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3. Migration of Mechanical Perturbations Estimated by Seismic Coda Wave Interferometry During the 2018 Pre‐Eruptive Period at Kīlauea Volcano, Hawaii

Author

Muzellec, Titouan, Lesage, Philippe, Caudron, Corentin, Got, Jean‐Luc, Muzellec, Titouan, Lesage, Philippe, Caudron, Corentin, and Got, Jean‐Luc

Abstract

We use seismic ambient noise correlation and coda wave interferometry to estimate velocity variations at high temporal resolution, during the pre‐eruptive period and the onset of the 2018 eruption of Kīlauea volcano. A progressive velocity increase is observed from March to the end of April. It is followed by rapid decrease starting a few days before the onset of the East Rift Zone (ERZ) eruption and then by sharp velocity drop when the eruption started. The change of trend from velocity increase to decrease is progressively delayed by a few days from the summit caldera toward the ERZ. The location of the velocity perturbations shows a migration of the sources of velocity changes from the summit caldera toward the ERZ before the eruption. Using a model of pressure source, we show that the simultaneous caldera inflation and velocity increase probably result from an anisotropic distribution of fault and crack orientations. The velocity decrease could be due to damaging processes above the shallow reservoir and to plastic deformations around the caldera. We introduce a forward model of rock damage associated with the volcano‐tectonic seismicity to calculate the velocity decrease. The good agreement between the calculated and the observed velocity variations shows that a large part of the velocity decrease results from damage of the medium. The delayed onsets of velocity decrease and the source migration of velocity perturbations are probably related to progressive fault openings in the Southern and Eastern parts of the caldera and to magma transfer toward the ERZ., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2023

4. Data, results and software for the article: PRE-ERUPTIVE DAMAGE, WEAKENING AND MAGMA-EDIFICE COUPLING AT PITON DE LA FOURNAISE VOLCANO

Author

GOT Jean-Luc

Subjects
Seismology, Rock Mechanics, Volcano-Seismology, Damage
Abstract

This file contains the data, results and software for the article: PRE-ERUPTIVE DAMAGE, WEAKENING AND MAGMA-EDIFICE COUPLING AT PITON DE LA FOURNAISE VOLCANO submitted to Journal of Geophysical Research - Solid Earth - version of Dec. 15, 2022.

Published
2022
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10. Deformation and rupture of the oceanic crust may control growth of Hawaiian volcanoes

Author

Got, Jean-Luc, Monteiller, Vadim, Monteux, Julien, Hassani, Riad, and Okubo, Paul

Subjects
Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Hawaiian volcanoes are formed by the eruption of large quantities of basaltic magma related to hot-spot activity below the Pacific Plate (1-2). Despite the apparent simplicity of the parent process--emission [...]

Published
2008

14. Streaks of microearthquakes along creeping faults

Author

Rubin, Allan M., Gillard, Dominique, and Got, Jean-Luc

Subjects
Seismological research -- Observations, Faults (Geology) -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Aseismically produced crustal faults generate large numbers of small earthquakes, which are usually interpreted as coming from localized patches of the fault. The accurate location of large numbers of microearthquakes from faults in California and Hawaii, shows that the locations actually define highly concentrated streaks, characteristically aligned in the direction of fault slip.

Published
1999

17. An analysis of the nonlinear magma-edifice coupling at Grimsvötn volcano (Iceland)

Author

Got, Jean-Luc, Carrier, Aurore, Marsan, David, Jouanne, François, Vogfjörd, Kristin, Villemin, Thierry, Géophysique des volcans & géothermie, Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Environnements, Dynamiques et Territoires de Montagne (EDYTEM), and Referent HAL Edytem, Christine Maury

Subjects
[SDE.BE] Environmental Sciences/Biodiversity and Ecology, [SDE.MCG] Environmental Sciences/Global Changes, [SDE.IE]Environmental Sciences/Environmental Engineering, [SHS.GEO] Humanities and Social Sciences/Geography, [SDE.MCG]Environmental Sciences/Global Changes, [SDE.IE] Environmental Sciences/Environmental Engineering, [SDE.ES] Environmental Sciences/Environmental and Society, [SHS.GEO]Humanities and Social Sciences/Geography, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, [SDE.ES]Environmental Sciences/Environmental and Society
Abstract

