Active tectonics of the Zagros front

Fathian Baneh, Aram; Reicherter, Klaus (Thesis advisor); Back, Stefan (Thesis advisor); Salvi, Stefano (Thesis advisor); Nazari, Hamid (Thesis advisor)

Aachen : RWTH Aachen University (2022, 2023)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022

Abstract

The northward movement of the Arabian plate has resulted in forming the Zagros orogen as one of the most tectonically active intracontinental fold-thrust belts. The ongoing rapid convergence presents a remarkable seismic and aseismic crustal deformation across the Zagros. This thesis copes with the crustal deformation and active tectonics within the Zagros front employing a multidisciplinary approach integrating Interferometric Synthetic Aperture Radar (InSAR) as well as seismology, earthquake geology, tectonic geomorphology, field investigations, photogrammetry, quaternary geochronology, and seismic data interpretation. In this thesis, in order to obtain an accurate, quantitative measurement across the tectonically active Zagros front, stacks of SAR images have been employed to provide important constraints used to model the mechanisms of stress accumulation along the active faults. I use the standard two-pass Differential SAR Interferometry (DInSAR) and Small Baseline Subset (SBAS) InSAR method (Berardino et al., 2002) to process a large number of SAR images to measure the coseismic and postseismic deformation due to the designated earthquakes—i.e., the Azgeleh, Tazehabad, and Sarpol-e Zahab (Chapter 3 and Chapter 6) earthquakes as well as the Shonbeh (Chapter 5) and Fin earthquakes (Chapter 7).Chapter 3 and Chapter 6 address the largest earthquake in the Zagros—the Azgeleh event—and the following seismic sequence with a hugely destructive impact on a widespread area on the Iran-Iraq border. With a strong focus on the application of the remotely sensed SAR data, I investigate three significant earthquakes and the relevant postseismic phase utilizing the constraints from our exclusive, temporary local seismic stations network. I quantify and introduce, for the first time, a complex fault setting involved in the seismic sequence. I additionally introduce the existence of unrecognized NE-SW trend and E-W trend for dextral and sinistral faulting within the Northwest Zagros. Providing the characteristics of the seismic sources, which is of high importance to the seismic hazard assessment, I also discuss the Coulomb stress changes within the region and emphasize some potential areas with a likelihood for future earthquake(s).The Bushehr area (Chapter 4) provides a textbook example of fold-and-thrust belts, manifesting contemporaneous uplift, truncation, folding, faulting, and synkinematic offshore sedimentation. I provide detailed morphotectonic and Quaternary maps of the Bushehr area and document geomorphic markers associated with newly identified active faults and young Quaternary folds in the area, such as the youngest and frontal-most active structures in the Zagros fold-and-thrust belt. Utilizing RTK GNSS/GPS surveys and Quaternary geochronology, I investigate and quantify the slip rates of the faults and the uplift rate within the Bushehr Peninsula. I interpret the offshore 2D seismic-reflection data and identify the subtle and young folding in the Persian Gulf. Integrating the onshore and offshore data, I evaluate and quantify the Quaternary and kinematic evolution of the truncated and uplifted structures in the Bushehr area, located in the lowland Zagros Foredeep. I examine some of the reactivated, basement-involved Pan-African faults within the Zagros front. The Khanaqin fault (Chapter 3) and the Kazerun-Qatar lineament (Chapter 4) control the western boundaries of the Lurestan Arc and Fars Arc, respectively. This study presents a regional scale overview of the linkage between the identified active structures and the N-S orientation of these transverse faults outlining the indenter tectonics in the Zagros. The Darang fault (Chapter 5), identified in the Shonbeh seismic sequence, is another N-S-oriented strike-slip fault elongated east of the Kazerun-Qatar lineament. I present a study on the Shonbeh earthquake of 9 April 2013 and the relevant seismic sequence (Chapter 5). I quantify the coseismic and postseismic deformation fields and reconstruct the sources, validated by the relocation and fault plane solutions of the aftershocks, recorded by a local seismic stations network, which reveals a complex set of faulting involved in the seismic sequence. I also study the Fin doublet earthquake (Chapter 7) in the easternmost corner of the Zagros Simply Folded Belt (SFB). The InSAR and back-projection analyses reveal the characteristics of the mainshocks and the sub-events along a low-angle, south-dipping thrust zone within the eastern termination of the Zagros fold-and-thrust belt. The thesis synthesizes and concludes the data and results provided in this study on a regional scale, and describes the indenter and escape tectonics within the Zagros, showing a successful application and integration of the InSAR, seismology, and neotectonics to elaborate on the mapped and unmapped tectonically active structures (e.g., active faults) as well as to hypothesize the interaction of the identified sources with the present-day morphology within the deformation front of the Zagros orogen.

Institutions

• Division of Earth Sciences and Geography [530000]
• Neotectonics and Natural Hazards Teaching and Research Area [531320]