3-D sediment-basement tomography of the Northern Marmara trough by a dense OBS network at the nodes of a grid of controlled source profiles along the North Anatolian fault

A 3-D tomographic inversion of first arrival times of shot profiles recorded by a dense 2-D OBS network provides an unprecedented constraint on the P-wave velocities heterogeneity of the upper-crustal part of the North Marmara Trough (NMT), over a region of 180 km long by 50 km wide. One of the specific aims of this controlled source tomography is to provide a 3-D initial model for the local earthquake tomography (LET). Hence, in an original way, the controlled source inversion has been performed by using a code dedicated to LET. After several tests to check the results trade-off with the inversion parameters, we build up a 3-D a priori velocity model, in which the sea-bottom topography, the acoustic and the crystalline basements and the Moho interfaces have been considered. The reliability of the obtained features has been checked by checkerboard tests and also by their comparison with the deep-penetration multichannel seismic profiles, and with the wide-angle reflection and refraction modelled profiles. This study provides the first 3-D view of the basement topography along the active North Anatolian fault beneath the Marmara Sea, even beneath the deepest part of three sedimentary basins of NMT. Clear basement depressions reaching down 6 km depth below the sea level (bsl) have been found beneath these basins. The North Imralı Basin located on the southern continental shelf is observed with a similar sedimentary thickness as its northern neighbours. Between Central and Çınarcık basins, the Central High rises up to 3 km depth below (bsl). Its crest position is offset by 10 km northwestward relatively to the bathymetric crest. On the contrary, Tekirdağ and Central basins appear linked, forming a 60-km-long basement depression. Beneath the bathymetric relief of Western High low velocities are observed down to 6 km depth (bsl) and no basement high have been found. The obtained 3-D Vp heterogeneity model allows the consideration of the 3-D supracrustal heterogeneity into the future earthquake relocations in this region. The topographic map of the pre-kinematic basement offers the possibility to take into account the locking depth variations in future geohazard estimations by geomechanical modelling in this region

Interaction between contrasting rice genotypes and soil physical conditions induced by hydraulic stresses typical of alternate wetting and drying irrigation of soil

Background and aims: Alternate wetting and drying (AWD) saves water in paddy rice production but could influence soil physical conditions and root growth. This study investigated the interaction between contrasting rice genotypes, soil structure and mechanical impedance influenced by hydraulic stresses typical of AWD. Methods: Contrasting rice genotypes, IR64 and deeper- rooting Black Gora were grown in various soil conditions for 2 weeks. For the AWD treatments the soil was either maintained in a puddled state, equilibrated to −5 kPa (WET), or dried to −50 kPa and then rewetted at thewater potential of −5 kPa (DRY-WET). There was an additional manipulated macropore structure treatment, i.e. the soil was broken into aggregates, packed into cores and equilibrated to −5 kPa (REPACKED). A flooded treatment (puddled soil remained flooded until harvest) was set as a control (FLOODED). Soil bulk density, penetration resistance and X-ray Computed Tomography (CT) derived macropore structure were measured. Total root length, root surface area, root volume, average diameter, and tip number were determined by WinRhizo. Results: AWD induced formation of macropores and slightly increased soil mechanical impedance. The total root length of the AWD and REPACKED treatments were 1.7–2.2 and 3.5–4.2 times greater than that of the FLOODED treatment. There was no significant difference between WET and DRY-WET treatments. The differences between genotypes were minimal. Conclusions: AWD influenced soil physical properties and some root characteristics of rice seedlings, but drying soil initially to −50 kPa versus −5 kPa had no impact. Macropores formed intentionally from repacking caused a large change in root characteristics

Serum levels of pentraxin-3 and other inflammatory biomarkers in migraine: Association with migraine characteristics

PMID = 2624375

Pre-stack depth Migration imaging of the Hellenic Subduction Zone

International audienceIn 365 AD, a major M>8-tsunamignic earthquake occurred along the southwestern segment of the Hellenic subduction zone. Although this is the largest seismic event ever reported in Europe, some fundamental questions remain regarding the deep geometry of the interplate megathrust, as well as other faults within the overriding plate potentially connected to it. The main objective here is to image those deep structures, whose depths range between 15 and 45 km, using leading edge seismic reflection equipment. To this end, a 210-km-long multichannel seismic profile was acquired with the 8 km-long streamer and the 6600 cu.in source of R/V Marcus Langseth. This was realized at the end of 2015, during the SISMED cruise. This survey was made possible through a collective effort gathering labs (Géoazur, LDEO, ISTEP, ENS-Paris, EOST, LDO, Dpt. Geosciences of Pau Univ). A preliminary processing sequence has first been applied using Geovation software of CGG, which yielded a post-stack time migration of collected data, as well as pre-stack time migration obtained with a model derived from velocity analyses. Using Paradigm software, a pre-stack depth migration was subsequently carried out. This step required some tuning in the pre-processing sequence in order to improve multiple removal, noise suppression and to better reveal the true geometry of reflectors in depth. This iteration of pre-processing included, the use of parabolic Radon transform, FK filtering and time variant band pass filtering. An initial velocity model was built using depth-converted RMS velocities obtained from SISMED data for the sedimentary layer, complemented at depth with a smooth version of the tomographic velocities derived from coincident wide-angle data acquired during the 2012-ULYSSE survey. Then, we performed a Kirchhoff Pre-stack depth migration with traveltimes calculated using the Eikonal equation. Velocity model were then tuned through residual velocity analyses to flatten reflections in common reflection point gathers. These new results improve the imaging of deep reflectors and even reveal some new features. We will present this work, a comparison with our previously obtained post-stack time migration, as well as some insights into the new geological structures revealed by the depth imaging

The Eastern North American Margin Community Seismic Experiment: An Amphibious Active- and Passive-Source Dataset

Abstract The eastern North American margin community seismic experiment (ENAM‐CSE) was conceived to target the ENAM Geodynamic Processes at Rifting and Subducting Margins (GeoPRISMS) primary site with a suite of both active‐ and passive‐source seismic data that would shed light on the processes associated with rift initiation and evolution. To fully understand the ENAM, it was necessary to acquire a seismic dataset that was both amphibious, spanning the passive margin from the continental interior onto the oceanic portion of the North American plate, and multiresolution, enabling imaging of the sediments, crust, and mantle lithosphere. The ENAM‐CSE datasets were collected on‐ and offshore of North Carolina and Virginia over a series of cruises and land‐based deployments between April 2014 and June 2015. The passive‐source component of the ENAM‐CSE included 30 broadband ocean‐bottom seismometers (OBSs) and 3 onshore broadband instruments. The broadband stations were deployed contemporaneously with those of the easternmost EarthScope Transportable Array creating a trans‐margin amphibious seismic dataset. The active‐source portion of the ENAM‐CSE included several components: (1) two onshore wide‐angle seismic profiles where explosive shots were recorded on closely spaced geophones; (2) four major offshore wide‐angle seismic profiles acquired with an airgun source and short‐period OBSs (SPOBSs), two of which were extended onland by deployments of short‐period seismometers; (3) marine multichannel seismic (MCS) data acquired along the four lines of SPOBSs and a series of other profiles along and across the margin. During the cruises, magnetic, gravity, and bathymetric data were also collected along all MCS profiles. All of the ENAM‐CSE products were made publicly available shortly after acquisition, ensuring unfettered community access to this unique dataset