International audience; Continuous monitoring of seismicity and surface displacement of active volcanoes can reveal important features of the eruptive cycle. Here high-quality GPS and earthquake data recorded at Grimsvotn volcano by the Icelandic Meteorological Office during the 2004-2011 intereruptive period are analyzed. These showed a characteristic pattern, with an initial similar to 2 year long exponential decay followed by similar to 3 year long constant surface displacement inflation rate. We model it by using a one magma reservoir model in an elastic damaging edifice, with incompressible magma and constant pressure at the base of the magma conduit. Seismicity rate and damage were first modeled, and simple analytical expressions were derived for the magma reservoir overpressure and surface displacement as functions of time. Very good fits of the seismicity and surface displacement data were obtained by fitting only three phenomenological parameters. Characteristic time and power strain show maxima from which reference times were inferred that split the intereruptive period into five periods. After the pressurization periods, damage occurring in the third period induced weakly nonlinear variations in magma overpressure and flow, and surface displacement. During the fourth period, the damage dominated and variations became more strongly nonlinear, the reservoir overpressure decreased, and magma flow increased. This process lasted until the power strain reached its second maximum, where instability was generalized. This maximum is a physical limit, the occurrence of which shortly precedes rupture and, eventually, eruption. This analysis allows characterization of the state of the volcanic edifice during the intereruptive period and supports medium-term prediction of rupture and eruption.

Published
2017

18. Changes in seismicity and stress loading on subduction faults in the Kanto region, Japan, 2011–2014

Author

Gardonio, Blandine, Marsan, David, Lengliné, Olivier, Enescu, Bogdan, Bouchon, Michel, Got, Jean-Luc, Mécanique des failles, Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Sismologie (IPGS) (IPGS-Sismologie), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Earth Evolution Sciences Department [Tsukuba], Université de Tsukuba = University of Tsukuba, Géophysique des volcans & géothermie, and Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Kanto earthquakes
Abstract

International audience; Seismic activity has increased in the Kanto region, Japan, following the 2011 M9.0 Tohoku earthquake. We here reassess this increase up to June 2014, to show that normal, Omori-like relaxation characterizes the activity on crustal faults as well as on the Philippine Sea plate, but not on the deeper Pacific plate. There repeating earthquakes display a twofold rate of occurrence (still ongoing in June 2014) as compared to the pre-Tohoku rate, suggesting enhanced creep. We compute the Coulomb stress changes on the upper locked portion of the Philippine Sea plate, which last ruptured in 1923. We find that this fault was little affected by either the coseismic, the postseismic, the accelerated creep, or the 2011 Boso silent slip event.

Published
2015
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19. Edifice strength and magma transfer modulation at Piton de la Fournaise volcano

Author

Got, Jean-Luc, Peltier, Aline, Staudacher, Thomas, Kowalski, Philippe, Boissier, Patrice, Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)

Subjects
rock rheology, eruptive cycle, [SDU]Sciences of the Universe [physics], volcano tectonics, deformation, magma transfer, magma/edifice interaction
Abstract

International audience; 2003 to 2007, eruptive activity at Piton de la Fournaise was shown to follow cycles, comprising many summit/proximal eruptions and finishing by a distal eruption. GPS measurements evidenced striking asymmetric deformation between its western and eastern flanks. Horizontal displacements recorded during interdistal periods showed a characteristic amplitude at the top of the eastern flank. Displacements recorded at the base of the summit cone showed a bimodal distribution, with low amplitudes during interdistal periods and large ones during distal eruptions. To account for displacement asymmetry, characteristic amplitude, and large flank displacement, we modeled the volcanic edifice using a Drücker-Prager elastoplastic rheology. Friction angles of 15° and >30° were needed to model the displacements respectively during distal eruptions and interdistal periods; this change shows that strain weakening occurred during distal events. Large plastic displacement that occurred in the eastern flank during distal eruptions relaxed the horizontal elastic stress accumulated during interdistal periods; it triggered summit deflation, horizontal magma transfer, and distal flank eruption and reset the eruptive cycle. Our elastoplastic models also show that simple source geometries may induce large eastern flank displacements that would be explained by a complex geometry in a linear elastic edifice. Magma supply is often thought to control volcano's eruptive activity, with surface deformation reflecting changes in magma supply rate, the volcano's response being linear. Our results bring some evidences that on Piton de la Fournaise time-space discretization of magma transfer may be the result of the edifice's nonlinear response, rather than changes in magma supply.

