88 research outputs found
Toward the understanding of seismic sequences : from spatial observation to numerical modeling. Application to the NE Lut earthquake sequence, Iran
No full textDe nombreuses études montrent que les transferts de contrainte co- et postsismiques jouent un rôle majeur dans l’occurrence des séquences de séismes. Cependant, la grande majorité de ces études implique des systèmes de failles à la configuration géométrique simple (e.g. failles parallèles ou colinéaires). Dans cette thèse, nous étudions une séquence de séismes s’étant produite au sein d’un système de failles à la configuration géométrique plus complexe (i.e. failles conjuguées), la séquence du NE Lut (1939-1997, NE Iran), afin d’évaluer (1) si les transferts de contrainte favorisent la succession de séismes de la séquence et (2) s’ils permettent sur le long-terme de synchroniser les ruptures des failles du système. Pour cela, nous mesurons d’abord les déformations de surface produites par la séquence afin de mieux contraindre par la suite la modélisation des transferts de contrainte. A partir de la technique de corrélation subpixel d'images optiques, nous mesurons les champs de déplacements de surface horizontaux produits par les séismes de Khuli-Boniabad (Mw 7.1, 1979) et de Zirkuh (Mw 7.2, 1997). Nous montrons que ces séismes sont caractérisés par la rupture de plusieurs segments dont les limites sont corrélées avec les complexités géométriques des failles. Nous interprétons les différences de leurs caractéristiques de rupture (longueur de rupture, glissement moyen, nombre de segments rompus) comme étant dues à des différences de maturité des failles de Dasht-e-Bayaz et d’Abiz. Nous détectons également les déplacements produits par un séisme historique modéré, le séisme de Korizan (Mw 6.6, 1979). C’est la première fois que les déplacements produits par un séisme historique de si petite taille sont mesurés par corrélation d’images optiques. Ensuite, en combinant le champ de déplacements InSAR déjà publié avec les données optiques proche-faille précédemment acquises, nous estimons un nouveau modèle de source pour le séisme de Zirkuh (Mw 7.2, 1997). Nous montrons que les données proche-faille sont essentielles pour mieux contraindre la géométrie de la rupture et la distribution du glissement en profondeur. Le modèle estimé montre que le séisme de Zirkuh a rompu trois aspérités séparées par des barrières géométriques où les répliques du séisme se localisent. Seul le segment central de la faille présente un déficit de glissement en surface que nous interprétons comme étant dû à de la déformation distribuée dans des dépôts quaternaires non consolidés. Enfin, à partir des informations précédemment acquises, nous modélisons les transferts de contrainte au cours de la séquence du NE Lut. Nous montrons que ceux-ci ont favorisé l’occurrence de 7 des 11 séismes de la séquence et que modéliser précisément la géométrie des ruptures est essentiel à une estimation robuste des transferts de contrainte. De plus, nous montrons que l’occurrence du séisme de Zirkuh (Mw 7.2, 1992) est principalement favorisée par les séismes modérés de la séquence. Pour finir, la simulation d’une multitude de cycles sismiques sur les failles du NE Lut montre que les transferts de contrainte, en particulier les transferts postsismiques liés à la relaxation viscoélastique de la lithosphère, sont le principal processus permettant la mise en place répétée de séquences de séismes sur les failles du NE Lut. Enfin, d'après les simulations réalisées, l'ordre dans lequel se sont produits les séismes majeurs durant la séquence du NE Lut est assez exceptionnel.Many studies show that static and postseismic stress transfers play an important role in the occurrence of seismic sequences. However, a large majority of these studies involves seismic sequences that occurred within fault systems having simple geometric configurations (e.g. collinear or parallel fault system). In this thesis, we study a seismic sequence that occurred within a complex fault system (i.e. conjugate fault system), the NE Lut seismic sequence (1939-1997, NE Iran), in order to assess if (1) stress transfers can explain the succession of earthquakes in the sequence and (2) stress transfers can lead to the synchronization of the NE Lut faults over multiple seismic cycles. To this end, we first measure the surface displacement field produced by the sequence in order to precisely constrain the stress transfer modeling afterwards. We use optical correlation technique to measure the surface displacement fields of the Khuli-Boniabad (Mw 7.1, 1979) and Zirkuh earthquake (Mw 7.2, 1997). We find that these