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51.
Historical tsunami in the Makran Subduction Zone off the southern coasts of Iran and Pakistan and results of numerical modeling 总被引:4,自引:0,他引:4
Mohammad Heidarzadeh Moharram D. Pirooz Nasser H. Zaker Ahmet C. Yalciner Mohammad Mokhtari Asad Esmaeily 《Ocean Engineering》2008,35(8-9):774-786
Tsunami hazard in the Makran Subduction Zone (MSZ), off the southern coasts of Iran and Pakistan, was studied by numerical modeling of historical tsunami in this region. Although the MSZ triggered the second deadliest tsunami in the Indian Ocean, among those known, the tsunami hazard in this region has yet to be analyzed in detail. This paper reports the results of a risk analysis using five scenario events based on the historic records, and identifies a seismic gap area in western Makran off the southern coast of Iran. This is a possible site for a future large earthquake and tsunami. In addition, we performed numerical modeling to explain some ambiguities in the historical reports. Based on the modeling results, we conclude that either the extreme run-up of 12–15 m assigned for the 1945 Makran tsunami in the historical record was produced by a submarine landslide triggered by the parent earthquake, or that these reports are exaggerated. The other possibility could be the generation of the huge run-up heights by large displacements on splay faults. The results of run-up modeling reveal that a large earthquake and tsunami in the MSZ is capable of producing considerable run-up heights in the far field. Therefore, it is possible that the MSZ was the source of the tsunami encountered by a Portuguese fleet in Dabhul in 1524. 相似文献
52.
李致家 《中国海洋湖沼学报》2008,26(2):142-151
Stochastic characteristics of the Benue River streamflow process are examined under conditions of data austerity. The streamflow process is investigated for trend, non-stationarity and seasonality for a time period of 26 years. Results of trend analyses with Mann-Kendall test show that there is no trend in the annual mean discharges. Monthly flow series examined with seasonal Kendall test indicate the presence of positive change in the trend for some months, especially the months of August, January, and February. For the stationarity test, daily and monthly flow series appear to be stationary whereas at 1%, 5%, and 10% significant levels, the stationarity alternative hypothesis is rejected for the annual flow series. Though monthly flow appears to be stationary going by this test, because of high seasonality, it could be said to exhibit periodic stationarity based on the seasonality analysis. The following conclusions are drawn: (1) There is seasonality in both the mean and variance with unimodal distribution. (2) Days with high mean also have high variance. (3) Skewness coefficients for the months within the dry season period are greater than those of the wet season period, and seasonal autocorrelations for streamflow during dry season are generally larger than those of the wet season. Precisely, they are significantly different for most of the months. (4) The autocorrelation functions estimated "over time" are greater in the absolute value for data that have not been deseasonalised but were initially normalised by logarithmic transformation only, while autocorrelation functions for i = 1, 2 365 estimated "over realisations" have their coefficients significantly different from other coefficients. 相似文献
53.
Ramin Vali Jie Li Gholamreza Shams Pieter van Gelder 《Marine Georesources & Geotechnology》2018,36(6):735-748
Evaluation of slope stability, especially in the absence of a proper bed such as marine soils, is one of the most important issues in geotechnical engineering. Using geogrid layers to enhance the strength and stability of embankments is regarded as a commendable stabilization method. On the other hand, groundwater level erratically fluctuates in coastal areas. Therefore, the aim of this research is to study the effects of groundwater level changes on stability of a geogrid-reinforced slope on loose marine soils in Qeshm Island, Iran. At first, geotechnical properties of the site were obtained by comprehensive series of geotechnical laboratory and in situ tests. Then, by simultaneous changes of groundwater level and several parameters such as embankment slope, loading, geogrid length, geogrid number, and tensile strength of geogrid, different characteristics such as embankment safety factor (SF), vertical and horizontal displacements at embankment top and embankment base were studied. It was observed that groundwater level had significant effects on behavior of the embankment. For most of the observations, by decreasing the groundwater level, the displacements decreased and consequently safety factor increased. Increasing the length, number, and tensile strength of geogrid led to the reduction of displacements and an increase in the safety factor. 相似文献
54.
On the occurrence and origin of anthropogenic radionuclides found in a fragment of the Chelyabinsk (LL5) meteorite 下载免费PDF全文
Rebecca Querfeld Mohammad R. Tanha Lars Heyer Franz Renz Georg Guggenberger Franz Brandstätter Ludovic Ferrière Christian Koeberl Georg Steinhauser 《Meteoritics & planetary science》2017,52(6):1244-1250
A piece of the 2013 Chelyabinsk meteorite was investigated for its content of anthropogenic radionuclides. In addition to traces of cesium‐137 that had been previously reported for this particular fragment, we found an unusually high amount of strontium‐90, which indicates that the source of this contamination was the Kyshtym accident (1957). A high Sr‐90/Cs‐137 activity ratio is characteristic for Kyshtym‐derived contaminations. Based on the cesium‐137 content in the soil from the finding site, it is estimated that the fragment was contaminated with soil particles in the milligram range upon impact. Investigation of the soil revealed very unusual ferromagnetic characteristics and an iron‐rich chemical composition. Mössbauer spectroscopy indicated the presence of steel components in this soil, suggesting that the investigated meteorite fragment was found in an industrial dumping site rather than natural soil. 相似文献
55.
