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ERS InSAR observations of Mt. Etna Volcano: Magma inflation and radial spreading

Paul Lundgren(1) and Paul Rosen(1)

(1) Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States

Abstract

We present a synthesis of ERS-1 and ERS-2 differential SAR interferometry (InSAR) observations of Mt. Etna volcano over roughly the past ten years from 1992-2002. Through this time period Mount Etna volcano underwent a cycle of activity starting with a large flank eruption that ended in March 1993, followed by two years quiescence, with resumed summit activity starting in the summer of 1995, culminating in the recent large flank eruptions of 2001 and 2002/2003. InSAR observations reveal patterns of surface deformation that result from the changing magma and structural dynamics of the volcano. Individual interferograms spanning each of these major volcanic episodes during the last ten years reveal the essential deformation patterns. Similarities between groups of similar time-span interferograms for both ascending and descending ERS satellite passes show that the common fringe patterns among each group and yet their distinctive differences are related to true ground deformation and are not dominated by atmospheric effects. In general the deformation patterns are related to a combination of magma chamber deflation/iinflation plus nearly radial flank motion to the W, S, and E. To make sense of the large number of interferograms computed and the temporal behavior of Etna's deformation, we compute a time series of ground deformation from 1992-2001. We find that during this time interval Mt. Etna experienced magmatic deflation from the initiation of measurements in 1992 through spring of 1993, followed by major inflation from 1993-1995, with smaller scale deflation and inflation episodes from 1996-2000. During the entire time period Etna experienced varying amounts of radial spreading to the West, South, and East. Steady motion between the West-South flanks and between the East-North flanks during this time interval suggests they are related to gravitational spreading of the volcanic edifice. In contrast, time series analysis shows that southeastern basal anticline growth initiated with the end of magma recharge in 1995, thus showing a direct link between deep-seated magma intrusions and edifice spreading. Together these observations support a more complex mode of radial gravitational collapse underlain by deeper magma driven basal spreading. The distinct ascending and descending interferograms accompanying the 2001 flank eruption support this model and demonstrate the direct connection between the magmatic and structural components of the volcano.

 

Full paper

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry