Do trench sediments affect great earthquake occurrence in subduction zones?

Seismic energy release is dominated by the underthrusting earthquakes in subduction zones, and this energy release is further concentrated in a few subduction zones. While some subduction zones are characterized by the occurrence of great earthquakes, others are relatively aseismic. This variation in maximum earthquake size between subduction zones is one of the most important features of global seismicity. Previous work has shown that the variation in maximum earthquake size is correlated with the variation in two other subduction zone properties: age of the subducting lithosphere and convergence rate. These two properties do not explain all the variance in maximum earthquake size. I propose that a third subduction zone property, “trench sediments”, explains part of the remaining variance in maximum earthquake size. Subduction zones are divided into two groups: (1) those with excess trench sediments, and (2) those with horst and graben structure at the trench. Thirteen of the 19 largest subduction zone events, including the three largest, occur in zones with excess trench sediments. About half the zones with excess trench sediments are characterized by great earthquake occurrence. Most of the other zones with excess trench sediments but without great earthquakes are predicted to have small earthquakes by the age-rate correlation. Two notable exceptions are the Oregon-Washington and Middle America zones. Overall, the presence of excess trench sediments appears to enhance great earthquake occurrence. One speculative physical mechanism that connects trench sediments and earthquake size is that excess trench sediments are associated with the subduction of a coherent sedimentary layer, which at elevated temperature and pressure, forms a homogeneous and strong contact zone between the plates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43133/1/24_2004_Article_BF00874629.pd

Esquisse photogéologique du domaine méditerranéen. Grands traits structuraux à partie des images du satellites landsat - 1 Photogeological Sketchmap of the Mediterranean Realm. Major Stuctural Features Determined from Landsat-I Satellite Images. Comments

Cette note est destinée à commenter l' « esquisse photogéologique du domaine méditerranéen ; grands traits structuraux à partir des images du satellite Landsat-I » réalisée au cours d'un travail mené en commun par l'Institut Français du Pétrole (IFP) et le Centre National pour l'Exploitation des Océans (CNEXO) avec la collaboration de l'Institut National d'Astronomie et de Géophysique (INAG), document publié par les Éditions Technip. Ces commentaires précisent d'abord le but de cette nouvelle carte qui vise à compléter la « Carte géologique et structurale des bassins tertiaires du domaine méditerranéen » établie précédemment : l'information contenue dans les images du satellite artificiel Landsat-I et son interprétation permettent en effet de préciser les grands traits structuraux du domaine émergé voisin des bassins profonds et des marges de la Méditerranée. Un grand nombre de linéaments peuvent être reconnus ; leur orientation et leur répartition dans les différentes provinces géologiques n'est pas quelconque. Les commentaires eux-mêmes comportent deux parties : - des commentaires techniques qui précisent les caractéristiques des images utilisées, la méthode de travail, le choix de la représentation adoptée lors de la réalisation de la carte ; - des commentaires géologiques qui analysent les difficultés de l'interprétation, la signification des linéaments cartographiés et qui reprennent, région par région, les principales conclusions que l'on peut tirer de cette étude pour la connaissance des marges de la Méditerranée. En conclusion on insiste d'une part sur l'intérêt de cette technique d'observation que constituent les images prises depuis des stations orbitales (télédétection) et d'autre part sur la nécessité, pour interpréter l'information recueillie, de travaux supplémentaires : sur documents géologiques ou géophysiques existants, sur le terrain, enfin à partir des bandes magnétiques enregistrées par le satellite. <br> This article comments on the photogeological sketchmap of the Mediterranean reolm and its major structural features as determined from Landsat I satellite images during a project carried out jointly by Institut François du Pétrole (IFP) and Centre National

Power of 22 microsatellite markers in fluorescent multiplexes for parentage testing in goats (Capra hircus)

Times Cited: 47International audienceTwo multiplex systems, each containing 11 microsatellite loci, were developed for semiautomated parentage testing in goats. Eight of the loci originate from goats, nine from cattle and five from sheep. Eighteen of the loci have been mapped to 16 different autosomes (in goats and cattle). Parentage exclusion probabilities were computed from allele frequencies in similar to 30 unrelated individuals from each of four economically important breeds: Mongolian Native Cashmere, Turkish Angora, Swiss Saanen, and Spanish Murciana-Grenadina. In cases where genotypes are known for one parent and an offspring, the 22 markers will exclude an (erroneously) alleged parent with a probability of > 0.999999 in the cashmere breed, > 0.99999 in Angora and Murciana-Grenadina, and > 0.9999 in Saanen. The multiplexes provide very high power for individual identification as the probability of finding two identical genotypes for the 22 loci is < 1 in 1.10(15) in each of the four breeds. The multiplexes will also be useful for studies of population structure, history, and diversity in goats and also in wild Capra species that represent important resources for genetic improvement of domestic breeds

Geochemistry and trace elements at DSDP Hole 78-543A

The upper part of the basaltic substratum of the Atlantic abyssal plain, approaching subduction beneath the Barbados Ridge and thus presumably beneath the Lesser Antilles island arc, is made of typical LREE-depleted oceanic tholeiites. Mineralogical (microprobe) and geochemical (X-ray fluorescence, neutron activation analyses) data are given for 12 samples from the bottom of Hole 543A, which is 3.5 km seaward of the deformation front of the Barbados Ridge complex. These basalts are overlain by a Quaternary to Maestrichtian-Campanian sedimentary sequence. Most of the basalts are relatively fresh (in spite of the alteration of olivine and development of some celadonite, clays, and chlorite in their groundmass), and their mineralogical and geochemical compositions are similar to those of LREE-depleted recent basalts from the Mid-Atlantic Ridge. The most altered samples occur at the top of the basaltic sequence, and show trends of enrichment in alkali metals typical of altered oceanic tholeiites