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Towards deciphering the origins of seismic tremor signals recorded in the Askja volcano region, Iceland

Jean Soubestre 1,2,3, Kristín Jónsdóttir1, Corentin Caudron4, Tom Winder5, Nikolai Shapiro2, Laure Brenot4, Richard W. Sanderson1, Thomas Lecocq6, Andres Barajas Ramirez2, Nicholas Rawlinson7

  • Affiliations: 1Icelandic Meteorological Office, Reykjavík, Iceland; 2ISTerre, Grenoble, France; 3Now at University of Geneva, Geneva, Switzerland; 4Université Libre de Bruxelles, Brussels, Belgium; 5University of Iceland, Reykjavík, Iceland; 6Royal Observatory of Belgium, Brussels, Belgium; 7University of Cambridge, Cambridge, UK

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 137

  • Programme No: 2.1.47

  • Theme 2 > Session 1

Abstract

We analyze seismic data from 39 seismic stations operated by two different institutions (Icelandic Meteorological Office and University of Cambridge) to document tremor episodes repeatedly recorded in the Askja region of Iceland over the past 18 years (2007--2024). The stations form a network with an aperture of around 100 km, centered on the Askja volcano. Tremor episodes are automatically detected and located by analyzing the eigenvalues and first eigenvector of the seismic network covariance matrix, respectively. Observed spatio-temporal tremor characteristics are compared with river discharge from Vatnajökull glacier, Hálslón reservoir elevation, and local seismicity. Preliminary results suggest the presence of distinct tremor patterns associated with different origins, with three main clusters. A first cluster of shallow co-eruptive tremor of magmatic origin is associated with the 2014--2015 Bárðarbunga Holuhraun eruption. A second cluster of tremor is persistent throughout almost the entire period in the 2--5 Hz frequency range, with sources located along the Jökulsá á Fjöllum river and mainly distributed between the surface and 2--3 km depth, possibly affected by seasonal changes in meltwater dynamics. A third cluster of weeks- to months-long tremor episodes containing lower frequencies down to 1 Hz, distributed throughout the transcrustal range at the top of the eastern end of the deep (13--19 km) 2007--2008 Upptyppingar magma intrusion, is possibly controlled by delayed poro-elastic effects induced by loading/unloading cycles of the Hálslón reservoir. Our observations highlight overlapping tremor-generating mechanisms in the Askja region and show the importance of careful signal characterization to improve monitoring capabilities.