earthquakes broke several segments limited by geometrical complexities of the faults. We interpret the differences in failure style of these earthquakes (i.e. rupture length, mean slip and number of broken segments) as being due to different level of structural maturity of the Dasht-e-Bayaz and Abiz faults. Furthermore, we succeed to detect offsets produced by the 1979 Mw 6.6 Korizan earthquake. It is the first time that surface displacements for such a small historical earthquake have been measured using optical correlation. Then, combining previously published intermediate-field InSAR data and our near-field optical data, we estimate a new source model for the Zirkuh earthquake (Mw 7.2, 1997). We show that near-field data are crucial to better constrain the fault geometry and the slip distribution at depth. According to our source model, the Zirkuh earthquake broke three asperities separated by geometrical barriers where aftershocks are located. No shallow slip deficit is found for the overall rupture except on the central segment where it could be due to off-fault deformation in quaternary deposits. Finally, we use the information acquired in the first parts of this work to model the stress transfers within the NE Lut sequence. We find that 7 out of 11 earthquakes are triggered by the previous ones and that the precise modeling of the rupture geometry is crucial to robustly estimate the stress transfers. We also show that the Zirkuh earthquake is mainly triggered by the moderate earthquakes of the NE Lut sequence. Lastly, the simulation of multiple seismic cycles on the NE Lut fault system shows that stress transfers, in particular postseismic stress transfers due to viscoelastic relaxation, enhance the number of seismic sequences and synchronize the rupture of the faults. The simulations also show that the order in which the Mw>7 earthquakes occurred during the NE Lut sequence is quite exceptional
Fault interaction and stress triggering of 20th century earthquakes in Mongolia
No full textJournal of Geophysical Research, v. 108, n. B10, p. 2503, 2003. http://dx.doi.org/10.1029/2002JB002375International audienceMogod earthquake (sequence). Each of the larger (M ! 8) earthquakes involved strike-slip faulting averaging more than 5 m and rupture lengths of several hundred kilometers. Available geologic data indicate that recurrence intervals on the major source faults are several thousands of years and distances of about 400 km separate the respective rupture areas. We propose that the occurrences of these and many smaller earthquakes are related and controlled to a large extent by stress changes generated by the compounded static deformation of the preceding earthquakes and subsequent viscoelastic relaxation of the lower crust and upper mantle beneath Mongolia. We employ a spherically layered viscoelastic model constrained by the 1994-2002 GPS velocity field in western Mongolia [Vergnolle et al., 2003]. Using the succession of twentieth century earthquakes as sources of deformation, we then analyze the time-dependent change in Coulomb failure stress (Ás f). At remote interaction distances, static Ás f values are small. However, modeled postseismic stress changes typically accumulate to several tenths of a bar over time intervals of decades. Almost all significant twentieth century regional earthquakes (M ! 6) with well-constrained fault geometry lie in positive Ás f lobes of magnitude about +0.5 bar. Our results suggest that significant stress transfer is possible among continental faults separated by hundreds of kilometers and on timescales of decades
Surface displacement measurements and fault slip models for the 1997 Mw 7.2 Zirkuh earthquake
No full text<p><strong>Source models of the 1997 Mw 7.2 Zirkuh earthquake inferred from InSAR and optical correlation displacement field </strong></p>
<p><strong>Introduction</strong></p>
<p>We provide the InSAR and optical correlation displacement fields of the 1997 Mw 7.2 Zirkuh earthquake (NE Iran).<br>
The InSAR data have been processed by Sudhaus and Jonsson (2011) and the optical correlation data by Marchandon et al. (2017). <br>
We also provide the different fault slip models for the earthquake inferred from these data and published in Marchandon et al. (2017). <br>
Finally, we include the source code of the genetic algorithm used in Marchandon et al. (2017) to infer the uniform slip models of the Zirkuh earthquake.<br>
This genetic algorithm (Sudhaus and Jonsson, 2011) allows estimating the geometry and a uniform slip value for each segment of the fault. The Abiz fault, that broke during the Zirkuh earthquake, <br>