Benoît Thibodeau Moritz F. Lehmann Jacqueline Kowarzyk Alfonso Mucci Yves Gélinas Denis Gilbert Roxane Maranger Mohammad Alkhatib 《Estuarine, Coastal and Shelf Science》2010
Water column concentrations and benthic fluxes of dissolved inorganic nitrogen (DIN) and oxygen (DO) were measured in the Gulf of St. Lawrence and the Upper and Lower St. Lawrence Estuary (USLE and LSLE, respectively) to assess the nitrogen (N) budget in the St. Lawrence (SL) system, as well as to elucidate the impact of bottom water hypoxia on fixed-N removal in the LSLE. A severe nitrate deficit, with respect to ambient phosphate concentrations (N*∼−10 μmol L−1), was observed within and in the vicinity of the hypoxic bottom water of the LSLE. Given that DO concentrations in the water column have remained above 50 μmol L−1, nitrate reduction in suboxic sediments, rather than in the water column, is most likely responsible for the removal of fixed N from the SL system. Net nitrate fluxes into the sediments, derived from pore water nitrate concentration gradients, ranged from 190 μmol m−2 d−1 in the hypoxic western LSLE to 100 μmol m−2 d−1 in the Gulf. The average total benthic nitrate reduction rate for the Laurentian Channel (LC) is on the order of 690 μmol m−2 d−1, with coupled nitrification-nitrate reduction accounting for more than 70%. Using average nitrate reduction rates derived from the observed water column nitrate deficit, the annual fixed-N elimination within the three main channels of the Gulf of St. Lawrence and LSLE was estimated at 411 × 106 t N, yielding an almost balanced N budget for the SL marine system. 相似文献
56.
Increasing population in urban areas and limitations of suitable lands for developing houses and urban infrastructure have led to the vertical development in cities. However, these developments are managed by a cadastral system which is mainly two-dimensional and cannot efficiently represent Rights, Restrictions, and Responsibilities (RRRs) in complex scenarios. In fact, a three-dimensional cadastre is required for efficiently registering and representing RRRs. In this paper, a 3D proximity analysis was proposed and implemented to determine RRRs and associated easement rights in non-topology-based data structures. This method can be used to investigate the surrounding spaces of a subject apartment unit or storage in a high-rise. The performance of the developed method was evaluated in a large complex high-rise in Tehran, Iran. The results confirmed that the proposed method can correctly identify the neighbor spaces in complex scenarios. 相似文献
57.
The problem of drained cavity expansion in soils of finite radial extent is investigated. Cylindrical and spherical cavities expanded from zero radius subjected to either constant stress or zero displacement at the finite boundary are considered. The generalised analytical solution procedure presented enables more advanced constitutive models to be implemented than have been possible in previous studies. Results generated for Sydney quartz sand highlight substantial differences between cavity limit pressures for the two boundary conditions and for boundaries of finite and infinite radial extent. This is of significance in accounting for boundary effects when interpreting cone penetration tests conducted in calibration chambers. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
58.
Prof. Dr. K. Hinz Dr. J. Fritsch Dr. E. H. K. Kempter Mr. A. Manaf Mohammad Dr. J. Meyer Mr. D. Mohamed Dipl. Geophys. H. Vosberg Dipl. Ing. J. Weber Mr. J. Benavidez 《International Journal of Earth Sciences》1989,78(3):705-730
Widely accepted plate tectonic models suggest that an inactive subduction zone lies along the north-west continental margin of Sabah. In contrast, interpretation of reflection seismic data acquired by BGR shows an autochthonous continental terrane comprising an Oligocene to Early Miocene carbonate platform being progressively overthrust by an allochthonous rock complex. Progressive compression resulted in the development of four structural zones: Imbricated thrust sheets (Zone III); two thrust sheet systems one on top of the other (Zone IV); a complex zone with multiphase deformation (Zone V); and piercement ridges (Zone VI).
Zusammenfassung Nach herkömmlichen plattentektonischen Vorstellungen soll eine inaktive Subduktionszone am nordwestlichen Kontinentalrand von Sabah liegen. Reflexionsseismische Meßdaten der BGR zeigen jedoch, daß hier autochthone kontinentale Kruste mit einer oligozänen-frühmiozänen Karbonatplattform progressiv von einem allochthonen Gesteinsverband überschoben wird. Fortschreitender Zusammenschub seit dem frühen Miozän führte zur Anlage von vier Deformationszonen: Tekonische Schuppen (Zone III); zwei übereinander geschobene Verschuppungssysteme (Zone IV); Gürtel mit mehrphasiger Deformation (Zone V) und Durchspießungsstrukturen (Zone VI).
Résumé Les modèles géodynamiques que l'on admet habituellement comportent une zone de subduction inactive le long de la marge continentale nord-occidentale de Sabah. Toutefois, des mesures de sismique-réflexion exécutées par le BGR font apparaître qu'à cet endroit, une croûte continentale autochtone, comportant une plateforme carbonatée oligocène à éomiocène, est chevauchée progressivement par un complexe allochtone. La compression, qui s'est manifestée progressivement depuis le Miocène inférieur, a engendré quatre zones structurales: un ensemble d'écailles tectoniques (zone III); deux systèmes de lames tectoniques charriés l'un sur l'autre (zone IV); une zone complexe à déformation multiphasée (zone V); des structures d'extrusion tectonique (zone VI).
, - Sabah'a. , - . 4-? : ( 3), ( 4) ( 5) ( 6).相似文献
59.
Mohammad Qausar 《Pure and Applied Geophysics》1989,131(4):703-713
The attenuation properties of eight rheological models have been studied theoretically. The expressions forQ have been obtained by using dissipated and stored energies and/or complex modulus for each model. The dependence ofQ on frequency has been demonstrated. The three-element elastic model appears to be the best one to represent the viscoelastic nature of the earth's material for a finite value ofQ. 相似文献
60.