Active mountain-building in Mongolia and Iran

Thesis

In this thesis I use a multi-disciplinary approach to investigate two areas of active mountain-building within the Alpine-Himalayan belt: the Altai range in western Mongolia, and the Zagros mountains in southern Iran. I begin by studying a clustered earthquake sequence that struck a previously unrecognised fault zone in the NW Altai mountains in 2003. By combining seismology and field observations with satellite radar interferometry (InSAR), I attempt to unravel the detailed history of faulting in time and space. Differences between body-wave and InSAR-based models prevent me from matching individual seismic events with individual fault segments, and I explore the cause of these discrepancies. In the following two chapters, I establish late Quaternary slip-rates on major right-lateral and thrust faults in the eastern part of the Altai. In particular, I explore the use of in situ-produced cosmogenic Be-10 and Optically Stimulated Luminescence (OSL) for dating offset alluvial fans and river terraces. My results suggest that faulting has migrated toward the eastern margin of the range from the high, interior Altai, presumably in response to stresses introduced by topography. In the final, main chapter, I investigate a link between buried reverse faulting and surface folding in the Zagros Simply Folded Belt. Using surface displacements measured with InSAR, I show that a major anticline on Qeshm Island was uplifted during an earthquake in 2005. However, the pattern of uplift is discordant with the growth of neighbouring folds, preventing us from establishing a simple connection between faulting and folding. All in all, my work demonstrates the importance of using several techniques in parallel when studying regions of active continental deformation.

Authors: Nissen, E; Edwin Nissen

• Publication date: 2009
• DOI: 10.5287/ora-zba5krjn0
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: tectonics; Earthquakes; faulting
• Subjects: Earth Sciences