Crustal deformation near Hengill volcano, Iceland 1993-1998: Coupling between magmatic activity and faulting inferred from elastic modeling of satellite radar interferograms

2000 ◽  
Vol 105 (B11) ◽  
pp. 25655-25670 ◽  
Author(s):  
Kurt L. Feigl ◽  
Jérôme Gasperi ◽  
Freysteinn Sigmundsson ◽  
Alexis Rigo
Keyword(s):  
Crustal Deformation ◽  
Magmatic Activity ◽  
Satellite Radar

scholarly journals The influence of elastic thickness non-uniformity on viscoelastic crustal response to magma emplacement: application to the Kutcharo caldera, eastern Hokkaido, Japan

2020 ◽  
Vol 224 (1) ◽  
pp. 701-718
Author(s):  
Tadashi Yamasaki ◽  
Hiroaki Takahashi ◽  
Mako Ohzono ◽  
Tim J Wright ◽  
Tomokazu Kobayashi
Keyword(s):  
Crustal Deformation ◽  
Elastic Layer ◽  
Viscoelastic Model ◽  
Geothermal Gradient ◽  
Deformation Field ◽  
Viscoelastic Layer ◽  
Magmatic Activity ◽  
Uniform Model ◽  
Magma Emplacement ◽  
The Difference

SUMMARY An elastic layer plays an important role in deformation of the crust. At active volcanoes, its thickness would be effectively thinned by a higher geothermal gradient, particularly in a region beneath which magmatic activity is relatively high. This study examines the influence of elastic thickness non-uniformity on viscoelastic crustal deformation by magma emplacement. A 3-D linear Maxwell viscoelastic model is employed, in which an elastic layer underlain by a viscoelastic layer with a spatially uniform viscosity is thinned to be hi in the volcano centre, compared with hi + Δh in the peripheral regions, and a sill-like magma emplacement occurs in the upper layer beneath the centre. It is found that the post-emplacement viscoelastic subsidence is diminished or enhanced by the elastic thickness non-uniformity, depending on whether or not the horizontal width of the magma emplacement (ωs) is greater than the horizontal width (ωe) over which the elastic layer is thinner. The available signature of the non-uniformity is explored by comparison with a model that has a spatially uniform elastic thickness (UET) of hi. If an apparent viscosity (ηa) of the UET model is adjusted so that the difference in post-emplacement subsidence is minimized at the deformation centre, the non-uniformity appears in the overall deformation field as a displacement anomaly over the perimeter of the sill in which viscoelastic subsidence is greater for the non-uniform model. The anomaly is, however, by no more than the magnitude of ∼15 per cent of the maximal syn-emplacement uplift, though ηa is necessarily modified to be ∼0.2–10 times the non-uniform model viscosity (ηc). If ωe is larger than a few times ωs, a weak signature is no longer expected in the deformation field, and ηa is not significantly deviated from ηc. Since the signature appears so faintly in a displacement field, the InSAR data in the Kutcharo caldera for a period from 1993 August 13 to 1998 June 9 do not allow us to capture the non-uniformity. However, it can be concluded that if ωe beneath the caldera is comparable with or greater than the topographic caldera diameter (ωc) as implied by the spatial variation of the geothermal gradient, the non-uniformity has no significant influence. Otherwise, if ωe < ωc, the non-uniformity influences the estimation of the crustal viscosity, but does not affect the overall deformation field. The elastic thickness non-uniformity can be theoretically captured in the deformation field, but in practice, its influence, particularly on estimating crustal viscosity, cannot be properly inferred without other geophysical data such as the geothermal gradient in and around the caldera.

Installation of New GNSS Network Around Kusatsu-Shirane Volcano, Japan: Its Perspective and the First Result

2019 ◽  
Vol 14 (5) ◽  
pp. 744-754
Author(s):  
Rina Noguchi ◽  
Tatsuji Nishizawa ◽  
Wataru Kanda ◽  
Takahiro Ohkura ◽  
Akihiko Terada ◽  
...  
Keyword(s):  
Crustal Deformation ◽  
Length Change ◽  
Satellite System ◽  
Baseline Length ◽  
Deformation Pattern ◽  
Magmatic Activity ◽  
Essential Information ◽  
Summit Area ◽  
Gnss Network ◽  
Global Navigation Satellite

Crustal deformation is essential information for monitoring volcanic activity. In the summit area of the Kusatsu-Shirane Volcano (KSV), a dense Global Navigation Satellite System (GNSS) network has been operating near the recent volcanic center, Yugama crater. This network is sensitive to shallow depth activity, such as phreatic eruptions at the summit area, but is not applicable to deep magmatic activity, suggested to have been occurring for thousands of years by recent geological studies. Aiming to detect magmatic activity at a certain depth, we installed a new GNSS network near KSV. The observation sites were selected based on the crustal deformation pattern calculated for several intrusive events of the deep-seated magma. First, the GNSS sites for campaign observation were installed at eight locations in 2017. Then, four continuous sites commenced operation after a phreatic eruption at Mt. Motoshirane in January 2018. Here, we show the results of the first and second observation campaigns, operating in October 2017 and February 2018. Coordinate values are computed by precise point positioning with ambiguity resolution (PPP-AR) analysis and are used to calculate the displacement and the baseline length change during this period. The uncertainties of the calculated coordinate values are sufficiently small (less than 4.5 mm) except at some sites for which the data possibly include multipath errors due to trees and snow. Although any deformation associated with the 2018 eruption of Mt. Motoshirane is not detected, subsequent observations would contribute to monitoring long-term activity near KSV.

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