is a complex structure with many fault strike variations that requires 16 segments to be properly modelled. Thus, a penalty function is implemented to constrain the algorithm to sample models<br>
with limited dip angle fluctuations between neighboring segments (Sudhaus and Jonsson, 2011). The rupture is modelled as a dislocation embedded in an elastic half-space (Okada, 1992). </p>
<p>For further information about the data, the method and the model results, see Marchandon et al. (2017). </p>
<p><strong>Content</strong></p>
<p>Data: InSAR data, optical Correlation data, weighting matrix files in .mat format, matlab script to plot the data. <br>
Fault: Abiz fault segment locations file in .mat format and matlab script to plot the fault.<br>
Scripts: All scripts needed to run the Non-linear optimization.<br>
Models: Fault slip models for the Zirkuh earthquake and matlab script to plot them. </p>
<p><strong>References</strong></p>
<p>Sudhaus, H., and S. Jonsson (2011), Source model for the 1997 Zirkuh earthquake (Mw=7.2) in Iran derived from JERS and ERS InSAR observations, Geophysical Journal International, <br>
185(2), 676–692, doi:10.1111/j.1365-246X.2011.04973.x.</p>
<p>Marchandon, M., Vergnolle M., Sudhaus, H., and Cavalié., O., (2017) Fault geometry and slip distribution at depth of the 1997 Mw 7.2 Zirkuh earthquake: <br>
contribution of near-field displacement data, accepted with minor revisions at Journal of Geophysical Research: Solid Earth. </p>
<p>Okada, Y. (1992), Internal deformation due to shear and tensite faults in a half-space, Bulletin of Seismological Society of America, pp. 1018–1040.</p>
<p> </p>
Rhéologie et déformation de la lithosphère continentale : apports de mesures GPS en Asie et de modèles numériques
No full textIn this work we study the current kinematic of Mongolia in the northern part of Asia and the dynamics of the deformation in Mongolia and Asia First we present the 1994-2002 Mongolia-Baikal GPS velocity field ( 50 sites) with respect to Eurasia Velocities show that 15% of the IN/EU convergence is accommodated north of the Tien Shan by N-S shortening and dextral shear in the Altay mountain and by E-SEward displacement of central and eastern Mongolia at 3-6 mm/yr Our results suggest that the Eward motion in Asia could be controlled by other processes than the IN/EU convergence such as the dynamic of the oceanic subduction zone or the gravitational potential energy gradient Then starting with the large mongolian EQ of the last century and the GPS velocities we model the postseismic deformation (current viscoelastic relaxation < 2mm/an) and estimate the lithosphere rheology under Mongolia (weak upper mantle and lower crust) Next with a study on viscoelastic and static stress transfer we suggest that significant stress transfer is possible among continental faults separated by 100s of km and on time scales of decades Finally we validate dynamic deformation models of Asia with a GPS velocity field covering most of Asia We estimate the average lithosphere rheology and quantify the different mechanisms of deforma- tion We show that the IN/EU collision is the major contribution to the asian deformation However the deformation in north and east Asia is also controlled by the body forces and the dynamic of the oceanic subduction zone Our results suggest that the deformation is mostly continuous but this last point should be confirmed by further measurementsCe travail s intéresse à la cinématique et à la dynamique des déformations continentales Nous présentons le champ de vitesse 1994-2002 mesuré par GPS dans la région Mongolie-Baïkal (située au nord de l Asie) par rapport à l Eurasie Il montre que 15% de la convergence IN/EU est accommodé au nord du Tien Shan par du raccourcissement N-S et du cisaillement dextre dans l Altaï et par du déplacement vers l E-SE (3-6 mm/an) en Mongolie centrale et orientale Nos résultats suggèrent que le mouvement vers l est pourrait être contrôlé par d autres processus que la convergence IN/EU seule A partir des grands séismes de Mongolie au 20ème siècle et de l inversion des vitesses obtenues nous modélisons la déformation postsismique (relaxation viscoélastique actuelle <2 mm/an) et estimons la rhéologie de la lithosphère sous la Mongolie (manteau supérieur et croûte inférieure peu visqueux) Par une étude de redistribution des contraintes à la suite de séismes nous montrons le possible transfert de contrainte entre failles continentales séparées de centaines de kilomètres et sur des dizaines d années Enfin à partir de modèles dynamiques de la déformation en Asie validés par les données GPS en Chine Mongolie et Sibérie nous estimons la rhéologie moyenne de la lithosphère et quantifions les mécanismes de la déformation Nous montrons que bien que la collision IN/EU soit la contribution majeure à la déformation les forces de volume et la dynamique des zones de subduction sont d une importance équivalente dans les zones septentrionales et orientales de l Asie D après nos résultats l accommodation de la déformation actuelle se ferait essentiellement de manière continue mais ceci reste à confirmer
