Institute Of Physique Du Globe

Strasbourg, France

Institute Of Physique Du Globe

Strasbourg, France
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Klein E.,Institute Of Physique Du Globe | Duputel Z.,Institute Of Physique Du Globe | Masson F.,Institute Of Physique Du Globe | Yavasoglu H.,Geomatics Engineering | Agram P.,Jet Propulsion Laboratory
Geophysical Research Letters | Year: 2017

Ever since the Mw7.4 Izmit earthquake in 1999, evaluation of seismic hazard associated with the last unbroken segments of the North Anatolian fault is capital. A strong controversy remains over whether Marmara fault segments are locked or are releasing strain aseismically. Using a Bayesian approach, we propose a preliminary probabilistic interseismic model constrained by published GPS data sets. The posterior mean model show that Ganos and Cinarcik segments are locked while creep is detected in the central portion of Marmara fault. Our analysis, however, reveals that creeping segments are associated with large model uncertainties, which mainly results from the sparsity of current geodetic observations. We then discuss how the GPS network can be improved to attain more reliable assessment of interseismic slip rates. With this purpose, we implement a network optimization procedure to identify the most favorable distribution of stations measuring strain accumulation in the Marmara Sea. ©2017. American Geophysical Union. All Rights Reserved.

Maouche S.,CRAAG | Maouche S.,University of Science and Technology Houari Boumediene | Meghraoui M.,Institute Of Physique Du Globe | Morhange C.,CEREGE | And 3 more authors.
Tectonophysics | Year: 2011

Major uplifts of late Quaternary marine terraces are visible along the coastline of the Tell Atlas of Algeria located along the Africa-Eurasia convergent plate boundary. The active tectonics of this region is associated with large shallow earthquakes (M ≥ 6.5), numerous thrust mechanisms and surface fault-related fold. We conducted a detailed levelling survey of late Pleistocene and Holocene marine notches in the Algiers region that experienced 0.50. m coastal uplift during the 2003 Zemmouri earthquake (Mw 6.8). East of Algiers, Holocene marine indicators show three pre-2003 main notch levels formed in the last 21.9. ka. West of Algiers on the Sahel anticline, the levelling of uplifted marine terraces shows a distinct staircase morphology with successive notches that document the incremental folding uplift during the late Pleistocene and Holocene. The timing of successive uplifts related to past coseismic movements along this coastal region indicates episodic activity during the late Holocene. Modelling of surface deformation in the Zemmouri earthquake area implies a 50-km-long, 20-km-wide, NE-SW trending, SE dipping fault rupture and an average 1.3 m coseismic slip at depth. Further west, the 70-km-long Sahel fold is subdivided in 3 sub-segments and shows ~0.84-1.2 mm/yr uplift rate in the last 120-140. ka. The homogeneous Holocene uplift of marine terraces and the anticline dimensions imply the possible occurrence of large earthquakes with Mw ≥ 7 in the past. The surface deformation and related successive uplifts are modelled to infer the size and characteristics of probable future earthquakes and their seismic hazard implications for the Algiers region. © 2011 Elsevier B.V.

Meghraoui M.,Institute Of Physique Du Globe
Journal of Seismology | Year: 2010

New historical data from primary sources, allow us to revisit the Djidjelli earthquakes of 21 and 22 August 1856 (I0 VIII, IX respectively). These two large seismic events are among the most significant events that have affected the North African coast. They have caused extensive damage and generated a tsunami that propagated at several harbours of the western Mediterranean Sea. The effects of each earthquake are analysed from all documentary source materials, emphasising the confrontation of observations and data for an accurate reconstruction of the macroseismic field of both events. The method used provides a more precise way to determine the characteristics of the Djidjelli earthquakes. © 2010 Springer Science+Business Media B.V.

Karabacak V.,Eskiehir Osmangazi University | Altunel E.,Eskiehir Osmangazi University | Meghraoui M.,Institute Of Physique Du Globe | Akyuz H.S.,Technical University of Istanbul
Tectonophysics | Year: 2010

The left-lateral strike-slip Dead Sea Fault Zone (DSFZ) extends from the Red Sea in the south to the East Anatolian Fault Zone (EAFZ) in the north. This study examines the northern part of the DSFZ around Amik Basin and presents surface and subsurface geological evidence for the Quaternary activity and initiation age of the northernmost DSFZ. The DSFZ extends N-S in the south of the Amik Basin where clear geological and morphological evidence exists for faulting. Geological observations around Amik Basin, analyses of borehole data and electrical resistivity profiles within the Amik Basin indicate that the activity of the northern DSFZ started after Pliocene in the Amik Basin. Subsurface data in the basin suggest that the DSFZ offsets a pre-Quaternary basin sinistrally by about 7.9 km. The offset pre-Quaternary basin suggests at least 4.94 ± 0.13 mm/year slip rate for the northern part of the DSFZ. The Karasu Fault Zone (KFZ) extends in an en-echelon pattern along the western margin of the Karasu Valley and it transfers the significant amount of slip from DSFZ to the EAFZ. © 2009 Elsevier B.V. All rights reserved.

