The Effects of the Earth’s Curvature on Gravity and Geoid Calculations   总被引：1，自引：0，他引：1  

Hasan??av?akEmail author 《Pure and Applied Geophysics》2012,169(4):733-740

While it is obvious that large-scale gravity studies should account for the sphericity of the Earth, each case should be examined. If a geometry model is very large for the 3D-gravity calculation, it cannot be correctly defined in Cartesian coordinates. Because of the Earth’s curvature it is necessary to use spherical coordinates, the importance of which is shown in this paper. The calculation of the gravity for a cylinder reveals, 1 m above the center of the cylinder, a relative difference of 13% between the models with Cartesian and spherical coordinates.  相似文献   

Sea level variability at Antalya and Mente? tide gauges in Turkey: atmospheric, steric and land motion contributions     

Mehmet Simav  Hasan Yildiz  Ali Türkezer  Onur Lenk  Emin ?zsoy 《Studia Geophysica et Geodaetica》2012,56(1):215-230

Sea level trends and interannual variability at Antalya and Menteş tide gauges are investigated during the 1985–2001 period, quantifying the roles of atmospheric, steric and local land motion contributions. Tide gauge sea level measurements, temperature/salinity climatologies and GPS data are used in the analyses and the results are compared with the output of a barotropic model forced by atmospheric pressure and wind. The overall sea level trends at two tide gauges collocated with GPS are in the range of 5.5 to 7.9 mm/yr during the study period, but showing different behaviour in the sub-periods 1985–1993 and 1993–2001 due to variations in the contributing factors both in space and time. After the removal of the atmospheric forcing and steric contribution from sea level records, the resulting trends vary between 1.9 to 4.5 mm/yr in Antalya and −1.2 to −11.6 mm/yr in Menteş depending on the period considered. Vertical land movement estimated from GPS data seems to explain the high positive residual trend in Antalya during the whole period. On the other hand, the source of the highly negative sea level trend of about −14 mm/yr in Menteş during 1985–1993 could not be resolved with the available datasets. Interannual variability of wind and atmospheric pressure appear to dominate the sea level at both tide gauges during the study period. Atmospheric and steric contributions together account for ∼50% of the total sea level variance at interannual time scales. Mass induced sea level variations which were not considered in this study may help to close the sea level trend budgets as well as to better explain the interannual sea level variance.  相似文献   

A study of regional gravity field recovery from GOCE vertical gravity gradient data in the Auvergne test area using collocation     

Hasan Yildiz 《Studia Geophysica et Geodaetica》2012,56(1):171-184

Gravity field and steady-state Ocean Circulation Explorer (GOCE) is the first satellite mission that observes gravity gradients from the space, to be primarily used for the determination of high precision global gravity field models. However, the GOCE gradients, having a dense data distribution, may potentially provide better predictions of the regional gravity field than those obtained using a spherical harmonic Earth Geopotential Model (EGM). This is investigated in Auvergne test area using Least Squares Collocation (LSC) with GOCE vertical gravity gradient anomalies (T_zz), removing the long wavelength part from EGM2008 and the short wavelength part by residual terrain modelling (RTM). The results show that terrain effects on the vertical gravity gradient are significant at satellite altitude, reaching a level of 0.11 E?tv?s unit (E.U.) in the mountainous areas. Removing the RTM effects from GOCE T_zz leads to significant improvements on the LSC predictions of surface gravity anomalies and quasigeoid heights. Comparison with ground truth data shows that using LSC surface free air gravity anomalies and quasi-geoid heights are recovered from GOCE T_zz with standard deviations of 11 mGal and 18 cm, which is better than those obtained by using GOCE EGMs, demonstrating that information beyond the maximal degree of the GOCE EGMs is present. Investigation of using covariance functions created separately from GOCE T_zz and terrestrial free air gravity anomalies, suggests that both covariance functions give almost identical predictions. However, using covariance function obtained from GOCE T_zz has the effect that the predicted formal average error estimates are considerably larger than the standard deviations of predicted minus observed gravity anomalies. Therefore, GOCE T_zz should be used with caution to determine the covariance functions in areas where surface gravity anomalies are not available, if error estimates are needed.  相似文献   

