References of "Geophysical Research Letters"
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See detailSingle station monitoring of volcanoes using seismic ambient noise
De Plaen, Raphaël UL; Lecocq, Thomas; Caudron, Corentin et al

in Geophysical Research Letters (2016)

Seismic ambient noise cross correlation is increasingly used to monitor volcanic activity. However, this method is usually limited to volcanoes equipped with large and dense networks of broadband stations ... [more ▼]

Seismic ambient noise cross correlation is increasingly used to monitor volcanic activity. However, this method is usually limited to volcanoes equipped with large and dense networks of broadband stations. The single station approach may provide a powerful and reliable alternative to the classical “cross-stations” approach when measuring variation of seismic velocities. We implemented it on the Piton de la Fournaise in Reunion Island, a very active volcano with a remarkable multi-disciplinary continuous monitoring. Over the past decade, this volcano was increasingly studied using the traditional cross-correlation technique and therefore represents a unique laboratory to validate our approach. Our results, tested on stations located up to 3.5 km from the eruptive site, performed as well as the classical approach to detect the volcanic eruption in the 1-2 Hz frequency band. This opens new perspectives to successfully forecast volcanic activity at volcanoes equipped with a single 3-component seismometer. [less ▲]

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See detailConstraints on the upper crustal magma reservoir beneath Yellowstone Caldera inferred from lake-seiche induced strain observations
Luttrell, Karen; Mencin, David; Francis, Olivier UL et al

in Geophysical Research Letters (2013), 40(3), 501--506

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See detailAn Evaluation of New Estimates from GPS, GRACE and Load Models compared to SLR
Lavalee, D.; Moore, P.; Clarke, Peter J. et al

in Geophysical Research Letters (2010), (37), 5-6

Changes in J2, resulting from past and present changes in Earth’s climate, are traditionally observed by Satellite Laser ranging (SLR). Assuming an elastic Earth, it is possible to infer changes in J2 ... [more ▼]

Changes in J2, resulting from past and present changes in Earth’s climate, are traditionally observed by Satellite Laser ranging (SLR). Assuming an elastic Earth, it is possible to infer changes in J2 from changes in Earth’s shape observed by GPS. We compare estimates of non‐secular J2 changes from GPS, SLR, GRACE, and a load model. The GPS and SLR annual signals agree but are different (16%) to the load model. Subtraction of the load model removes the annual variation from GPS, SLR, and GRACE, and the semi‐annual variation in GPS. The GPS and SLR long‐term signals are highly correlated, but GPS is better correlated with the loading model. Subtraction of the load model removes the 1998 anomaly from the GPS J2 series but not completely from the SLR J2 series, suggesting that the SLR anomaly may not be entirely due to mass re‐distribution as has been presumed. [less ▲]

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See detailElastic uplift in southeast Greenland due to rapid ice mass lost
Khan, Shfaqat A.; Wahr, John; Stearns, Leigh A. et al

in Geophysical Research Letters (2007), 34(L21701), 1-6

The rapid unloading of ice from the southeastern sector of the Greenland ice sheet between 2001 and 2006 caused an elastic uplift of ~35 mm at a GPS site in Kulusuk. Most of the uplift results from ice ... [more ▼]

The rapid unloading of ice from the southeastern sector of the Greenland ice sheet between 2001 and 2006 caused an elastic uplift of ~35 mm at a GPS site in Kulusuk. Most of the uplift results from ice dynamic-induced volume losses on two nearby outlet glaciers. Volume loss from Helheim Glacier, calculated from sequential digital elevation models, contributes about ~16 mm of the observed uplift, with an additional ~5 mm from volume loss of Kangerdlugssuaq Glacier. The remaining uplift signal is attributed to significant melt-induced ice volume loss from the ice sheet margin along the southeast coast between 62°N and 66°N. [less ▲]