Schmid A.,CNRS Institute of Earth Sciences | Grasso J.R.,CNRS Institute of Earth Sciences | Clarke D.,CNRS Paris Institute of Global Physics | Ferrazzini V.,Institute Of Physique Du Globe | And 3 more authors.
Journal of Geophysical Research: Solid Earth | Year: 2012

Volcanic eruptions impact on societal risk, and volcanic hazard assessment is a necessary ingredient for decision-makers. However, the prediction of volcanic eruptions remains challenging due to the complexity and the non-linearity of volcanic processes. Identified forerunners such as increasing seismicity or deformation of the volcanic edifice prior to eruption are not deterministic. In this study, we use statistical methods to identify and discriminate precursory patterns to eruptions, on three sets of observables of Piton de la Fournaise volcano. We analyzed the short-term (i.e. the inter-eruptive period) time series of the seismicity rate, the deformation and the seismic velocity changes (deduced from seismic noise cross-correlations) over the period 1999-2006, with two main goals. First, we characterize the average pre-eruptive time patterns before 22 eruptions using superposed epoch analysis for the three observables. Using daily rate values, we resolve (1) a velocity change within 100-50days from the eruptions onsets, then a plateau value up to eruption onset; (2) a power law increase in seismicity rate from noise level 15-10days before eruption time; (3) an increase of displacement rate on the eruption day. These results support a three step mechanism leading to magma transfers toward the surface. Second we use pattern recognition techniques and the formalization of error diagrams to quantify the predictive power of each forerunner either as used independently or as combined to each other. We show that when seismicity rate alone performs the best prediction in the failure to predict versus alarm duration space, the combination of the displacement and seismicity data reduces the false alarm rate. We further propose a tool which explores the prediction results in order to optimize prediction strategy for decision-makers, as a function of the risk value. © 2012 American Geophysical Union. All Rights Reserved.

Sbeinati M.R.,Syrian Atomic Energy Commission | Meghraoui M.,Institute Of Physique Du Globe | Suleyman G.,Directorate General of Antiquities and Museums | Gomez F.,University of Missouri | And 4 more authors.
Special Paper of the Geological Society of America | Year: 2010

We studied the faulted Al Harif Roman aqueduct, located on the north-trending, ∼90-km-long Missyaf segment of the Dead Sea fault, using four archaeological excavations, three paleoseismic trenches, and the analysis of six tufa cores. Damage to the aqueduct wall exhibits successive left-lateral fault offsets that amount to 13.6 ± 0.2 m since the aqueduct construction, which is dated younger than 65 B.C. Radiocarbon dating of sedimentary units in trenches, building cement of the aqueduct wall, and tufa cores constrain the late Holocene aqueduct history. The building stone types, related cement dating, and tufa deposits of the aqueduct indicate two reconstructionrepair episodes in A.D. 340 ± 20 and A.D. 720 ± 20. The combined analysis of trench results; successive building and repair of aqueduct wall; and tufa onsets, growths, and interruptions suggests the occurrence of four faulting events in the last ∼3500 yr, with a cluster of three events in A.D. 160-510, A.D. 625-690, and A.D. 1010-1210, the latter being correlated with the 29 June 1170 large earthquake. Our study provides the timing of late Holocene earthquakes and infers a lower and upper bound of 4.9-6.3 mm/yr slip rate along the Missyaf segment of the Dead Sea fault in Syria. The inferred successive faulting events, fault segment length, and related amount of coseismic slip yield Mw = 7.3-7.5 for individual earthquakes. The identification of the temporal cluster of large seismic events suggests periods of seismic quiescence reaching 1700 yr along the Missyaf fault segment. © 2010 The Geological Society of America. All rights reserved.

Demeter F.,CNRS Eco-anthropology and Ethnobiology | Patole-Edoumba E.,Museum dHistoire Naturelle de La Rochelle | Duringer P.,University of Strasbourg | Bacon A.,French National Center for Scientific Research | And 5 more authors.
Geoarchaeology | Year: 2010

In 1963, E. Saurin and J.-P. Carbonnel discovered the Sre Sbov site on an alluvial terrace of the Mekong River in central Cambodia. Saurin described a lithic typology dating to the Lower/Middle Pleistocene from this site. Although the original lithic assemblage has been lost, this typology has been used continuously as a reference by Southeast Asian prehistorians. In 2007, a Khmer-French team conducted excavations at Sre Sbov that yielded numerous pebbles and cobbles showing apparently convincing handmade removals, as Saurin had previously described. However, an in-depth study of this assemblage, combined with a geological survey of the area, led to the conclusion that the stones were, in fact, of natural origin, and that for this reason their typology should be disregarded. Using satellite imagery and geological surveys, we explain how such a misinterpretation may have occurred and define a "buffer zone," corresponding to the maximal extent of the proto-Mekong River, where fluvially reworked pebbles and cobbles resembling artifacts may be recovered. © 2009 Wiley Periodicals, Inc.

