Volcanoes have dormancy periods that may last decades to centuries meaning that eruptions at volcanoes with no historical records of eruptions are common. Baseline monitoring to detect the early stages of reawakening is therefore important even in regions with little recent volcanic activity. Satellite techniques, such as InSAR, are ideally suited for routinely surveying large and inaccessible regions, but the large datasets typically require expert interpretation. Here we focus on Turkey where there are 10 Holocene volcanic systems, but no eruptions since 1855 and consequently little ground-based monitoring. We analyse data from the first five years of the European Space Agency Sentinel-1 mission which collects data over Turkey every 6 days on both ascending and descending passes. The high relief edifices of Turkey’s volcanoes cause two challenges: 1) snow cover during the winter months causes a loss of coherence and 2) topographically-correlated atmospheric artefacts could be misinterpreted as deformation. We propose mitigation strategies for both. The raw time series at Hasan Dag volcano shows uplift of ~ 10 cm between September 2017 and July 2018, but atmospheric corrections based on global weather models demonstrate that this is an artefact and reduce the scatter in the data to < 1 cm. We develop two image classification schemes for dealing with the large datasets: one is an easy to follow flowchart designed for non-specialist monitoring staff, and the other is an automated flagging system using a deep learning approach. We apply the deep learning scheme to a dataset of ~ 5000 images over the 10 Turkish volcanoes and find 4 possible signals, all of which are false positives. We conclude that there has been no cm-scale volcano deformation in Turkey in 2015–2020, but further analysis would be required to rule out slower rates of deformation (< 1 cm/yr). This study has demonstrated that InSAR techniques can be used for baseline monitoring in regions with few historical eruptions or little reported deformation.

Western Anatolia has been shaped N–S-trending extensional tectonic regime and W-E trending horst, grabens and active faults due to the collision of Africa, Arabian and Eurasia plates. The borders of the Aegean Sea tectonic is limited between eastern of Greece, western of Anatolia and Hellenic subduction zone in the south of Crete. To evaluate these tectonic elements gravity disturbance data of the Aegean Sea and Western Anatolia was used in this study. It is thought that the gravity disturbance data reflects the tectonic elements and discontinuities way better than gravity anomaly due to the calculation from the difference between gravity and normal gravity at the same point so thus the tensors and invariants of the study area were calculated and the power spectrum method was applied to the gravity disturbance data. Various boundary analysis methods were applied to the gravity disturbance data to compare the discontinuities obtained from the tensors both theoretical and case study. These methods were tested initially on theoretical data. Within the scope of the theoretical study, a single model and three bodies model were taken into consideration. When the results are examined, it is observed that the Tzz tensor component gives very clear information about the location of the structure. Likewise, when the Txx, Tyy components and invariant results are examined, the vertical and horizontal boundaries were successfully obtained. In addition, the mean depths of these structures were determined using the power spectrum method. In the case application stage, the gravity disturbance data obtained from the Earth Gravitational Model of the eastern of the Aegean Sea and western of Anatolia were evaluated. The tensor and invariants of this gravity disturbance data were first calculated. New possible discontinuities have been identified in the tensors and some of the obtained discontinuities were clarified in their previous discussions. Also, the mean depths of the possible structures were calculated by the power spectrum method at four profiles taken from gravity disturbance data. These depth values are consistent with the depth values of the structural discontinuities obtained from previous studies. Finally, the upward continuation was applied to Tyy, Tyz and Tzz tensors up to 20 km. The positive anomaly values in Tyz and Tzz components and negative anomaly values in Tyy component are consistent with the Western Anatolia Transfer Zone. The structural differences between the eastern and the western of Western Anatolia are noteworthy in the upward continued results of the tensors. In addition, the positive and negative anomalies are notable in areas where the big earthquakes occurred in the last 3 years in the Tyz invariants.

No abstract