Baseline monitoring of volcanic regions with little recent activity: application of Sentinel-1 InSAR to Turkish volcanoes

Juliet Biggs,Stanley Yip,Nantheera Anantrasirichai,Sarah Brown,Fikret Dogru,Gökhan Atıcı,Fabien Albino,Ayse Dagliyar

doi:10.1186/s13617-021-00102-x

Abstract

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.

Highlights

Many volcanoes have periods of dormancy of decades to centuries between eruptions and eruptions from volcanoes with little historical record of activity are highly problematic because the populations and emergency managers have no experience of volcanism
Methods: satellite data and processing There are four types of satellite observations that are relevant for volcano monitoring: 1) Deformation measurements made from radar imagery using a technique called Interferometric Synthetic Aperture Radar (InSAR) (e.g. Biggs et al 2014; Pritchard et al 2018; Richter and Froger 2020) 2) Measurements of active or passive degassing using either infrared or UV spectrometers (e.g. Carn et al 2016); 3) Measurements of thermal anomalies associated with erupted material (e.g. Wright et al 2004; Coppola et al 2016) or fumarole activity (Reath et al 2019a; Jay et al 2013), 4) Mapping of volcanic products using visual observation of footprints, or topographic measurements for height changes (Poland 2014; Arnold et al 2019; Meyer et al 2015)
We conclude that the Sentinel-1 InSAR dataset has the potential to be used for baseline monitoring of Turkish volcanoes

Summary

Introduction

Many volcanoes have periods of dormancy of decades to centuries between eruptions and eruptions from volcanoes with little historical record of activity are highly problematic because the populations and emergency managers have no experience of volcanism. Methods: satellite data and processing There are four types of satellite observations that are relevant for volcano monitoring: 1) Deformation measurements made from radar imagery using a technique called Interferometric Synthetic Aperture Radar (InSAR) (e.g. Biggs et al 2014; Pritchard et al 2018; Richter and Froger 2020) 2) Measurements of active or passive degassing using either infrared or UV spectrometers (e.g. Carn et al 2016); 3) Measurements of thermal anomalies associated with erupted material (e.g. Wright et al 2004; Coppola et al 2016) or fumarole activity (Reath et al 2019a; Jay et al 2013), 4) Mapping of volcanic products using visual observation of footprints, or topographic measurements for height changes (Poland 2014; Arnold et al 2019; Meyer et al 2015).

Results

Conclusion