Plio-Quaternary stress states along the Kütahya Fault and surroundings, NW Turkey

Elif Akgün,Süha Özden

doi:10.3906/yer-1812-10

Abstract

The Kutahya Fault, which is one of the major neotectonic structures in western Anatolia, Turkey, is an active fault constraining the southern margin of the approximately E-W trending Kutahya Basin between the Eskisehir Fault to the north and the Simav Fault to the south. In the present study, inversion of both fault kinematic analysis of fault-slip data and focal mechanism solutions from the Kutahya Fault and surroundings is used to understand the Late Cenozoic stress states. The fault kinematic analysis result yielded three different stress regimes from Mio-Pliocene to Quaternary. Firstly, strike-slip faulting developed under a NE-SW trending local compressional regime with 51° ± 24° (σ1) and 140° ± 7° (σ3) trends and Rm ratio was calculated as 0.61, consistent with this faulting. NW-SE trending consistent extensional direction produced local normal faulting with 144° ± 3° (σ3) trend. Secondly, strike-slip faulting developed under a NW-SE trending local compressional regime showing 143° ± 17° (σ1) and 51° ± 10° (σ3) trends and Rm ratio was calculated as 0.51. Finally actual normal faulting developed under a NNE-SSW trend with a regional extensional direction showing 42° ± 14° (σ3) and Rm ratio of 0.56 at the present time. Inversion of the earthquakes gives a NNE-SSW extension direction with 21° ± 19° (σ3) trend and Rm ratio calculated as 0.68 at the triaxial. The Kutahya Fault and surroundings are under an extensional regime at the present time. The reason for the regionally effective NNE-SSW trending extensional regime in western and southwestern Anatolian is complex subduction processes (roll-back, retreat, delamination, slab-tear, slab-break-off and/or slab-pull) of the African Plate and the Anatolian Platelet in the Mediterranean region.

Highlights

The Anatolian Block is an important continental area within the Alpine-Himalaya mountain belt between the Eurasian Plate to the north and the Arabian/African Plates to the south (Figure 1)
In the present study for the first time, both data obtained from kinematic analysis of fault assemblages and inversion of the focal mechanism solutions of earthquakes will be used together to determine the local and regional scale stress tensors, stress states, and geodynamic evolution of the region on the Late Cenozoic (Plio-Quaternary) Kütahya Fault (Figure 1) and to interpret the relationships with other structures in the region and especially the situation in west and SW Anatolia
This study was conducted with the aim of determining the stress situation and kinematic evolution in the Late Cenozoic of the Kütahya Fault and surrounding area

Summary

Introduction

The Anatolian Block is an important continental area within the Alpine-Himalaya mountain belt between the Eurasian Plate to the north and the Arabian/African Plates to the south (Figure 1). Three important models are proposed for this extension: the postorogenic collapse model (Dewey, 1988; Seyitoğlu and Scott, 1991, 1992), the tectonic escape model (Dewey and Şengör, 1979), and southward roll-back of the African slab or the back-arc spreading model (Le Pichon and Angelier, 1979, 1981) Within this process continuing from the Late Miocene to the present day, Western Anatolia was tectonically pulled toward the African Plate and a significant N–S oriented extensional (opening) area was formed. In the present study for the first time, both data obtained from kinematic analysis of fault assemblages and inversion of the focal mechanism solutions of earthquakes will be used together to determine the local and regional scale stress tensors, stress states, and geodynamic evolution of the region on the Late Cenozoic (Plio-Quaternary) Kütahya Fault (Figure 1) and to interpret the relationships with other structures in the region and especially the situation in west and SW Anatolia. This method may be used for inverse solutions of focal mechanisms of faults occurring in the region as well as being applicable to faults compiled in the field (Methodology as a detail in Över et al, 2010)

Fault kinematic analysis results

Discussion and conclusion