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SUMMARY Although the Dead Sea Transform (DST) fault system has been extensively studied in the past, little has been known about the present-day kinematics of its southernmost portion that is offshore in the Gulf of Aqaba. Here, we present a new GPS velocity field based on three surveys conducted between 2015 and 2019 at 30 campaign sites, complemented by 11 permanent stations operating near the gulf coast. Interseismic models of strain accumulation indicate a slip rate of $4.9^{+0.9}_{-0.6}~\mathrm{ mm}\,\mathrm{ yr}^{-1}$ and a locking depth of $6.8^{+3.5}_{-3.1}~\mathrm{ km}$ in the gulf’s northern region. Our results further indicate an apparent reduction of the locking depth from the inland portion of the DST towards its southern junction with the Red Sea rift. Our modelling results reveal a small systematic left-lateral residual motion that we postulate is caused by, at least in part, late post-seismic transient motion from the 1995 MW 7.2 Nuweiba earthquake. Estimates of the moment accumulation rate on the main faults in the gulf, other than the one that ruptured in 1995, suggest that they might be near the end of their current interseismic period, implying elevated seismic hazard in the gulf area.

WEGENER is originally the acronym for Working Group of European Geoscientists for the Establishment of Networks for Earth-science Research. It was founded in March 1981 in response to an appeal delivered at the Journées Luxembourgeoises de Geodynamique in December 1980 to respond with a coordinated European proposal to a NASA Announcement of Opportunity inviting participation in the Crustal Dynamics and Earthquake Research Program. WEGENER, during the past 32 years, has always kept a close contact with the Agencies and Institutions responsible for the development and maintenance of the global space geodetic networks with the aim to make them aware of the scientific needs and outcomes of the project which might have an influence on the general science policy trends. WEGENER was serving as Inter-commission Project 3.2, between Commission 1 and Commission 3, of the International Association of Geodesy (IAG) until 2012. Since then, WEGENER project has became the Sub-commission 3.5 of IAG commission 3, namely Tectonics and Earthquake Geodesy. In this study, we briefly review the accomplishments of WEGENER as originally conceived and outline and justify the new focus of the WEGENER consortium. The remarkable and rapid evolution of the present state of global geodetic monitoring in regard to the precision of positioning capabilities (and hence deformation) and global coverage, the development of InSAR for monitoring strain with unprecedented spatial resolution, and continuing and planned data from highly precise satellite gravity and altimetry missions, encourage us to shift principal attention from mainly monitoring capabilities by a combination of space and terrestrial geodetic techniques to applying existing observational methodologies to the critical geophysical phenomena that threaten our planet and society. Our new focus includes developing an improved physical basis to mitigate earthquake, tsunami, and volcanic risks, and the effects of natural and anthropogenic climate change (sea level, ice degradation). In addition, expanded applications of space geodesy to atmospheric studies will remain a major focus with emphasis on ionospheric and tropospheric monitoring to support forecasting extreme events. Towards these ends, we will encourage and foster interdisciplinary, integrated initiatives to develop a range of case studies for these critical problems. Geological studies are needed to extend geodetic deformation studies to geologic time scales, and new modeling approaches will facilitate full exploitation of expanding geodetic databases. In light of this new focus, the WEGENER acronym now represents, “World Earthquake GEodesy Network for Environmental Hazard Research”.

