The Spectrum and Dips of RE 0751+14: A Joint Evaluation of ROSAT and ASCA Archival Data     

Ümit Kiziloğlu  Altan Baykal  Murat Alev  Ersin Göğüş 《Astrophysics and Space Science》1998,259(2):191-203

Using archival ASCA and ROSAT observations of RE 0751+14, X- ray energy spectra, pulse profiles and the results of pulse timing analysis are presented. The energy spectra are well-fitted by a blackbody model at low energy and a Raymond-Smith model at high energy, together with a partial covering absorber. A fluorescence emission line at 6.4 keV with an equivalent width ∼ 220 eV was resolved for the first time. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Asteroseismic modelling of the solar-like star β Hydri     

G. Doğan  I. M. Brandão  T. R. Bedding  J. Christensen-Dalsgaard  M. S. Cunha  H. Kjeldsen 《Astrophysics and Space Science》2010,328(1-2):101-104

We present the results of modelling the subgiant star β Hydri using seismic observational constraints. We have computed several grids of stellar evolutionary tracks using the Aarhus STellar Evolution Code (ASTEC, Christensen-Dalsgaard in Astrophys. Space Sci. 316:13, 2008a), with and without helium diffusion and settling. For those models on each track that are located at the observationally determined position of β Hydri in the Hertzsprung-Russell (HR) diagram, we have calculated the oscillation frequencies using the Aarhus adiabatic pulsation package (ADIPLS, Christensen-Dalsgaard in Astrophys. Space Sci. 316:113, 2008b). Applying the near-surface corrections to the calculated frequencies using the empirical law presented by Kjeldsen et al. (Astrophys. J. 683:L175, 2008), we have compared the corrected model frequencies with the observed frequencies of the star. We show that after correcting the frequencies for the near-surface effects, we have a fairly good fit for both l=0 and l=2 frequencies. We also have good agreement between the observed and calculated l=1 mode frequencies, although there is room for improvement in order to fit all the observed mixed modes simultaneously.  相似文献   

CCD BV and 2MASS photometric study of the open cluster NGC 1513     

S. Bilir  T. Güver  I. Khamitov  T. Ak  S. Ak  K. B. Coşkunoğlu  E. Paunzen  E. Yaz 《Astrophysics and Space Science》2010,326(1):139-150

We present CCD BV and JHK _s 2MASS photometric data for the open cluster NGC 1513. We observed 609 stars in the direction of the cluster up to a limiting magnitude of V∼19 mag. The star-count method showed that the centre of the cluster lies at α ₂₀₀₀=04 ^h 09 ^m 36 ^s , δ ₂₀₀₀=49°28^′43^″ and its angular size is r=10 arcmin. The optical and near-infrared two-colour diagrams revealed the colour excesses in the direction of the cluster as E(B−V)=0.68±0.06, E(J−H)=0.21±0.02 and E(J−K _s )=0.33±0.04 mag. These results are consistent with normal interstellar extinction values. Optical and near-infrared Zero Age Main-Sequences (ZAMS) provided an average distance modulus of (m−M)₀=10.80±0.13 mag, which can be translated into a distance of 1440±80 pc. Finally, using Padova isochrones we determined the metallicity and age of the cluster as Z=0.015±0.004 ([M/H]=−0.10±0.10 dex) and log (t/yr)=8.40±0.04, respectively.  相似文献   

Field evidences of secondary surface ruptures occurred during the 20 February 1956 Eskişehir earthquake in the NW Anatolia     

Faruk Ocakoğlu  Sanem Açikalin 《Journal of Earth System Science》2010,119(6):841-851

Surface rupture and source fault of the 20 February 1956 Eskişehir earthquake have been a matter of debate that potentially contributes towards the understanding of the active deformation and seismic risk in the highly populated NW Anatolia. Field observations on the two fault segments (namely Kavacık and Uludere faults) in the north of the Eskişehir graben revealed evidences of co-seismic surface rupture and mass movements during the Eskişehir earthquake. Surface rupture was observed as a 2.5m wide, a 100m long and ca. 20 cm deep asymmetric depression in the Gümüşlü valley, 2 km east of the Uludere village. A trench dug on this depression confirms a prominent high-angle south dipping fault (dominantly left lateral strike slip) and two faint north-dipping antithetics as clear noticeable shear zones in organic-rich thick soil. Mass failures are particularly observed in spring depressions filled with loose torrent and carbonaceous material in front of the fault scarp. Some rock slides of several tens of meters in size that obviously require significantly high ground shaking were also developed on steep fault scarps. The orientation of the principal stress tensor as deduced from the surface rupture of the Eskişehir earthquake displays clear inconsistency with the geometry of prominent faults in the area. We concluded that this disagreement may be explained by a curved surface rupture. The western and eastern tips of this rupture are EW trending and the probable NW-running part in the middle would correspond to the bounding zone between two right-stepping faults.  相似文献   

Late Ordovician climbing‐dune cross‐stratification: a signature of outburst floods in proglacial outwash environments?     

