Mohamed Chlieh

• PhD
• Chargé de Recherche IRD at Institute of Earth Science

The Central Andes subduction has been the theater of numerous large earthquakes since the beginning of the 21st Century, notably the 2001 Mw = 8.4 Arequipa, 2007 Mw = 8.0 Pisco and 2014 Mw = 8.1 Iquique earthquakes. We present an analysis of 47 permanent and 26 survey global navigation satellite system (GNSS) measurements acquired in Central‐South...

The Colombia–Ecuador subduction zone is an exceptional natural laboratory to study the seismic cycle associated with large and great subduction earthquakes. Since the great 1906 Mw = 8.6 Colombia–Ecuador earthquake, four large Mw > 7.5 megathrust earthquakes occurred within the 1906 rupture area, releasing altogether a cumulative seismic moment of...

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...

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...

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...

Measurement of interseismic strain along subduction zones reveals the location of both locked asperities, which might rupture during Megathrust earthquakes, and creeping zones, which tend to arrest such seismic ruptures. The heterogeneous pattern of interseismic coupling presumably relates to spatial variations of frictional properties along the su...

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...

We analysed the coseismic and early postseismic deformation of the 2015, Mw 8.3 Illapel earthquake by inverting 13 cGPS time series. The seismic rupture concentrated in a shallow (<20 km depth) and 100 km long asperity, which slipped up to 8 m, releasing a seismic moment of 3.6 × 1021 Nm (Mw = 8.3). After 43-days, postseismic afterslip encompassed...

Characterizing the time evolution of slip over different phases of the seismic cycle is crucial to a better understanding of the factors controlling the occurrence of large earthquakes. In this study, we take advantage of interferometric synthetic aperture radar data and 3.5 years of continuous Global Positioning System (GPS) measurements to determ...

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...

Considerable improvements in the measurement of the Earth gravity field from GOCE satellite mission have provided global gravity field models with homogeneous coverage, high precision and good spatial resolution. In particular, the vertical gravity gradient (Tzz), in comparison to the classic Bouguer anomaly, defines more accurately superficial mas...

Considerable improvements in the measurement of the Earth gravity field from GOCE satellite mission have provided global gravity field models with homogeneous coverage, high precision and good spatial resolution. In particular, the vertical gravity gradient (Tzz), in comparison to the classic Bouguer anomaly, defines more accurately superficial mas...

The 2011 moment magnitude (M w) 9.0 Tohoku-Oki Japan earthquake occurred in a region where giant megathrust earthquakes were not expected. This earthquake proved the difficulty in assessing seismic hazard by relying mainly on information from historical and instrumental seismicity. To help improve the seis-mic-hazard assessment for such rare events...

Considerable improvements in the measurement of the Earth gravity field from GOCE satellite mission have provided global gravity field models with homogeneous coverage, high precision and good spatial resolution. In particular, the vertical gravity gradient (Tzz), in comparison to the classic Bouguer anomaly, defines more accurately superficial mas...

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...

The North-Andean subduction zone generates recurrent tsunamigenic earthquakes. The seismicity is usually considered to be segmented because of different specific morphological features of the Nazca Plate driving the subduction motion. Most of the recent powerful earthquakes in the margin were located in its northern part. To the south, the region o...

Along thewestern margin of South America, plate convergence is accommodated by slip on the subduction interface and deformation of the overriding continent. In Chile, Bolivia, Ecuador and Colombia, continental deformation occurs mostly through the motion of discrete domains, hundreds to thousands of kilometres in scale. These continental slivers ar...

Along the western margin of South America, plate convergence is accommodated by slip on the subduction interface and deformation of the overriding continent(1-6). In Chile(1-4), Bolivia(6), Ecuador and Colombia(5, 7), continental deformation occurs mostly through the motion of discrete domains, hundreds to thousands of kilometres in scale. These co...

