ABSTRACT Albian–Cenomanian successions (Kazhdumi and Sarvak formations) represent remarkable variations in thickness, facies, fauna, and environments throughout the Zagros area. In the Coastal Fars (Charmu section), sedimentological and paleontological data evidence an intrashelf, with depths of 10s–100s m, surrounded by a shallow carbonate platform. Due to its depth, deposition of sequences in this setting has been controlled by eustatic sea-level changes rather than eurybathic changes, and several condensation episodes occurred related to marine transgressions. These observations are different from those in the adjacent sections in the Coastal Fars which recorded subaerial exposures instead. Combined with previous studies, this study denotes several intrashelf basins enclosed by a shallow carbonate platform on the southeastern margin of the Neo-Tethys during the Albian–Cenomanian. Development of intrashelf basins corresponds to basement faults in the Fars Salient. Likely, an extensional tectonic regime associated with a rifting event created horst–graben architecture by exerting extension along the basement faults and reactivating salt structures. Deposition on these troughs and highs led to the facies and thickness variations of the concomitant sequences. Development of several intrashelf basins on the southeastern margin of the Neo-Tethys indicates that syn-depositional continental rifting event could occur during the Albian–Cenomanian, prior to the tectonic inversion around the earliest Turonian. 相似文献
Regular solutions at the 3/2 commensurability are investigated forSitnikovs problem. Utilizing a rotating coordinate system and theaveraging method, approximate analytical equations are obtained for thePoincare sections by means of Jacobian elliptic functions and 3periodicsolutions are generated explicitly. It is revealed that the system exhibitsheteroclinic orbits to saddle points. It is also shown that chaotic regionemerging from the destroyed invariant tori, can easily be seen for certaineccentricities. The procedure of the current study provides reliable answersfor the long-time behavior of the system near resonances. 相似文献
In this paper, an advanced formulation of the time-domain, two-dimensional hybrid finite element–boundary element method (FEM/BEM) is presented, and applied to carry out site response analysis of homogeneous and non-homogeneous topographic structures subjected to incident in-plane motions. Seismic responses of half-plane, horizontally layered site, alluvial valley and ridge sections subjected to incident P and SV waves are analyzed in order to demonstrate the applicability and efficiency of the presented method. The numerical results show that hybrid BE/FE methods require smaller time steps than those needed by BEM schemes. They also show that in case of surface irregularities with height to half-width ratio of up to one, the topography effect could be noticeable, if incident waves have wavelengths of less than approximately eight times the width. 相似文献
This paper gives a brief explanation of the earthquake in Bam. It also reports on the rescue and relief operations, including
the construction of emergency shelters and temporary housing, and on the country’s plan for the reconstruction of the city,
which includes debris removal, the rebuilding of rural and urban residential and commercial units, the reconstruction of state
and public buildings and public facilities such as schools, rural and urban water aqueducts and grids, the construction of
a sewage system, power network and telecommunication system, the provision of water to orchards and farmlands, the renovation
of industries and the revival of the cultural heritage, particularly the historical Bam citadel, among others. We also report
briefly on the effect of the Bam earthquake on the Iran Earthquake Risk Reduction Strategy and actions.
In this study, the nonlinear seismic analysis of a typical three-dimensional concrete faced rockfill dam is reported. Three components of the Loma Prieta (Gilroy 1 station) earthquake acceleration time history are used as input excitation. The dam under study is considered as if it were located in a prismatic canyon with a trapezoidal cross-section. A nonlinear model for the rockfill material is used, and contact elements with Coulomb friction law are utilized at the slab–rockfill interface. Vertical joints in the face slab are also considered in the finite element model. A substructure method, in which the unbounded soil is modelled by the scaled boundary finite element method (SBFEM), is used to obtain the scattered motion and interaction forces along the canyon. The dam is subjected to spatially variable P, SV, and SH waves, and the effect of dam–foundation interaction and the reservoir water effects are considered. The results are compared with the non-scattered input motion analysis. Results of the analyses indicate that due to applying the scattered motion to the canyon the response of the dam and concrete face slab significantly increases. The reservoir water pressure affects the tensile stresses induced in the face slab by reducing the uplift movement of the concrete panels.Large horizontal axial forces are induced in the face slab due to out-of-phase and out-of-plane motions of the abutments. Although the normal movements of vertical joints are reduced due to the reservoir water confinement, the opening movements are still significant, and the local failure of construction joints is inevitable. 相似文献
Located on the Alpine-Himalayan earthquake belt, Iran is one of the seismically active regions of the world. Northern Iran, south of Caspian Basin, a hazardous subduction zone, is a densely populated and developing area of the country. Historical and instrumental documented seismicity indicates the occurrence of severe earthquakes leading to many deaths and large losses in the region. With growth of seismological and tectonic data, updated seismic hazard assessment is a worthwhile issue in emergency management programs and long-term developing plans in urban and rural areas of this region. In the present study, being armed with up-to-date information required for seismic hazard assessment including geological data and active tectonic setting for thorough investigation of the active and potential seismogenic sources, and historical and instrumental events for compiling the earthquake catalogue, probabilistic seismic hazard assessment is carried out for the region using three recent ground motion prediction equations. The logic tree method is utilized to capture epistemic uncertainty of the seismic hazard assessment in delineation of the seismic sources and selection of attenuation relations. The results are compared to a recent practice in code-prescribed seismic hazard of the region and are discussed in detail to explore their variation in each branch of logic tree approach. Also, seismic hazard maps of peak ground acceleration in rock site for 475- and 2,475-year return periods are provided for the region. 相似文献
More than 80% of sewage sludge (SS) produced in Iran is landfilled with high environmental impact. The chemical properties of SS produced from wastewater plants of cites of Arak, Isfahan, Kermanshah, Rasht, Saveh, Shiraz, Sanandaj, Tehran, Takestan, and Toyserkan were studied to assess the potential beneficial effects of their application to agricultural soil as sustainable SS management. The pH and EC values, total content and water-soluble concentration of nutrients and heavy metals, their water-extractable pools were determined, and their speciation was done through the NICA–Donnan model using the Visual MINTEQ software. Relatively high contents of N, P, and physiologically active cations indicated potential beneficial effects of SS for land application in the agro-ecosystems, whereas the heavy metal content depended on the SS production site, with higher levels found in the SS of the Arak and Saveh wastewater treatment plants. The pH value was the main factor controlling the metal speciation, with Cu and Pb having the highest affinity for the organic matter, and Zn and Mn being mainly present as free ions or inorganic species. Results showed that SS from different locations in Iran differed in their main chemical properties and elemental composition and that speciation analysis could be used to predict potential beneficial and harmful effects of SS, particularly upon the modeling of metal–organic complexes by the NICA–Donnan approach. Globally, our results confirmed that while the SS produced in Iran has potential suitable chemical properties for use in agriculture, their heavy metals load should not be ignored.