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See detailEffect of gravitational consistency and mass conservation on seasonal surface mass loading models
Clarke, Peter J.; Lavallée, David A.; Blewitt, Geoffrey et al

in Geophysical Research Letters (2005), 32(L08306), 1-5

Increasingly, models of surface mass loads are used either to correct geodetic time coordinates by removing seasonal and other ‘‘noise’’, or for comparison with other geodetic parameters. However, models ... [more ▼]

Increasingly, models of surface mass loads are used either to correct geodetic time coordinates by removing seasonal and other ‘‘noise’’, or for comparison with other geodetic parameters. However, models of surface loading obtained by simply combining the mass redistribution due to individual phenomena will not in general be self- consistent, in that (i) the implied global water budget will not be mass-conserving, and (ii) the modelled sea level will not be an equipotential surface of Earth’s total gravity field. We force closure of the global water budget by allowing the ‘‘passive’’ ocean to change in mass. This medium-term passive ocean response will not be a uniform change in non- steric ocean surface height, but must necessarily be spatially variable to keep the ‘‘passive’’ ocean surface on an equipotential. Using existing load models, we demonstrate the effects of our consistency theory. Geocenter motion is amplified significantly, by up to 43%. [less ▲]

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See detailAtmospheric loading corrections applied to GPS data at the observation level
Tregoning, T.; van Dam, Tonie UL

in Geophysical Research Letters (2005), 32(L22310), 1-4

Space-geodetic techniques can detect elastic deformation of the Earth caused by atmospheric pressure loading (ATML). However, it has not yet been demonstrated whether these surface displacements should be ... [more ▼]

Space-geodetic techniques can detect elastic deformation of the Earth caused by atmospheric pressure loading (ATML). However, it has not yet been demonstrated whether these surface displacements should be accounted for at the time of reduction of the observations or by applying time-averaged values to the coordinates after the analysis of the observations. An analysis of the power spectral density of the ATML predicted vertical deformation shows that, aside from the diurnal and semi-diurnal periods, there is very little power in the sub-daily frequencies. The present tidal ATML models improve the analysis at sites near the equator but seem to degrade the height estimates elsewhere. The majority of the non-tidal deformation can be modelled by applying a daily-averaged correction to daily estimates of coordinates but a greater improvement in height RMS is found if non-tidal ATML is applied at the observation level. [less ▲]

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See detailObserving and assessing non-tidal ocean loading using ocean, continuous GPS and gravity data in the Adriatic area
Zerbini, S.; Matonti, F.; Raicich, R. et al

in Geophysical Research Letters (2004), 31(L23609), 1-5

The effect of nontidal ocean loading (NTOL) is observed in the height series of four permanent GPS stations in the northern Adriatic. A validation of the ECCO model is performed by comparing model ... [more ▼]

The effect of nontidal ocean loading (NTOL) is observed in the height series of four permanent GPS stations in the northern Adriatic. A validation of the ECCO model is performed by comparing model estimates of sea-level anomalies from tide-gauges with TOPEX/ POSEIDON data, and ECCO model estimates of bottom pressure with those derived from temperature and salinity observations. The amplitudes of theECCO sea-level anomaly are found to be 1.4 times smaller than observations; bottom pressure is 2 times smaller. Using a Green’s functions approach to determine elastic deformations, the ECCO ocean bottom pressure is used to estimate surface displacements at the GPS sites. Model results were compared with the height series and with the observed NTOL effect. The height series and the predicted NTOL are highly correlated at all four stations. The analysis performed on superconducting gravimeter data at the Medicina station also shows high correlation. [less ▲]

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See detailCrustal displacements due to continental water loading
van Dam, Tonie UL; Wahr, J.; Milly, P. C. D. et al

in Geophysical Research Letters (2001), 28(4), 651-654

The effects of long-wavelength (>100 km), seasonal variability in continental water storage on vertical crustal motions are assessed. The modeled vertical displacements (ΔrM) have root-mean-square (RMS ... [more ▼]

