Up to date geodetic velocity field of the Belledonne region (Western Alps, France)

&#160;&#160;&#160;&#160;&#160;&#160; The Belledonne region, located on the western edge of the French Alps, behaves as a deformation transfer zone between the inner part of the western Alps, where geodesy and seismicity show extensional deformation, and its compressional surrounding basin (the Rh&#244;ne Valley). Seismological and geodetic networks are less dense and younger in the Rh&#244;ne Valley, which makes it more difficult to characterize its deformation. Nevertheless, these two regions have a moderate historical and instrumental seismicity. A large part of these earthquakes is concentrated on the Belledonne range and accommodated by the active NE&#8211;SW Belledonne fault, located at the western foot of this chain. The fault characteristics, such as its connection at depth with surrounding fault systems (e.g. Cl&#233;ry fault), still need better constraints. The dense seismological network present in the Alpine region has made it possible to highlight its dextral strike-slip kinematics. To complete these observations, we present here an update of the geodetic velocity field around this fault from GNSS data recorded over the last two decades.To do so, we first computed daily positions for a total of about 200 stations provided by different European networks (IGS, RENAG, RGP, GAIN, DGFI networks) over a period of 23 years (from 1997 to 2020), by using a double-difference processing with the GAMIT software (Herring et al. 2015). Then, we constrained a velocity field with the Kalman filter GLOBK with respect to the fixed European plate. We finally analyzed the residual motions in our area of interest with respect to stable Europe, as provided by our updated velocity field.Across the Belledonne range, our results show a deformation pattern consistent with the dextral strike-slip mechanism observed by the current seismicity. Methodological studies concern the expected decrease of uncertainty on the velocity field thanks to the increase of recordings through time. These tests aim at quantifying the Belledonne fault present-day slip rate, including a well-constrained velocity uncertainty. We also exploit the new 3D velocity field to confirm and precise the local amplitude, in the Belledonne area, of the general uplift of the Alpine belt, as observed by previous geodetic studies.

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Miocene to Messinian deformation and hydrothermal activity in a pre-Alpine basement massif of the French western Alps: new U-Th-Pb and argon ages from the Lauzière massif

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.181.3.227 ◽

2010 ◽

Vol 181 (3) ◽

pp. 227-241 ◽

Cited By ~ 79

Author(s):

Dominique Gasquet ◽

Jean-Michel Bertrand ◽

Jean-Louis Paquette ◽

Jérémie Lehmann ◽

Gueorgui Ratzov ◽

...

Keyword(s):

