Nachweis eines mononuclearen Mangan (II)-Zentrums in der Ribonucleotid-Reduktase aus Corynebacterium ammoniagenes ATCC 6872 nach Überexpression des den Metallocofaktor codierenden nrdF-Gens im Originalstamm

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Rifting of the north-western South China Sea Basin from MCS images

European Geosciences Union General Assembly 2014 (EGU2014), 27 april - 2 may 2014, Vienna, Austria.-- 1 pageWe have reprocessed about 2250 km of multichannel seismic reflection data collected during cruise Sonne 49 across the NW South China Sea. We present images across four regional lines that cross the outer continental shelf and slope, and extend into the deep-water basin. The seismic images are of high quality and show the crustal structure from clear base-of-the-crust reflections to continuous top-of-basement reflections and a well imaged syn-rift and post rift stratigraphy and intrusive magmatic layering. In addition, fault reflections in the basement are also common. The crystalline basement and sediment strata display a series of structures that change laterally from the continental shelf to the deep-water basin and that have been used to define a continental domain, an abrupt continent to ocean transition and an oceanic domain. Existing wide-angle data coincident with our lines support our interpretation. The style of continental extension, the structures defining the continent to ocean transition, and the distribution of oceanic crust in the basin has been used to propose a tectonic model of the formation of the NW South China Sea continental margin. The data document the three-dimensional temporal evolution of the interplay between rifting processes and seafloor spreading leading to the current structural configurationPeer Reviewe

Subducting seamounts control interplate coupling and seismic rupture in the 2014 Iquique earthquake area

To date, the parameters that determine the rupture area of great subduction zone earthquakes remain contentious. On 1 April 2014, the Mw 8.1 Iquique earthquake ruptured a portion of the well-recognized northern Chile seismic gap but left large highly coupled areas un-ruptured. Marine seismic reflection and swath bathymetric data indicate that structural variations in the subducting Nazca Plate control regional-scale plate-coupling variations, and the limited extent of the 2014 earthquake. Several under-thrusting seamounts correlate to the southward and up-dip arrest of seismic rupture during the 2014 Iquique earthquake, thus supporting a causal link. By fracturing of the overriding plate, the subducting seamounts are likely further responsible for reduced plate-coupling in the shallow subduction zone and in a lowly coupled region around 20.5°S. Our data support that structural variations in the lower plate influence coupling and seismic rupture offshore Northern Chile, whereas the structure of the upper plate plays a minor role

Seismic reflection evidence for a Dangerous Grounds miniplate: No extrusion origin for the South China Sea

The collision of India and Asia has caused large strike-slip faults to form in east Asia, resulting in the extrusion of crustal blocks toward the southeast since the Eocene as a result of the indentation of rigid India into Asia. It has been suggested that the South China Sea opened as a result of relative motion between a rigid Indochina (Sundaland) block and China. Alternative models propose that riffing and seafloor spreading were driven by trench forces to the south. We test these competing models by analysis of seismic reflection profiles across the boundary between Sundaland and the southern rifted margin, known as the Dangerous Grounds. We show that the southern boundary of the Dangerous Grounds is a subduction zone that jammed in the middle Miocene. To the west the Dangerous Grounds are bounded by a strike-slip zone, also active until ∼16 Ma, that becomes diffuse south of the now inactive South China Sea seafloor spreading center. We place the western edge of the Dangerous Grounds just to the east of the Natuna Arch (Lupar Line). The West Baram Line is confirmed as originating as a major strike-slip fault within the Dangerous Grounds and is continuous with the Red River Fault Zone. Because the Dangerous Grounds were independent of Sundaland until ∼16 Ma, its motion cannot have been constrained by motion of this block, making extrusion impossible as a mechanism to rift the South China Sea. SE motion by both the Dangerous Grounds and Sundaland suggests subduction forces were the primary trigger for plate motions. Our reconstruction places a ∼280 km upper limit on the motion on the Red River Fault and a ∼1400 km width to the paleo-South China Sea. Copyright 2008 by the American Geophysical Union

Thermal regime of the Costa Rican convergent margin: 1. Along-strike variations in heat flow from probe measurements and estimated from bottom-simulating reflectors

