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111.
112.
The geoarchaeological record of the Phoenician necropolis of Al Bass (Lebanon) provides information concerning the geomorphological evolution of a late Holocene tombolo. Physical and chemical analysis of sediments indicates that the cemetery (9th century B.C.) was located near a littoral lagoon, between the dunes of a cuspate spit pointing toward the island of Tyre. From the sea apex of this spit, the moles mentioned in historical chronicles were constructed. Once mainland and island were connected, at the northern coast (where the port of Sidon was located), a sediment trap was formed, which quickly filled with silt. Afterwards, an extensive field of sand dunes buried all the archaeological remains from Phoenician to Roman times. © 2008 Wiley Periodicals, Inc. 相似文献
113.
S.R. Arellano M. Hall P. Samaniego J.-L. Le Pennec A. Ruiz I. Molina H. Yepes 《Journal of Volcanology and Geothermal Research》2008
This paper presents the results of 7 years (Aug. 1999–Oct. 2006) of SO2 gas measurements during the ongoing eruption of Tungurahua volcano, Ecuador. From 2004 onwards, the operation of scanning spectrometers has furnished high temporal resolution measurements of SO2 flux, enabling this dataset to be correlated with other datasets, including seismicity. The emission rate of SO2 during this period ranges from less than 100 to 35,000 tonnes/day (t d− 1) with a mean daily emission rate of 1458 t d− 1 and a standard deviation of ± 2026 t d− 1. Average daily emissions during inferred explosive phases are about 1.75 times greater than during passive degassing intervals. The total amount of sulfur emitted since 1999 is estimated as at least 1.91 Mt, mostly injected into the troposphere and carried westwards from the volcano. Our observations suggest that the rate of passive degassing at Tungurahua requires SO2 exsolution of an andesitic magma volume that is two orders of magnitude larger than expected for the amount of erupted magma. Two possible, and not mutually exclusive, mechanisms are considered here to explain this excess degassing: gas flow through a permeable stagnant-magma-filled conduit and gas escape from convective magma overturning in the conduit. We have found that real-time gas monitoring contributes significantly to better eruption forecasting at Tungurahua, because it has provided improved understanding of underlying physical mechanisms of magma ascent and eruption. 相似文献
114.
Alfredo Reyes-Salazar José M. Sauceda-Pimentel Sonia E. Ruiz Edén Bojórquez Juan Bojorquez 《Bulletin of Earthquake Engineering》2018,16(11):5557-5590
A numerical investigation regarding the seismic behavior of complex-3D steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (GF) is conducted. The interior connections are assumed to be first perfectly pinned (PP) and then semi-rigid (SR); the two model responses are compared. Three steel building models representing low-, medium- and high-rise buildings, and several strong motions are used. The relative stiffness of SR connections is calculated according to the Richard Model and the Beam Line Theory. The Ruaumoko Computer Program is used to perform the required step-by-step nonlinear seismic analysis. Results indicate that interstory shears and interstory displacements at PMRF may be significantly reduced when interior connections are modeled as SR. Average reductions of up to 20, 46 and 11% are observed for interstory shears, for low-, medium-, and high-rise buildings, respectively. The corresponding reductions for interstory displacements are about 14, 44 and 15%. The contribution of GF to the lateral resistance is considerable, which significantly increases when the connections are modeled as SR; relative contributions larger than 80% are observed. The dissipated energy (DE) at PMRF is larger for the buildings with PP than for the buildings with SR connections indicating that damage at PMRF is reduced. Thus, the effect of the stiffness and the DE at interior connections should not be ignored. However, the design of some elements, particularly columns of the GF, has to be revised; these members may not be able to support the loads produced by the neglected lateral contribution if they are not properly designed. 相似文献
115.
Evaluation of seismic displacement demands from the September 19, 2017 Puebla‐Morelos (Mw = 7.1) earthquake in Mexico City 下载免费PDF全文
This short communication presents the assessment of seismic inelastic and elastic displacement demands computed from earthquake ground motions (EQGMs) recorded in Mexico City during the intermediate‐depth intraslab Puebla‐Morelos earthquake on 19 September 2017 (Mw = 7.1). Evaluation is conducted by means of peak elastic and inelastic displacement demand spectra, inelastic displacement ratio, CR, spectra, and generalized interstory drift spectra computed for selected recording stations located in different soil sites of Mexico City, including those located in areas of reported collapsed buildings. Results of this study confirm previous observations made from interplate (subduction) EQGMs that peak inelastic displacement demands are greater than corresponding elastic counterparts for short‐to‐medium period structures, while the opposite is true for medium‐to‐long period structures. Possible basin site effects were identified from generalized interstory drift spectra. It is also shown that an equation introduced in the literature to obtain estimates of CR developed from interplate EQGMs provides also a good estimate for mean CR computed from the intermediate‐depth intraslab EQGMs. 相似文献
116.