Published
2013
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20. Strain localization and fluid migration from earthquake relocation and seismicity analysis in the western Vosges (France)

Author

Got, Jean-Luc, Monteiller, Vadim, Guilbert, Jocelyn, Marsan, David, Cansi, Yves, Maillard, Carole, Santoire, Jean-Paul, Géophysique des volcans & géothermie, Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Dynamique terrestre et planétaire (DTP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Laboratoire de Détection et de Géophysique (CEA) (LDG), DAM Île-de-France (DAM/DIF), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Mécanique des failles, This work was carried out under LDG-CEA contract #4600101825/P6H53., Géophysique des volcans, Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Earthquake source observations, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Seismicity and tectonics, Intra-plate processes
Abstract

International audience; To understand the mechanisms of intraplate earthquakes, well-documented seismological and geodynamical studies are needed, to provide information for adequate mechanical modelling. This paper describes a detailed analysis of the earthquake sequence associated with the Rambervillers (France) M∼ 5.4 earthquake (2003 February 22), which occurred in the western Vosges massif (France), some tens of kilometres to the north of the sites of the Epinal (1973-1974) and Remiremont (1984-1985) earthquake sequences. We computed the location of the mainshock and focal mechanism, together with the double-difference locations of 419 aftershocks of the subsequent earthquake sequence, which included 195 well-recorded similar events (earthquakes with similar waveforms). We combined pP phases recorded by remote dense seismic networks with waveform modelling, to accurately determine the mainshock depth (12.5 ± 1.5 km). Computations of focal mechanisms from regional waveform inversions showed a normal fault plane with a N315°± 10° strike and a 45°± 15° dip. A detailed space-time analysis allowed two earthquake sequences to be identified: a classic mainshock-aftershock sequence and a secondary sequence that began 250 days after the mainshock. More events were recorded during the secondary sequence than during the main sequence. Very few similar events were recorded during the first 2 days after the mainshock, although data were recorded continuously. Double-difference locations from traveltime differences show that these immediate, non-similar aftershocks occurred in a 4 km × 2 km subhorizontal area at a depth of about 12 km. Similar events were far more numerous during the secondary earthquake sequence. Double-difference relocation of these similar events revealed a N315° striking, 65° dipping fault plane that is compatible with the mainshock source mechanism. During this later sequence, seismicity oscillated over a vertical range of 2-3 km around a mean depth of approximately 12 km. This observation strongly suggests fluid migration. Normal faulting, subhorizontal faulting and fluid transfer at about 12 km depth can be interpreted in terms of the crust's response (mainshock and post-seismic relaxation) to flexural stresses induced by the alpine compression. This relaxation involves weakening and collapse of the crust, and fluid transfer.

Published
2011
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23. Monitoring temporal variations of physical properties inside the lithosphere by cross-correlating P and S arrivals and the coda of doublets

Author

Poupinet, Georges, Got, Jean-Luc, Brenguier, Florent, Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), Institut de Physique du Globe de Paris (IPGP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Haruo Sato, Michael C. Fehler, Laboratoire Central des Ponts et Chaussées (LCPC)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, earthquake forecasting, Microearthquakes, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], temporal variation of properties
Abstract

Doublets or multiplets are earthquakes with nearly identical waveforms. First observed on volcanoes, doublets are found in tectonic environments. Doublets can be relocated relatively with a precision of a few meters. Very good doublets separated by a large time lapse are essential for detecting slow temporal variations of crustal properties. We present basic techniques for selecting and processing doublets. In a seismic database, coherency between all pairs of seismograms is computed and high coherency pairs are candidate doublets. Time delays between waveforms are measured by cross-correlation techniques; a precision of 1 ms is common for good pairs sampled at 100 Hz. Several techniques can relocate one event relatively to the other and P and S delay residuals are obtained. Clock precision remains critical when searching for a few millisecond anomalies. Delays in the coda are analyzed by a cross-spectral moving window (CSMW) or a cross-correlation moving window (CCMW) analysis. Time delay measured in the coda shows variations even when the time elapsed between the two events of a doublet is extremely short. These variations are due to hypocenter separation and to changes in the waves which form the early coda. When seismic velocity is changing homogeneously in the propagation medium, the delay of the coda is proportional to lapse time. Thus, the slope α of the delay in the coda is a very precise (up to 10−4) measurement of the change in S-wave velocity ΔVS/VS, α = −ΔVS/VS. Relative changes of delay on the horizontal components can detect temporal variations in S-wave splitting and anisotropy. Temporal changes in coda Q may be reflected in the coda amplitude ratio measured in several frequency bands. However, minor changes in sources induce variations in early coda (the coda that just follows the S wave) amplitude ratios, comparable to those due to attenuation changes. Therefore, the interpretation of coda amplitude ratios in terms of coda Q changes should be undertaken in the late coda only, using a statistical approach. Good doublets are seldom, so we present a technique that creates “virtual doublets” from the correlation of seismic noise long sequences. Temporal variations of physical properties in surface layers are recovered by a CCMW analysis of these “virtual doublets.” This is an interesting method for measuring strain variations preceding volcanic eruptions. Many other applications should blossom in the near future. At last, we present teleseismic doublets which are a tool for measuring the rate of rotation of the inner core of the Earth. The goal of this chapter is to show that doublet processing is elementary but that the detection of temporal variations of velocity or attenuation remains quite difficult. Excellent doublets should be selected to study temporal variations and such very good natural doublets are few in most seismic regions.