Fault Interactions and Synchronization: Insight from the 1936-1997 NE Lut, Iran, Earthquake Sequence
No full textInternational audienc
Mechanical deformation model of the western United States instantaneous strain-rate field
No full textInternational audienceWe present a relationship between the long-term fault slip rates and instantaneous velocities as measured by Global Positioning System (GPS) or other geodetic measurements over a short time span. The main elements are the secularly increasing forces imposed by the bounding Pacific and Juan de Fuca (JdF) plates on the North American plate, viscoelastic relaxation following selected large earthquakes occurring on faults that are locked during their respective interseismic periods, and steady slip along creeping portions of faults in the context of a thin-plate system. In detail, the physical model allows separate treatments of faults with known geometry and slip history, faults with incomplete characterization (i.e. fault geometry but not necessarily slip history is available), creeping faults, and dislocation sources distributed between the faults. We model the western United States strain-rate field, derived from 746 GPS velocity vectors, in order to test the importance of the relaxation from historic events and characterize the tectonic forces imposed by the bounding Pacific and JdF plates. Relaxation following major earthquakes (Mγ 8.0) strongly shapes the present strain-rate field over most of the plate boundary zone. Equally important are lateral shear transmitted across the Pacific-North America plate boundary along ∼1000 km of the continental shelf, downdip forces distributed along the Cascadia subduction interface, and distributed slip in the lower lithosphere. Post-earthquake relaxation and tectonic forcing, combined with distributed deep slip, constructively interfere near the western margin of the plate boundary zone, producing locally large strain accumulation along the San Andreas fault (SAF) system. However, they destructively interfere further into the plate interior, resulting in smaller and more variable strain accumulation patterns in the eastern part of the plate boundary zone. Much of the right-lateral strain accumulation along the SAF system is systematically underpredicted by models which account only for relaxation from known large earthquakes. This strongly suggests that in addition to viscoelastic-cycle effects, steady deep slip in the lower lithosphere is needed to explain the observed strain-rate field
Rhéologie et déformation de la lithosphère continentale (apports de mesures GPS en Asie et de modèles numériques)
No full textCe travail s intéresse à la cinématique et à la dynamique des déformations continentales. Nous présentons le champ de vitesse 1994-2002 mesuré par GPS dans la région Mongolie-Baïkal (située au nord de l Asie) par rapporte à l Eurasie. Il montre que 15% de la convergence IN/EU est accommodé au nord du Tien Shan par raccourcissement NS et cisaillement dextre dans l Altaï et par déplacement vers l E-SE (3-9 mm/an) en Mongolie centrale et orientale. Nos résultats suggèrent que le mouvement vers l est pourrait être contrôlé par d autres processus que la convergence IN/EU seule. A partir des grands séismes de Mongolie au 20e siècle et de l inversion des vitesses obtenues, nous modélisons la déformation postsismique (relaxation viscoélastique actuelle <2 mm/an) et estimons la rhéologie de la lithosphère sous la Mongolie (manteau supérieur et croûte inférieure peu visqueux). Par une étude de redistribution des contraintes à la suite de séismes, nous montrons le possible transfert de contrainte entre failles continentales séparées de centaines de kilomètres et sur des dizaines d années. Enfin, à partir de modèles dynamiques de la déformation en Asie validés par les données GPS en Chine, Mongolie et Sibérie, nous estimons la rhéologie moyenne de la lithosphère et quantifions les mécanismes de déformation. Nous montrons que bien que la collision IN/EU soit la contribution majeure à la déformation, les forces de volume et la dynamique des zones de subduction sont d une importance équivalente dans les zones septentrionales et orientales de l Asie. D après nos résultats, l accommodation de la déformation actuelle se