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Maurizio Battaglia - One of the best experts on this subject based on the ideXlab platform.

  • the mechanics of unrest at long valley caldera california 1 modeling the geometry of the Source using gps leveling and two color edm data
    Journal of Volcanology and Geothermal Research, 2003
    Co-Authors: Maurizio Battaglia, Paul Segall, Jessica R Murray, Peter F Cervelli, John Langbein
    Abstract:

    We surveyed 44 existing leveling monuments in Long Valley caldera in July 1999, using dual frequency global positioning system (GPS) receivers. We have been able to tie GPS and leveling to a common reference frame in the Long Valley area and computed the vertical deformation by differencing GPS-based and leveled orthometric heights. The resurgent dome uplifted 74±7 cm from 1975 to 1999. To define the inflation Source, we invert two-color EDM and uplift data from the 1985–1999 unrest period using spherical or ellipsoidal Sources. We find that the ellipsoidal Source satisfies both the vertical and horizontal deformation data, whereas the spherical point Source cannot. According to our analysis of the 1985–1999 data, the main Source of deformation is a prolate ellipsoid located beneath the resurgent dome at a depth of 5.9 km (95% bounds of 4.9–7.5 km). This body is vertically elongated, has an aspect ratio of 0.475 (95% bounds are 0.25–0.65) and a volume change of 0.086 km3 (95% bounds are 0.06–0.13 km3). Failure to account for the ellipsoidal nature of the Source biases the Estimated Source depth by 2.1 km (35%), and the Source volume by 0.038 km3 (44%).

  • the mechanics of unrest at long valley caldera california 2 constraining the nature of the Source using geodetic and micro gravity data
    Journal of Volcanology and Geothermal Research, 2003
    Co-Authors: Maurizio Battaglia, Paul Segall, Carter W Roberts
    Abstract:

    Abstract We model the Source of inflation of Long Valley caldera by combining geodetic and micro-gravity data. Uplift from GPS and leveling, two-color EDM measurements, and residual gravity change determinations are used to estimate the intrusion geometry, assuming a vertical prolate ellipsoidal Source. The U.S. Geological Survey occupied the Long Valley gravity network six times from 1980 to 1985. We reoccupied this network twice, in the summer of 1998 (33 stations), and the summer of 1999 (37 stations). Before gravity data can be used to estimate the density of the intrusion, they must be corrected for the effect of vertical deformation (the free-air effect) and changes in the water table. We use geostatistical techniques to interpolate uplift and water table changes at the gravity stations. The inflation Source (a vertical prolate ellipsoid) is located 5.9 km beneath the resurgent dome with an aspect ratio equal to 0.475, a volume change from 1982 to 1999 of 0.136 km 3 and a density of around 1700 kg/m 3 . A bootstrap method was employed to estimate 95% confidence bounds for the parameters of the inflation model. We obtained a range of 0.105–0.187 km 3 for the volume change, and 1180–2330 kg/m 3 for the density. Our results do not support hydrothermal fluid intrusion as the primary cause of unrest, and confirm the intrusion of silicic magma beneath Long Valley caldera. Failure to account for the ellipsoidal nature of the Source biases the Estimated Source depth by 2.9 km (a 33% increase), the volume change by 0.019 km 3 (a 14% increase) and the density by about 1200 kg/m 3 (a 40% increase).

Carter W Roberts - One of the best experts on this subject based on the ideXlab platform.

  • the mechanics of unrest at long valley caldera california 2 constraining the nature of the Source using geodetic and micro gravity data
    Journal of Volcanology and Geothermal Research, 2003
    Co-Authors: Maurizio Battaglia, Paul Segall, Carter W Roberts
    Abstract:

    Abstract We model the Source of inflation of Long Valley caldera by combining geodetic and micro-gravity data. Uplift from GPS and leveling, two-color EDM measurements, and residual gravity change determinations are used to estimate the intrusion geometry, assuming a vertical prolate ellipsoidal Source. The U.S. Geological Survey occupied the Long Valley gravity network six times from 1980 to 1985. We reoccupied this network twice, in the summer of 1998 (33 stations), and the summer of 1999 (37 stations). Before gravity data can be used to estimate the density of the intrusion, they must be corrected for the effect of vertical deformation (the free-air effect) and changes in the water table. We use geostatistical techniques to interpolate uplift and water table changes at the gravity stations. The inflation Source (a vertical prolate ellipsoid) is located 5.9 km beneath the resurgent dome with an aspect ratio equal to 0.475, a volume change from 1982 to 1999 of 0.136 km 3 and a density of around 1700 kg/m 3 . A bootstrap method was employed to estimate 95% confidence bounds for the parameters of the inflation model. We obtained a range of 0.105–0.187 km 3 for the volume change, and 1180–2330 kg/m 3 for the density. Our results do not support hydrothermal fluid intrusion as the primary cause of unrest, and confirm the intrusion of silicic magma beneath Long Valley caldera. Failure to account for the ellipsoidal nature of the Source biases the Estimated Source depth by 2.9 km (a 33% increase), the volume change by 0.019 km 3 (a 14% increase) and the density by about 1200 kg/m 3 (a 40% increase).

Paul Segall - One of the best experts on this subject based on the ideXlab platform.