21 pages, 9 figures, 1 tableThe thermal structure of convergent margins provides information related to the tectonics, geodynamics, metamorphism, and fluid flow of active plate boundaries. We report 176 heat flow measurements made with a violin bow style probe across the Costa Rican margin at the Middle America Trench. The probe measurements are collocated with seismic reflection lines. These seismic reflection lines show widespread distribution of bottom-simulating reflectors (BSRs). To extend the spatial coverage of heat flow measurements we estimate heat flow from the depth of BSRs. Comparisons between probe measurements and BSR-derived estimates of heat flow are generally within 10% and improve with distance landward of the deformation front. Together, these determinations provide new information on the thermal regime of this margin. Consistent with previous studies, the margin associated with the northern Nicoya Peninsula is remarkably cool. We define better the southern boundary of the cool region. The northern extent of the cool region remains poorly determined. A regional trend of decreasing heat flow landward of the deformation front is apparent, consistent with the downward advection of heat by the subducting Cocos Plate. High wave number variability at a scale of 5–10 km is significantly greater than the measurement uncertainty and is greater south of the northern Nicoya Peninsula. These heat flow anomalies vary between approximately 20 and 60 mW m−2 and are most likely due to localized fluid flow through mounds and faults on the margin. Simple one-dimensional models show that these anomalies are consistent with flow rates of 7–15 mm yr−1. Across the margin toe variability is significant and likely due to fluid flow through deformation structures associated with the frontal sedimentary prismThis research was support by an NSF award (OCE‐0637120) to R.N.H. We thank R. von Huene, P. Fulton, and G. Spinelli for helpful comments. Heat flow data acquisition was funded by the German Science Foundation (DFG) through grant Vi 133/7‐1 to H.V. and I.G. and the SFB 574 “Volatiles and fluids in subduction zones” at Christan‐Albrechts University, Kiel. This is a contribution of the Barcelona Center for Subsurface Imaging (Barcelona‐CSI) supported by the Kaleidoscope project of REPSOLPeer Reviewe

Middle to Late Miocene Contractional Deformation in Costa Rica Triggered by Plate Geodynamics

Contractional deformation in Costa Rica is usually attributed to the subduction of the aseismic Cocos Ridge. In this work, we review the evidences for contraction in the middle to late Miocene, prior to the arrival of the Cocos Ridge at the Middle America Trench. We find that the Miocene phase of contractional deformation is found in all of Costa Rica, probably extending to Nicaragua as well. The widespread distribution of this event requires a regional or plate geodynamic trigger. We analyze the possible mechanisms that could produce the onset of contractional deformation, using the better known case of subduction orogeny, the Andes, as an analog. We propose that a change in the direction of the Cocos plate since ∼19 Ma led to a change from oblique to orthogonal convergence, producing contractional deformation of the upper plate.Fil: Mescua, Jose Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Porras, Hernan. Observatorio Vulcanológico y Sismológico de Costa Rica; Costa RicaFil: Duran, Patrick. Universidad de Costa Rica; Costa RicaFil: Giambiagi, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: de Moor, Maerten. Observatorio Vulcanológico y Sismológico de Costa Rica; Costa RicaFil: Cascante, Monserrat. Observatorio Vulcanológico y Sismológico de Costa Rica; Costa RicaFil: Salazar, Esteban. Servicio Nacional de Geología y Minería; ChileFil: Protti, Marino. Observatorio Vulcanológico y Sismológico de Costa Rica; Costa RicaFil: Poblete, Fernando. Universidad de O’Higgins; Chil

Does permanent extensional deformation in lower forearc slopes indicate shallow plate-boundary rupture?

Highlights • We document marine forearc deformation in the Northern Chile seismic gap. • Upper-plate normal faulting off Northern Chile locally extends close to the trench. • Normal faults indicate that past earthquakes may reached the shallow plate-boundary. Abstract Seismic rupture of the shallow plate-boundary can result in large tsunamis with tragic socio-economic consequences, as exemplified by the 2011 Tohoku-Oki earthquake. To better understand the processes involved in shallow earthquake rupture in seismic gaps (where megathrust earthquakes are expected), and investigate the tsunami hazard, it is important to assess whether the region experienced shallow earthquake rupture in the past. However, there are currently no established methods to elucidate whether a margin segment has repeatedly experienced shallow earthquake rupture, with the exception of mechanical studies on subducted fault-rocks. Here we combine new swath bathymetric data, unpublished seismic reflection images, and inter-seismic seismicity to evaluate if the pattern of permanent deformation in the marine forearc of the Northern Chile seismic gap allows inferences on past earthquake behavior. While the tectonic configuration of the middle and upper slope remains similar over hundreds of kilometers along the North Chilean margin, we document permanent extensional deformation of the lower slope localized to the region 20.8°S–22°S. Critical taper analyses, the comparison of permanent deformation to inter-seismic seismicity and plate-coupling models, as well as recent observations from other subduction-zones, including the area that ruptured during the 2011 Tohoku-Oki earthquake, suggest that the normal faults at the lower slope may have resulted from shallow, possibly near-trench breaking earthquake ruptures in the past. In the adjacent margin segments, the 1995 Antofagasta, 2007 Tocopilla, and 2014 Iquique earthquakes were limited to the middle and upper-slope and the terrestrial forearc, and so are upper-plate normal faults. Our findings suggest a seismo-tectonic segmentation of the North Chilean margin that seems to be stable over multiple earthquake cycles. If our interpretations are correct, they indicate a high tsunami hazard posed by the yet un-ruptured southern segment of the seismic gap