Impact of climate change on floodplain inundation and hydrological connectivity between wetlands and rivers in a tropical river catchment   总被引：1，自引：0，他引：1       下载免费PDF全文

Fazlul Karim  Cuan Petheram  Steve Marvanek  Catherine Ticehurst  Jim Wallace  Masud Hasan 《水文研究》2016,30(10):1574-1593

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Variation of modal parameters of a highway bridge extracted from six earthquake records     

Hugo C. Gomez  Hasan S. Ulusoy  Maria Q. Feng 《地震工程与结构动力学》2013,42(4):565-579

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Environmental isotopic evaluation of the springs located in Kazan Trona basin in Central Turkey     

Sebnem Arslan  Hasan Yazicigil 《Journal of the Geological Society of India》2012,80(5):707-714

Kazan Trona ore field, the second discovered deposit in Central Turkey, is planned to be extracted by solution mining technology. Understanding the hydrogeology of the springs in such an area is vital since they can be affected during mining operations. The aim of this study is to provide an isotopic approach by utilizing environmental isotope techniques to the springs in the study area, thereby, to enhance the understanding of their occurrence by complementing the previous geochemical studies. Here, the isotopic signatures and the recharge elevations of the springs are demonstrated together with their field parameters. The relationship between ??D and ??¹⁸O suggest strong evaporation in some of the samples after recharge. For those springs, the unmodified signatures were determined and the recharge elevations were calculated to be between 1100 and 1248 m. These elevations correspond to Incirlik and Asmalidere Members and upper Neogene units. The relationship between Tritium and Electrical Conductivity suggested that SP-6, SP-3 and SP-4 have shallow circulation when compared to SP-7 having both the lowest tritium and highest EC value. This finding is in accordance with the geochemical data, which suggests SP-7 emerges from the deeper, older groundwater present above the trona deposit.  相似文献   

System identification of a building from multiple seismic records     

Hasan S. Ulusoy  Maria Q. Feng  Paul J. Fanning 《地震工程与结构动力学》2011,40(6):661-674

This paper describes the identification of finite dimensional, linear, time‐invariant models of a 4‐story building in the state space representation using multiple data sets of earthquake response. The building, instrumented with 31 accelerometers, is located on the University of California, Irvine campus. Multiple data sets, recorded during the 2005 Yucaipa, 2005 San Clemente, 2008 Chino Hills and 2009 Inglewood earthquakes, are used for identification and validation. Considering the response of the building as the output and the ground motion as the input, the state space models that represent the underlying dynamics of the building in the discrete‐time domain corresponding to each data set are identified. The time‐domain Eigensystem Realization Algorithm with the Observer/Kalman filter identification procedure are adopted in this paper, and the modal parameters of the identified models are consistently determined by constructing stabilization diagrams. The four state space models identified demonstrate that the response of the building is amplitude dependent with the response frequency and damping, being dependent on the magnitude of ground excitation. The practical application of this finding is that the consistency of this building response to future earthquakes can be quickly assessed, within the range of ground excitations considered (0.005g–0.074g), for consistency with prior response—this assessment of consistent response is discussed and demonstrated with reference to the four earthquake events considered in this study. Inclusion of data sets relating to future earthquakes will enable the findings to be extended to a wider range of ground excitation magnitudes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Deterministic approach to the seismic hazard of dam sites in Kızılırmak basin,Turkey     

Evren Seyrek  Hasan Tosun 《Natural Hazards》2011,59(2):787-800

Dams constructed on the seismically active regions have a high-risk potential for downstream life and property. Strong ground motion can result in instability of the dam and strength loss of foundation. Active faults within the foundation of dam have the potential to cause damaging displacement of the structures. Appropriate design measures should be considered to obtain rational solution to the problem of catastrophic release of water from the reservoir, and especially to resist earthquake loads. Safety concerns for dams under the earthquake loads involve the seismic hazard evaluation of dam site for the overall stability of structure. Various types of analyses can be used, ranging from a simplified analysis to more complex procedures based on ground motion parameters and response spectra. This paper briefly evaluates seismic hazard analyses for dam structures, and introduces the analyses for thirty-six dams with height ranging from 15 to 195 m in Kızılırmak basin, Turkey. The seismic hazard analyses have indicated that peak ground acceleration varies within a wide range (0.09–0.45 g) for the dam sites of the basin.  相似文献   

