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CH Wendy Tsai (University of Oxford) ; Aisling O'Kane (University of Cambridge)
1. Probing the Upper End of Intra-continental Earthquake Magnitude: a Prehistoric Example from the Dzhungarian and Lepsy Faults of Kazakhstan.

CH Wendy Tsai

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.

2. Seismotectonics of the NW Himalayas with insights for seismic hazard.

Aisling O'Kane

In this webinar, I will discuss how we used field, satellite, and seismological observations to determine the fault geometry beneath the NW Himalayas, and investigate the relationship between thrust faulting and folding. These results were used to construct seismic wavefield models, to determine earthquake ground motion estimates if the Main Himalayan Thrust in the region were to rupture. I will present our results which show that peak ground velocities are extremely sensitive to minor variations in the fault geometry, with ~3 times larger PGVs generated from ruptures on the buried, shallow part of the locked Main Himalayan Thrust, compared to earthquakes of the same magnitude on its deeper portions. This webinar will highlight why it is important to accurately determine the shallow geometry of thrust faults along the margins of mountain ranges for estimating seismic hazard.

Aug 24, 2022 04:00 PM in London

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