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We present a 3-D shear wave velocity model of the Mauleon and Arzacq Basins from the surface down to 10 km depth, inverted from phase velocity maps at periods between 2 and 9 s. These phase velocity maps were obtained by analyzing coherent surface wave fronts extracted from ambient seismic noise recorded by the large-N Maupasacq seismic array with a matched filtering approach. This new model is in good agreement with a local earthquake tomography study performed on the same acquisition dataset. Our passive imaging models reveal the upper crustal architecture of the Mauleon and Arzacq Basins, with new details on the basement and its relationship with the overlying sedimentary cover. Combining these new tomographic images with surface and subsurface geological information allows us to trace major orogenic structures from the surface down to the basement. In the basin, the models image the first-order basin architecture with a kilometric resolution. At depth, high velocity anomalies suggest the presence of dense deep crustal and mantle rocks in the hanging wall of north-vergent Pyrenean Thrusts. These high velocity anomalies spatially coincide with a positive gravity anomaly in the western Mauleon Basin. In addition, our models reveal major changes from the Chainons Bearnais to the western Mauleon Basin across a set of orogen-perpendicular structures, the Saison and the Barlanes transfer zones. These changes reflect the along-strike variation of the orogenic evolution that led to the preservation of the former rifted domain and its underlying mantle in the orogenic wedge of the Western Pyrenees. We discuss the implications of these results for the 3-D architecture of the Mauleon Basin and its underlying basement.

Large continental faults extend for thousands of kilometres to form boundaries between rigid tectonic blocks. These faults are associated with prominent topographic features and can produce large earthquakes. Here we show the first evidence of a major tectonic structure in its initial-stage, the Al-Idrissi Fault System (AIFS), in the Alboran Sea. Combining bathymetric and seismic reflection data, together with seismological analyses of the 2016 Mw 6.4 earthquake offshore Morocco – the largest event ever recorded in the area – we unveil a 3D geometry for the AIFS. We report evidence of left-lateral strike-slip displacement, characterise the fault segmentation and demonstrate that AIFS is the source of the 2016 events. The occurrence of the Mw 6.4 earthquake together with historical and instrumental events supports that the AIFS is currently growing through propagation and linkage of its segments. Thus, the AIFS provides a unique model of the inception and growth of a young plate boundary fault system.

We develop and apply a full waveform inversion method that incorporates seismic data on a wide range of spatio-temporal scales, thereby constraining the details of both crustal and uppermantle structure. This is intended to further our understanding of cr

Geomechanical characterisation of altered volcanic rocks and their role in flank volcanoes stability are evaluated in this study. Physical and mechanical properties and their variation with the degree of alteration are described in detailed. A series of multidisciplinary tests were performed to identify and quantify the progressive degradation of the properties. They are as follow: 1) petrographycal and chemical studies (thin-sections, x-ray diffractions and x-ray fluorescence); 2) effective and total porosity (standard test procedure, mercury intrusion porosimetry, pycnometer tests, two-dimensional and x-ray CT image analysis); 3) Ultrasonic pulse velocity measurements; 4) uniaxial compressive tests (with p-wave measurements, cyclic loading); tensile tests (with strain gauge measurements); and 5) triaxial tests (single-stage and multi-stage). Preliminary numerical modelling was mainly focus on the effect of altered rocks content and gravity effects, even if different perturbations such as pore water pressure (e.g. rainfall, vapour and gas), and regional or local tectonics (e.g. faults, earthquakes and dynamic loading) are presented in volcanoes nature. Collected samples are representative of four different classes of volcanic deposits: i) trachytic lava with abundant crystals; ii) pyroclastic deposits, with lava clasts and pumice elements with different sizes; iii) Green tuff, constructed prevalently by pumice clasts; and iv) ignimbrite deposits characterized by low density. Petrographical and chemical characteristics, in particular weathering indexes reveal large differences not only between lithotypes, but also between samples. These differences are well quantified by physical properties, in particular porosity and shear wave velocity values. Decay of the properties, well represented by regression analysis with significant correlation parameter (R2>85), is observed when average values of the compressive strength, tensile strength and Young’s modulus are compared

We have begun to apply ambient noise surface wave tomography to broad-band seismic data obtained in Europe, North Africa, the Middle East, and Central Asia. The goal is to improve the calibration of surface wave propagation in aseismic area. Ambient noise tomography (ANT) generates surface wave dispersion maps to periods as short as 6 across large areas and, therefore, provides new, high resolution constraints on crustal structures homogeneously over extended regions. Current work concentrates on the application of ANT in Europe where station coverage is highest, which allows improvements in the method to be made rapidly and transported elsewhere later. In earlier work, we applied ambient noise tomography across Europe to one year of data from approximately 125 stations composing the Virtual European Seismic Network (VEBSN) (available from the ORFEUS Data Center) to produce Rayleigh wave group velocity maps from an 8-40 sec period. Current work builds on these results by using longer time series (to improve signal quality and provide measurement uncertainties) and assimilating data from temporary or emerging regional networks in the Mediterranean region to generate Rayleigh wave phase and group speed maps across Europe with better resolution and reliability. The study concentrates on improvements in three focus areas where regional array data are available: (1) the western Mediterranean, particularly the Iberian Peninsula, (2) the central Mediterranean, notably Italy and Switzerland, and (3) the eastern Mediterranean, including Israel, Syria, and Turkey. The western Mediterranean results are based on the Spanish National Network data, which provides much tighter constraints on the crustal structures of the Iberian Peninsula. In the Central Mediterranean, the RETREAT and CAT-SCAN Program for the Array Seismic Studies of the Continental Lithosphere (PASSCAL) experiments yield data that improve resolution in this area considerably., Presented at the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (29th) held in Denver, CO on 25-27 Sep 2007. Published in Proceedings of the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (29th), p226-235, Sep 2007. The original document contains color images.

As an intermediate step to producing a integrated P and S model of the crust and upper mantle beneath most of Eurasia to predict regional station specific travel time correction surfaces, we present maps of isotropic Pn and Sn velocities across Eurasia. These maps are constructed using a groomed version of the ISC/NEIC data that are described, in part, by Engdahl et al. (1998). The locations and origin times of the events are replaced with local ground truth locations whenever possible (e.g., Sultanov et al., 1999). We use the tomographic method of Barmin et al. (2000) to estimate Pn and Sn maps on a 1.5 x 1.5 degree grid, augmented to include station and event static corrections and an epicentral distance or range correction. The starting model is CRUST5.1 (Mooney et al., 1998). We call the Pn and Sn maps together with these corrections the CU Pn=Sn model. Data are used in the inversion if the residual relative to the prediction from the spherical model AK135 (Kennett et al., 1995) is less than 7.5 s for P and 15 s for S, if the event depth is within the crust or less than 50 km deep, if the azimuthal gap to all reporting stations for the event is less than 180 degrees, and if the nominal error ellipse is less than 1000 km2 in area. We define the phases Pn and Sn as arriving between epicentral distances of 3 and 15 degrees. The resulting data set consists of about 1,600,000 Pn and 400,000 Sn travel times inhomogeneously distributed across Eurasia., Proceedings of the 22nd Annual DoD/DOE Seismic Research Symposium: Planning for Verification of and Compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) held in New Orleans, Louisiana on September 13-15, 2000. U.S. Government or Federal Rights. The original document contains color images.