Paris Institute of Earth Physics

Paris, France

Paris Institute of Earth Physics

Paris, France

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.

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News Article | May 26, 2017
Site: www.newscientist.com

Saturn’s mid-sized moons are like the monsters in late-night horror movies. Smash them into tiny pieces, and they glue themselves back together as new versions of the old moons. This new finding contradicts a theory that Saturn’s rings were caused by moons colliding. All four giant planets in our solar system have rings, but Saturn’s are by far the brightest and most massive. It’s not yet clear where the material needed to form rings comes from. Last year, a study of Saturn’s moons pointed to a collision as the cause of the gas giant’s rings. Matija Cuk of the SETI Institute and colleagues found that the orbits of Tethys and Dione hadn’t changed much since the solar system formed more than 4 billion years ago. They suggested that resonant interactions of an earlier generation of moons caused a catastrophic collision just 100 million years ago that resulted in the debris that makes up Saturn’s rings. Their theory was that largest pieces of this debris then formed Tethys, Dione and Rhea, while fine particles spread out to form rings. These mid-sized moons orbit Saturn in the diffuse area beyond its rings, and as time goes on, they hoover up everything in their path, so particles that spread inward formed the present rings inside the so-called Roche limit, where tidal forces break up large objects like moons. To investigate if a collision could have caused the rings, Sébastien Charnoz and Ryuki Hyodo of the Paris Institute of Earth Physics in France modelled the event. They found that if big chunks of the moons survived this smash-up, the debris would form a single new moon so fast that particles would not drift inward to form rings. On the other hand, if the impact completely shattered both original moons, it could form two or more new moons, and “the particles would stop spreading within a few tens of years, giving them no time to spread enough to reach the Roche limit” and form the rings, says Charnoz. “The process is so efficient that 20 to 30 generations of moons could have formed,” he says. “This is an important result,” says Larry Esposito of the University of Colorado in Boulder, a specialist in planetary rings. “Although some large moons may repeatedly reform, Saturn’s rings cannot be produced by this scenario.”


Massin F.,University of Reunion Island | Massin F.,Paris Institute of Earth Physics | Ferrazzini V.,Paris Institute of Earth Physics | Bachelery P.,University of Reunion Island | And 3 more authors.
Journal of Volcanology and Geothermal Research | Year: 2011

Analysis of seismic activity associated with the eruptions of 2007, which led to the collapse of the Dolomieu crater on April 5th, reveals the link between the seismicity and the magma transfers at Piton de la Fournaise. Three eruptive phases occurred on February 18th, March 30th and April 2nd, 2007, at the summit, 2,000 m, and 600 m high on the South-East flank respectively, illustrating the three types of eruptions defined for the current Piton de la Fournaise activity. We use cross-correlation of seismic waveforms and clustering to improve the earthquake locations and determine the best-constrained focal mechanisms (with an average of 78 P phase polarities). The pre-eruptive seismicity of the February and March eruptions is composed of time extended clusters that also preceded other distal eruptions from 2000 to 2007. Our analysis shows that the seismic swarm prior to the February eruption initiated the intrusion that led to the April 2007 eruption. The seismicity preceding the Dolomieu crater collapse consists of numerous, but time-limited, clusters and specific seismic activity that accompanied the Dolomieu crater collapse. From April 1st to April 5th, earthquakes with CLVD mechanisms combined with normal faulting sources occurred between 0.8 and 0 km. asl, until the complete rupture of the shallow magma storage roof. This collapse induced the propagation of a de-pressurization front and triggered a migration of seismicity from 0 to - 8 km along a very narrow path. © 2011 Elsevier B.V.


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.


Carbone D.,Italian National Institute of Geophysics and Volcanology | Gibert D.,Paris Institute of Earth Physics | Marteau J.,French National Center for Scientific Research | Diament M.,Paris Institute of Earth Physics | And 2 more authors.
Geophysical Journal International | Year: 2013

Interactions of conduit geometry with gas-liquid flows control volcanic activity, implying that the evaluation of volcanic hazards requires quantitative understanding of the inner structure of the volcano. The more established geophysical imaging techniques suffer from inherent ambiguity, may require spatially dense measurements in active areas and may not provide sufficient spatial resolution in the uppermost part of the conduit system. It is thus desirable to develop new imaging techniques allowing a better spatial resolution of a volcano's upper feeding system, with reduced ambiguity and a low level of risk for operators. Muon particles can be utilized to image the internal density distribution of volcanic structures. The principle of muon radiography is essentially the same as X-ray radiography, except for substituting penetrating particles in place of photons.Muons are more attenuated by higher density parts inside the target and thus information about its inner structure are obtained from the differential muon absorption. We report on a muon-imaging experiment that was conducted at Mt Etna in 2010. The target structure was one of the summit craters of the volcano. This experiment was performed using a muon telescope suitably designed to withstand the harsh conditions in the summit zone of a high volcano. We found a marked difference between synthetic and observed attenuation of muons through the target. This discrepancy is likely due to the bias on the observed flux, arising from false muon tracks. They are caused by low-energy particles that, by chance, hit simultaneously the two matrixes of the telescope, leading to detection of a false positive. We separated the useful from the unwanted signal through a first-order model of the background noise. The resulting signal is compared with the corresponding synthetic flux. Eventually, we found regions of higher- and lower-than-expected muon flux, that are possibly related to inner features of the target crater. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.


