Volcanic unrest possibilities in response to recent Obruk seismic swarm on and around Hasandağ stratovolcano (Central Anatolia, Turkey)

Abstract

In Turkey, the record of earthquakes with the use of devices began in 1900. On September 20, 2020, an earthquake of Mw 5.1 happened near Obruk village of Nigde-Bor province (Central Anatolia, Turkey) and a swarm consisting of >100 aftershocks continued for one month. This swarm happened in an area where no seismic activity had been recorded before, according to the earthquake catalog covering the period 1900-2020. The area concerned is known for its monogenetic volcano sequences and is located immediately south of the active Hasandag volcano of the Central Anatolian Volcanic Province, Turkey. In this paper, we reported a volcano-structural interpretation of the seismic events, and evaluate the volcanic unrest possibilities related to the seismic activity on and around Hasandag.

Investigating Stress Transfer Between the Tuz Gölü Fault Zone and Hasan Dağ Volcano (Turkey)

“…On the September 20, 2020, a M5.1 earthquake located 35 km to the southwest of Hasan Dağ's summit at a depth of ∼8 km reactivated a segment of the previously thought inactive Karaman-Niğde shear zone (KNSZ) (Aydar et al, 2021). The earthquake and subsequent aftershocks occurred in a volume predicted by this study to have undergone unclamping due to gradual slip along the AKFS (Figure 8).…”

“…Moment magnitude of earthquake (M w ), horizontal distance (D) distance between earthquake epicenter and volcanic system. and fumarolic degassing on its western flank with temperatures of up to 68.7 °C and CO 2 levels ∼10,000 ppm are indicative of the presence of an active magmatic system (Dİker et al, 2018;Ulusoy et al, 2020;Aydar et al, 2021). Mid-crustal low-seismic velocity layers beneath the volcanic province may represent magma reservoirs feeding active surface volcanism (Abgarmi et al, 2017).…”

“…Elevated footwall uplift rates towards the south-eastern end of the TGFZ may pertain to interactions between the fault zone and the Hasan Dağ magmatic system (Krystopowicz et al, 2020). Seismicity in proximity to Hasan Dağ includes hypocentral depths that are deeper ( > 10 km) than common for the region (Aydar et al, 2021), and may perhaps be indicative of a volcanogenic origin (Kürçer and Gökten, 2014).…”

“…Here, we investigate stress transfer between a major strike-slip fault system (the Tuz Gölü fault zone) and the active Hasan Dağ volcanic complex of the Central Anatolian Volcanic Province. A seismic swarm culminating in a M5.1 to M5.2 earthquake on September 20, 2020 occurred within 10 km of the summit of Hasan Dağ and within 20 km from the Tuz Gölü fault zone, in a volume with no recorded historic seismicity (Aydar et al, 2021). This raises questions about possible stress transfer from the major fault zone to the surrounding crust and secondary fault systems.…”

A New Method for Selecting the Phase and Group Velocity Dispersion Curves of Rayleigh and Love Surface Waves: Real Data Case of Central Anatolia, Turkey (Türkiye)

“…1) where the corresponding seismicity produces earthquakes with focal depths mostly shallower than 40 km (Demirsıkan et al, 2019). The TGFZ with ~135-km length has SW-and NE-dipping fault planes and strikes in the NW-SE direction (Özsayın et al, 2013;Aydar et al, 2021). The CAFZ with ~730 km length and 2-80 km width strikes in the NE-SW direction and continues southward where it intersects the TGFZ (Koçyiğit & Beyhan, 1998).…”