Seismic structure of the volcanic apron north of Gran Canaria

High-resolution reflection seismic profiles through the volcanic apron north of Gran Canaria collected during Meteor Cruise 24 were interpreted in the light of results from Leg 157 (Sites 953 and 954). The shape of the submarine island flanks of Gran Canaria and the two adjacent islands of Fuerteventura to the east and Tenerife to the west were reconstructed by interpretating seismic profiles that penetrated the sediments covering the deeper portions of the volcanic pedestals. The ~4750-m-deep flank of Fuerteventura is the oldest submarine island flank, influencing the subsequent shield-building of Gran Canaria to the east, whose 16- to 15-Ma shield is ponded against Fuerteventura, forming a topographic barrier between the islands. The associated reduction of the current cross section has caused strong bottom currents, indicated by erosional features and contourites. To the north, the flank of Gran Canaria extends 60 km seaward to a depth of ~4500 m. The shield of the Anaga massif on northeast Tenerife onlaps the flank of Gran Canaria to the east. Seismic correlation of the feathered edge of the Anaga shield (~50 km off Tenerife at a depth of 4000 m) to the bio- and magnetostratigraphy at Site 953 results in an age of ~6 Ma. The surrounding sedimentary basin is characterized by chaotic and discontinuous reflection patterns of the slope facies, turning into well-stratified basin facies ~30–40 km off the coast. The westward decrease of reflectivity in the northern apron is interpreted to be caused by the submarine ridge off Galdar at the western limit of the north coast of Gran Canaria, through which mass flows from Gran Canaria entering the sea in the north were diverted to the northeastern part of the apron. The volcanic activity correlates with the sedimentation rates in the apron. The lowest rate corresponds to the volcanic hiatus on Gran Canaria (9–5 Ma) with 3–4 cm/k.y., and the highest rate (up to 12 cm/k.y.) was found during the voluminous Miocene volcanism on the island. A number of large mass-wasting events could be identified, interbedded with the pelagic background sedimentation. The basaltic breccia drilled at Site 954 (lithologic Unit IV) is interpreted to represent the deposits associated with a slope failure at the northern flank of Gran Canaria at 12 Ma. The seismic mapping reveals >60 km3 of debris advanced at least 70 km into the apron. The volume fits well with the dimensions of an amphitheater at the northern flank of Gran Canaria. The Quaternary volcanism on La Isleta at northeast Gran Canaria extends further seaward, where the seismic data show young lava flows. Other submarine volcanism occurred in the channel between Gran Canaria and Fuerteventura

Comparison of seismic reflection data to a synthetic seismogram in a volcanic apron at Site 953

The volcanic apron of Gran Canaria at Site 953 is characterized by numerous, closely spaced reflectors, allowing a highresolution stratigraphic correlation. The calibration of the presite survey seismic data (during the Meteor Cruise 24) with regard to the lithology and stratigraphy found at the drill site was achieved by computing a synthetic seismogram serving as the link between seismic and borehole data. Because logging data were available for only 53% of the hole, velocity and density measurements taken from the recovered cores were used in the missing intervals to obtain a complete synthetic seismogram. Most reflectors in the upper ~900 m of the sequence (lithologic Units I–V) turned out to be thin volcaniclastic layers intercalated to the nonvolcanic background sediments. Their thicknesses are generally <2 m, and the reflections from their tops and bases overlap, forming a single reflection. The limit of the seismic detection of such interbeds is on the order of several decimeters and thus requires special care for the processing of the velocity and density data to avoid destruction of the signal from these thin layers

A review of the NE Atlantic conjugate margins based on seismic refraction data

The NE Atlantic region evolved through several rift episodes, leading to break-up in the Eocene that was associated with voluminous magmatism along the conjugate margins of East Greenland and NW Europe. Existing seismic refraction data provide good constraints on the overall tectonic development of the margins, despite data gaps at the NE Greenland shear margin and the southern Jan Mayen microcontinent. The maximum thickness of the initial oceanic crust is 40 km at the Greenland–Iceland–Faroe Ridge, but decreases with increasing distance to the Iceland plume. High-velocity lower crust interpreted as magmatic underplating or sill intrusions is observed along most margins but disappears north of the East Greenland Ridge and the Lofoten margin, with the exception of the Vestbakken Volcanic Province at the SW Barents Sea margin. South of the narrow Lofoten margin, the European side is characterized by wide margins. The opposite trend is seen in Greenland, with a wide margin in the NE and narrow margins elsewhere. The thin crust beneath the basins is generally underlain by rocks with velocities of >7 km s−1 interpreted as serpentinized mantle in the Porcupine and southern Rockall basins; while off Norway, alternative interpretations such as eclogite bodies and underplating are also discussed