Indirect Effects of Salinity and Temperature on Kuwait’s Shrimp Stocks     

James Marcus Bishop  Weizhong Chen  Adel Hasan Alsaffar  Hussain Mahmoud Al-Foudari 《Estuaries and Coasts》2011,34(6):1246-1254

Discharge of the Shatt Al-Arab is believed to be a dominating component of the northern Arabian Gulf’s ecology and largely responsible for productivity of Kuwait’s fisheries. With major construction of dams on the Tigris and Euphrates Rivers in Turkey, river discharge has been substantially reduced, and flooding essentially eliminated. We attempted to relate river flow and shrimp landings indirectly by correlating 19 years of salinity and temperature data from Kuwait’s waters with corresponding annual shrimp landings. For green tiger prawns (Penaeus semisulcatus), the combination of October salinities and January temperatures provided the best correlation (r = 0.67) with landings in the following shrimping season. For the combined landings of jinga and kiddi shrimps (Metapenaeus affinis and Parapenaeopsis stylifera, respectively), December salinity during season and May temperature prior to season resulted in the best correlation (r = 0.87). Landings of these two species also correlated well with spring and summer temperatures. Under normal conditions, late winter or early spring temperatures prior to fishing season influence recruitment of the green tiger prawn, whereas December salinities during harvest season influence the abundance of jinga–kiddi shrimps. With further reductions in the Shatt Al-Arab discharge and the elimination of flood events, Kuwait’s shrimp landings will most likely decrease over time.  相似文献   

Tectonic implications of transtensional supradetachment basin development in an extension‐parallel transfer zone: the Kocaçay Basin,western Anatolia,Turkey     

Hasan Sözbilir  Bilal Sarι  Bora Uzel  Ökmen Sümer  Serkan Akkiraz 《Basin Research》2011,23(4):423-448

The Kocaçay Basin (KÇB) is a key area in western Anatolia – a well‐known extended terrane where regional segmentation has received limited attention – for investigating strike‐slip faults kinematically linked to detachment faults. In this paper, we present results of an integrated sedimentologic, stratigraphic, and structural study of Miocene alluvial fan/fan‐delta/lacustrine deposits that accumulated in the KÇB, a NE‐trending basin with connections to the Menderes Metamorphic Core Complex (MCC). We mapped and evaluated most of the key faults in the KÇB, many for the first time, and recognised different deformation events in the study area near the E margin of the MCC. We also present field evidence for kinematic connections between low‐angle normal and strike‐slip faults which were developed in an intermittently active basement‐involved transfer zone in western Anatolia. We find that the KÇB contains a detailed record of Miocene transtensional sedimentation and volcanism that accompanied exhumation of the MCC. Structural data reveal that the basin was initially formed by transtension (D1 phase) and subsequently uplifted and deformed, probably as a result of early Pliocene wrench‐ to extension‐dominated deformation (D2 phase) overprinted by Plio‐Quaternary extensional tectonics (D3 phase). These results are consistent with progressive deformation wherein the axis of maximum extension remained in the horizontal plane but the intermediate and maximum shortening axes switched position in the vertical plane. Combining our results with published studies, we propose a new working hypothesis that the KÇB was a transtensional supradetachment basin during the Miocene. The hypothesis could provide new insights into intermittently active extension‐parallel zone of weakness in western Anatolia.These results also suggest that the termination of low‐angle normal fault systems within an extension parallel transfer zone may have resulted in a transtensional depressions which are different from classical supradetachment basins with respect to the sedimentation and deformational pattern of the basin infills.  相似文献