Philippe Vernant

• PhD
• Professor (Associate) at Université de Montpellier

The spatiotemporal pattern of surface displacements from large earthquakes provides crucial insights about the deformation of Earth’s crust at various scales and the interactions among tectonic plates. However, the lack of extensive and large-scale geodetic networks near such seismic events hinders our thorough understanding of the large-scale crus...

Although underground topography methods have significantly evolved in the past two decades, it is still challenging and often costly to create comprehensive 3D models of caves or artificial cavities. Modern methods used by speleologists, involving the generation of a topographic ‘skeleton’ through laser pointer measurements, enable surveying extens...

We present 35 new burial ages (27 sites) based on 26Al / 10Be ratios of terrestrial cosmogenic radionuclides measured in clasts and sediments deep within 12 caves in the southern Massif Central, France. Our results, together with previously published burial ages, verify that cave morphogenesis has been continuously active in this region for at leas...

Elevated Plio-Pleistocene coastal and marine markers in stable continental regions are commonly explained by a combination of eustatic sea-level variations and regional geodynamics (e.g., mantle dynamics, active faults). In this study, we test the role of erosion rates on the Late Pleistocene uplift and landform evolution of the Armorican Massif, w...

In many regions formerly glaciated during the Last Glacial Maximum (LGM), glacial isostatic adjustment (GIA) explains most of the measured uplift and deformation rates. GIA is also proposed as a key process contributing to fault activity and seismicity shortly after the LGM and potentially up to the present day. Here, we study the impact of GIA on...

Karst systems represent an important carbon and freshwater reservoirs. Although karst systems have been studied for many years, a new paradigm has emerged that suggests some of them could be formed by ghost-rock processes (Dubois et al. 2014 ) . Contrarily to the classical total karstification, ghost-rock karstification leaves in place a weathered...

Stable Continental Regions (SCR) feature very low seismicity levels, but historical seismicity reveals that these areas can experience large damaging earthquakes of magnitude up to Mw ≈ 7, on faults that were previously undocumented or thought to be stable. Glacial Isostatic Adjustment (GIA) is commonly considered as a factor of SCR deformation and...

We present 27 new burial ages based on 26Al / 10Be ratios of terrestrial cosmogenic radionuclides measured in clasts and sediments deep within 12 caves in the southern Massif Central, France. Our results together with previously published burial ages, verifies that cave morphogenesis has been continuously active in this region for at least the past...

The causes of seismicity in stable continental regions (SCRs) remain an open question, in particular with respect to (1) the transient or steady-state nature of the forcing mechanisms and (2) the bias toward shallow seismicity. In this study, we test the impact of long-term localized erosion on crustal stresses and the promotion or inhibition of se...

In regions formerly glaciated during the Last Glacial Maximum (LGM), Glacial Isostatic Adjustment (GIA) explains most of the measured uplift and deformation rates. GIA is also proposed as a key process contributing to fault activity and seismicity shortly after the LGM and potentially up to present-day. Here, we study the impact of GIA on present-d...

Stable Continental Regions (SCR) feature very low seismicity levels, but historical seismicity reveals that these areas can experience large damaging earthquakes of magnitude up to Mw ≈ 7, on faults that were previously undocumented or thought to be stable. Glacial Isostatic Adjustment (GIA) is commonly considered as a factor of SCR deformation and...

This supplementary material addresses the details and construction of the rheological models used for GIA modeling. It is organized as: 1) lithosphere flexural rigidity, 2) mantle viscoelasticity.

Earthquakes occur in stable continental regions (SCR) with Mw>5 and up to Mw≈7, and research on the origins of SCR seismicity is ongoing. Glacial Isostatic Adjustment (GIA) is commonly considered as a factor of SCR stress perturbation that can trigger seismicity in past glaciated areas, and studies suggest that fault failure may occur around those...

The about 12 km of the Garrel cave located in Southern France have been surveyed. It corresponds to 6815 survey stations. We use these data to conduct a statistical study of the network geometry using the Karstnet software and perform a plane fitting to the fault mirrors evidences seen in the cave. Both approaches give the same main direction of th...