Moho and basement depth in the NE Atlantic Ocean based on seismic refraction data and receiver functions

Seismic refraction data and results from receiver functions were used to compile the depth to the basement and Moho in the NE Atlantic Ocean. For interpolation between the unevenly spaced data points, the kriging technique was used. Free-air gravity data were used as constraints in the kriging process for the basement. That way, structures with little or no seismic coverage are still presented on the basement map, in particular the basins off East Greenland. The rift basins off NW Europe are mapped as a continuous zone with basement depths of between 5 and 15 km. Maximum basement depths off NE Greenland are 8 km, but these are probably underestimated. Plate reconstructions for Chron C24 (c. 54 Ma) suggest that the poorly known Ammassalik Basin off SE Greenland may correlate with the northern termination of the Hatton Basin at the conjugate margin. The most prominent feature on the Moho map is the Greenland–Iceland–Faroe Ridge, with Moho depths >28 km. Crustal thickness is compiled from the Moho and basement depths. The oceanic crust displays an increased thickness close to the volcanic margins affected by the Iceland plume

Constraints on s→dγs\to d \gamma from Radiative Hyperon and Kaon Decays

The quark-level process $b \to s \gamma$ has been used extensively to place constraints on new interactions. These same interactions can be further constrained from the enhancement they induce in the quark-level $s \to d \gamma$ transition, to the extent that the short distance contributions can be separated from the long distance contributions. We parameterize what is known about the long distance amplitudes and subtract it from the data in radiative hyperon and kaon decays to constrain new interactions.Comment: Latex 11 page

CLPLOSS : analyzing green-end veneer recovery and loss

This paper is a detailed description of a method for calculating and analyzing losses and recoveries in a veneer peeling/clipping operation. The method involves filming veneer sheets as they exit the clipper, digitizing this film, and using the digitized information in a computer analysis

Key international comparison of AC-DC current transfer standards CCEM-K12

The circulation of the travelling standards in the CIPM key comparison CCEM-K12 of AC–DC current transfer difference began in March 2005 and was completed in April 2007. The travelling standards were lost on their way from the last participant to the pilot laboratory. Since, prior to their disappearance, the travelling standards exhibited exceptional stability, the CCEM Working Group on Low-Frequency Quantities decided in June 2008 to accept the results of the comparison as valid without the final measurement by the pilot laboratory. The AC–DC transfer differences of the travelling standards have been measured at 10 mA and 5 A, and at the frequencies 10 Hz, 55 Hz, 1 kHz, 10 kHz, 20 kHz, 50 kHz and 100 kHz. The key comparison reference values were calculated as the weighted means of the results of the National Metrology Institutes (NMIs) with independent realizations of primary standards and low reported uncertainties. The degrees of equivalence relative to the key comparison reference values, as well as between pairs of NMIs, have been determined for the measurement points and show very good agreement. All but three of the calculated degrees of equivalence relative to the key comparison reference values are within the limits of the expanded uncertainties.Fil: Budovsky, Ilya. National Measurement Institute (NMIA); AustraliaFil: Lipe, Thomas E. National Institute of Standards and Technology (NIST); Estados UnidosFil: Filipski, Peter S. National Research Council Canada. Institute for National Measurement Standards (NRC-INMS); CanadáFil: Laiz, Hector. Instituto Nacional de Tecnología Industrial (INTI); ArgentinaFil: Funck, Torsten. Physikalisch-Technische Bundesanstalt (PTB); AlemaniaFil: Garcocz, Martin. Bundesamt für Eich- und Vermessungswesen (BEV); AustriaFil: Espedalen, Jeanne H. Justervesenet (JV); NoruegaFil: Rydler, Karl-Erik. SP Technical Research Institute of Sweden; SueciaFil: Chua. Sze Wey. National Metrology Centre (NMC); SingapurFil: Borghi, Giovanna. Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMetro); BrasilFil: Wheaton, Adrian. National Physical Laboratory (NPL); Reino UnidoFil: Telitchenko, G. P. D. I. Mendeleev Institute for Metrology (VNIIM); Rusi

The standard model at low energies

The hadronic sector of the standard model at low energies is described by a non--decoupling effective field theory, chiral perturbation theory. An introduction is given to the construction of effective chiral Lagrangians, both in the purely mesonic sector and with inclusion of baryons. The connection between the relativistic formulation and the heavy baryon approach to chiral perturbation theory with baryons is reviewed.Comment: Lectures given at the 6th Indian-Summer School on Intermediate Energy Physics, Prague, Aug. 1993, Latex, 26 pages (with a4.sty), UWThPh-1993-3