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331.
Earthquake imprints on a lacustrine deltaic system: The Kürk Delta along the East Anatolian Fault (Turkey) 下载免费PDF全文
Aurélia Hubert‐Ferrari Meriam El‐Ouahabi David Garcia‐Moreno Ulaş Avşar Sevgi Altınok Sabine Schmidt Nathalie Fagel M. Namık Çağatay 《Sedimentology》2017,64(5):1322-1353
Deltas contain sedimentary records that are not only indicative of water‐level changes, but also particularly sensitive to earthquake shaking typically resulting in soft‐sediment‐deformation structures. The Kürk lacustrine delta lies at the south‐western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault, which has generated earthquakes of magnitude 7. This study re‐evaluates water‐level changes and earthquake shaking that have affected the Kürk Delta, combining geophysical data (seismic‐reflection profiles and side‐scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water‐level changes provides a temporal framework for the depositional record. In addition to the common soft‐sediment deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake‐induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a palaeoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the East Anatolian Fault. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating (137Cs and 210Pb), two major sedimentary events were attributed to the ad 1874 to 1875 East Anatolian Fault earthquake sequence. Their sedimentological characteristics were determined by X‐ray imagery, X‐ray diffraction, loss‐on‐ignition, grain‐size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post‐seismic sediment reworking of earthquake‐triggered landslides. 相似文献
332.
Aurea Garcia Laerte Sodré Jr Francisco J. Jablonski Roberto J. Terlevich † 《Monthly notices of the Royal Astronomical Society》1999,309(3):803-816
We present an analysis of quasar variability from data collected during a photometric monitoring of 50 objects carried out at CNPq/Laboratório Nacional de Astrofísicá, Brazil, between 1993 March and 1996 July. A distinctive feature of this survey is its photometric accuracy, ∼0.02 V mag, achieved through differential photometry with CCD detectors, which allows the detection of faint levels of variability. We find that the relative variability, δ σ L , observed in the V band is anticorrelated with both luminosity and redshift, although we have no means of discovering the dominant relation, given the strong coupling between luminosity and redshift for the objects in our sample. We introduce a model for the dependence of quasar variability on frequency that is consistent with multiwavelength observations of the nuclear variability of the Seyfert galaxy NGC 4151. We show that correcting the observed variability for this effect slightly increases the significance of the trends of variability with luminosity and redshift. Assuming that variability depends only on the luminosity, we show that the corrected variability is anticorrelated with luminosity and is in good agreement with predictions of a simple Poissonian model. The energy derived for the hypothetical pulses, ∼1050 erg, agrees well with those obtained in other studies. We also find that the radio-loud objects in our sample tend to be more variable than the radio-quiet ones, for all luminosities and redshifts. 相似文献
333.
Patrick Raimbault Wilfried Pouvesle Frdric Diaz Nicole Garcia Richard Sempr 《Marine Chemistry》1999,66(3-4)
We developed a simple and reliable method which allows simultaneous determination of organic forms of carbon (DOC), nitrogen (DON) and phosphorus (DOP) dissolved in seawater. Conversion of dissolved organic matter (DOM) to inorganic products (carbon dioxide, nitrate+nitrite and soluble reactive phosphate) is performed by a persulfate wet-oxidation in low alkaline condition. After oxidation, the concentration of the inorganic products dissolved in the sample was measured automatically by colorimetry using a 3-channel Technicon AutoAnalyzer system. A number of pure organic compounds were tested in the concentration range encountered in coastal and open ocean, indicating a high efficiency of the digestion procedure. The recovery range is similar to that obtained by other wet-oxidation procedures and by high-temperature catalytic oxidation techniques. Direct comparisons with usual methods used for separate determination of DOC, DON and DOP indicated a high efficiency of the procedure. Reproducibility tests demonstrated a very good precision (around 5%) for lagoonal and coastal waters, while precision was sometimes around 10–25% in oligotrophic oceanic waters, especially for DOP where values approached limits of detection for measuring phosphate. This method is highly suitable for routine analysis and especially appropriate for shipboard work. 相似文献
334.