International audience; The North Anatolian Fault Zone (NAFZ) is the major transform system that accommodates thewestward movement of the relatively rigid Anatolian block with respect to Eurasia. Mitigating the hazard associated with devastating earthquakes requires understanding how the NAFZ accumulates and releases the potential energy of elastic deformation both in space and in time. In this study, we focus on the central bend of the NAFZ where the strike of the North Anatolian Fault (NAF) changes from N75◦to N105◦within less than 100 km, and where a secondary fault system veers southwards within the interior of Anatolia. We present interseismic velocity fields obtained from a Persistent-Scatterers (PS) Interferometric radar analysis of ERS and Envisat radar archives. Despite the high vegetation cover, the spatial density of measurementsis high (∼10 PS/km2 in average). Interseismic velocities presented below indicate a velocitychange of∼6–8 mm/yr along the satellite line-of-sight (LOS) mainly centred on the NAF surface trace, and are in good agreement with the GPS velocity field published previously. The observed deformation is accommodated within a zone of ∼20 to 30 km width, in this area where no surface creep has been reported, contrary to the Ismetpasa segment located ∼30 km to the west of this study zone. Although less conspicuous, ∼2–3 mm/yr (∼1 mm/yra long the LOS) of the total deformation seems to be localized along the Lacin Fault. Theoverall agreement with horizontal GPS measurements suggests that the vertical component of the ground deformation is minor. This is confirmed, over the western part of our study zone, by the 3-D estimation of the ground deformation from the combination of the GPS-and the PS-mean velocity fields. However, a specific pattern of the PS velocity fields suggests that an area, enclosed between two faults with roughly south–north orientation, experiences uplift. The PS analyses of radar time-series both prior and posterior to the Izmit and Dûzce earthquakes indicate that these events did not induce detectable velocity changes in this central bend. The only temporal changes we identify are due to a moderate local earthquake (Mw5.7,1996 August 14) whose precise location and coseismic deformation are determined here. Finally, we propose a model of slip-rate distribution at depth along the NAF from the joint inversion of the GPS and PS mean velocity fields. This model suggests a long-term slip-rate of ∼20 mm/yr for a rather uniform locking depth in the range of 15–20 km. However, thelocking depth increases to ∼25–30 km in the section comprised between longitudes E34◦20’and E34◦50’. This lateral evolution is in general agreement with the earthquake distributionat depth from three different catalogues.

International audience; Understanding the behavior of active faults in response to tectonic stresses is a critical issue in earthquake physics and seismic hazard assessments (Carpenter et al., 2011). While most active faults are unstable and move abruptly, releasing in seconds to a few minutes the strain accumulated around them for decades to centuries, some faults slip continuously, storing little or no strain and are therefore considered to be unlikely to produce signifi cant earthquakes as long as this behavior persists (Bürgmann et al., 2000). Although aseismic fault creep was fi rst reported over half a century ago along some major plate boundary faults, including the San Andreas fault in California (United States) and the North Anatolian fault in Turkey, the origin and physical processes of fault creep remain subjects of debate (Schleicher et al., 2010). Two primary, complementary, and competing mechanisms have been proposed to explain the mechanics of aseismic fault creep: (1) the presence of weak mineral phases such as clay and phyllosilicates in the bulk composition of fault zones (Carpenter et al., 2011) or the formation of highly localized, phyllosilicate-rich interconnected networks of shear planes or foliations (Collettini et al., 2009) via chemical and mechanical processes, and/ or (2) trapped fl uid overpressures within fault zones (Byerlee, 1990). Although recent observations (Lockner et al., 2011) support the idea that aseismic creep is controlled by the presence of weak rocks in the fault zone rather than by high fl uid pressures, analysis of rock samples from active (Holdsworth et al., 2011) and exhumed (Warr and Cox, 2001) fault zones suggests that transient fl uid overpressures do occur in many fault zones and are most likely generated during coseismic faulting due to shear heating, low per-meability, high water content, and low strength of clay-rich shear zones. Whether due to mineralogy and/or fl uid pressure affects, how or when stable aseismic surface creep initiates on active faults remains uncertain. The fact that creeping segments of the North Anatolian fault at Ismetpasa and the San Andreas fault in the San Francisco Bay area also rupture coseismically suggests to us that fault creep may be initiated as postseismic after-slip (Çakir et al., 2005; Schmidt et al., 2005), a mechanism that could not be confi rmed previously due to the lack of pre-and post-earthquake observations on these fault sections. In this study we use space geodetic data and recent fi eld observations along the A.D. 1999 Izmit earthquake rupture (Fig. 1) to demonstrate continuing afterslip that appears to grade into steady-state creep on a >60-km-long segment of the Izmit coseismic fault, supporting seismic slip as one of the possible mechanisms for initiating steady-state creep on mature strike-slip faults. THE 1999 IZMIT EARTHQUAKE The M w 7.4 Izmit earthquake on 17 August 1999 occurred on the North Anatolian fault

