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Title: Earthquakes and active faults in Central Asia
Author: Ainscoe, Eleanor
ISNI:       0000 0004 7654 4426
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2018
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This thesis presents the results of research centred on three large Central Asian earthquakes from recent decades: the 1985 Wuqia (China), 1992 Suusamyr (Kyrgyzstan) and 2015 Pishan (China) earthquakes. For the Pishan earthquake I construct a fault slip model based on coseismic interferograms. It shows that the earthquake took place on a well-established fault that is visible in a seismic reflection profile. However, the coseismic and early postseismic deformations are misaligned with the longer-term topographic uplift pattern. Therefore, other mechanisms must be considered to explain the growth of topography. In a reinvestigation of the Wuqia earthquake, I combine data from several techniques to show that although surface ruptures were produced along a well-known fault, the existing models of that fault are not compatible with the earthquake's focal mechanism or depth. Instead, most of the earthquake's moment was released below a detachment. The detachment acts as a barrier to geomorphic expression of the basement fault, even though the observations require slip to have taken place both above and below the detachment within a month or less. In a study on the 1992 Suusamyr earthquake, I examine the significance of surface ruptures more closely. I use remote sensing and field observations to measure the extent and scarp height of the fresh ruptures, and to construct a paleoseismic record for the fault. The results reveal significant variability in the surface rupture pattern between successive earthquakes on the fault. Finally, I use those results to inform a broader study on the Suusamyr Basin. I map the tectonic structures across the entire basin and provide a slip rate estimate for the Suusamyr Fault. Overall this thesis extends the body of knowledge on continental reverse faulting earthquakes, and demonstrates the challenges and complexities of interpreting the fault structure and seismic hazard of an area based on surface observations.
Supervisor: Walker, Richard ; Parsons, Barry ; Elliott, John Sponsor: Natural Environment Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available