335.
J. M. Jouanneau C. Garcia A. Oliveira A. Rodrigues J. A. Dias O. Weber 《Progress in Oceanography》1998,42(1-4)
The Portuguese margin in front of the Tagus and Sado rivers is characterized by a narrow shelf incised by numerous canyons and by a large mud deposit. The two estuaries that feed this continental margin have distinct impact. The suspended particulate matter concentration values in the mouth of the Tagus are four times higher than in the Sado. During the summer the surface nepheloid layer is always larger than during the winter when it is restricted near the mouth of the estuary. This nepheloid layer may reach 30 km in length extending westward. The bottom nepheloid layer usually shows higher nephelometer values, and has a typical distribution: it is usually diverted southward in the direction of the Lisbon Submarine Canyon. We estimate the amount of suspended matter being discharged annually from the Tagus estuary to be between 0.4 and 1×106 t. The area covered by fine deposits is about 560 km2. Hence the thickness of sediments deposited annually should be between 0.07 and 0.18 cm. The sedimentation rates calculated from the 210Pb excess vary between 0.16 and 2.13 cm y−1 which correspond to the maximum rate. For a layer of 1 cm thick, 81,000 t of particulate organic carbon (POC) should be trapped. That would represent, with a minimum sedimentation rate between 0.07 and 0.18 cm y−1, an entrapment of 6000–15,000 t POC y−1. The trace metals content of box core samples clearly shows the anthropogenic impact in the uppermost level (5 cm thick) in the Tagus estuary and in all the sedimentary deposits (15 cm thick) on the shelf muddy area. Despite the narrowness of the shelf, a significant part of continental fluxes fails to reach the deep ocean. 相似文献
336.
Riegel Roberta Plangg Alves Darlan Daniel Schmidt Bruna Caroline de Oliveira Guilherme Garcia Haetinger Claus Osório Daniela Montanari Migliavacca Rodrigues Marco Antônio Siqueira de Quevedo Daniela Muller 《Natural Hazards》2020,103(1):497-511
Natural Hazards - The increase in the frequency of natural disasters in recent years and its consequent social, economic and environmental impacts make it possible to prioritize areas of risk as an... 相似文献
337.
Much has been written on the subject of objective functions to calibrate rainfall–runoff models. Many studies focus on the best choice for low-flow simulations or different multi-objective purposes. Only a few studies, however, investigate objective functions to optimize the simulations of low-flow indices that are important for water management. Here, we test different objective functions, from single objective functions with different discharge transformations or using low-flow indices, to combinations of single objective functions, and we evaluate their robustness and sensitivity to the rainfall–runoff model. We find that the Kling and Gupta efficiency (KGE) applied to a transformation of discharge is inadequate to fulfil all assessment criteria, whereas the mean of the KGE applied to the discharge and the KGE applied to the inverse of the discharge is sufficient. The robustness depends on the climate variability rather than the objective function and the results are insensitive to the model.
EDITOR A. Castellarin; ASSOCIATE EDITOR C. Perrin 相似文献
338.
339.
M. E. Varela S.-L. Hwang P. Shen L. N. Garcia M. Saavedra T. Maruoka M. Bose 《Meteoritics & planetary science》2024,59(3):421-434
The combined SEM and TEM studies on the metal (Fe-Ni alloy ±C) portion of the Vaca Muerta mesosiderite reveal structural and compositional evidence at micro to nanoscale, which sheds light on the solidification of taenite + graphite as a cement, and later solid-state precipitation process for the kamacite formation as grain boundary allotriomorph. Besides, it is proposed that the graphite veinlets formed through a complex partial melting process followed by a solidification toward the final eutectic transient coupled with the solid-state precipitation and later decomposition ordering of taenite. The presence of defects and taenite in graphite signal formation in a liquid environment. The δ13C values of graphite in the graphite-rich areas (e.g., ranging from −0.8 ± 1.7‰ to +15.3 ± 2.5‰) suggest a short-circuit diffusion path for C isotope fractionation. 相似文献