Bodin T.,University of California at Berkeley | Yuan H.,University of California at Berkeley | Romanowicz B.,University of California at Berkeley | Romanowicz B.,Collège 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.


Soloviev A.,Russian Academy of Sciences | Chulliat A.,Paris Institute of Earth Physics | Bogoutdinov S.,Russian Academy of Sciences | Gvishiani A.,Russian Academy of Sciences | And 3 more authors.
Earth, Planets and Space | Year: 2012

In the present paper we apply a recently developed pattern recognition algorithm SPs to the problem of automated detection of artificial disturbances in one-second magnetic observatory data. The SPs algorithm relies on the theory of discrete mathematical analysis, which has been developed by some of the authors for more than 10 years. It continues the authors' research in the morphological analysis of time series using fuzzy logic techniques. We show that, after a learning phase, this algorithm is able to recognize artificial spikes uniformly with low probabilities of target miss and false alarm. In particular, a 94% spike recognition rate and a 6% false alarm rate were achieved as a result of the algorithm application to raw one-second data acquired at the Easter Island magnetic observatory. This capability is critical and opens the possibility to use the SPs algorithm in an operational environment. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).


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.


Cherniak I.,Space Weather Laboratory | Cherniak I.,University of Warmia and Mazury | Zakharenkova I.,Paris Institute of Earth Physics
Earth, Planets and Space | Year: 2016

We present an analysis of ionospheric irregularities at high latitudes during the 2015 St. Patrick's Day storm. Our study used measurements from ~2700 ground-based GPS stations and GPS receivers onboard five low earth orbit (LEO) satellites - Swarm A, B and C, GRACE and TerraSAR-X - that had close orbit altitudes of ~500 km, and the Swarm in situ plasma densities. An analysis of the rate of TEC index (ROTI) derived from LEO-GPS data, together with Swarm in situ plasma probe data, allowed us to examine the topside ionospheric irregularities and to compare them to the main ionospheric storm effects observed in ground-based GPS data. We observed strong ionospheric irregularities in the topside ionosphere during the storm's main phase that were associated with storm-enhanced density (SED) formation at mid-latitudes and further evolution of the SED plume to the polar tongue of ionization (TOI). Daily ROTI maps derived from ground-based and LEO-GPS measurements show the pattern of irregularities oriented in the local noon-midnight direction, which is a signature of SED/TOI development across the polar cap region. Analysis of the Swarm in situ plasma measurements revealed that, during the storm's main phase, all events with extremely enhanced plasma densities (>106 el/cm3) in the polar cap were observed in the Southern Hemisphere. When Swarm satellites crossed these enhancements, degradation of GPS performance was observed, with a sudden decrease in the number of GPS satellites tracked. Our findings indicate that polar patches and TOI structures in the topside ionosphere were predominantly observed in the Southern Hemisphere, which had much higher plasma densities than the Northern Hemisphere, where SED/TOI structures have already been reported earlier. LEO-GPS data (ROTI and topside TEC) were consistent with these results. © 2016 The Author(s).


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.


He W.,CNRS Paris Institute of Global Physics | Plessix R.-E.,Paris Institute of Earth Physics
Geophysical Prospecting | Year: 2016

In a multi-parameter waveform inversion, the choice of the parameterisation influences the results and their interpretations because leakages and the tradeoff between parameters can cause artefacts. We review the parameterisation selection when the inversion focuses on the recovery of the intermediate-to-long wavenumbers of the compressional velocities from the compressional body (P) waves. Assuming a transverse isotropic medium with a vertical axis of symmetry and weak anisotropy, analytical formulas for the radiation patterns are developed to quantify the tradeoff between the shear velocity and the anisotropic parameters and the effects of setting to zero the shear velocity in the acoustic approach. Because, in an anisotropic medium, the radiation patterns depend on the angle of the incident wave with respect to the vertical axis, two particular patterns are discussed: a transmission pattern when the ingoing and outgoing slowness vectors are parallel and a reflection pattern when the ingoing and outgoing slowness vectors satisfy Snell's law. When the inversion aims at recovering the long-to-intermediate wavenumbers of the compressional velocities from the P-waves, we propose to base the parameterisation choice on the transmission patterns. Since the P-wave events in surface seismic data do not constrain the background (smooth) vertical velocity due to the velocity/depth ambiguity, the preferred parameterisation contains a parameter that has a transmission pattern concentrated along the vertical axis. This parameter can be fixed during the inversion which reduces the size of the model space. The review of several parameterisations shows that the vertical velocity, the Thomsen parameter δ, or the Thomsen parameter ε have a transmission pattern along the vertical axis depending on the parameterisation choice. The review of the reflection patterns of those selected parameterisations should be done in the elastic context. Indeed, when reflection data are also inverted, there are potential leakages of the shear parameter at intermediate angles when we carry out acoustic inversion. © 2016 European Association of Geoscientists & Engineers.

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