Late Miocene ◽

Shear Zones ◽

Hydrothermal Activity ◽

Western Alps ◽

Strike Slip ◽

Quartz Veins ◽

The North ◽

Slip Regime ◽

Tectonically Active ◽

Dextral Strike Slip

Abstract U-Pb and Th-Pb dating of monazite from hydrothermal quartz veins (“Alpine veins”) from the Lauzière massif (North Belledonne) together with Ar/Ar ages of adularias from the same veins constrain the age of the last tectono-metamorphic events that affected the External Crystalline Massifs (ECM). Ages obtained are surprisingly young. The study of the structural context of the veins combined with our chronological data, allow us to propose a tectonic scenario of the northern ECM for the 15-5 Ma period, which was poorly documented so far. The quartz veins are of two types: (i) the oldest are poorly mineralized (chlorite and epidote), flat-lying veins. The quartz fibres (= extension direction) are near vertical and seem to be associated with a subvertical dissolution schistosity superimposed upon an early Alpine deformation underlined by “mini-biotite”. They bear a sub-horizontal stretching lineation; (ii) the youngest veins are very rich in various minerals (anatase, rutile, phénacite, meneghinite, beryl, synchysite, ….). They are almost vertical. Their “en echelon” geometry as well as the horizontal attitude of their quartz fibres show a dextral strike-slip regime. Two groups of Th-Pb ages have been obtained: 11 to 10 Ma and 7 to 5 Ma. They were obtained from the most recent veins (vertical veins) sampled in different areas of the massif. The ca. 10 Ma ages are related to veins in the Lauzière granite and its metamorphic country-rocks at about 2 km from the eastern contact of the massif, while the ages of ca. 5 Ma correspond to veins occurring in mylonites along this contact. Adularias provided Ar/Ar ages at ca. 7 Ma. By contrast, a monazite from a vein of the Pelvoux massif (Plan du Lac) yielded a Th-Pb age of 17.6 Ma but in a different structural setting. Except fission track ages, there are very little ages of this range published in the recent literature on the Alps. The latter concern always gold mineralized veins (NE Mont Blanc and SW Lepontine dome). The last compressive tectonic regime dated between 15 and 12 Ma is coeval with (i) the late “Roselend thrust” event, which is recorded in the Mont Blanc by shear-zones with vertical lineation, (ii) the last movements in the basal mylonites of the Swiss Nappes, (iii) the horizontal Alpine veins from the Mont Blanc and Belledonne massifs (with vertical quartz fibres), which are similar to the early veins of the Lauzière. On the contrary, the vertical veins of the Lauzière, dated between 11 and 5 Ma, correspond to a dextral strike slip regime. This suggests that most of the strike-slip tectonics along the ECM took place during two stages (ca. 10 Ma and ca. 7-5 Ma) and not only at 18 Ma as had been proposed previously. Our ages are consistent with the late Miocene-Pliocene overlap of the Digne thrust to the South and to part of the normal movement along the Simplon fault to the North. Thus, all the external crystalline massifs were tectonically active during the late Miocene. This suggests that tectonic events in the external alpine belt may have contributed to some extent to the geodynamical causes of the Messinian crisis.

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Ion microprobe dating of fissure monazite in the Western Alps: insights from the Argentera Massif and the Piemontais and Briançonnais Zones

Swiss Journal of Geosciences ◽

10.1186/s00015-020-00365-3 ◽

2020 ◽

Vol 113 (1) ◽

Cited By ~ 1

Author(s):

Emmanuelle Ricchi ◽

Edwin Gnos ◽

Daniela Rubatto ◽

Martin John Whitehouse ◽

Thomas Pettke

Keyword(s):

High Pressure ◽

Western Alps ◽

Strike Slip ◽

Tectonic Activity ◽

Ion Microprobe ◽

Eu Anomaly ◽

Slip Activity ◽

Ion Probe ◽

Anticlockwise Rotation ◽

Dextral Strike Slip

AbstractIon probe 208Pb/232Th fissure monazite ages from the Argentera External Massif and from the high-pressure units of the Western Alps provide new insights on its Cenozoic tectonic evolution. Hydrothermal monazite crystallizes during cooling/exhumation in Alpine fissures, an environment where monazite is highly susceptible to fluid-mediated dissolution-(re)crystallization. Monazite growth domains visualized by BSE imaging all show a negative Eu anomaly, positive correlation of Sr and Ca and increasing cheralite component (Ca + Th replacing 2REE) with decreasing xenotime (Y) component. The huttonite component (Th + Si replacing REE and P) is very low. Growth domains record crystallization following chemical disequilibrium in a fissure environment, and growing evidence indicates that they register tectonic activity. Fissure monazite ages obtained in this study corroborate previous ages, recording crystallization at ~ 36 Ma, ~ 32–30 Ma, and ~ 25–23 Ma in the high-pressure regions of the Western Alps, interpreted to be respectively related to top-NNW, top-WNW and top-SW thrusting in association with strike-slip faulting. During this latter transpressive phase, younger fissure monazite crystallization is recorded between ~ 20.6 and 14 Ma in the Argentera Massif, interpreted to have occurred in association with dextral strike-slip faulting related to anticlockwise rotation of the Corsica-Sardinia Block. This strike-slip activity is predating orogen-parallel dextral strike-slip movements along and through the internal part of all other External Crystalline Massifs (ECM), starting only at ~ 12 Ma. Our combined compositional and age data for hydrothermal monazite track crystallization related to tectonic activity during unroofing of the Western Alps for over more than 20 million years, offering chronologic insights into how different tectonic blocks were exhumed. The data show that fissures in the high-pressure units formed during greenschist to amphibolite facies retrograde deformation, and later in association with strike-slip faulting.

