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The Institut de Physique du Globe de Paris is a French governmental, non-profit research and higher education establishment located in Paris, dedicated to the study of earth and planetary science by combining observations, laboratory analysis and construction of conceptual analogical and numerical models.IPGP is part of CNRS , CNAP, University of Paris VI and University of Paris VII. It is the second largest CNRS research unit in France. The institute has 14 research divisions and 6 observatories. IPGP is also in charge by the French government of monitoring the active volcanoes on French territories in addition to the management of the worldwide network of seismological stations GEOSCOPE, and a major contribution to the worldwide network of magnetic observatories Intermagnet. IPGP maintains permanent volcanologic observatories on the islands of Réunion , Guadeloupe , and Martinique . The institute also maintains several analytical facilities in applied geophysics as well as a park of a variety of geophysical instruments.IPGP maintains three campuses in the Paris area. Until 2010, its main headquarter location is inside the Jussieu Campus in the 5th arrondissement of Paris. After 2010, it moved into a state of the art dedicated facility adjacent to the Jussieu Campus, in front of the Jardin des Plantes. IPGP has a second campus located 6 km to the east of Paris where it conducts space and planetary science activities ranging from building geophysical space instruments and sensors to planetary data analysis. The third campus is located in Paris VII university and is mainly dedicated for teaching. IPGP maintain a staff of nearly 500 persons. Wikipedia.

Cherniak I.,University of Warmia and Mazury | Cherniak I.,Space Weather Laboratory | Zakharenkova I.,Paris Institute of Earth Physics
Earth, Planets and Space | Year: 2015

The magnetosphere substorm plays a crucial role in the solar wind energy dissipation into the ionosphere. We report on the intensity of the high-latitude ionospheric irregularities during one of the largest storms of the current solar cycle - the St. Patrick's Day storm of 17 March 2015. The database of more than 2500 ground-based Global Positioning System (GPS) receivers was used to estimate the irregularities occurrence and dynamics over the auroral region of the Northern Hemisphere. We analyze the dependence of the GPS-detected ionospheric irregularities on the auroral activity. The development and intensity of the high-latitude irregularities during this geomagnetic storm reveal a high correlation with the auroral hemispheric power and auroral electrojet indices (0.84 and 0.79, respectively). Besides the ionospheric irregularities caused by particle precipitation inside the polar cap region, evidences of other irregularities related to the storm enhanced density (SED), formed at mid-latitudes and its further transportation in the form of tongue of ionization (TOI) towards and across the polar cap, are presented. We highlight the importance accounting contribution of ionospheric irregularities not directly related with particle precipitation in overall irregularities distribution and intensity. © 2015 Cherniak and Zakharenkova.

De Zeeuw-van Dalfsen E.,Paris Institute of Earth Physics | Pedersen R.,University of Iceland | Hooper A.,Technical University of Delft | Sigmundsson F.,University of Iceland
Journal of Volcanology and Geothermal Research | Year: 2012

Many calderas in the world show long-term unrest in the form of elevated rates of deformation and seismicity, related to pressure changes and magma movements within their magmatic plumbing systems. We present new observations of the style of deformation at the Askja caldera, Iceland, since 2000, using interferometric analysis of synthetic aperture radar images (InSAR) acquired by the Canadian RADARSAT-2 satellite. When combined with previously acquired detailed geodetic observations, by various techniques, we obtain an overview of Askja's behaviour through more than four decades. The combined dataset reveals that, during this non-eruptive period, Askja continuously subsides at a rate of 2.5-3cm/yr in 2000-2009, somewhat lower than the ~5cm/yr rate inferred for the 1983-1998 period. This behaviour of Askja is evaluated and compared to those of other restless calderas. The wrapped interferograms show three main features: (1) concentric fringes depicting subsidence in the centre of the main Askja caldera, (2) oval fringes elongated along the rift portraying subsidence and (3) subsidence in an area north of the Vatnajökull glacier. The average line-of-sight (LOS) velocity from ground to satellite was used as input for inverse modelling, of a deflating pressure source beneath the caldera, embedded in a homogeneous, elastic half-space. Two different source geometries were tested: a point pressure source and a horizontal penny shaped crack. The concentric fringes centred in the Askja caldera are best fit by a point source located at 65.05°N 16.78°W, at a depth of 3.2-3.8km with a volume decrease of 0.0012-0.0017km 3/yr from 2000 to 2009, consistent with previous studies. Provisional 2D FEM models including structural complexities in the crustal layers indicate that the tectonic setting of Askja plays an important role in the continuous, long-term high subsidence rates observed there. In order to fully understand the cause and effects of the complicated tectonic setting we encourage the use of a more realistic rheological model of the area, which could lead to reinterpretation of previous model results. © 2011 Elsevier B.V.

