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Introduction
Publications
Publications (151)
We use continuous and survey GNSS data to image the spatial and temporal evolution of afterslip during the two-months following the Mw8.3 2015 Illapel earthquake. Our approach solves for the incremental daily slip at the subduction interface using non-negative least-squares with spatial and temporal Laplacian regularization constraints. We find tha...
The 2019/05/26 Northern Peru earthquake (Mw=8) is a major intermediate-depth earthquake that occurred close to the eastern edge of the Nazca slab flat area. We analyze its rupture process using high-frequency back-projection and seismo-geodetic broadband inversion. The latter approach shows that the earthquake propagated with almost purely normal f...
We use new GPS data to determine an updated Euler pole describing the present-day motion of the oceanic Nazca plate. Our solution includes continuous GPS (cGPS) measurements at Malpelo Island offshore Colombia, two sites in the Galapagos archipelago, Easter Island and Salas y Gomez Island in the western part of the plate and Robinson Crusoe Island...
We investigate the relationship between the long‐term (Quaternary) interplate coupling and the short‐term geodetically derived interseismic coupling at the Central Ecuador subduction zone. At this nonaccretionary margin, the Cabo Pasado shelf promontory and coastal area are associated with two inter‐plate geodetically locked patches. The deepest pa...
Over the last 3 decades, GPS measurements have been instrumental in quantifying tectonic plates current motion and deformation. Complex patterns of deformation along the plate boundaries revealed heterogeneous coupling on the plates interface and imaged seismic segments at different stages of their seismic cycle. Along the South-American trench in...
The International Symposium on Andean Geodynamics (ISAG) is an international conference that was held, on average, every 3–4 years in different European cities between 1990 (Grenoble) and 2008 (Nice). These symposia usually offer an opportunity for researchers from Latin American countries and Europe as well as other countries to review the state o...
We studied the along-dip influence of the Copiapó ridge subduction in the Atacama region, North-Central Chile by building a new seismicity catalog, including similar events and non-volcanic tremors (NVTs). We also obtained a 3-D tomographic model for P- and S-waves velocity (and the implied Vp/Vs ratio). We identify down-dip segmentation involving...
We studied the along-dip influence of the Copiapó ridge subduction in the Atacama region, North-Central Chile by building a new seismicity catalog, including similar events and non-volcanic tremors (NVTs). We also obtained a 3-D tomographic model for P- and S-waves velocity (and the implied Vp/Vs ratio). We identify down-dip segmentation involving...
We use Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data to quantify the interseismic coupling along the Xianshuihe‐Xiaojiang fault system (XXFS). Our results confirm 7–11 mm/a of left‐lateral strike‐slip motion along the XXFS. South of the Shimian County, high interseismic coupling is found down to 20 km‐dep...
We combine Global Positioning System (GPS) velocity field (2009–2017) with Interferometric Synthetic Aperture Radar (InSAR, 2003–2011) results from Daout et al. (2018) to study the interseismic deformation across the western Altyn Tagh fault (ATF) at longitude 86° E. GPS and InSAR data are consistent after correcting for the contribution from verti...
An earthquake sequence occurred in the Atacama region of Chile throughout September 2020. The sequence initiated by a mainshock of magnitude Mw6.9, followed 17 hours later by a Mw6.4 aftershock. The sequence lasted several weeks, during which more than a thousand events larger than Ml 1 occurred, including several larger earthquakes of magnitudes b...
An earthquake sequence occurred in the Atacama region of Chile throughout September 2020. The sequence initiated by a mainshock of magnitude Mw6.9, followed 17 hours later by aMw6.4 aftershock. The sequence lasted several weeks, during which more than a thousand events larger than Ml 1 occurred, including several larger earthquakes of magnitudes be...
We investigated the spatial distribution of aseismic creep on the Laohushan‐Haiyuan fault using Global Positioning System (GPS) data (1999–2017) and Interferometric Synthetic Aperture Radar (InSAR) data (2003–2010). Comparisons among GPS, InSAR line‐of‐sight (LOS) rates, and leveling show that neither leveling nor GPS vertical velocities can fit th...
Repeating earthquakes repeatedly rupture the same seismic asperity and are strongly linked to aseismic slip. Here, we study the repeating aftershocks of the April 16, 2016 MW 7.8 Pedernales earthquake in Ecuador, which generated a large amount of afterslip. Using temporary and permanent stations, we correlate waveforms from a one‐year catalog of af...
