Abstract
Faulting, magmatism and volcanism are intrinsically linked by plate tectonics. Fault slip imparts stress changes to the surrounding crust and other faults and fractures. Volcano-tectonic hazard assessment in areas with long recurrence intervals of volcanic and tectonic activity requires an assessment of current stress levels. Here we investigate stress transfer between the Akhisar-Kiliç fault segment (AKFS) of the seismically active Tuz Gölü fault zone in the Central Anatolian Volcanic Province and the active Hasan Dağ volcanic complex. Current stress accumulation by protracted gradual slip on the AKFS since its most recent rupture (5.45 ka±0.16 BP) is quantified using the Coulomb Failure Stress change (ΔCFS). We calculate currently accrued ΔCFS magnitudes of between 2.5±0.2 and 15±0.5 MPa on the fault plane for published lower and upper-bound estimates of right-lateral slip rates, respectively. These changes are sufficient to promote failure of the segment. The M5.1 September 20, 2020 earthquake SW of Hasan Dağ occurred in a volume predicted by this study to have undergone fault unclamping by gradual slip along the AKFS. We also show that gradual slip of the AKFS contributes to the progressive unclamping of fractures and transtensional opening of potential magma pathways oriented perpendicularly to the AKFS both above and below Hasan Dağ’s magma reservoir, while pathways oriented parallel to the AKFS are being clamped. Earthquake moment magnitudes of between Mw5.94 and Mw6.76 due to hypothetical partial or complete rupture of the segment exacerbate these trends. The spatial pattern of Coulomb failure stress changes on Hasan Dağ’s magma reservoir is predominantly controlled by the location of rupture relative to the reservoir with the magnitude of the earthquake playing a subordinate role. We explore implications of our findings for the assessment of interconnected seismo-volcanic hazards and associated risks.
Highlights
At local scales, the temporal and spatial patterns of volcanic and seismic events are stochastic, statistically unrelated to one another (Hill et al, 2002)
We show that gradual slip of the Akhisar-Kiliç fault segment (AKFS) contributes to the progressive unclamping of fractures and transtensional opening of potential magma pathways oriented perpendicularly to the AKFS both above and below Hasan Dağ’s magma reservoir, while pathways oriented parallel to the AKFS are being clamped
Faulting and magmatic processes are intrinsically linked by plate tectonics (e.g., Perfit and Davidson, 2000; Karaoğlu et al, 2017) and there are several examples of stress transfer between tectonic and magmatic systems where fault rupture led to volcanic activity (Table 1)
Summary
The temporal and spatial patterns of volcanic and seismic events are stochastic, statistically unrelated to one another (Hill et al, 2002). The tectonics of Central Anatolia are dominated by two active NW-SE trending strikeslip fault systems: 1) the left-lateral Ecemiş fault zone and 2) the transtensive dextral Tuz Gölü fault zone (TGFZ) (Toprak and Göncöoglu, 1993). Sets of older normal faults with a NE-SW trend have been identified buried beneath Pleistocene volcanic products (Toprak and Göncöoglu, 1993; Kürçer and Gökten, 2014). The 200 km long (Kürçer and Gökten, 2014) TGFZ marks the western border of the Central Anatolian Volcanic Province (CAVP). Block modelling across Central Anatolia by Aktuğ et al (2013) indicates a normal component of the slip rate along the TGFZ of about 1 mm yr−1, in addition to a right-lateral slip rate of about 5 mm yr−1 along the middle and/or southern part of the TGFZ (Aktuğ et al, 2013)
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