JEAN‐FRANÇOIS GHIENNE  FLAVIA GIRARD  JULIEN MOREAU  JEAN‐LOUP RUBINO 《Sedimentology》2010,57(5):1175-1198

Climbing dune‐scale cross‐statification is described from Late Ordovician paraglacial successions of the Murzuq Basin (SW Libya). This depositional facies is comprised of medium‐grained to coarse‐grained sandstones that typically involve 0·3 to 1 m high, 3 to 5 m in wavelength, asymmetrical laminations. Most often stoss‐depositional structures have been generated, with preservation of the topographies of formative bedforms. Climbing‐dune cross‐stratification related to the migration of lower‐flow regime dune trains is thus identified. Related architecture and facies sequences are described from two case studies: (i) erosion‐based sandstone sheets; and (ii) a deeply incised channel. The former characterized the distal outwash plain and the fluvial/subaqueous transition of related deltaic wedges, while the latter formed in an ice‐proximal segment of the outwash plain. In erosion‐based sand sheets, climbing‐dune cross‐stratification results from unconfined mouth‐bar deposition related to expanding, sediment‐laden flows entering a water body. Within incised channels, climbing‐dune cross‐stratification formed over eddy‐related side bars reflecting deposition under recirculating flow conditions generated at channel bends. Associated facies sequences record glacier outburst floods that occurred during early stages of deglaciation and were temporally and spatially linked with subglacial drainage events involving tunnel valleys. The primary control on the formation of climbing‐dune cross‐stratification is a combination between high‐magnitude flows and sediment supply limitations, which lead to the generation of sediment‐charged stream flows characterized by a significant, relatively coarse‐grained, sand‐sized suspension‐load concentration, with a virtual absence of very coarse to gravelly bedload. The high rate of coarse‐grained sand fallout in sediment‐laden flows following flow expansion throughout mouth bars or in eddy‐related side bars resulted in high rates of transfer of sands from suspension to the bed, net deposition on bedform stoss‐sides and generation of widespread climbing‐dune cross‐stratification. The later structure has no equivalent in the glacial record, either in the ancient or in the Quaternary literature, but analogues are recognized in some flood‐dominated depositional systems of foreland basins.  相似文献   

A combined hydrologic and hydraulic modeling approach for testing efficiency of structural flood control measures   总被引：3，自引：2，他引：1  

Gülay Onuşluel Gül  Nilgün Harmancıoğlu  Ali Gül 《Natural Hazards》2010,54(2):245-260

The necessity of estimating the degree and spatial extent of positive impacts with regard to protecting communities and properties through potential flood control projects can be considered one of the main reasons for performing flood modeling. This paper presents an overall systematic approach based on the simulation of some extreme event conditions, using a hydrological model to generate the resulting river flows and then using a hydraulic modeling exercise to decide upon floodplain evolution in the case-study area, Bostanli river basin, which has been under the threat of flooding for many years. The potential serviceability of the planned Bostanli Dam in the study area was examined by using the HEC-HMS and HEC-RAS modeling tools, both integrated with GIS functions for spatial operations. The results indicate that the dam construction as planned would have a somewhat positive impact as a potential flood control measure, since it seems to decrease the flood peaks of 68.9 and 158.7 m³/s (that would potentially be generated by 100- and 500-year storm events under current conditions) to 65.5 and 150.7 m³/s (when the dam is in operation), respectively. However, this seems to contribute little to the overall flood mitigation performance in the basin.  相似文献   

Designing a flood forecasting and inundation-mapping system integrated with spatial data infrastructures for Turkey     

Halil Akıncı  Sevsin Erdoğan 《Natural Hazards》2014,71(1):895-911

Turkey currently lacks a fully functional flood forecasting system (FFS). However, the studies necessary for establishing such a system are still being performed by the Turkish State Meteorological Service. The main purpose of this study was to determine the technical architecture of the FFS intended to be developed in Turkey and to design a flood forecasting and inundation-mapping system integrated with spatial data infrastructure (SDI). Because SDIs provide interoperability among the institutions by enabling collective use of data and services, this enables decision makers to take correct and rapid decisions regarding the forecasting. In the design of the system, the Web services architecture presented by the open geospatial consortium that develops international standards for SDI realizations was taken as a basis. Designed with flexibility and an expandable architecture, the system will enable instant access to up-to-date data from different institutions through Web services and meets the requirements of a real-time FFS. While the criteria requiring the expansion of the designed system were explained, its implementation was left for future studies.  相似文献   

Pushover and nonlinear time history analysis evaluation of a RC building collapsed during the Van (Turkey) earthquake on October 23, 2011     