We document a one week long slow-slip event (SSE) with an equivalent moment magnitude of 6.0-6.3 which occurred in August 2010 below La Plata Island (Ecuador), south of the rupture area of the Mw=8.8 1906 megathrust earthquake. GPS data reveal that the SSE occurred at a depth of about 10km, within the downdip part of a shallow (<15km), isolated, lo...

We use about two decades of geodetic measurements to characterize interseismic strain build up along the Central Andes subduction zone from Lima, Peru, to Antofagasta, Chile. These measurements are modeled assuming a 3-plate model (Nazca, Andean sliver and South America Craton) and spatially varying interseismic coupling (ISC) on the Nazca megathru...

We use GPS measurements in the first geodetic study of the Nazca/South America subduction zone along northern Peru and southern Ecuador (from 1°S to 10°S). Rapid subduction of the Nazca plate (~ 6 cm/yr) under the northern Andes margin gives rise to heterogeneous interseismic plate interface coupling, changing with latitude. Very weak to null coupl...

A numerical simulation of the 26th December 2004 Indian Ocean tsunami for the entire coast of Sri Lanka is presented. The simulation approach is based on a fully nonlinear Boussinesq tsunami propagation model and a robust coseismic source. The simulation is first confronted to available measured wave height. The agreement between observations and t...

In the last couple of decades, advances in the analysis techniques and instrumentation have improved significantly our capability to document the different stages of the seismic cycle, namely the co-, post- and inter-seismic phases. To this respect, the Mw8.0 Pisco, Peru, earthquake of August 2007 is exemplary, with numerous data sets allowing expl...

Rapid subduction of the Nazca plate beneath the northen Andes margin (~6 cm/yr) results in two different processes: (1) elastic stress is accumulating along the Nazca/South American plate interface which is responsible for one of the largest megathrust earthquake sequences during the last century. The 500-km-long rupture zone of the 1906 (Mw= 8.8)...

A numerical simulation of the 26th December, 2004 Indian Ocean tsunami of the Tamil Nadu coastal zone is presented. The simulation approach is based on a fully nonlinear Boussinesq tsunami propagation model and included an accurate computational domain and a robust coseismic source. The simulation is first confronted to available tide gauge and run...

Slip on a subduction megathrust can be seismic or aseismic, with the two modes of slip complementing each other in time and space to accommodate the long-term plate motions. Although slip is almost purely aseismic at depths greater than about 40 km, heterogeneous surface strain suggests that both modes of slip occur at shallower depths, with aseism...

In the last couple of decades, advances in the analysis techniques and instrumentation have improved significantly our capability to document the different stages of the seismic cycle, namely the co-, post- and inter-seismic phases. To this respect, the Mw8.0 Pisco, Peru, earthquake of August 2007 is exemplary, with numerous data sets allowing to e...

[1] The Tian Shan Mountains constitute central Asia's longest and highest mountain range. Understanding their Cenozoic uplift history thus bears on mountain building processes in general, and on how deformation has occurred under the influence of the India-Asia collision in particular. In order to help decipher the uplift history of the Tian Shan,...

Recent observations of heterogeneous strain build up reported from subduction zones and seismic sources of large and great interplate earthquakes indicate that seismic asperities are probably persistent features of the megathrust. The Peru Megathrust produce recurrently large seismic events like the 2001 Mw 8.4, Arequipa earthquake or the 2007 Mw 8...

The great Sumatra-Andaman earthquake and tsunami of 2004 was a dramatic reminder of the importance of understanding the seismic and tsunami hazards of subduction zones. In March 2005, the Sunda megathrust ruptured again, producing an event of moment magnitude (M(w)) 8.6 south of the 2004 rupture area, which was the site of a similar event in 1861 (...

The Sumatra Megathrust has recently produced a flurry of large interplate earthquakes starting with the giant Mw 9.15, Aceh earthquake of 2004. All of these earthquakes occurred within the area monitored by the Sumatra Geodetic Array (SuGAr), which provided exceptional records of near-field co-seismic and postseismic ground displacements. The most...