We present a new burial age obtained from cosmogenic dating on quartz alluvium sampled in a cave of the Larzac plateau (France). The recent age obtained (0.28 ± 0.1Ma) for a cave located at more than 8km from the plateau edges and 250 to 400m above the regional base level show that the classical speleogenesis model of sub-horizontal galleries direc...

The largest French speleological networks have been explored in the French mountains (Alps and Pyrenees). They combine considerable depths and total lengths (8 networks exceed -1000 m, 92 exceed -500m, nearly 50 networks are longer than 10 km). They present a widemorphological diversity and interest for reconstructions of the past. Through seven ou...

Le paysage ardéchois est marqué par une zone de hauts plateaux cristallins au nord-ouest (altitude de l'ordre de 1000 à 1200 m) et une zone de plateaux calcaires de plus faible altitude (~ 300 m) au sud-est dominant la vallée du Rhône (~ 70 m). D'après les études géomorphologiques et géologiques précédentes, ces reliefs seraient principalement liés...

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 o...

The salt mining industrial exploitation located in Vauvert (France) has been injecting water at high pressure into wells to dissolve salt layers at depth. The extracted brine has been used in the chemical industry for more than 30 years, inducing a subsidence of the surface. Yearly leveling surveys have monitored the deformation since 1996. This da...

New burial ages of cave deposits, based on the 26Al/10Be cosmogenic isotope ratio technique, from three caves in the Vis Valley, located in the south-east perimeter of the “Grands-Causses” in southern France are challenging the validity of classic karstic evolution models to explain the structure and evolution of the karstic network in the region....

On November 11, 2019, a Mw 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to...

On November 11, 2019, a Mw 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to...

The salt mining industrial exploitation located in Vauvert (France) has been injecting water at high pressure in wells to dissolve salt layers at depth. The extracted brine is used in chemical industry for more than thirty years, inducing a subsidence of the surface. Yearly levelling surveys monitor the deformation since the 1996. This dataset is s...

Although more and more processes are discussed and discovered on the genesis and evolution of cave systems, the tiered karsts are often explained by a control of the base level evolution. In this classical model, the horizontal galleries are explained by a stability of the base level elevation. To the contrary, the shafts and network segments with...

In the 60's, the formulation of the plate tectonic theory changed our understanding of the Earth dynamics. Aiming at explaining the earth first order kinematics, this primary theory of plate tectonic assumed rigid plates, a necessity to efficiently transfer stress from one boundary to another. If successful to explain, at first order, the plate-bou...

The evolution of intraplate orogens is still poorly understood. Yet, it is of major importance for understanding the Earth and plate dynamics, as well as the link between surface and deep geodynamic processes. The French Massif Central is an intraplate orogen with a mean elevation of 1000 m, with the highest peak elevations ranging from 1500 to 188...

We use 2 decades of data from a dense geodetic network to extract regionally coherent velocities and deformation rates in France and neighboring western European countries. This analysis is combined with statistical tests on synthetic data to quantify the deformation detection thresholds and significance levels. By combining two distinct methods –...

The evolution of intra-plate orogens is still poorly understood. Yet, this is of major importance for understanding the Earth and plate dynamic, as well as the link between surface and deep geodynamic processes. The French Massif Central is an intraplate orogen with a mean elevation of 1000 m, with the highest peak elevations ranging from 1500 m to...

We use dense geodetic networks and large GPS datasets to extract regionally coherent velocities and deformation rates in France and neighboring Western Europe. This analysis is combined with statistical tests on synthetic data to quantify the deformation detection thresholds and significance levels. By combining two distinct methods, Gaussian smoot...

We present a 3D crustal deformation velocity field of the Iberian Peninsula based on the analysis of more than 400 continuous GPS stations covering the period from 2010 to 2018 and distributed throughout the Iberian Peninsula, northern Africa and southern France. We describe the procedures followed to obtain a combined uniform velocity solution fro...

Global Navigation Satellite System (GNSS) is a powerful tool to decipher the present-day deformation along plate boundaries, but it is usually overlooked in slow deformation regions because of the resolution limit. France is a part of the Western Eurasian plate and is commonly considered stable or having low velocities in terms of horizontal motion...

We use statistical analyses of synthetic position time series to estimate the potential precision of GPS (Global Positioning System) velocities. The synthetic series represent the standard range of noise, seasonal, and position offset characteristics, leaving aside extreme values. This analysis is combined with a new simple method for automatic off...