Özlem Çavdar  Alemdar Bayraktar 《Natural Hazards》2014,70(1):657-673

The nonlinear seismic behavior of a collapsed reinforced concrete (RC) residential building in the city of Van in Turkey is investigated by the static pushover and nonlinear time history analyses. The selected RC structure was designed according to the 1975 version of Turkish Earthquake Code (TEC-1975). The building had experienced heavy damage, and it was demolished in the Van earthquake on October 23, 2011. The 2007 version of Turkish Earthquake Code (TEC-2007) is considered for the assessing seismic performance evaluation of the selected RC building. The RC structure presents collapse performance level under the earthquake loads. Besides, the analytical solutions show that different performance levels for the sections are obtained from the pushover and nonlinear time history methods.  相似文献   

Volcanic facies and mineral chemistry of Tertiary volcanics in the northern part of the Eastern Pontides,northeast Turkey: implications for pre-eruptive crystallization conditions and magma chamber processes     

Cem Yücel  Mehmet Arslan  İrfan Temizel  Emel Abdioğlu 《Mineralogy and Petrology》2014,108(3):439-467

Tertiary volcanics in the northern zone of the Eastern Pontides are characterized by subaerial and shallow-subaqueous facieses, and are divided into three volcanic suites: Eocene aged (1) basalt-trachybasalt-basaltic trachyandesite (BTB) and (2) trachyte-trachyandesite (TT), and Miocene aged (3) basanite-tephrite (BT) suites. Clinopyroxene is a common phase in all three volcanic suites, and has different compositions with Mg# varying from 0.57 to 0.91 in BTB suite and 0.57–0.84 in TT suite to 0.65–0.90 in BT suite. Feldspars in all suites generally exhibit wide range of compositions from sanidine to albite or anorthite and have weak normal and reverse compositional zoning. Olivines in BTB and BT suites have Fo_60–92. Hornblendes in BTB, TT and BT suites are commonly magnesio-hastingsite and rare pargasite in composition (Mg#: 0.67–0.90). Brown mica is mainly phlogopite with Mg# ranging from 0.56 to 0.92 in the BTB suite, 0.59–0.84 in the TT suite, and 0.75–0.93 in the BT suite. Analcime is present only in the BT suite rocks. Fe–Ti oxides in all suites are mainly composed of magnetite and titanomagnetite. Textural petrographic and mineral chemical data suggest that magmas had undergone hydrous and anhydrous crystallizations in deep-, mid-, and shallow-crustal magma chambers. Clinopyroxene thermobarometric calculations show that Eocene magma chambers were characterized by temperature ranging from 1,100 to 1,244 °C and pressure ranging from 1.84 to 5.39 kbar. Similarly, the Miocene magma chambers were characterized by temperature ranging from 1,119 to 1,146 °C and pressure ranging from 4.23 to 4.93 kbar. Hornblende thermobarometry, oxygen fugacity, and hygrometer reveal that the crystallization temperature of Eocene volcanics range from 956 to 959 °C at pressure ranging from 6.49 to 6.52 kbar. Eocene volcanics were characterized by water content ranging from 7.83 to 8.57 wt.% and oxygen fugacity of 10^?9.36 to 10^?9.46 (ΔNNO+2). Miocene volcanics had crystallization temperature ranging from 970 to 978 °C at pressure ranging from 8.70 to 9.00 kbar with water content ranging from 8.04 to 8.64 wt.% and oxygen fugacity ranging from 10^?8.75 to 10^?8.87 (ΔNNO+2). Brown mica thermobarometric data show that Eocene volcanics were characterized by relatively high oxygen fugacity varying from 10^-10.32 to 10^-12.37 (HM) at temperature ranging from 858 to 953 °C and pressure ranging from 1.08 to 1.41 kbar. Miocene volcanics were crystallized at highly oxidized conditions, which are characterized by high oxygen fugacity of 10^?12.0 (HM) at temperature of 875 °C and pressure of 2.09 kbar. The wide range of obtained temperatures for clinopyroxenes of the suites denotes that the equilibration of clinopyroxene crystals initiates from depth until close to the surface before magma eruption. The compositional variations, resorbed core and reverse zoning patterns in clinopyroxene phenocrysts, as well as variable pressures of crystallization, further indicate that the magmas that formed the suites were polybaric in origins and were composite products of more than one petrogenetic stage. The observed range of phenocryst assemblage and different compositional trends possibly originated from fractionation of magmas with different initial water contents under variable pressures of crystallization. The repeated occurrence of magmas from different suites during a single period of activity suggests that the magmatic system consists of several conduit systems and that magma reservoirs are dispersed at different levels of crustal magma chambers.  相似文献   

Issues with the earthquake vulnerability of Istanbul     

Eser Çaktı 《Natural Hazards》2013,68(1):227-228

Istanbul today is probably unique in the world not only in terms of the recognition of its earthquake risk by its inhabitants and administrators, but also in terms of significant steps taken in a such a short time toward the mitigation of its earthquake vulnerabilities. This paper, however, deals with the issues that still remain unattended.  相似文献