Evolving plate boundaries in the Aegean–Anatolian region

Abstract

My thesis focuses on evolving and (geologically) short-lived plate boundary segments, their segmentation processes and geological imprints in the eastern Mediterranean. In Chapter 2, I investigate the nature/type of the plate boundary between the eastern Aegean region and the Africa plate. The work involves an integrative analysis of geological and geophysical information. I conclude that these surface observations document that the “Pliny-Strabo trench” is a predominantly strike-slip plate boundary. My interpretation is that this plate boundary represents an expression of slab tearing related to an active STEP (c.f. Figure 1.1). The paper represents the first detailed account of surface deformation related to a STEP fault, and constitutes a novel contribution to the understanding of the relation between deep processes and (near-) surface deformation, a key topic in geodynamic research. In Chapter 3, I investigate the location and nature of currently active plate boundaries and other major faults in the southern Anatolia-Aegean region, in the transition region from the Hellenic Arc to the Cyprus Arc. The question is particularly relevant for accessing earthquake hazard. I use mechanical models based on the finite element method. I explore various options for these faults, most of them proposed in the scientific literature, to explore how they would affect the deformation at locations where there are actual observations. The (mis)fit between model predictions and observations allows us to conclude that the active plate boundary is located offshore. The research question that I address in Chapter 4 is what the cause is of deformation in one of the seismically most active fault zones in Europe, the Kefalonia Transform Fault. I present results from a recent full-waveform tomographic model which particularly improves our understanding of the structure of the upper few hundred kilometers of the Earth. The cause of the deformation along the Kefalonia Transform Fault is likely rooted in a fragmented slab that we image for the first time. The geometry of the slab fragment leads me to conclude that it became disconnected from the larger Hellenic slab around 5 Ma, at about the time of opening of the Gulf of Corinth in the overriding plate, which suggests a highly interesting causal relation.