We present the most extensive and up-to-date unified GPS velocity field for Iran. We processed the data collected during 10 years (2006–2015) from the Iranian Permanent GNSS Network (IPGN) and combined them with previously published velocity solutions from GPS survey measurements during 1997–2013. We analysed this velocity field using a continuum a...

The availability of GPS survey data spanning 22 years, along with several independent velocity solutions including up to 16 years of permanent GPS data, presents a unique opportunity to search for persistent (and thus reliable) deformation patterns in the Western Alps, which in turn allow a reinterpretation of the active tectonics of this region. W...

The present-day horizontal movements in Morocco have been the subject of several studies using two decades of GPS measurements. These studies suggested models on the geodynamic processes in the western Mediterranean region. However, vertical movements, often of smaller magnitude, are still poorly constrained. In this work we use continuous GPS meas...

We use statistical analyses of synthetic position time series to estimate the potential precision of GPS velocities. The synthetic series represent the standard range of noise, seasonal, and position offset characteristics, leaving aside extreme values. This analysis is combined with a new simple method for automatic offset detection that allows an...

The availability of GPS survey data spanning 22 years, along with several independent velocity solutions including up to 16 years of permanent GPS data, presents a unique opportunity to search for persistent (and thus reliable) deformation patterns in the Western Alps, which in turn allow a reinterpretation of the active tectonics of this region. W...

The magnitude of epikarstic water storage variation is evaluated in various karst settings using a relative spring gravimeter. Gravity measurements are performed over a 1.5-year period at the surface and inside caves at different depths on three karst hydro-systems in southern France: two limestone karst systems and one dolomite karst system. We fi...

L’âge de formation des morphologies de la marge cévenole, à l’instar des gorges du Tarn ou de l’Hérault est discutée depuis plus d’un siècle. Cette étude s’inscrit dans cette démarche et, par l’apport de nouvelles contraintes temporelles précise, et parfois questionne, les derniers modèles morphogénétiques. Les datations absolues complétées par l’a...

In this paper, we present the first estimate of the Holocene deformation along the southern front of Gibraltar arc (Morocco) and the first field constraints on the local 1755 CE Fes-Meknes surface rupturing earthquake which could be associated to the “Great Lisbon Earthquake” (M > 8.5) in November 1st, 1755. Using satellite imagery, aerial photogra...

In this study we attempt to evaluate the magnitude of epikarstic water storage variation in various karst settings using a relative spring gravimeter. Gravity measurements are performed two times a year at the surface and inside caves at different depths on three karst aquifers in southern France: two limestone karst systems and one dolomite karst...

Although subject to significant earthquakes, the region covering theWestern Alps and Pyrenees in southern France, northern Spain, and northern Italy is characterized by very slow deformation rates (below 1 mm a-1), leading to ongoing debates regarding the driving processes and characteristics of this seismicity. We present a new 3-D velocity field...

In this study we present an up-to-date velocity field of Iran, including the largest number of data ever presented on this region. It includes both a synthesis of all previously published campaign data (Raeesi et al., 2016) and all data from the Iranian Permanent GNSS Network (IPGN). The IPGN data cover some parts of Iran which were previously scar...

On the southern margin of the Western Mediterranean sea, the Moroccan Rif Cordillera is a thin-skinned fold and thrust belt resulting from the NW-SE convergence between the African and Eurasian lithospheric plates. At the present-day, the kinematics of the western and southern borders of the Rif are characterized by active thrusting consistent with...

Although the first-order pattern of present-day deformation is relatively well resolved across the Himalayas, irregular data coverage limits detailed analyses of spatial variations of interseismic coupling. We provide the first GPS velocity field for the Bhutan Himalaya. Combined with published data, these observations show strong East - West varia...

The quantification of interseismic coupling along the Himalayan arc is a primary question to address the seismic hazard. How much of the strain is accommodated along the fault during earthquake or elastically during the interseismic period is a key question to characterize the deficit accumulation along the Himalayan arc. From the GPS data acquired...