Probabilistic seismic hazard assessment relies on long-term earthquake forecasts and ground-motion models. Our aim is to improve earthquake forecasts by including information derived from geodetic measurements, with an application to the Colombia–Ecuador megathrust. The annual rate of moment deficit accumulation at the interface is quantified from...
Megathrust ruptures and the ensuing postseismic deformation cause stress changes that may induce seismicity on upper plate crustal faults far from the coseismic rupture area. In this study, we analyze seismic swarms that occurred in the north Ecuador area of Esmeraldas, beginning two months after the 2016 Mw 7.8 Pedernales, Ecuador megathrust earth...
Plain Language Summary
Earthquakes are thought to occur on coupled fault portions, which are “locked” during the time separating two earthquakes, while tectonic plates are steadily moving. The spatial distribution of coupling has been imaged along numerous large faults in the world, but despite its considerable associated seismic hazard, not on the...
Both laboratory experiments and dynamic simulations suggest that earthquakes can be preceded by a precursory phase of slow slip. Observing processes leading to an acceleration or spreading of slow slip along faults is therefore key to understand the dynamics potentially leading to seismic ruptures. Here, we use continuous GPS measurements of the gr...
The North Anatolian Fault (NAF) is one of the most hazardous fault in the world. After decades of low seismicity, the $\rm{M_w}$ 6.8 Elazi\u{g} earthquake (January 24, 2020) has recently reminded us that the East Anatolian Fault (EAF) is also capable of producing large earthquakes. To better estimate the seismic hazard associated with these two fau...
Abstract
The heterogeneous seafloor topography of the Nazca Plate as itenters the Ecuador subduction zone provides an opportunity to document the influence of seafloor roughness on slip behavior and megathrust rupture. The 2016 Mw 7.8 Pedernales Ecuador earthquake was followed by a rich and active postseismic sequence. An internationally coordinated...
Quito, the capital city of Ecuador hosting ∼2 million inhabitants, lies on the hanging wall of a ∼60 km long reverse fault offsetting the Inter-Andean Valley in the northern Andes. Such an active fault poses a significant risk, enhanced by the high density of population and overall poor building construction quality. Here, we constrain the present-...
In the paper entitled “Two independent real-time precursors of the 7.8 M earthquake in Ecuador based on radioactive and geodetic processes – Powerful tools for an early warning system”, Toulkeridis et al. (2019) claim that they found radiation and GPS signal anomalies before the April 16th 2016 Pedernales earthquake (Ecuador) and that their finding...
High-Rate (HR) GPS time series following the 2016 M-w 7.8 Pedernales earthquake suggest significant postseismic deformation occurring in the early postseismic period (i.e. first few hours after the earthquake) that is not resolved with daily GPS time series. To understand the characteristics of early postseismic deformation, and its relationship wi...
On April 16th 2016 a Mw 7.8 earthquake ruptured the central coastal segment of the Ecuadorian subduction zone. Shortly after the earthquake, the Institute Geofisico de la Escuela Politecnica Nacional of Ecuador, together with several international institutions deployed a dense, temporary seismic network to accurately categorize the post-seismic aft...
In the paper entitled “Two independent real-time precursors of the 7.8 M earthquake in Ecuador based on radioactive and geodetic processes – Powerful tools for an early warning system”, Toulkeridis et al. (2019) claim that they found radiation and GPS signal anomalies before the April 16th 2016 Pedernales earthquake (Ecuador) and that their finding...
We characterise the aftershock sequence following the 2016 Mw=7.8 Pedernales earthquake. More than 10,000 events were detected and located, with magnitudes up to 6.9. Most of the aftershock seismicity results from interplate thrust faulting, but we also observe a few normal and strike-slip mechanisms. Seismicity extends for more than 300 km along s...
The recent development of a national seismic broadband network in Ecuador enables us to determine a comprehensive catalog of earthquake focal mechanisms at the country-scale. Using a waveform inversion technique accounting for the spatially variable seismic velocity structure across the country, we provide location, depth, focal mechanism and seism...