ferait essentiellement de manière continue mais ceci reste à confirmer.In this work, we study the current kinematic of Mongolia, in the northern part of Asia and the dynamics of the deformation in Mongolia and Asia. First, we present the 1994-2002 Mongolia-Baikal GPS velocity fields (-50 sites) with respect to Eurasia. Velocities show that 15% of th IN/EU convergence is accommodated north of the Tien Shan by NS shortening and dextral shear in the Altay mountains and by E-SE displacement of central and eastern Mongolia at 3-6mm/yr. Our results suggest that the Eward motion in Asia could be controlled by other processes then the IN/EU convergence such as the dynamic of the oceanic subduction zone of the gravitational potential energy gradient. Then starting with the large Mongolian EQ of the last century and the GPS velocities, we model the postseismic deformation (current viscoelastic relaxation < 2 mm/an) and estimate he lithosphere rheology under Mongolia (weak upper mantle and lower crust). Next, with a study on viscoelastic and static stress transfer, we suggest that significant stress transfer is possible among continental faults separated by 100s of km and on time scales of decades. Finally, we validate dynamic deformation models of Asia With a GPS velocity field covering most of Asia. We estimate the average lithosphere rheology and quantify the different mechanisms of deformation. We show that the IN/EU collision is the major contribution to the Asian deformation. However, the deformation in north and East Asia is also controlled by the body forces and the dynamic of the oceanic subduction zone. In the first part, we define a new programming language with a functional core and generalized recursion, by using Boudol s type system with degrees to rule out unsafe recursions. The language is extended first with recursive records, then with mixins, allowing the programmer to fully mix functional and object-oriented paradigms. We also present an implementation, MlObj, and an abstract machine for execution. In a second part, we design a new inference algorithm for intersection type systems, on an extension of the lambda-calculus. After proving its correctness, we study its generalisation to references and recursion, we compare it with existing inference algorithms, mainly System l, and we show that its finite rank version becomes decidable. Our results suggest that the current deformation is mostly continuous but this last point should be confirmed by further measurements.NICE-BU Sciences (060882101) / SudocSudocFranceF
Monitoring of the 2018 Pu’u ‘Ō’ō, Hawaii, volcanic eruption using high-rate GNSS data
No full textInternational audienc
Fault Geometry and Slip Distribution at Depth of the 1997 Mw 7.2 Zirkuh Earthquake: Contribution of Near-Field Displacement Data
No full textInternational audienceIn this study, we reestimate the source model of the 1997 Mw 7.2 Zirkuh earthquake (northeastern Iran) by jointly optimizing intermediate‐field Interferometry Synthetic Aperture Radar data and near‐field optical correlation data using a two‐step fault modeling procedure. First, we estimate the geometry of the multisegmented Abiz fault using a genetic algorithm. Then, we discretize the fault segments into subfaults and invert the data to image the slip distribution on the fault. Our joint‐data model, although similar to the Interferometry Synthetic Aperture Radar‐based model to the first order, highlights differences in the fault dip and slip distribution. Our preferred model is ∼80° west dipping in the northern part of the fault, ∼75° east dipping in the southern part and shows three disconnected high slip zones separated by low slip zones. The low slip zones are located where the Abiz fault shows geometric complexities and where the aftershocks are located. We interpret this rough slip distribution as three asperities separated by geometrical barriers that impede the rupture propagation. Finally, no shallow slip deficit is found for the overall rupture except on the central segment where it could be due to off‐fault deformation in quaternary deposits
Le portail européen de données Epos-GNSS
No full textDans le cadre de l’intégration aux dispositions européens EPOS, Résif s'est transformé en octobre 2023 en Epos-France, une nouvelle infrastructure de recherche aux contours thématiques plus larges et en accord avec ceux de sa grande sœur européenne.National audienceLe système de distribution Epos-GNSS est une e-infrastructure conçue pour diffuser des données et produits GNSS. Le portail de données Epos-GNSS est le point d'accès central du système à ces données
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