  • the mechanics of unrest at long valley caldera california 1 modeling the geometry of the Source using gps leveling and two color edm data
    Journal of Volcanology and Geothermal Research, 2003
    Co-Authors: Maurizio Battaglia, Paul Segall, Jessica R Murray, Peter F Cervelli, John Langbein
    Abstract:

    We surveyed 44 existing leveling monuments in Long Valley caldera in July 1999, using dual frequency global positioning system (GPS) receivers. We have been able to tie GPS and leveling to a common reference frame in the Long Valley area and computed the vertical deformation by differencing GPS-based and leveled orthometric heights. The resurgent dome uplifted 74±7 cm from 1975 to 1999. To define the inflation Source, we invert two-color EDM and uplift data from the 1985–1999 unrest period using spherical or ellipsoidal Sources. We find that the ellipsoidal Source satisfies both the vertical and horizontal deformation data, whereas the spherical point Source cannot. According to our analysis of the 1985–1999 data, the main Source of deformation is a prolate ellipsoid located beneath the resurgent dome at a depth of 5.9 km (95% bounds of 4.9–7.5 km). This body is vertically elongated, has an aspect ratio of 0.475 (95% bounds are 0.25–0.65) and a volume change of 0.086 km3 (95% bounds are 0.06–0.13 km3). Failure to account for the ellipsoidal nature of the Source biases the Estimated Source depth by 2.1 km (35%), and the Source volume by 0.038 km3 (44%).

  • the mechanics of unrest at long valley caldera california 2 constraining the nature of the Source using geodetic and micro gravity data
    Journal of Volcanology and Geothermal Research, 2003
    Co-Authors: Maurizio Battaglia, Paul Segall, Carter W Roberts
    Abstract:

    Abstract We model the Source of inflation of Long Valley caldera by combining geodetic and micro-gravity data. Uplift from GPS and leveling, two-color EDM measurements, and residual gravity change determinations are used to estimate the intrusion geometry, assuming a vertical prolate ellipsoidal Source. The U.S. Geological Survey occupied the Long Valley gravity network six times from 1980 to 1985. We reoccupied this network twice, in the summer of 1998 (33 stations), and the summer of 1999 (37 stations). Before gravity data can be used to estimate the density of the intrusion, they must be corrected for the effect of vertical deformation (the free-air effect) and changes in the water table. We use geostatistical techniques to interpolate uplift and water table changes at the gravity stations. The inflation Source (a vertical prolate ellipsoid) is located 5.9 km beneath the resurgent dome with an aspect ratio equal to 0.475, a volume change from 1982 to 1999 of 0.136 km 3 and a density of around 1700 kg/m 3 . A bootstrap method was employed to estimate 95% confidence bounds for the parameters of the inflation model. We obtained a range of 0.105–0.187 km 3 for the volume change, and 1180–2330 kg/m 3 for the density. Our results do not support hydrothermal fluid intrusion as the primary cause of unrest, and confirm the intrusion of silicic magma beneath Long Valley caldera. Failure to account for the ellipsoidal nature of the Source biases the Estimated Source depth by 2.9 km (a 33% increase), the volume change by 0.019 km 3 (a 14% increase) and the density by about 1200 kg/m 3 (a 40% increase).

John Langbein - One of the best experts on this subject based on the ideXlab platform.

  • the mechanics of unrest at long valley caldera california 1 modeling the geometry of the Source using gps leveling and two color edm data
    Journal of Volcanology and Geothermal Research, 2003
    Co-Authors: Maurizio Battaglia, Paul Segall, Jessica R Murray, Peter F Cervelli, John Langbein
    Abstract:

    We surveyed 44 existing leveling monuments in Long Valley caldera in July 1999, using dual frequency global positioning system (GPS) receivers. We have been able to tie GPS and leveling to a common reference frame in the Long Valley area and computed the vertical deformation by differencing GPS-based and leveled orthometric heights. The resurgent dome uplifted 74±7 cm from 1975 to 1999. To define the inflation Source, we invert two-color EDM and uplift data from the 1985–1999 unrest period using spherical or ellipsoidal Sources. We find that the ellipsoidal Source satisfies both the vertical and horizontal deformation data, whereas the spherical point Source cannot. According to our analysis of the 1985–1999 data, the main Source of deformation is a prolate ellipsoid located beneath the resurgent dome at a depth of 5.9 km (95% bounds of 4.9–7.5 km). This body is vertically elongated, has an aspect ratio of 0.475 (95% bounds are 0.25–0.65) and a volume change of 0.086 km3 (95% bounds are 0.06–0.13 km3). Failure to account for the ellipsoidal nature of the Source biases the Estimated Source depth by 2.1 km (35%), and the Source volume by 0.038 km3 (44%).

Hitoshi Hirose - One of the best experts on this subject based on the ideXlab platform.

  • non volcanic deep low frequency tremors accompanying slow slips in the southwest japan subduction zone
    Tectonophysics, 2006
    Co-Authors: Kazushige Obara, Hitoshi Hirose
    Abstract:

    Non-volcanic deep low-frequency tremors in southwest Japan exhibit a strong temporal and spatial correlation with slow slip detected by the dense seismic network. The tremor signal is characterized by a low-frequency vibration with a predominant frequency of 0.5–5 Hz without distinct P- or S-wave onset. The tremors are located using the coherent pattern of envelopes over many stations, and are Estimated to occur near the transition zone on the plate boundary on the forearc side along the strike of the descending Philippine Sea plate. The belt-like distribution of tremors consists of many clusters. In western Shikoku, the major tremor activity has a recurrence interval of approximately six months, with each episode lasting over a week. The tremor Source area migrates during each episode along the strike of the subducting plate with a migration velocity of about 10 km/day. Slow slip events occur contemporaneously with this tremor activity, with a coincident Estimated Source area that also migrates during each episode. The coupling of tremor and slow slip in western Shikoku is very similar to the episodic tremor and slip phenomenon reported for the Cascadia margin in northwest North America. The duration and recurrence interval of these episodes varies between tremor clusters even on the same subduction zone, attributable to regional difference in the frictional properties of the plate interface.