We present a new 3-D GPS velocity solution for 182 sites for the region encompassing the Western Alps, Pyrenees, and southern France. The velocity field is based on a Precise Point Positioning (PPP) solution, to which we apply a common-mode filter, defined by the 26 longest time series, in order to correct for network-wide biases (reference frame,...

We present a new 3D GPS velocity solution for 182 sites for the region encompassing the Western Alps, Pyrenees, and southern France. The velocity field is based on a Precise Point Positioning (PPP) solution, to which we apply a common-mode filter, defined by the 26 longest time series, in order to correct for network-wide biases (reference frame, e...

Collisional mountain belts grow as a consequence of continental plate convergence and eventually disappear under the combined effects of gravitational collapse and erosion. Using a decade of GPS data, we show that the western Alps are currently characterized by zero horizontal velocity boundary conditions, offering the opportunity to investigate or...

More than 10 years of geodetic measurements demonstrate an uplift rate of 1-3 mm/yr of the high topography region of the Western Alps. By contrast, no significant horizontal motion has been detected. Two uplift mechanisms have been proposed: (1) the isostatic response to denudation, responsible for only a fraction of the observed uplift and, (2) th...

Normal faulting mechanisms observed in the northern foothills of the Central-Western Pyrenees are remarkable since one expects thrust faults at a convergent plate boundary. To understand the mechanisms involved, we used numerical modeling and investigated the impact of the following processes: 1) Gravitational Potential Energy associated with topog...

The Pyrenean mountain range is a slowly deforming belt with continuous and moderate seismic activity. To quantify its deformation field, we present the velocity field estimated from a GPS survey of the Pyrenees spanning 18 yr. The PotSis and ResPyr networks, including a total of 85 GPS sites, were installed and first measured in 1992 and 1995–1997,...

We present new GPS velocities for the Arabia-Africa-Eurasia region determined with GAMIT/GLOBK (>830 velocities) spanning the period 1994-2014. Here we consider the E Mediterranean region of plate interaction. We use DEFNODE software to develop block models and estimate slip rates on major faults and strain of some blocks. The wrms of residual velo...

Les Pyrénées sont une chaîne de montagne à déformation lente avec une activité sismique continue et modérée. Afin de quantifier la déformation horizontale actuelle, nous présentons un champ de vitesses estimé à partir de mesures GPS couvrant une période de 18 ans. Le réseau PotSis installé en 1992, et le réseau ResPyr installé en deux phases en 199...

Rivers incision results from the interaction of vertical surface displacement (uplift, tectonic), climate, and base-level lowering. Recent numerical modelling shows that erosion-induced isostatic rebound triggers uplift and extension in low convergent mountain, such as Alps and Pyrenees. Quantify valley incision is a proxy of erosion rate and can b...

The Pyrenean mountain range is a slowly deforming belt with continuous and moderate seismic activity. To quantify its deformation field, we present the velocity field estimated from a GPS survey of the Pyrenees spanning 18 yr. The PotSis and ResPyr networks, including a total of 85 GPS sites, were installed and first measured in 1992 and 1995–1997,...

GPS data reveal that the Brahmaputra Valley has broken from the Indian plate and rotates clockwise relative to India about a point a few hundred km west of the Shillong plateau The GPS velocity vectors define two distinct blocks separated by the Kopili fault upon which 2–3 mm/yr of dextral slip is observed: the Shillong block between longitudes 89-...

We present results of a geomorphological and morphotectonic analysis of the Rif Mountains (Morocco). We show that the present day kinematics of the Rif is characterized by active deformation along normal and left-lateral strike-slip faults in the NorthEast (Trougout, Rouadi, Boujibar and Nekor faults), reverse fault in the South (the South Rif Fron...

The Southern Rif Front (SRF) is located at the southernmost frontal part of the Rif Cordillera (Morocco) and overthrusts the foreland basins of Saiss and Gharb. Extending over a length of ∼150km between Fez, Meknes and Rabat cities, the SRF stands out as a major active structure. It represents an important seismic hazard for these highly-populated...

Very high resolution digital elevation models are a key component of modern quantitative geomorphology. In parallel to high-precision but time-consuming kinematic GPS and/or total station surveys and dense coverage but expensive LiDAR campaigns, we explore the usability of affordable, flexible, wide coverage digital surface models (DSMs) derived fr...