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New Insights into Long-Term Aseismic Deformation and Regional Strain Rates from GNSS Data Inversion: The Case of the Pollino and Castrovillari Faults

Remote Sensing ◽

10.3390/rs12182921 ◽

2020 ◽

Vol 12 (18) ◽

pp. 2921

Author(s):

Gabriele Cambiotti ◽

Mimmo Palano ◽

Barbara Orecchio ◽

Anna Maria Marotta ◽

Riccardo Barzaghi ◽

...

Keyword(s):

Strain Rate ◽

Strike Slip ◽

Deformation Pattern ◽

Fault Creep ◽

Slip Mechanism ◽

Regional Deformation ◽

Regional Strain ◽

Geodetic Strain Rate ◽

Gnss Velocities

We present a novel inverse method for discriminating regional deformation and long-term fault creep by inversion of GNSS velocities observed at the spatial scale of intraplate faults by exploiting the different spatial signatures of these two mechanisms. In doing so our method provides a refined estimate of the upper bound of the strain accumulation process. As case study, we apply this method to a six year GNSS campaign (2003–2008) set up in the southern portion of the Pollino Range over the Castrovillari and Pollino faults. We show that regional deformation alone cannot explain the observed deformation pattern and implies high geodetic strain rate, with a WSW-ENE extension of 86±41×10−9/yr. Allowing for the possibility of fault creep, the modelling of GNSS velocities is consistent with their uncertainties and they are mainly explained by a shallow creep over the Pollino fault, with a normal/strike-slip mechanism up to 5 mm/yr. The regional strain rate decrease by about 70 percent and is characterized by WNW-ESE extension of 24±28×10−9/yr. The large uncertainties affecting our estimate of regional strain rate do not allow infering whether the tectonic regime of the area is extensional or strike-slip, although the latter is slightly more likely.

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Postglacial strain rate – stress paradox, example of the Western Alps active faults

10.5194/se-2021-141 ◽

2021 ◽

Author(s):

Juliette Grosset ◽

Stéphane Mazzotti ◽

Philippe Vernant

Keyword(s):

Strain Rate ◽

Active Faults ◽

Western Alps ◽

Fault Reactivation ◽

Deformation Pattern ◽

Isostatic Adjustment ◽

Flexural Response ◽

Coulomb Failure ◽

Direct Corollary ◽

Gnss Data

Abstract. The understanding of the origins of seismicity in intraplate regions is crucial to better characterize seismic hazards. In formerly glaciated regions such as Fennoscandia North America or the Western Alps, stress perturbations from Glacial Isostatic Adjustment (GIA) have been proposed as a major cause of large earthquakes. In this study, we focus on the Western Alps case using numerical modeling of lithosphere response to the Last Glacial Maximum icecap. We show that the flexural response to GIA induces present-day stress perturbations of ca. 1–2 MPa, associated with horizontal extension rates up to ca. 2.5 × 10−9 yr−1. The latter is in good agreement with extension rates of ca. 2 × 10−9 yr−1 derived from high-resolution geodetic (GNSS) data and with the overall seismicity deformation pattern. In the majority of simulations, stress perturbations induced by GIA promote fault reactivation in the internal massifs and in the foreland regions (i.e., positive Coulomb Failure Stress perturbation), but with predicted rakes systematically incompatible with those from earthquake focal mechanisms. Thus, although GIA explains a major part of the GNSS strain rates, it tends to inhibit the observed seismicity in the Western Alps. A direct corollary of this result is that, in cases of significant GIA effect, GNSS strain rate measurements cannot be directly integrated in seismic hazard computations, but instead require detailed modeling of the GIA transient impact.