We characterise the aftershock sequence following the 2016 Mw=7.8 Pedernales earthquake. More than 10,000 events were detected and located, with magnitudes up to 6.9. Most of the aftershock seismicity results from interplate thrust faulting, but we also observe a few normal and strike-slip mechanisms. Seismicity extends for more than 300 km along s...
We use GPS data of Ecuador's national continuous geodetic network to constrain ongoing post-seismic deformation associated with the destructive 2016 M w 7.8 Pedernales, Ecuador subduction earthquake. The main shock's occurrence produced a maximum co-seismic slip of 6 m with a southward rupture of 2 main asperities.
Recent measurements of surface vertical displacements of the European Alps show a correlation between vertical velocities and topographic features, with widespread uplift at rates of up to ~2-2.5 mm/a in the North-Western and Central Alps, and ~1 mm/a across a continuous region from the Eastern to the South-Western Alps. Such a rock uplift rate pat...
Displacement waveforms derived from Global Navigation Satellite System (GNSS) data have become more commonly used by seismologists in the past 15 yrs. Unlike strong‐motion accelerometer recordings that are affected by baseline offsets during very strong shaking, GNSS data record displacement with fidelity down to 0 Hz. Unfortunately, fully processe...
Comment, depuis plusieurs décennies, la recherche scientifique contribue-t-elle au développement des pays du Sud ? À travers plus de 100 succès emblématiques de la recherche en partenariat, cet ouvrage nous plonge au coeur des grandes questions de développement : oeuvrer pour des sociétés plus justes, lutter contre les maladies, faire face aux risq...
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...
Despite surface displacements observed by geodesy are linear combinations of slip at faults in an elastic medium, determining the spatial distribution of fault slip remains a ill-posed inverse problem. A widely used approach to circumvent the illness of the inversion is to add regularization constraints in terms of smoothing and/or damping so that...
A temporary onshore-offshore seismic network deployed during the 2-year period of the Observación SISmológica en ECuador project provides a detailed and well-focused image of the seismicity for magnitudes as low as 2.1 at the Central Ecuadorian subduction zone. During this 2-year experiment, the shallow and locked subduction patch shows little evid...
We present a comprehensive probabilistic seismic hazard study for Ecuador, a country exposed to a high seismic hazard from megathrust subduction earthquakes and moderate-to-large shallow crustal earthquakes. Building on knowledge gained during the last decade about historical and contemporary seismicity, active tectonics, geodynamics, and geodesy,...
The continuous Global Positioning System (cGPS) network operating in the northern Andes (Ecuador and Colombia) for about a decade has the main objectives of quantifying interseismic coupling along the subduction interface, detecting occurrence of transient aseismic episodic slip, detailing the rupture kinematics of large earthquakes, recording long...
At subduction zones, transient aseismic slip occurs either as afterslip following a large earthquake or as episodic slow slip events during the interseismic period. Afterslip and slow slip events are usually considered as distinct processes occurring on separate fault areas governed by different frictional properties. Continuous GPS (Global Positio...
The northern Ecuador segment of the Nazca/South America subduction zone shows spatially heterogeneous interseismic coupling. Two highly coupled zones (0.4° S–0.35° N and 0.8° N–4.0° N) are separated by a low coupled area, hereafter referred to as the Punta Galera-Mompiche Zone (PGMZ). Large interplate earthquakes repeatedly occurred within the coup...
Cotopaxi volcano started a period of volcanic unrest in April 2015 that led to a series of eruptions between August and November 2015. We use COSMO-SkyMed Interferometric Synthetic Aperture Radar supported by continuous GPS observations spanning the period of 2014–2016 to obtain time-dependent ground deformation data over Cotopaxi volcano related t...
Whether subducted oceanic reliefs such as seamounts promote seismic rupture or aseismic slip remains controversial. Here, we use swath bathymetry, pre-stack-depth-migrated multichannel seismic reflection lines and wide-angle seismic data collected across the Central Ecuador subduction segment to reveal a broad ~55-km x 50-km, ~ 1.5-2.0-km-high, low...
Probabilistic seismic hazard assessment (PSHA) consists in developing earthquake recurrence models, selecting ground-motion prediction equations, and determining probabilities of exceedance of ground-motion levels over future time windows. PSHA results, hazard maps for given spectral periods and return periods, are used to derive countrywide seismi...
