Active shortening in the Alpine-Himalayan belt

Thesis

In this thesis, I use a multi-disciplinary approach to investigate the accommodation of tectonic strain within the Alpine--Himalayan Belt by thick-skinned compressional faulting, to constrain seismic hazard potential and probe the earthquake cycle in regions of distributed deformation. A case study on the fault which generated the 2011 Van Earthquake is used to link the instrumentally observed earthquake behaviour to the late Quaternary slip rate and the regional tectonics of the Turkish-Iranian Plateau. At the Van fault, the surface geomorphology and topography are dominated by slip in the uppermost ∼10km, and so models based on surface observations are likely to underestimate the full depth extent of seismogenic structures in the region. A second case study focuses on the Karkara Rangefront of the Terskey Range in the Tien Shan, which regional GPS suggests is creeping at a significant fraction of the total shortening rate across the northern Tien Shan. Dating river terraces along the rangefront, I estimate a late Quaternary slip-rate consistent with the present day creep rate, though it is unclear whether creep is the long-term deformation mechanism. Building on the Karkara Rangefront case study, I construct a transect of late Quaternary slip rates and earthquake recurrence intervals through the Kazakh Tien Shan and Dzhungarian Alatau. I find that deformation is distributed across numerous faults with slip rates of <0.6mm/yr and recurrence intervals of &RT;5ka (and maybe significantly longer). Finally, I develop a new method to exploit the full power of new high resolution digital elevation models in estimating fault slip from surface fault scarps.Combining multiple measurements along strike, I use the variation in surface offset with topographic geometry to solve for the three-dimensional slip vector.

Authors: Mackenzie, D

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford