Graduation date: 1997

Thesis (Ph. D.) -- l'Université de Rennes, 2007. / "Thése de Doctorat de l'Université de Rennes 1 réalisée en co-tutelle avec l'Université de Canterbury (Christchurch, Nouvelle-Zélande)." "Soutenue le 9 novembre 2007." Includes bibliographical references. Also available via WWW.

Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). "Ph.D. thesis realized in cotutelle with the University of Rennes 1, Rennes, France." Includes bibliographical references. Also available via the World Wide Web.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [137]-146).

Thesis (Ph. D.)--Université de Paris-Sud, 1987. / "Thèse présentée pour obtenir le titre de Docteur en Sciences ... soutenue le 22 octubre 1987." At head of title: Sujet. Includes bibliographical references.

Thesis (M.S.)--Naval Postgraduate School, 1993. / "September 1993." Includes bibliographical references (p. 70-72).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 74-82).

The neotectonic evolution of the eastern Mediterranean is intimately tied to interactions between the underthrusting/subducting slab along the southern margin of Anatolia and the overriding plate. The lateral variations in the subduction zone can be viewed as a temporal analogue of the transition between continuous subduction and subduction termination by continent-continent collision. By investigating the lateral variations along this subduction zone in the overriding plate, we can gain insight into the processes that precede continent collision. This dissertation summarizes the results of three studies that focus on different parts of the subduction margin: 1) In the west, where the development of a slab tear represents the transition between continuous and enigmatic subduction, 2) In the east, where continent-continent collision between the Arabian and Eurasian Plate is leading to the development of the third largest orogenic plateau on earth after complete slab detachment, and 3) In central Anatolia, where the subducting slab is thought to be in the processes of breaking up, which is affecting the flow of mantle material leading to volcanism and uplift along the margin. In the first study, we interpret that variations in the composition of material in the downgoing plate (i.e. a change from the subduction of oceanic material to continental material) may have led to the development of a slab tear in the eastern Aegean. This underthrusting, buoyant continental fragment is controlling overriding plate deformation, separating the highly extensional strains of western Anatolia from the much lower extensional strains of central Anatolia. Based on intermediate depth seismicity, it appears that the oceanic portion of the slab is still attached to this underthrusting continental fragment. In the second study, we interpret that the introduction of continental lithosphere into the north-dipping subduction zone at the Arabian-Eurasian margin led to the rollback and eventual detachment of the downgoing oceanic lithosphere attached to the Arabian Plate. After detachment, high rates of exhumation in the overriding plate are recorded due to the removal of the oceanic lithosphere and accompanying rebound of the Arabian continental lithosphere. In the third study, we image a transitional stage between the complete slab breakoff of the second study and the continuous subduction slab of the first study. We interpret that trench-perpendicular volcanism and ~2 km of uplift of flat-lying carbonate rocks along the southern margin of Turkey can be attributed to the rollback and ongoing segmentation of the downgoing slab as attenuated continental material is introduced into the subduction zone. Combining these three studies allows us to understand the terminal processes of a long-lived subduction zone as continental material is introduced.

This dissertation investigates the temporal and spatial variations in deformation of the Calabrian forearc during the evolution of the subduction-rollback system. In addition to contributing new data to the area, I develop three strategies for understanding recent and active deformation by linking long-term structural data with short-term geomorphological data. First, setting a “baseline” of deformation is important when studying plate boundaries. Through the structural mapping of an uplifted forearc basin, I conclude that rapid rollback is characterized by tectonic quiescence in the Calabrian forearc when it is located far from collision (from ~12 Ma – ~5 Ma). This “baseline” provides a framework from which I interpret younger phases of deformation. In the middle Pliocene (~5-4 Ma), an arc-parallel shortening event characterizes the first stage of forearc collision in my field area. These folded sediments are later tilted, but structural data from the field cannot constrain the age or structure responsible for this youngest phase of deformation. The Neto River dissects this tilted surface opening up the possibly of linking structural data with geomorphic data from river erosion. I collected a transect of river sediment samples for 10Be analysis to determine variation in catchment-wide erosion rates through the modern day deformation. I, then, developed a numerical model that describes changes in erosion rate through time with the structural growth of the tilted surface. The model is the first of its kind to use catchment-wide erosion rates to constrain a structural model. The model results constrain the age of the beginning of deformation to 850 ka and suggest that a fold with a migrating hinge caused tilting of the surface. The model provides the basis for my hypothesis that the forearc is experiencing an arc-perpendicular shortening strain, which contradicts conclusions from GPS data and the well-documented extension in the western part of the forearc. To further investigate surficial deformation, I carry out geomorphic analyses of 87 river drainages. I interpret my findings in terms of structural framework and find that surficial deformation varies tremendously from east to west. The rivers draining eastward are characterized by low concavities and higher erosion rates, consistent with shortening. While just 50 km away, the westward-draining rivers are characterized by high concavities and lower erosion rates, consistent with extension. Overall, the drainages are shifting from east-draining to west-draining, likely due to the topographic growth that decreases concavities on the eastern side. Although a new interpretation, this finding is consistent with previous structural, paleomagnetic, and seismological datasets. In each of the chapters, I interpret the structural and geomorphic data in a regional framework. This extra step is critical in interpreting deformation along active plate boundaries because it is highly variable and can be seemingly contradictory. In my final chapter, I present a cross section of the plate boundary that incorporates my data and interpretations from the geomorphic results and the most recent structural event as well as data from multiple other sources (GPS, seismological, paleomagnetics, structural, tomographic, geomorphic, etc.). This approach confirms the importance of boundary conditions on deformation in a subduction-rollback system. More intriguingly, the cross-section highlights the spatial variations along the surface and with depth suggesting that there is significant interplay between active structures.

The largest earthquakes and the majority of the seismic energy are released on megathrust faults in subduction zones. The goal of this dissertation is to characterize the seismic behavior, structural and physical properties of the megathrust fault, so that we can better understand the controls on slip behavior and large earthquakes. To address this goal, I analyzed seismicity data collected by a local seismic network deployed in southern Alaska and multi-channel seismic (MCS) data from an active-source survey offshore of the Alaska Peninsula. This dissertation work revealed seismicity patterns associated with a large asperity, downdip transitions in megathrust fault structure, and along-strike variations in the properties of subducting sediment on the shallow part of the subduction zone. All of these observations have important implications for seismic behavior of the megathrust.