Extending over a length of ~150km and located close to the cities of Fez, Meknes and Rabat, the Southern Rif Front (SRF) stands out as a major active structure of the Rif Cordillera (Morocco). It represents an important seismic hazard for these highly populated cities of the region as evidenced by the historical seismic activity. The last historica...

Surface displacements due to temporal changes in environmental mass redistributions are observable in the coordinate time series of many Global Navigation Satellite System (GNSS) sites. In this study, we investigated the effect of loading on estimates of tectonic velocity computed from campaign-style GNSS observations. The study region is in the Py...

estimates of the geodetic and geologic slip rates of the 1500 km long Altyn Tagh fault bordering the northern edge of the Tibetan plateau vary by a factor of five. Proposed reasons for these discrepancies include poor GPS geometry, interpretative errors in terrace morphology, and changes in fault slip rate over time. Here we present results from a...

Abstract / Discussion Poster RESIF (Octobre 2013) Fifteen years of GPS measurements in France have led to unexpected results : - horizontal deformation is very low (<0.5 mm/year) like in an intracontinal domain. - uplift in the Alps can reach 1 to 2 mm/year(1). Despite their low tectonic activity, mountain belts of Western Europe exhibit seismogeni...

Iran is an active continental domain accommodating the convergence between the Arabia and Eurasia plates. In northwestern Iran, deformation between the Central Iranian block and the Caucasus domain is mainly accommodated by right lateral strike-slip on the Tabriz fault. Cities and villages, including the city of Tabriz, have been destroyed by sever...

We present results of a geomorphological and morphotectectonic analysis of the Rif. Our study area encompasses a region running from the eastern border of the Rif up to the Atlantic coast to the west, and including the southwestern foreland of the range. We show that the present day kinematics of the Rif is characterized by active deformations alon...

Mechanisms that control seismic activity in low strain rate areas such as western Europe remain poorly understood. For example, in spite of low shortening rates of <0.5 mm/yr, the Western Alps and the Pyrenees are underlain by moderate but frequent seismicity detectable by instruments. Beneath the elevated part of these mountain ranges, analysis of...

We present the 1998–2009 GPS-derived velocity field for the Armenia region based on a survey-mode observation network of 31 GPS sites. We combine our results with previous GPS studies of the region to better assess the deformation of the Lesser Caucasus and Kura basin region. The results show that the Kura basin and the Lesser Caucasus regions are...

Compared to Nepal, seismogenic potential of Bhutan remains enigmatic due to its low present-day seismicity rate. Over the last three centuries, the only large reported event in this area is a Mw=8.1 earthquake in 1897 that occurred further south of the Main Himalayan Thrust (MHT) near the Shillong Plateau. New insights from a GPS network in Bhutan...

The assessment of water storage in the unsaturated zone in karstic areas is particularly challenging. Indeed, water flow path and water storage occur in quite heterogeneous ways through small scale porosity, fractures, joints and large voids. Due to this large heterogeneity, it is therefore difficult to estimate the amount of water circulating in t...

Iran is an active continental domain accommodating the convergence between the Arabia and Eurasia plates. In the north-western part of Iran, the deformation between the Central Iranian Block and the Caucasus domain is mainly accommodated by right lateral strike-slip on the Tabriz fault. The Tabriz fault produced several strong destructive earthquak...

We have established a new survey mode GPS network across the Altyn Tagh Fault in the northern central Tibetan plateau. This network consists of 19 sites between 34° N and 39 ° N and 85 ° E and 86 ° E. From 2009 to 2011, the network has been surveyed for 2 to 3 times. Each site has been surveyed for at least 48 hours with Trimble NetRS receivers and...

Normal faults parallel to the strike of the mountain ranges have always been though as an evidence of gravitational collapse. The Pyrenees and the Alps (western Europe) provide an invaluable laboratory to check for gravitational collapse. Indeed, earlier GPS studies show extremely low deformation if any within the Eurasia-Iberia plate, new GPS resu...

Measurements of interseismic strain across active faults are an important key to better assess faults dynamics and seismic hazard. Based on geodetic observations across the San Andreas fault Savage and Burford in 1973 have proposed a dislocation in an elastic half space model to fit the observations. Since then, the advent of the Global Positioning...