A remote sensing / radar satellite interferometric (InSAR) time series analysis of volcanoes in Chile, and how the seismic cycle influences magma chamber in- and deflation
Zusammenfassung der Projektergebnisse
The main research in this project was concerned with the use of geodetic data to study crsutal deformations related to earthquake and volcanoes. My principle tools were the remote sensing techniques of SAR Interferometry (InSAR) and Small BAseline Subset (SBAS), which I used to detect crustal deformation at various scales in time and space. By employing inversion techniques, I then tried to understand source parameters of deepseated processes in the earth that caused deformation. I used these methods to analyse source parameters of the 2007 Pisco earthquake in Peru and the 2007 Tocopilla earthquake in Chile. Coseismic model of the Pisco event suggested that that the slip reached values of about 5.5 m at a depth of ∼18–20 km. The slip was confined to less than 40 km depth, with most of the moment release located on the shallow parts of the interface above 30 km depth. For the Tocoippla earthquake, we found that an area of ∼160 km by ∼50 km along the Nazca–South America convergent margin between latitudes 22°S and 23.5°S ruptured during the event. The main slip was concentrated on two asperities, the largest being located in the southern part of the rupture area at a depth of approximately 30–50 km with a magnitude of about 2.5 m. A part of my research was focused on volcano geodesy, in which I explored time-dependent deformation signals at a number of volcanoes in South America, in particular Lazufre volcano in Chile and Uturuncu volcano in Bolivia, to investigate crustal deformation associated with volcano processes. For the Lazufre volcano, our analysis revealed a clear uplift signal with a with a peak velocity of 3 cm year−1, affecting an area of ~50 km by ~38 km during 2003-2008 time-period. We used this observation to evaluate the geometry and time-dependent progression of a horizontally extended pressurized source beneath the Lazufre volcanic system. For the Uturuncu volcano, we analysed current deformation activity for the time period 2003-2009 using Envisat InSAR time-series data and combined them with lineament analysis to understand the relation between present-day deformation and long-term geological deformation. The results show that the strength and pattern of present deformation can be explained by a pressurized source such as an inflating flattopped magma body at ~ 22±9 km depth below the surface. In contrast, lineament mapping and their Coulomb criterion simulation in stress field models suggest a deflating magma body. As the location and flat-topped geometry is confirmed by both methodologies, we interpret the Uturuncu volcano to be subject to episodic subsidence and tumescence, possibly underlain by a stable magma body.
Projektbezogene Publikationen (Auswahl)
- (2008). Land subsidence in Iran caused by widespread water reservoir overexploitation, Geophysical Research Letters, 35, L16403
Motagh, M., Walter, T.R., Sharifi, M.A., Fielding, E., Schenk, A., Anderssohn, J., & Zschau, J.
(Siehe online unter https://doi.org/10.1029/2008GL033814) - (2008): Caldera-scale inflation of the Lazufre volcanic area, South America: Evidence from InSAR, Journal of Volcanology and Geothermal Research, 174, 4, 337-344
Ruch, J., Anderssohn, J., Walter, T.R., & Motagh, M.
- (2008): Coseismic slip model of the August 2007 Pisco earthquake (Peru) as constrained by Wide Swath radar observations, Geophysical Journal International
Motagh, M., Wang, R., Walter, T.R., Bürgmann, R., Fielding, E., Anderssohn, J., & Zschau, J.
(Siehe online unter https://doi.org/10.1111/j.1365-246X.2008.03852.x) - (2009): Surface deformation time-series and source modeling for a volcanic complex system based on satellite wide swath and image mode interferometry: The Lazufre system, Central Andes, Remote Sensing of Environment, 113, 10, 2062-2075
Anderssohn, J., Motagh, M., Walter, T.R., Rosenau, M., Kaufmann H., & Oncken O.
- (2010): Subduction earthquake deformation associated with 14 November 2007, Mw 7.8 Tocopilla earthquake in Chile: Results from InSAR and aftershocks. Tectonophysics, 490, 1-2, 66-68
Motagh, M., Schurr, B., Anderssohn, J., Cailleau, B., Walter, T. R., Wang, R., & Villotte, J.P.
- (2014), Deflation and inflation of a large magma body beneath Uturuncu volcano, Bolivia? Insights from InSAR data, surface lineaments and stress modeling. Geophysical Journal International, Volume 198, Issue 1, 1 July 2014, Pages 462–473
Walter, T., & Motagh, M.
(Siehe online unter https://doi.org/10.1093/gji/ggu080)