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Strike-slip fault reactivation in the Western Alps due to Glacial Isostatic Adjustment

10.5194/egusphere-egu2020-8505 ◽

2020 ◽

Author(s):

Juliette Grosset ◽

Stéphane Mazzotti ◽

Philippe Vernant ◽

Jean Chéry ◽

Kevin Manchuel

Keyword(s):

Slip Rate ◽

Western Alps ◽

Strike Slip ◽

Strike Slip Fault ◽

Fault Reactivation ◽

Maximum Effect ◽

Glacial Isostatic Adjustment ◽

Fault Systems ◽

Isostatic Adjustment ◽

The Impact

The Western Alps represent the zone of highest seismicity density in metropolitan France. The seismicity is mainly located along two NE-SW strike-slip fault systems: the right-lateral Belledonne Fault and the left-lateral Durance Fault. Glacial Isostatic Adjustment (GIA) is one of the most common processes given to explain intraplate seismicity (e.g., Scandinavia, North America) and is also proposed as a cause of present-day deformation in the Alps. In order to test the impact of deglaciation from the Last Glacial Maximum on pre-existing vertical strike-slip faults in the Western Alps (Belledonne and Durance Faults), we use a finite-element approach to model fault reactivation throughout the deglaciation period, from ca. 18 kyr up to today. The models are tuned to fit present-day deformation rates observed by geodesy (uplift rate up to 2 mm/yr and horizontal radial extension). Simplified models (homogeneous icecap and Earth rheology) show that, under optimum conditions, GIA stress perturbations can activate a NE-SW right-lateral strike-slip fault such as the Belledonne Fault, requiring the fault to have been pre-stressed up to near-failure equilibrium before the onset of deglaciation. The maximum effect of GIA is 1.7 meters of right-lateral slip over 20&#160;kyr, with a peak of displacement between 20 and 10&#160;ka. These models indicate that GIA can result in a maximum slip rate of 0.08 mm/yr averaged over the Holocene, in association with earthquakes up to Mw = 7 (if all displacement is taken in one event). These results are consistent with local paleoseismicity and geomorphology evidence on the Durance fault. However, the impact of GIA on the left-lateral Belledonne Fault is poorly constrained by these simple models. Additional models based on realistic Alpine icecap reconstructions and regional rheology structures will also be presented, that allow us to test the specific effects of GIA on Holocene deformation along both the Belledone and Durance Fault systems.

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The 10 June 2012 MW 6.0 earthquake sequence in the easternmost end of the Hellenic arc.

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.10969 ◽

2016 ◽

Vol 47 (3) ◽

pp. 1138

Author(s):

A. Kiratzi ◽

M. Aktar ◽

N. Svigkas

Keyword(s):

Moment Tensor ◽

Strike Slip ◽

Earthquake Sequence ◽

Deformation Pattern ◽

Slip Vector ◽

Hellenic Arc ◽

Finite Fault Inversion ◽

Finite Fault ◽

Dextral Strike Slip ◽

Shed Light

The 10 June 2012 (UTC 12:44:17.3; lat. 36.441°N, long. 28.904°E, Mw6.0) earthquake sequence, 60 km to the west of Rodos Island, is studied, in an attempt to shed light to the obscure deformation pattern at the easternmost end of the Hellenic Arc. Moment tensor solutions for the mainshock and the strongest aftershocks revealed the operation of WNW-ESE dextral strike-slip faulting, with slip vector at~N295°E, approximately orthogonal to the GPS velocity vectors. The strike of the activated structure generally aligns with bathymetric linear escarpments observed in the region, bordering the eastern section of the Rodos basin. The best constrained focal depths are in the range 10 to 25 km, with the mainshock at the depth of 24 km.The slip model for the mainshock, obtained through a finite-fault inversion scheme, showed that slip was mainly concentrated in a single patch, with the locus of peak slip (~125 cm) located ~ 4km to the NW of the hypocenter. The sequence which lies in the western continuation of the Fethiye – Burdur sinistral strike-slip zone into theAegean Sea and Rodos basin, is not connected with activation of this zone. Its characteristics comply with the activation of a dextral strike-slip structure, oblique to this zone, which accommodates along – arc NE-SW extension.