Large earthquakes are usually assumed to release all of the strain accumulated since the previous event, implying a reduced seismic hazard after them. However, long records of seismic history at several subduction zones suggest supercycle behaviour, where centuries-long accumulated strain is released through clustered large earthquakes, resulting i...
Cotopaxi volcano’s 2015-16 unrest resulted in GPS displacements, increased GPS velocities and reversal of vectors and positive tilt, coinciding with increased long period (LP) seismicity, high frequency tremor and accentuated accumulative seismic energy. Seismicity at Cotopaxi in late April-15 was typified by abundant LPs and VLPs, located 3-15 km...
We estimate the strength of the lithosphere in Anatolia and the Aegean, and the boundary forces acting upon it, using a dynamical model that treats the lithosphere as a thin fluid sheet deforming in response to variations in gravitational potential energy. This model has one free material parameter, the power-law exponent, n, of the vertically-aver...
Over 100 GPS sites measured in 2008-2013 in Peru provide new insights into the present-day crustal deformation of the 2200km long Peruvian margin. This margin is squeezed between the eastward subduction of the oceanic Nazca Plate at the South America trench axis and the westward continental subduction of the South American Plate beneath the Eastern...
Magma movement or reservoir pressurisation can drive swarms of low-magnitude volcano-tectonic earthquakes, as well as occasional larger earthquakes (> M 5) on local tectonic faults. Earthquakes > M 5 near volcanoes are challenging to interpret in terms of evolving volcanic hazard, but are often associated with eruptions, and in some cases enhance t...
On April 16 2016, a magnitude 7.8 earthquake occurred along the Nazca-South America plate interface near the city of Pedernales in Ecuador. GPS measurements in the years prior to the earthquake had indeed shown a partial and spatially heterogeneous pattern of interseismic coupling in central-northern Ecuador (Nocquet et al., 2014, Chlieh et al., 20...
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...
Along the Ecuadorian margin, oblique subduction induces deformation of the overriding continental plate. For the last 15Ma, both exhumation and tectonic history of Ecuador suggest that the northeastward motion of the North Andean Sliver (NAS) was accompanied by an eastward migration of its eastern boundary and successive progressively narrowing res...
Along the Ecuadorian margin, oblique subduction of the Nazca plate induces deformation and partitioning of the overriding continental plate and provokes the northeastward motion of the North Andean Sliver (NAS) (Nocquet et al., 2014). The Eastern tectonic boundary of the NAS in northern Ecuador is comprised of an N-NE striking family of faults with...
In subduction zones, stress is released by earthquakes and transient aseismic slip. The latter falls into two categories: slow slip and afterslip. Slow-slip events emerge spontaneously during the interseismic phase, and show a progressive acceleration of slip with a negligible contribution of synchronous tremors or microseismicity to the energy, or...
A new interpretation is proposed for the 2010 Jia-Shian earthquake (Mw 6.2) which occurred on March 4, 2010 in southwestern Taiwan. Among the few tens of CGPS stations which recorded the mainshock at a distance less than 50 km we identified a few stations displaying horizontal displacements in disagreement with the dominant pattern of horizontal co...
Ecuador has now a wide and continuous GSP of around 90 stations network which was acquired and implemented from 2009 to 2014 with funds from the national government (Senescyt, Environmental ministry) and international collaborations (DIPECHO, IRD, GEOAZUR, University of Miami). Together with an array of about 60 permanent broadband seismometers and...
The March 11, 2011, Mw9.0 Tohoku-Oki earthquake was recorded by an exceptionally large amount of diverse data offering a unique opportunity to investigate the details of this major megathrust rupture. Many studies have taken advantage of the very dense Japanese on land strong motion, broad-band and continuous GPS networks in this sense. But, resolu...
A dense GPS network deployed in Ecuador reveals a highly heterogeneous pattern of interseismic coupling confined in the first 35 km depth of the contact between the subducting oceanic Nazca plate and the North Andean Sliver. Interseismic models indicate that the coupling is weak and very shallow (0–15 km) in south Ecuador and increases northward, w...
We present an updated velocity field for Ecuador based on the network developed by the Instituto Geofisico de la Escuela Politecnica Nacional, Quito, Ecuador. The network now include twenty years of measurements. The processing was made using the GAMIT/GLOBK software and uses a classical two-step approach for geodynamics: loosely daily solutions ar...