Published
2008
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26. New insights into Kilauea's volcano dynmaics brought by large-scale relative relocation of microearthquakes

Author

Got, Jean-Luc, Okubo, P., Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]
Abstract

We investigated the microseismicity recorded in an active volcano to infer information concerning the volcano structure and long‐term dynamics, by using relative relocations and focal mechanisms of microearthquakes. There were 32,000 earthquakes of the Mauna Loa and Kilauea volcanoes recorded by more than eight stations of the Hawaiian Volcano Observatory seismic network between 1988 and 1999. We studied 17,000 of these events and relocated more than 70%, with an accuracy ranging from 10 to 500 m. About 75% of these relocated events are located in the vicinity of subhorizontal decollement planes, at a depth of 8–11 km. However, the striking features revealed by these relocation results are steep southeast dipping fault planes working as reverse faults, clearly located below the decollement plane and which intersect it. If this decollement plane coincides with the pre‐Mauna Loa seafloor, as hypothesized by numerous authors, such reverse faults rupture the pre‐Mauna Loa oceanic crust. The weight of the volcano and pressure in the magma storage system are possible causes of these ruptures, fully compatible with the local stress tensor computed by Gillard et al. [1996]. Reverse faults are suspected of producing scarps revealed by kilometer‐long horizontal slip‐perpendicular lineations along the decollement surface and therefore large‐scale roughness, asperities, and normal stress variations. These are capable of generating stick‐slip, large–magnitude earthquakes, the spatial microseismic pattern observed in the south flank of Kilauea volcano, and Hilina‐type instabilities. Rupture intersecting the decollement surface, causing its large‐scale roughness, may be an important parameter controlling the growth of Hawaiian volcanoes.

Published
2003
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27. Location of Long Period events belo Kilauea using seismic amplitudes and precise relative relocation

Author

Battaglia, Jean, Got, Jean-Luc, Okubo, P., Laboratoire de Géophysique Interne et Tectonophysique (LGIT), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Laboratoire Central des Ponts et Chaussées (LCPC)-Centre National de la Recherche Scientifique (CNRS), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Laboratoire Central des Ponts et Chaussées (LCPC)-Institut des Sciences de la Terre (ISTerre), and Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)

Subjects
[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]
Abstract

International audience; We present methods for improving the location of long-period (LP) events, deep andshallow, recorded below Kilauea Volcano by the permanent seismic network. LP eventsmight be of particular interest to understanding eruptive processes as their sourcemechanism is assumed to directly involve fluid transport. However, it is usually difficultor impossible to locate their source using traditional arrival time methods because ofemergent wave arrivals. At Kilauea, similar LP waveform signatures suggest the existenceof LP multiplets. The waveform similarity suggests spatially close sources, while catalogsolutions using arrival time estimates are widely scattered beneath Kilauea’s summitcaldera. In order to improve estimates of absolute LP location, we use the distribution ofseismic amplitudes corrected for station site effects. The decay of the amplitude as afunction of hypocentral distance is used for inferring LP location. In a second stage, weuse the similarity of the events to calculate their relative positions. The analysis of theentire LP seismicity recorded between January 1997 and December 1999 suggests that avery large part of the LP event population, both deep and shallow, is generated by a smallnumber of compact sources. Deep events are systematically composed of a weak high-frequency onset followed by a low-frequency wave train. Aligning the low-frequencywave trains does not lead to aligning the onsets indicating the two parts of the signal aredissociated. This observation favors an interpretation in terms of triggering and resonanceof a magmatic conduit. Instead of defining fault planes, the precise relocation ofsimilar LP events, based on the alignment of the high-energy low-frequency wave trains,defines limited size volumes.

Published
2003
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35. Estimating Crustal Heterogeneity from Double-difference Tomography.