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ACTIVE SEISMOTECTONIC STRUCTURES IN THE AREA OF CHIOS ISLAND, NORTH AEGEAN SEA, REVEALED FROM MICROSEISMICITY AND FAULT PLANE SOLUTIONS

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11396 ◽

2017 ◽

Vol 43 (4) ◽

pp. 2064 ◽

Cited By ~ 2

Author(s):

V. G. Karakostas ◽

E. E. Papadimitriou ◽

M. D. Tranos ◽

C. B. Papazachos

Keyword(s):

West Coast ◽

Aegean Sea ◽

Strike Slip ◽

Focal Mechanisms ◽

Deformation Pattern ◽

The West ◽

Complex Deformation ◽

North Aegean ◽

North Aegean Sea ◽

Dextral Strike Slip

Data from a digital seismological network operating during April–July 2002 were used for the microseismicity study of the area around Chios Island (East Aegean Sea, Greece). Numerous microearthquakes were detected and more than 950 well–located hypocenters were obtained along with 96 reliably determined focal mechanisms. The epicentral distribution and focal mechanisms of several earthquakes revealed that the NE–SW striking dextral strike–slip faults dominate in the study area as is the dominant pattern in North Aegean Sea. An earthquake swarm near Psara Island and a cluster offshore the west coast of Chios Island are associated with NW–SE trending left–lateral strike–slip faults, orthogonal to the dextral ones. Near the west coast of the Island the microseismicity evidences that oblique faulting dominates, whereas onshore and offshore the North Chios Island, clusters of events manifest the activation of either E–W or N–S striking normal faults. This complex deformation pattern is the manifestation of the dextral strike–slip faulting termination against conjugate sinistral ones, the transition from strike–slip to normal through the oblique faulting, as well as the activation of biaxial normal faulting in places.

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Large-scale interseismic deformation along the Altyn Tagh Fault determined from Sentinel-1 InSAR

10.5194/egusphere-egu21-10278 ◽

2021 ◽

Author(s):

Lin Shen ◽

Andy Hooper ◽

John Elliott ◽

Tim Wright

Keyword(s):

Velocity Field ◽

Tibetan Plateau ◽

Shear Zone ◽

Large Scale ◽

Slip Rate ◽

Shear Zones ◽

Elastic Half Space ◽

Strike Slip ◽

Space Model ◽

Altyn Tagh

The 1600 km-long Altyn Tagh Fault (ATF) is a major intra-continental strike-slip fault along the Northern Tibetan Plateau, the slip rate of which has significant implications for our understanding of the present-day tectonic processes of the Tibetan Plateau region. We present an interseismic velocity field along ~1500 km length of the fault, derived from Sentinel-1 interferograms spanning the period between late 2014 and 2019. It is the first time such a large-scale analysis has been carried out for this fault with Interferometric Synthetic Aperture Radar (InSAR).Using a modified elastic half-space model, we find significant strain accumulation along the 1500 km length of the ATF, at a relatively fast rate of ~10 mm/yr and quite localised along the fault. The results indicate an eastward decrease of the slip rate along the fault from 11.6 &#177; 1.0 mm/yr to 7.5 &#177; 1.2 mm/yr over the western portion to the central portion, whereas it increases again to 11.1 &#177; 1.1 mm/yr over the eastern portion. Furthermore, the results suggest that no significant creeping occurs along the fault.We find a high slip rate of 11.5 &#177; 1.0 mm/yr along the south-western segment of the ATF, a region not typically covered by previous studies, is transferred to the structurally linked left-lateral strike-slip Longmu-Gozha Co Fault. It demonstrates that the generation of the NS-trending normal faulting events in this region, such as the 2008 Mw 7.2 Yutian earthquake, is ascribed to the EW-trending extensional stress at the Ashikule step-over zone between the two left-lateral faults. We also find a high surface shear strain rate greater than 0.4 &#956;strain/yr in this region, which could be caused by the stress loading effects of the recent seismic activities.To investigate the pattern of strain localisation along the ATF, we fit a shear zone model to the derived long-term InSAR velocity field. Inverting for shear zone width reveals two broad shear zones along the ATF, where the strain is distributed over multiple strands rather than concentrated on a single narrow strand. The broad shear zones explain the high estimates of the locking depth found when using the elastic half-space model and also off-fault seismic activity on the strands away from the ATF in these areas. The results also show a relatively wider shear zone from the central portion eastward, where the ATF breaks into three parallel strands.&#160;This study suggests that a slip deficit of around 1 m has been accumulated along the ATF over the last century, and indicates that the fault is capable of rupturing with the potential for a magnitude 7.5 or larger earthquake.