International audience; We use velocities from 65 continuous stations and 31 survey-mode GPS sites as well as kinematic modeling to investigate present day deformation along the Africa-Iberia plate boundary zone in the western Mediterranean region. The GPS velocity field shows southwestward motion of the central part of the Rif Mountains in northern Morocco with respect to Africa varying between 3.5 and 4.0 mm/yr, consistent with prior published results. Stations in the southwestern part of the Betic Mountains of southern Spain move west-southwest with respect to Eurasia (similar to 2-3 mm/yr). The western component of Betics motion is consistent with partial transfer of Nubia-Eurasia plate motion into the southern Betics. The southward component of Betics motion with respect to Iberia is kinematically consistent with south to southwest motion of the Rif Mountains with respect to Africa. We use block modeling, constrained by mapped surface faults and seismicity to estimate the geometry and rates of strain accumulation on plate boundary structures. Our preferred plate boundary geometry includes one block between Iberia and Africa including the SW Betics, Alboran Sea, and central Rif. This geometry provides a good fit to the observed motions, suggesting a wide transpressive boundary in the westernmost Mediterranean, with deformation mainly accommodated by the Gloria-Azores fault system to the West and the Rif-Tell lineament to the East. Block boundaries encompass aspects of earlier interpretations suggesting three main deformation styles: (i) extension along the NE-SW trending Trans-Alboran shear zone, (ii) dextral strike-slip in the Betics corresponding to a well defined E-W seismic lineament, and (iii) right lateral strike-slip motion extending West to the Azores and right-lateral motion with compression extending East along the Algerian Tell. We interpret differential motion in the Rif-Alboran-Betic system to be driven both by surface processes related the Africa-Eurasia oblique convergence and sub-crustal dynamic processes associated with the long history of subduction of the Neotethys ocean lithosphere. The dextral slip identified in the Betic Mountains in Southern Spain may be related to the offshore fault that produced the Great 1755 Lisbon Earthquake, and as such may represent a significant seismic hazard for the West Mediterranean region.

International audience; We present GPS observations in Morocco and adjacent areas of Spain from 15 continuous (CGPS) and 31 survey-mode (SGPS) sites extending from the stable part of the Nubian plate to central Spain. We determine a robust velocity field for the W Mediterranean that we use to constrain models for the Iberia-Nubia plate boundary. South of the High Atlas Mountain system, GPS motions are consistent with Nubia plate motions from prior geodetic studies. We constrain shortening in the Atlas system to

Approximately 4 yr of campaign and continuous Global Positioning System (GPS) measurements across the Dead Sea fault system (DSFS) in Lebanon provide direct measurements of interseismic strain accumulation along a 200-km-long restraining bend in this continental transform fault. Late Cenozoic transpression within this restraining bend has maintained more than 3000 m of topography in the Mount Lebanon and Anti-Lebanon ranges. The GPS velocity field indicates 4-5 mm yr(-1) of relative plate motion is transferred through the restraining bend to the northern continuation of the DSFS in northwestern Syria. Near-field GPS velocities are generally parallel to the major, left-lateral strike-slip faults, suggesting that much of the expected convergence across the restraining bend is likely accommodated by different structures beyond the aperture of the GPS network (e.g. offshore Lebanon and, possibly, the Palmyride fold belt in SW Syria). Hence, these geodetic results suggest a partitioning of crustal deformation involving strike-slip displacements in the interior of the restraining bend, and crustal shortening in the outer part of the restraining bend. Within the uncertainties, the GPS-based rates of fault slip compare well with Holocene-averaged estimates of slip along the two principal strike-slip faults: the Yammouneh and Serghaya faults. Of these two faults, more slip occurs on the Yammouneh fault, which constitutes the primary plate boundary structure between the Arabia and Sinai plates. Hence, the Yammouneh fault is the structural linkage that transfers slip to the northern part of the transform in northwestern Syria. From the perspective of the regional earthquake hazard, the Yammouneh fault is presently locked and accumulating interseismic strain.