A numerical simulation of the 26th December 2004 Indian Ocean tsunami for the Andaman and Nicobar Islands case study is presented. The simulation approach is based on a fully nonlinear Boussinesq tsunami propagation model and included an accurate computational domain and a robust coseismic source. The simulation is first confronted to available tid...

Geodetic and paleogeodetic measurements of interseismic strain above the Sumatran portion of the Sunda subduction zone reveal a heterogeneous pattern of coupling. Annual banding in corals provides vertical rates of deformation spanning the last half of the 20th century, and repeated GPS surveys between 1991 and 2001 and continuous measurements at G...

Assessing the characteristics of large earthquakes along the Himalayan arc, such as their rupture extent, magnitude, return period and effects, is a major societal concern as well as a challenging scientific issue. To address that issue a number of complementary approaches need be applied to provide constraints on sub- surface structure, detect act...

This epicentral area of the 2007 Pisco earthquake marks a major transition in the characteristics of the Nazca subduction zone: 1) the megathrust dip angle is shallower (15-20) to the north than to the south (25-30); 2) megathrust earthquakes have distinctly smaller magnitudes and are more fragmented to the north; 3) the distance between the trench...

The advent of space geodesy has revolutionized our ability to measure surface displacements and crustal strain along plate boundaries or across deforming continental areas. Some examples from Taiwan, the Nepal Himalaya and Sumatra where geologic, geodetic and plate motion data can be compared will be reviewed in the presentation. It will be shown t...

On September 12, 2007, the Mw8.4 South Pagai earthquakes ruptured the subduction interface offshore southern Sumatra. The earthquake occurred within the area monitored by the Sumatra Geodetic Array (SuGAr). The cGPS stations on South Pagai Island show about 1.5 m of southwestward displacement, up to 0.6 m of uplift of the western coast of the islan...

The geomorphology and internal stratigraphy of modern coral microatolls show that all the outer arc Mentawai islands of West Sumatra have been subsiding over the past several decades. These same islands rose as much as 3 m during the giant megathrust earthquakes of 1797 and 1833, and the current subsidence probably reflects strain accumulation that...

We determine coseismic and the first-month postseismic deformation associated with the Sumatra–Andaman earthquake of 26 December 2004 from near- field Global Positioning System (gps) surveys in northwestern Sumatra and along the Nicobar-Andaman islands, continuous and campaign gps measurements from Thailand and Malaysia, and in situ and remotely se...

A long section of the Sunda megathrust south of the great tsunamigenic earthquakes of 2004 and 2005 is well advanced in its seismic cycle and a plausible candidate for rupture in the next few decades. Our computations of tsunami propagation and inundation yield model flow depths and inundations consistent with sparse historical accounts for the las...

We determine coseismic and the first-month postseismic deformation associated with the Sumatra-Andaman earthquake of December 26, 2004 from near-field Global Positioning System (GPS) surveys in northwestern Sumatra and along the Nicobar-Andaman islands, continuous and campaign GPS measurements from Thailand and Malaysia, and in-situ and remotely se...

We investigate the focal mechanisms after the Mw 9.15 2004 Aceh-Andaman earthquake and find a dramatic change of faulting type near the West Andaman Fault and the Seuliman Fault. Before the 2004 earthquake, the type of focal mechanism is mainly strike-slip, while it becomes normal faulting after the earthquake. We study the stress regime from the i...

Continuously recording Global Positioning System stations near the 28 March 2005 rupture of the Sunda megathrust [moment magnitude (Mw) 8.7] show that the earthquake triggered aseismic frictional afterslip on the subduction megathrust, with a major fraction of this slip in the up-dip direction from the main rupture. Eleven months after the main sho...

Large uplifts and tilts occurred on the Sumatran outer arc islands between 0.5° and 3.3°S during great historical earthquakes in 1797 and 1833, as judged from relative sea level changes recorded by annually banded coral heads. Coral data for these two earthquakes are most complete along a 160-km length of the Mentawai islands between 3.2° and 2°S....

