期刊
JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH
卷 271, 期 -, 页码 11-23出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jvolgeores.2013.11.005
关键词
Volcano geodesy; Crustal deformation; Magma chambers; Finite element analysis; Philippines
资金
- NSF [EAR-0073992]
We investigate active crustal deformation patterns associated with magmatic activity at Taal Volcano, an active tholeiitic volcano located in southwestern Luzon, Philippines. We present comparisons of elastic and combined elastic-viscoelastic modeling results with deformation observed by continuous GPS measurements on and near the volcano. Continuous dual-frequency and single-frequency (L1) GPS data between 1998 and 2005 provide evidence for smoothly transitioning periods of inflation and deflation centered under the volcano. Within deformation phases that typically last 3-9 months (with rates exceeding 200 mm yr(-1)), prominent inflationary phases were observed in February-November 2000 and June 2004-March 2005. The 2000 period of inflation was characterized by up to 145 mm yr(-1) surface extension and 220 mm yr(-1) of uplift of the center of Volcano Island relative to the northern caldera rim, while the 2005 inflation was characterized by as much as 116 mm yr(-1) horizontal extension of the volcanic edifice and 180 mm yr(-1) uplift. Inversions of observed surface deformation to determine the source location points to a relatively stable spherical source, situated under Volcano Island's central crater, at depths of similar to 5 km (based on the preferred Mogi model). Using this source geometry, we develop axisymmetric finite element models with annuli of concentric shells around the magma reservoir, embedded within a multi-layered elastic lithosphere. Using simply varying pressure histories as input, a variety of forward models are fit to the time history of continuously observed deformation for GPS stations located on Volcano Island. Though the inferred source geometry, volume and near-source rheological properties are non-unique, they represent more physically appropriate material properties than those assumed in simple elastic half-space models. The sources inferred using viscoelastic shell models suggest simpler pressure histories and reduced overall pressure changes, relative to equivalent elastic half-space models. (C) 2013 Elsevier B.V. All rights reserved.
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