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Albian syndepositional block rotation and its geological consequences, Basque–Cantabrian Basin (western Pyrenees)

Geological Magazine ◽

10.1017/s0016756813000149 ◽

2013 ◽

Vol 150 (6) ◽

pp. 986-1001 ◽

Cited By ~ 7

Author(s):

LUIS MIGUEL AGIRREZABALA ◽

JAUME DINARÈS-TURELL

Keyword(s):

Slip Rate ◽

Vertical Axis ◽

Strike Slip ◽

Block Rotation ◽

Minimum Block ◽

Magmatic Intrusions ◽

Axis Rotation ◽

High Level ◽

Basque Cantabrian Basin ◽

Dextral Strike Slip

AbstractStratigraphic, structural, palaeocurrent and palaeomagnetic analyses of Upper Albian deep-water deposits in and around the Deba block (Northern Iberia) are presented. Results indicate an anticlockwise vertical-axis rotation of this block by 35° during a maximum time span of c. 1 Ma (Late Albian intra-C. auritus ammonite Subzone). This Albian syndepositional block rotation is interpreted to be the consequence of the coeval activity of conjugate major sinistral strike-slip faults and minor (antithetic) dextral strike-slip faults, which border the Deba block. On the base of conservative estimations, a minimum block-rotation rate of 35° Ma−1 and a sinistral strike-slip rate of 1.2 km Ma−1 are calculated. As a consequence of the interaction of the rotated Deba block with adjacent non-rotated blocks, its corners experienced coeval transpressive (NW and SE corners) and transtensional deformations (SW and, possibly, NE corners). At the transtensional SW corner, two domal high-reflective seismic structures have been recorded and interpreted as high-level magmatic laccoliths. These magmatic intrusions triggered the development of a mineralizing hydrothermal system, which vented to the Late Albian seafloor warm to hot hydrocarbon-rich fluids. Vented hydrocarbon was generated from Albian organic-rich sediments by contact alteration with hydrothermal fluids.

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Kinematic partitioning in the Southern Andes (39° S–46° S) inferred from lineament analysis and reassessment of exhumation rates

International Journal of Earth Sciences ◽

10.1007/s00531-021-02068-y ◽

2021 ◽

Author(s):

Paul Leon Göllner ◽

Jan Oliver Eisermann ◽

Catalina Balbis ◽

Ivan A. Petrinovic ◽

Ulrich Riller

Keyword(s):

Fault Zone ◽

Vertical Displacement ◽

Strike Slip ◽

Structural Studies ◽

Southern Andes ◽

Plate Convergence ◽

Exhumation Rates ◽

Lineament Analysis ◽

Dextral Strike Slip ◽

Data Call

AbstractThe Southern Andes are often viewed as a classic example for kinematic partitioning of oblique plate convergence into components of continental margin-parallel strike-slip and transverse shortening. In this regard, the Liquiñe-Ofqui Fault Zone, one of Earth’s most prominent intra-arc deformation zones, is believed to be the most important crustal discontinuity in the Southern Andes taking up margin-parallel dextral strike-slip. Recent structural studies, however, are at odds with this simple concept of kinematic partitioning, due to the presence of margin-oblique and a number of other margin-parallel intra-arc deformation zones. However, knowledge on the extent of such zones in the Southern Andes is still limited. Here, we document traces of prominent structural discontinuities (lineaments) from the Southern Andes between 39° S and 46° S. In combination with compiled low-temperature thermochronology data and interpolation of respective exhumation rates, we revisit the issue of kinematic partitioning in the Southern Andes. Exhumation rates are maximal in the central parts of the orogen and discontinuity traces, trending predominantly N–S, WNW–ESE and NE–SW, are distributed across the entire width of the orogen. Notably, discontinuities coincide spatially with large gradients in Neogene exhumation rates and separate crustal domains characterized by uniform exhumation. Collectively, these relationships point to significant components of vertical displacement on these discontinuities, in addition to horizontal displacements known from published structural studies. Our results agree with previously documented Neogene shortening in the Southern Andes and indicate orogen-scale transpression with maximal vertical extrusion of rocks in the center of the transpression zone. The lineament and thermochronology data call into question the traditional view of kinematic partitioning in the Southern Andes, in which deformation is focused on the Liquiñe-Ofqui Fault Zone.

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