Bodin T.,University of California at Berkeley | Yuan H.,University of California at Berkeley | Romanowicz B.,University of California at Berkeley | Romanowicz B.,College de France | Romanowicz B.,Paris Institute of Earth Physics
Geophysical Journal International | Year: 2013

Receiver functions are a powerful tool to isolate and interpret receiver-side structure effects in teleseismic seismic records. They are easily constructed by deconvolving one component of a seismogram by another. Deconvolution is the inverse of convolution, and hence can be mathematically viewed as an inverse problem. It is a numerically unstable procedure that needs to be stabilized (i.e. regularized). This points to a recurring problem in geophysical imaging: there is a trade-off between variance and resolution, where the user needs to arbitrarily define a level of compromise. Here we propose a novel misfit function for inversion of converted phases that avoids deconvolution. In this way, the choice of regularization parameters (e.g. water level, width of a low pass filter) is avoided, and statistics of data errors can be correctly accounted for. We use this misfit measure to construct a likelihood probability function and carry out a transdimensional Bayesian inversion for shear wave structure. After illustrating the method with a synthetic test, a real data application is shown where teleseismic signals recorded at HYB station (Hyderabad, India) and surface wave dispersion measurements are jointly inverted to provide a probabilistic 1-D seismic model beneath the station. The results help address the debate on the thickness of the lithosphere in this region. We show that the sharp negative velocity jump at 110 km that was previously interpreted as the lithosphere- asthenosphere boundary (LAB) is actually a mid-lithospheric discontinuity. The actual LAB is seen deeper as a milder gradient between 150 and 200 km. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.

Pavlov V.E.,Russian Academy of Sciences | Fluteau F.,Paris Institute of Earth Physics | Veselovskiy R.V.,Russian Academy of Sciences | Fetisova A.M.,Moscow State University | Latyshev A.V.,Russian Academy of Sciences
Izvestiya, Physics of the Solid Earth | Year: 2011

Detailed paleomagnetic studies have shown that the effusive Permian-Triassic traps in the Kotui River valley were formed as the result of volcanic activity, which occurred in the form of volcanic pulses and individual eruptions with net duration of at most 7000-8000 years, excluding the periods of volcanic quiescence. According to the analysis of the paleomagnetic data earlier obtained by Heunemann and his coauthors [2004b] on the Abagalakh and Listvyanka sections in the Norilsk region, those geological units were formed during 25 volcanic pulses and separate eruptions, which all lasted up to 8000 years altogether, whereas the total time of formation (including the periods of volcanic quiescence) exceeded 10000-100000 years for the Norilsk section and was probably a bit shorter for the Kotui section. Comparison of the positions of virtual geomagnetic poles calculated for the Norilsk and the Kotui sections provides no grounds to suggest that these sections were formed at different geological times. The scatter in the positions of the virtual geomagnetic poles (VGP) for the directional groups and individual directions (58 altogether) jointly for the two sections (more than 160 lava flows) indicates that the secular geomagnetic variations at the Permian-Triassic boundary had similar amplitudes to those that occurred in the past 5 Ma. © 2011 Pleiades Publishing, Ltd.

Lesparre N.,Paris Institute of Earth Physics | Gibert D.,Paris Institute of Earth Physics | Marteau J.,French National Center for Scientific Research
Geophysical Journal International | Year: 2012

Density tomography of rock volumes with cosmic muons involves telescopes equipped with pixelized matrices of scintillator strips able to simultaneously measure the flux of muons in hundredths of directions. The resulting muon radiography images are a measure of the amount of matter integrated along each line of sight inside the geological target. This information constitutes the primary data at the root of muon density 3-D tomography. Before being used for either interpretation or tomography inversion, the radiographies must be corrected from artefacts due to imperfect detection capacity of the detection matrices. We present a correction method based on a Bayesian inversion to construct a probabilistic model of the distorted telescope acceptance from which undistorted radiographies may be obtained. The method also allows to simultaneously derive a stochastic model for the incident flux of muons. The resulting non-linear inverse problem is solved with the Metropolis-annealing algorithm, which allows to easily implement symmetry constraints to reduce the non-uniqueness. An inversion of real data acquired with one of our field muon telescopes is presented and discussed. © 2011 The Authors Geophysical Journal International © 2011 RAS.

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