Crustal strain and seismic hazard of the NE Tibetan Plateau

Thesis

This thesis focuses on the seismic hazard of the NE Tibetan Plateau, an area that hosted one of the largest and most deadly earthquakes in China’s recorded his- tory. In order to estimate rates of earthquake occurrence from strain rates, it is necessary to use the Gutenberg-Richter relationship and assume a maximum magnitude. The largest recorded earthquake in the NE Tibetan Plateau is the 1920 Haiyuan Earthquake. It has often been quoted as of M 8.7, on a magnitude scale of uncertain meaning, a result of unknown origin and an outlier in empirical magnitude and rupture parameter relationships. Therefore, I first use historical seismograms, modern Pleiades imagery and field-acquired drone data to re-estimate the magnitude of the 1920 Haiyuan Earthquake, which is corrected to MW 7.9±0.2. Literature re- view suggests the possibility that many magnitudes of historical Chinese earthquakes based on the intensity and magnitude scaling relationships could be systematically overestimated. An existing conversion method is highlighted for quick magnitude re- estimations for historical earthquakes, though careful systematic revisits to historical earthquake magnitudes are recommended. Second, 10 ascending and 13 descending frames of Sentinel-1 interferometric synthetic aperture radar (InSAR) data acquired between 2014 to 2019 and covering the NE Tibetan Plateau are analysed to determine crustal velocities in the satellite line of sight. These frame-based line-of-sight velocities are combined with constraints from Global Navigation Satellite System (GNSS) velocities to derive a high-resolution 3-dimensional velocity field for the region in a well-defined frame of reference. The crustal velocities can be used to constrain geodetic slip rates across the Haiyuan, Gulang and East Kunlun Faults, creep time series over the Laohushan Section of the Haiyuan fault, as well as enabling the determination of crustal strain rates that can be used to determine the rates of earthquake occurrence for the region.

Authors: Ou, Q

• DOI: 10.5287/ora-449rvzzz4
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Hexi Corridor; Continental Earthquakes; Pleiades; Tibetan Plateau; Geomorphology; Historical Seismograms; Active Tectonics; Seismic Hazard; Remote Sensing; Interseismic Strain; 1920 Haiyuan Earthquake; InSAR; Drone; Seismology
• Subjects: Geomorphology; Remote sensing; Earthquake hazard analysis; Seismology