Author

Ben-Zion, Yehuda, Lee, William H. K., Got, Jean-Luc, Monteiller, Vadim, Virieux, Jean, and Okubo, Paul

Abstract

Seismic velocity parameters in limited, but heterogeneous volumes can be inferred using a double-difference tomographic algorithm, but to obtain meaningful results accuracy must be maintained at every step of the computation. Monteiller et al. (2005) have devised a double-difference tomographic algorithm that takes full advantage of the accuracy of cross-spectral time-delays of large correlated event sets. This algorithm performs an accurate computation of theoretical travel-time delays in heterogeneous media and applies a suitable inversion scheme based on optimization theory. When applied to Kilauea Volcano, in Hawaii, the double-difference tomography approach shows significant and coherent changes to the velocity model in the well-resolved volumes beneath the Kilauea caldera and the upper east rift. In this paper, we first compare the results obtained using Monteilleret al.'s algorithm with those obtained using the classic travel-time tomographic approach. Then, we evaluated the effect of using data series of different accuracies, such as handpicked arrival-time differences ("picking differences"), on the results produced by double-difference tomographic algorithms. We show that picking differences have a non-Gaussian probability density function (pdf). Using a hyperbolic secant pdf instead of a Gaussian pdf allows improvement of the double-difference tomographic result when using picking difference data. We completed our study by investigating the use of spatially discontinuous time-delay data. [ABSTRACT FROM AUTHOR]

Published
2006
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39. Analyse de doublets sismiques par une méthode de rapport spectral

Author

Got, Jean-Luc, Talour, Pascale, Laboratoire Interdisciplinaire de Recherche Impliquant la Géologie et la Mécanique (LIRIGM), Université Joseph Fourier - Grenoble 1 (UJF), Université Scientifique et Médicale de Grenoble, and Julien Fréchet

Subjects
Prédiction sismique, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [PHYS.PHYS.PHYS-GEO-PH] Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, Coda des séismes, Californie centrale, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Doublets de séismes, Rapport spectral, Sismologie, [SDE.MCG] Environmental Sciences/Global Changes, Sismogenèse, Atténuation, [SDU.STU.GP] Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]
Abstract

Ce travail est une étude détaillée des rapports spectraux de doublets de séismes.Ses objectifs sont l'étude des sources de petits séismes et la mise au point d'une technique de mesure des variations temporelles du facteur de qualité de la coda des séismes, une mesure clef pour les études de prédiction de séismes. La première partie du mémoire est consacrée à l'estimation des erreurs sur le rapport spectral. Cette analyse méthodologique permet de définir les limites d'application de la méthode du rapport spectral, en particulier pour évaluer les variations de Q dans la coda, dans la mesure où la cohérence à haute fréquence est mauvaise pour de grands temps de parcours. La deuxième partie traite de doublets spatiaux et met en évidence de très faibles changements du processus d'ouverture entre les deux séismes. Plusieurs doublets montrent une organisation azimutale des pentes de rapports spectraux des ondes de volume: celle-ci est expliquée par des décalages du point d'initiation de la rupture par rapport aux limites du plan de faille. Des changements de chute de contrainte et du déplacement moyen sont observés dans un autre cas. Il existe des variations du rapport spectral dans la coda de doublets spatiaux. Elles sont expliquées par la rétrodiffraction des ondes de la coda, et l'organisation azimutale des pentes du rapport spectral. Cette observation incite à la prudence en ce qui concerne l'interprétation de variations du rapport spectral dans la coda en terme de changements temporels de l'atténuation dans la croûte supérieure. La troisième partie est consacrée à ce problème de la mesure précise des changements d'atténuation en fonction du temps. De nombreux auteurs insistent sur l'intérêt de cette mesure pour suivre l'ouverture et la fermeture de microfissures dans la croute et pour prédire des séismes. Les doublets temporeIs sont en théorie un outil privilégié pour détecter de très petites variations de l'atténuation dans le milieu. Cependant, même des doublets localisés à quelques mètres de distance peuvent avoir des sources légèrement différentes, la difficulté étant de bien séparer ce qui est dû à la source de ce qui est dû au milieu. Les résultats de ce travail montrent qu'il n'y a pas eu de variations de l'atténuation supérieure à 1 % à l'échelle régionale, malgré l'occurence d'un séisme de magnitude 6. Par contre, les variations du rapport spectral à basse fréquence, localisée dans la région de Hollister où ont été détectée une variation de la vitesse des ondes 5, sont à relier à un Changement local des conditions de la propagation., pas de résumé

Published
1987

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