The effects of long-wavelength (>100 km), seasonal variability in continental water storage on vertical crustal motions are assessed. The modeled vertical displacements (ΔrM) have root-mean-square (RMS) values for 1994–1998 as large as 8 mm, with ranges up to 30 mm, and are predominantly annual in character. Regional strains are on the order of 20 nanostrain for tilt and 5 nanostrain for horizontal deformation. We compare ΔrM with observed Global Positioning System (GPS) heights (ΔrO) (which include adjustments to remove estimated effects of atmospheric pressure and annual tidal and non-tidal ocean loading) for 147 globally distributed sites. When the ΔrO time series are adjusted by ΔrM, their variances are reduced, on average, by an amount equal to the variance of the ΔrM. Of the ΔrO time series exhibiting a strong annual signal, more than half are found to have an annual harmonic that is in phase and of comparable amplitude with the annual harmonic in the ΔrM. The ΔrM time series exhibit long-period variations that could be mistaken for secular tectonic trends or postglacial rebound when observed over a time span of a few years. [less ▲]

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See detailAccurate transfer function determination for superconducting gravimeters
Van Camp, Michel; Wenzel, H.-G.; Schott, P. et al

in Geophysical Research Letters (2000), 27(1), 37-40

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See detailMeasuring postglacial rebound with GPS and absolute gravity
Larson, Kristine M.; van Dam, Tonie UL

in Geophysical Research Letters (2000), 27(23), 3925-3928

We compare vertical rates of deformation derived from continuous Global Positioning System (GPS) observations and episodic measurements of absolute gravity. We concentrate on 4 sites in a region of North ... [more ▼]

We compare vertical rates of deformation derived from continuous Global Positioning System (GPS) observations and episodic measurements of absolute gravity. We concentrate on 4 sites in a region of North America experiencing postglacial rebound. The rates of uplift from gravity and GPS agree within one standard deviation for all sites. The GPS vertical deformation rates are signi cantly more precise than the gravity rates, primarily because of the denser temporal spacing provided by continuous GPS tracking. We conclude that continuous GPS observations are more cost e cient and provide more precise estimates of vertical deformation rates than campaign style gravity observations where systematic errors are di cult to quantify. [less ▲]

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See detailCalibration of a superconducting gravimeter by comparison with an absolute gravimeter FG5 in Boulder
Francis, Olivier UL; Niebauer, T. M.; Sasagawa, G. et al

in Geophysical Research Letters (1998), 25(7), 1075-1078

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See detailTwo years of continuous measurements of tidal and nontidal variations of gravity in Boulder, Colorado
van Dam, Tonie UL; Francis, Olivier UL

in Geophysical Research Letters (1998), 25(3), 393-396

We report here on the results of an analysis of 2 years of data from NOAA’s superconducting gravimeter located at the Table Mountain Gravity Observatory in Boulder, Colorado. Observed tidal parameters ... [more ▼]

We report here on the results of an analysis of 2 years of data from NOAA’s superconducting gravimeter located at the Table Mountain Gravity Observatory in Boulder, Colorado. Observed tidal parameters, corrected for ocean loading effects, are compared with theoretical tidal parameters predicted for a non-hydrostatic inelastic Earth model and demonstrate excellent agreement. Tidal residuals, corrected for polar motion and a linear instrument drift are highly correlated with gravity changes measured by two absolute gravimeters over the same time period. The admittance to local pressure i s found to be -0.356 mGal/mbar. However, this admittance factor is found to be seasonally and frequency dependent. Correlations between rainfall events and gravity changes are observed. Attempts to model these gravity changes as exponential functions of time were unsuccessful. [less ▲]

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See detailTidal loading in south western Europe: A test area
Francis, Olivier UL; Melchior, P.

in Geophysical Research Letters (1996), 23(17), 2251-2254

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See detailM2 World Ocean Tide from Tide Gauge Measurements
Francis, Olivier UL; Mazzega, P.

in Geophysical Research Letters (1991), 18(6), 1167-1170

Detailed reference viewed: 65 (4 UL)