukambayev, A.; Elliott, A. J.; Elliott, J. R.; Grützner, C.; Rhodes, E. J.; Ivester, A. H.; Walker, R. T.; Wilkinson, R.
- 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 4,000 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, most of the sites along the two faults are consistent with a most recent event 2,000–4,000 years ago. Rupture on the Dzhungarian Fault alone is likely to have exceeded Mw 8, and the combined Lepsy‐Dzhungarian rupture scenario 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 intracontinental earthquakes in Central Asia. Plain Language Summary: Numerous large, destructive earthquakes have occurred on faults inside the continents in recent centuries. However, comparing to plate‐boundary faults, the behaviors of intracontinental faults are not well understood. We undertake a detailed survey of the surface ruptures along the Dzhungarian Fault, one of the major faults in Central Asia. We map and analyze high‐resolution satellite and drone imagery. We identify fresh surface ruptures distributed along the southern 250 km of the Dzhungarian Fault. We suggest that these ruptures were produced in a single event which probably caused displacements of up to ∼20 m and no <6 m. We also present evidence that the Dzhungarian Fault and its neighboring Lepsy Fault may have ruptured together. Using their combined length, we calculate a slip‐to‐length ratio which lies within the expected range instead of an unusually high ratio mentioned previously. Our age constraints indicate the most recent event for the two fault ruptures occurred 2,000–4,000 years ago. We estimate the potential maximum earthquake magnitudes to be Mw 8.2 for the Dzhungarian Fault rupturing alone and Mw 8.4 for the combined rupture of the Lepsy‐Dzhungarian Faults. This second scenario would be one of the largest magnitudes ever inferred for a continental earthquake. Key Points: We present evidence for a large paleo‐earthquake on a major intracontinental strike‐slip fault from analysis of high‐resolution imageryThe Dzhungarian and Lepsy Faults might have ruptured together in a single event (up to Mw 8.4) with fault slip of up to ∼20 m at one siteA compilation of intracontinental earthquakes shows these faults follow the global earthquake scaling relationships of slip and length
- Publication
Tectonics, 2022, Vol 41, Issue 10, p1
- ISSN
0278-7407
- Publication type
Article
- DOI
10.1029/2022TC007300