The Sumatra-Andaman earthquake of 26 December 2004 is the first giant earthquake (moment magnitude M(w) > 9.0) to have occurred since the advent of modern space-based geodesy and broadband seismology. It therefore provides an unprecedented opportunity to investigate the characteristics of one of these enormous and rare events. Here we report estima...

We are investigating the evolution of fault slip in subduction zones using a method based on principal component analysis (PCA) and slip inversion of paleogeodetic and geodetic time series. First, the PCA of the time series is performed to emphasize the principal time-dependent trends (principal components) between stations. The principal component...

The Sumatra-Andaman earthquake of December 26, 2004 is the first giant earthquake to occur since the advent of modern space-based geodesy and broadband seismology and therefore provides an unprecedented opportunity to investigate the characteristics of one of these most dreadful and rare events. We determine co-seismic and post-seismic deformation...

A 1650-km long section of the Sunda megathrust, from the Equator to about 14°N, ruptured during the 2004 and 2005 giant earthquakes. Immediately south of the 2005 rupture, from about the Equator to 0.5°S is a short section of the megathrust that has failed only by aseismic slip and moderate earthquakes throughout the past 250 years. From 0.5° to ab...

The south equatorial segment of the sumatra subduction zone (the Mentawai segment) is known to have produced giant earthquakes in 1797 and 1833 (Mw higher than 8.5). The northern adjacent segment (Nias) that broke in 1861 and again in March 2005 (Mw=8.7) highlights the potential of a future giant earthquake in the Mentawai segment. Paleogeodetic an...

Coral microatolls on the fringing reefs of northwestern Simeuleu Island emerged as much as 150 cm during the 2004 earthquake. The pattern of uplift constrains the southern terminus of the 2004 rupture to be under the northwestern part of the island. It also constrains the downdip limit of coseismic rupture to be between Simeuleu and the mainland co...

The seismic cycle concept offers a convenient kinematic framework to integrate geodetic and geological observations. Generally the integration is made through elastic dislocation modeling, eventually based on Savage's backslip model. This sort of kinematic description is valid insofar as there is no permanent strain accumulating off the main fault...

Rupture of a large patch of the Sumatran subduction zone produced a giant earthquake in 1797. Roughly the same patch ruptured again in 1833, just 36 years later. The magnitude of slip in 1833 was several times greater than that in 1797. Two large earthquakes dominate the historical seismic record of the Sumatran subduction zone south of the Equator...

The different phases of the earthquake cycle can produce measurable deformation of the Earth's surface. This work is aimed at describing the evolution of that deformation in space and time, as well as the distribution of causal slip on the fault at depth. We have applied GPS and synthetic aperture radar (SAR) interferometry (InSAR) techniques to no...

Paleoseismic, paleogeodetic and GPS data from the Sumatran subduction zone provide an unusual opportunity to understand the physical parameters that control the behavior of a subduction interface. Interseismic strains recorded over the last several decades by coral growth rings and GPS instruments allow us to model subduction zone behavior using a...

The North Chile region between 18S and 23S is one of the most important seismic gaps in the world with no rupture having occurred since 1877 in this area. The two ex- tremities of this gap have experienced major earthquakes in recent years (the Mw=8.1 Antofagasta earthquake in 1995 ; the Mw=8.4 South Peru earthquake in 2001). SAR interferometry and...

Geodetic and paleogeodetic measurements of strain above the Sumatran portion of the Sunda subduction zone reveal a heterogeneous pattern of coupling along the subduction megathrust. Annual banding in coral heads provides vertical rates of deformation spanning the last half of the 20th century, and repeated GPS surveys between 1991 and 2001 and cont...

The recent 2011 Tohoku-oki earthquake occurred in a region where giant megathrust earthquakes were not expected. This earthquake proved the difficulty to assess seismic hazard mainly based on information from historical earthquakes. In this study we propose a methodology to estimate the slip distribution of megathrust earthquakes likely to occur in...