K. Puschmann B. Ruiz Cobo M. Vzquez J.A. Bonet A. Hanslmeier 《Astronomische Nachrichten》2003,324(4):352-353
From inversion of a time series of slit spectra, observed in a quiet region of the solar photosphere, averaged models of a granular cell have been obtained showing the stratification of physical quantities versus optical depth and geometrical height. Furthermore a semi‐empiric dynamic model of a mean granular cell has been derived and the results are presented. 相似文献
117.
Large wood clogging during floods in a gravel‐bed river: the Długopole bridge in the Czarny Dunajec River,Poland 下载免费PDF全文
Virginia Ruiz‐Villanueva Bartłomiej Wyżga Paweł Mikuś Maciej Hajdukiewicz Markus Stoffel 《地球表面变化过程与地形》2017,42(3):516-530
During floods, large quantities of wood can be mobilized and transported downstream. At critical sections, such as bridges, the transported wood might be entrapped and a quick succession of backwater effects can occur as a result of the reduction of the cross‐sectional area. The aim of this work is to explore large wood‐related hazards during floods in the gravel‐bed river Czarny Dunajec (Polish Carpathians), where the river flows through the village of D?ugopole. This work is based on the numerical modelling of large wood transport together with flow dynamics in which inlet and boundary conditions were designed based on field observations. The exploratory approach developed in this study uses multiple scenarios (193) to analyse the factors controlling bridge clogging: wood size, wood supply, flow conditions, morphology and obstacles in the riverbed. Results highlighted the strong control of log length (stronger than that of log diameter) on potential blockage probability; however, according to our results the main factor controlling bridge clogging was the flood discharge. River morphology and wood supply play an important role as well. The river morphology may reduce bridge blockage, as it influences flow velocity and depth, and creates natural retention zones for wood. In addition, the impacts of bridge blockage were analysed in terms of afflux depth and length, and flooded area. Results showed that bridge blockage may result in a significant increase in water depth (up to 0.7 m) and flooded area (up to 33% more), therefore increasing flood risk in the village. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
118.
119.
F. Ruiz M. L. González-Regalado J. Borrego J. A. Morales J. G. Pendón J. M. Muñoz 《Environmental Geology》1998,34(4):270-278
The Holocene filling of the Tinto-Odiel Estuary comprises seven lithofacies over a Mio-Pliocene substrate. The sequence includes
three system tracts: lowstand system (10 000 to 8700 years BP), transgressive system (8700 to 7000 years BP), and regressive
system (7000 to Recent). Twenty sediment samples from the 50-m borehole were analyzed for their major components and minor
element concentrations. Two multivariate analysis methods, principal component analysis and cluster analysis, were performed
in the analytical data set to help visualize the sample clusters and the element associations. Samples corresponding to unpolluted,
pre-mining sediments are clearly separated by cluster analysis, mainly as a result of the low content in sulphide-associated
heavy metals such as Cu, Zn, As, Ag, and Pb. So, these sediments may be utilized as a background for geochemical analysis
(bulk sample) in other adjacent estuaries, both in sandy and silty-clayey sediments. As a consequence of large-scale mining
and smelting operations occurred since prehistoric times on the river banks, a rapid rise in the metal pollution was found
in the upper 2.5 m of the natural filling, with values exceeding up to ten times the natural background levels. In addition,
since the mid-1960s, large amounts of waste and pollutant effluents have been discharged from industries located around the
estuary, increasing the heavy metal content in the last 0.3 m of the natural sedimentation.
Received: 18 August 1997 · Accepted: 19 January 1998 相似文献
120.
Electron-probe microanalysis of a series of garnets in metapelitic rocks of the chloritoid staurolite, kyanite and sillimanite metamorphic zones, eastern area of the Sierra de Guadarrama, Sistema Central, Spain, manifest the well-known cryptozonation commonly observed in these minerals, with MgO and FeO increasing and MnO and CaO decreasing from the center to the outer rim of the crystals.The differences in composition of the garnets, from one metamorphic zone to another, is mainly a result of small differences in composition of the host-rock, since: (1) the amounts of MnO in the garnet are controlled by the amounts of SiO2, Al2O3 and FeO present in the host-rock; and (2) the percentages of MnO and MgO of the parent-rock influence in some way the concentration of CaO in the garnet, and those of MnO, Al2O3 and CaO influence the concentration of FeO. Nevertheless, the amount of FeO in the garnet is finally controlled, due to the diadochy, by the concentration of MnO + CaO in this mineral. 相似文献