Ferry M.,University of Évora | Meghraoui M.,Institute Of Physique Du Globe | Karaki N.A.,University of Jordan | Al-Taj M.,Hashemite University | Khalil L.,University of Jordan
Bulletin of the Seismological Society of America | Year: 2011

The continuous record of large surface-rupturing earthquakes along the Dead Sea fault brings unprecedented insights for paleoseismic and archaeoseismic research. In most recent studies, paleoseismic trenching documents the late Holocene faulting activity, while tectonic geomorphology addresses the long-term behavior (>10 ka), with a tendency to smooth the effect of individual earthquake rupture events (Mw >7). Here, we combine historical, archaeological, and paleoseismic investigations to build a consolidated catalog of destructive surface-rupturing earthquakes for the last 14 ka along the left-lateral Jordan Valley fault segment. The 120- km-long fault segment limited to the north and the south by major pull-apart basins (the Hula and the Dead Sea, respectively) is mapped in detail and shows five subsegments with narrow stepovers (width < 3 km). We conducted quantitative geomorphology along the fault, measured more than 20 offset drainages, excavated four trenches at two sites, and investigated archaeological sites with seismic damage in the Jordan Valley. Our results in paleoseismic trenching with 28 radiocarbon datings and the archaeoseismology at Tell Saydiyeh, supplemented with a rich historical seismic record, document 12 surface-rupturing events along the fault segment with a mean interval of ~1160 yr and an average 5 mm=yr slip rate for the last 25 ka. The most complete part of the catalog indicates recurrence intervals that vary from 280 yr to 1500 yr, with a median value of 790 yr, and suggests an episodic behavior for the Jordan Valley fault. Our study allows a better constraint of the seismic cycle and related short-term variations (late Holocene) versus long-term behavior (Holocene and late Pleistocene) of a major continental transform fault.

De Michele M.,Bureau de Recherches Géologiques et Minières | Raucoules D.,Bureau de Recherches Géologiques et Minières | Lasserre C.,Joseph Fourier University | Pathier E.,Joseph Fourier University | And 4 more authors.
Earth, Planets and Space | Year: 2010

L-band spaceborne Synthetic Aperture Radar (SAR) amplitude images are used to map the Sichuan earthquake rupture (China, Aw 7.9, 12 May 2008) and to identify the faults activated by the earthquake. A sub-pixel correlation method is used to retrieve the coseismic displacement field projected into the line of sight of the satellite and the horizontal along-track direction, and to map the surface rupture. The earthquake broke ~270 km of the Beichuan fault and ~70 km of the Guanxian fault, with a complex thrust-dextral slip mechanism. Along the southwestern part of the rupture, slip seems to be partitioned into a dextral-dominant component on the Beichuan fault and a thrust-dominant component on the Guanxian fault. Dextral slip may also be dominant at the northeastern tip of the Beichuan ruptured fault. Coseismic surface displacements reach on average 3 to 4 m in both measured directions. The SAR rupture mapping has proven complementary to field studies extending the zone of co-seismic displacements and identifying other possible co-seismic rupture strands. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).

Salomon E.,University of Munster | Salomon E.,Johannes Gutenberg University Mainz | Schmidt S.,University of Munster | Schmidt S.,Institute Of Physique Du Globe | And 3 more authors.
Bulletin of the Seismological Society of America | Year: 2013

In 1861, one of the most destructive earthquakes in the history of Argentina destroyed the city of Mendoza (currently 1 million inhabitants). The magnitudeMS ~7.0 earthquake is inferred to have occurred on the 31-km-long La Cal thrust fault, which extends from Mendoza to the north, where it offsets an alluvial fan and small inset terraces along a well-preserved fault scarp. A trench excavated on a terrace that is vertically offset by ~2.5 m exposes two main stratigraphic units separated by an erosional unconformity. The coarse-grained upper unit is deformed by three eastvergent folds (F1-F3). Retrodeformation of these folds yields total displacements of ~2.0 m,~2.4 m, and~0.5 mon the underlying fault splays, respectively. The displacement of ~2.0 m recorded by fold F1 is interpreted as the result of the fault rupture that caused the 1861 earthquake. F2 and F3 were presumably generated during the penultimate event with an inferred magnitude of Mw ~7.0, although formation during two distinct ruptures cannot be excluded. Finite-element modeling shows that coseismic folding above the tip of a blind thrust fault is a physically plausible mechanism to generate these folds.Apublished luminescence age of 770 ± 76 years, which is interpreted to date the formation of the deformed terrace, indicates that the two (or possibly three) scarp-forming events occurred during the last ~800 years. The fine-grained sediments below the erosional unconformity-that contain evidence for at least one older earthquake- are dated at ~12 kyr. Our results indicate that elastic strain energy, which is accumulating at the front of the Precordillera today as shown by Global Positioning System (GPS) data, was repeatedly released during earthquakes on the La Cal fault in the past. Hence, the La Cal thrust fault poses a serious threat to the city of Mendoza.

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