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Thị Trấn Hùng Quốc, Vietnam

Stattegger K.,University of Kiel | Tjallingii R.,Netherlands Institute for Sea Research | Saito Y.,Geological Survey of Japan | Michelli M.,University of Kiel | And 2 more authors.
Global and Planetary Change | Year: 2013

Beachrocks, beach ridge, washover and backshore deposits along the tectonically stable south-eastern Vietnamese coast document Holocene sea level changes. In combination with data from the final marine flooding phase of the incised Mekong River valley, the sea-level history of South Vietnam could be reconstructed for the last 8000. years. Connecting saltmarsh, mangrove and beachrock deposits the record covers the last phase of deglacial sea-level rise from 5 to + 1.4 m between 8.1 to 6.4 ka. The rates of sea-level rise decreased sharply after the rapid early Holocene rise and stabilized at a rate of 4.5. mm/year between 8.0 and 6.9. ka. Southeast Vietnam beachrocks reveal that the mid-Holocene sea-level highstand slightly above +. 1.4. m was reached between 6.7 and 5.0. ka, with a peak value close to +. 1.5. m around 6.0. ka. This highstand is further limited by a backshore and beachridge deposit that marks the maximum springtide sea-level just below the base of the overlying beach ridge. After 5.0. ka sea level dropped below +. 1.4. m and fell almost linearly at a rate of 0.24. mm/year until 0.63. ka and +. 0.2. m as evidenced by the youngest beachrocks.The Holocene sea-level fluctuations observed in Southeast Vietnam resulted from eustatic and isostatic processes. The sea-level rise up to the mid-Holocene highstand was provoked by the last melting phase of glacial polar ice-sheets. The sea-level drop after the mid-Holocene highstand was induced by the isostatic processes of continental levering with an uplift of continents in low latitudes and depression of adjacent flooded continental shelf areas and Equatorial Ocean Siphoning transferring oceanic waters from low latitudes to the increasing volume of oceanic basins in higher latitudes. The regional expression in terms of magnitude and timing of relative sea-level change might contribute to validation of geophysical model simulations. © 2013 Elsevier B.V.

Rozhnoi A.,Russian Academy of Sciences | Shalimov S.,Russian Academy of Sciences | Solovieva M.,Russian Academy of Sciences | Levin B.,Institute of Marine Geology and Geophysics | And 2 more authors.
Journal of Geophysical Research: Space Physics | Year: 2012

A network of VLF receivers, sited in the Far East, has been used to observe the response of the lower ionosphere to tsunamis resulting from the November 15, 2006 (Kuril region) and the March 11, 2011 (Tohoku region) earthquakes. Specific perturbations in the phase and amplitude of VLF signals have been found for both cases. A qualitative interpretation of the observed effects is suggested in terms of the interaction of internal gravity waves with lower ionosphere. © 2012. American Geophysical Union.

Geptner A.R.,Russian Academy of Sciences | Petrova V.V.,Russian Academy of Sciences | Pha P.D.,Institute of Marine Geology and Geophysics | Huyen N.X.,Vietnam Union of Geological science | Nginh L.T.,Vietnam Union of Geological science
Lithology and Mineral Resources | Year: 2016

Siderites forming beds and lenses in the Neogene lacustrine—swampy sediments of the Rinh Chua Formation (northern Vietnam) are considered in detail. Results of the mineralogical and chemical study of siderites and host terrigenous–clayey siltstones are reported. New analytical data characterize the composition and structure of microbiomorphic (bacterial) bodies in the siderites and terrigenous sediments. Microstructures (porosity) and compositional peculiarities (up to 18% P2O5) of individual horizons of the sediments testify to their lacustrine-swampy genesis. It is established that the siderites in association with the layer silicates were formed during the microbiochemogenic decomposition of terrigenous components, including quartz. © 2016, Pleiades Publishing, Inc.

Fyhn M.B.W.,Geological Survey of Denmark | Phach P.V.,Institute of Marine Geology and Geophysics
Tectonics | Year: 2015

Continental extrusion may take up much of the deformation involved in continental collisions. Major strike-slip zones accommodate the relative extrusion displacement and transfer deformation away from the collision front. The Red River fault zone (RRFZ) accommodated left- and right-lateral displacements when Indochina and South China were extruded during the Indian-Eurasian collision. The northern Song Hong basin onshore and offshore in the Gulf of Tonkin delineates the direct extension of the RRFZ and thus records detailed information on the collision-induced continental extrusion. We assess the rapidly evolving kinematics of the fault zone buried within the basin based on seismic analysis. Contrary to previous studies, we do not identify indications for latest Miocene left-lateral motion across the RRFZ. We tentatively consider the shift from left- to right-lateral motion to have occurred already during the middle Late Miocene as indicated by inversion of NE-SW-striking faults in the Bach Long Vi area. Right-lateral displacement terminated around the end of the Miocene in the Song Hong basin. However, continued inversion in the Bach Long Vi area and NNW-SSE-striking normal faulting suggests a stress regime compatible with right-lateral motion across the onshore part of the RRFZ continuing to the present. Inversion around the Bach Long Vi Island may have accommodated up to a few kilometers of right-lateral displacement between the Indochina and South China blocks. Comparable NE-SW-striking fault zones onshore may have accommodated a larger fraction of the right-lateral slip across the RRFZ, thus accounting for the restricted transfer of lateral displacement to the offshore basins. © 2015. American Geophysical Union. All Rights Reserved.

Matoza R.S.,CEA DAM Ile-de-France | Le Pichon A.,CEA DAM Ile-de-France | Vergoz J.,CEA DAM Ile-de-France | Herry P.,CEA DAM Ile-de-France | And 4 more authors.
Journal of Volcanology and Geothermal Research | Year: 2011

Sarychev Peak (SP), located on Ostrov Matua, Kurils, erupted explosively during 11-16 June 2009. Whereas remote seismic stations did not record the eruption, we report atmospheric infrasound (acoustic wave ~. 0.01-20. Hz) observations of the eruption at seven infrasound arrays located at ranges of ~. 640-6400. km from SP. The infrasound arrays consist of stations of the International Monitoring System global infrasound network and additional stations operated by the Korea Institute of Geoscience and Mineral Resources. Signals at the three closest recording stations IS44 (643. km, Petropavlovsk-Kamchatskiy, Kamchatka Krai, Russia), IS45 (1690. km, Ussuriysk, Russia), and IS30 (1774. km, Isumi, Japan) represent a detailed record of the explosion chronology that correlates well with an eruption chronology based on satellite data (TERRA, NOAA, MTSAT). The eruption chronology inferred from infrasound data has a higher temporal resolution than that obtained with satellite data. Atmosphere-corrected infrasonic source locations determined from backazimuth cross-bearings of first-arrivals have a mean centroid ~. 15. km from the true location of SP. Scatter in source locations of up to ~. 100. km result from currently unresolved details of atmospheric propagation and source complexity. We observe systematic time-variations in trace-velocity, backazimuth deviation, and signal frequency content at IS44. Preliminary investigation of atmospheric propagation from SP to IS44 indicates that these variations can be attributed to solar tide variability in the thermosphere. It is well known that additional information about active volcanic processes can be learned by deploying infrasonic sensors with seismometers at erupting volcanoes. This study further highlights the significant potential of infrasound arrays for monitoring volcanic regions such as the Kurils that have only sparse seismic network coverage. © 2010 Elsevier B.V.

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