Seismotectonics of the Cyprian Arc   总被引：1，自引：0，他引：1  

Shimon Wdowinski  Zvi Ben-Avraham  Ronald Arvidsson  Goran Ekström 《Geophysical Journal International》2006,164(1):176-181

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Active tectonic morphology and submarine deformation of the northern Gulf of Eilat/Aqaba from analyses of multibeam data   总被引：1，自引：0，他引：1  

Gideon Tibor  Tina M. Niemi  Zvi Ben-Avraham  Abdallah Al-Zoubi  Ronnie A. Sade  John K. Hall  Gal Hartman  Emad Akawi  Abdelrahmem Abueladas  Rami Al-Ruzouq 《Geo-Marine Letters》2010,30(6):561-573

A high-resolution marine geophysical study was conducted during October-November 2006 in the northern Gulf of Aqaba/Eilat, providing the first multibeam imaging of the seafloor across the entire gulf head spanning both Israeli and Jordanian territorial waters. Analyses of the seafloor morphology show that the gulf head can be subdivided into the Eilat and Aqaba subbasins separated by the north-south-trending Ayla high. The Aqaba submarine basin appears starved of sediment supply, apparently causing erosion and a landward retreat of the shelf edge. Along the eastern border of this subbasin, the shelf is largely absent and its margin is influenced by the Aqaba Fault zone that forms a steep slope partially covered by sedimentary fan deltas from the adjacent ephemeral drainages. The Eilat subbasin, west of the Ayla high, receives a large amount of sediment derived from the extensive drainage basins of the Arava Valley (Wadi ’Arabah) and Yutim River to the north–northeast. These sediments and those entering from canyons on the south-western border of this subbasin are transported to the deep basin by turbidity currents and gravity slides, forming the Arava submarine fan. Large detached blocks and collapsed walls of submarine canyons and the western gulf margin indicate that mass wasting may be triggered by seismic activity. Seafloor lineaments defined by slope gradient analyses suggest that the Eilat Canyon and the boundaries of the Ayla high align along north- to northwest-striking fault systems—the Evrona Fault zone to the west and the Ayla Fault zone to the east. The shelf–slope break that lies along the 100 m isobath in the Eilat subbasin, and shallower (70–80 m isobaths) in the Aqaba subbasin, is offset by approx. 150 m along the eastern edge of the Ayla high. This offset might be the result of horizontal and vertical movements along what we call the Ayla Fault on the east side of the structure. Remnants of two marine terraces at 100 m and approx. 150 m water depths line the southwest margin of the gulf. These terraces are truncated by faulting along their northern end. Fossil coral reefs, which have a similar morphological appearance to the present-day, basin margin reefs, crop out along these deeper submarine terraces and along the shelf–slope break. One fossil reef is exposed on the shelf across the Ayla high at about 60–63 m water depth but is either covered or eroded in the adjacent subbasins. The offshore extension of the Evrona Fault offsets a fossil reef along the shelf and extends south of the canyon to linear fractures on the deep basin floor.  相似文献   

Common reflecting elements (CRE) ray tracing for the calculation of the global multi-offset time field     

Z. Koren  B. Gelchinsky 《Geophysical Journal International》1989,99(2):391-400

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Origin and role of major strike-slip transfers during plate collision in the central Mediterranean     

Claus-Dieter Reuther  Zvi Ben-Avraham  Mario Grasso 《地学学报》1993,5(3):249-257

Variations in the crustal structure along the northern African plate margin have caused different modes of collision with Eurasia. Lateral density variations along the central Mediterranean collision zone are expressed in a change of the angle of the downbending African Plate and lead to the formation of strike-slip transfers in these transition zones that are roughly perpendicular to the trend of the collisional zone. In some cases these transfer zones are developed into hinge faults, while in others they can be developed into transform faults. This process governs the segmentation of the collision zone in the central Mediterranean region south of the Maghrebian thrust belt in Tunisia and Sicily through the Calabrian Arc to the northeastern Hellenic Arc, extending further to the Cyprian Arc and to the Taurus-Zagros chain.  相似文献   

Planetary Wave Periods in <Emphasis Type="Italic">foF</Emphasis>2 Time Variations Based on Winter Data from Kaliningrad Station in 2008−2010     

Yu. N. Koren’kov  F. S. Bessarab  N. A. Koren’kova  V. S. Leshchenko 《Geomagnetism and Aeronomy》2018,58(3):420-429

The study presents the results of the analysis of the F2-layer critical frequency variations obtained for the winter periods of 2008–2010, during which sudden stratospheric warmings were observed. The data were obtained at Kaliningrad ionospheric station (54.6° N, 20° E) with the Parus digital ionosonde in standard sounding mode. The mean daily foF2 values were used in the analysis. The results of spectral analysis based on continuous wavelet transform showed that, during all of the warmings that occurred in 2008–2010, the foF2 time variations demonstrated the presence of wave processes with periods of approximately 5?6 days, as well as more extended processes with periods of ~10?13 and 23?30 days. These periods coincide with the characteristic periods of planetary waves observed in the mesosphere during sudden stratospheric warmings, while the 13- and 30-day periods can be conditioned by the influence of the Sun.  相似文献   

Slowness-domain kinematical characteristics for horizontally layered orthorhombic media. Part II: Pre-critical slowness match     

Zvi Koren  Igor Ravve 《Geophysical Prospecting》2019,67(5):1134-1162

Part II of this paper is a direct continuation of Part I, where we consider the same types of orthorhombic layered media and the same types of pure-mode and converted waves. Like in Part I, the approximations for the slowness-domain kinematical characteristics are obtained by combining power series coefficients in the vicinity of both the normal-incidence ray and an additional wide-angle ray. In Part I, the wide-angle ray was set to be the critical ray (‘critical slowness match’), whereas in Part II we consider a finite long offset associated with a given pre-critical ray (‘pre-critical slowness match’). Unlike the critical slowness match, the approximations in the pre-critical slowness match are valid only within the bounded slowness range; however, the accuracy within the defined range is higher. Moreover, for the pre-critical slowness match, there is no need to distinguish between the high-velocity layer and the other, low-velocity layers. The form of the approximations in both critical and pre-critical slowness matches is the same, where only the wide-angle power series coefficients are different. Comparing the approximated kinematical characteristics with those obtained by exact numerical ray tracing, we demonstrate high accuracy. Furthermore, we show that for all wave types, the accuracy of the pre-critical slowness match is essentially higher than that of the critical slowness match, even for matching slowness values close to the critical slowness. Both approaches can be valuable for implementation, depending on the target offset range and the nature of the subsurface model. The pre-critical slowness match is more accurate for simulating reflection data with conventional offsets. The critical slowness match can be attractive for models with a dominant high-velocity layer, for simulating, for example, refraction events with very long offsets.  相似文献   

Moveout approximation for horizontal transversely isotropic and vertical transversely isotropic layered medium. Part I: 1D ray propagation‡     

Igor Ravve  Zvi Koren 《Geophysical Prospecting》2010,58(4):577-597

Anisotropy in subsurface geological models is primarily caused by two factors: sedimentation in shale/sand layers and fractures. The sedimentation factor is mainly modelled by vertical transverse isotropy (VTI), whereas the fractures are modelled by a horizontal transversely isotropic medium (HTI). In this paper we study hyperbolic and non‐hyperbolic normal reflection moveout for a package of HTI/VTI layers, considering arbitrary azimuthal orientation of the symmetry axis at each HTI layer. We consider a local 1D medium, whose properties change vertically, with flat interfaces between the layers. In this case, the horizontal slowness is preserved; thus, the azimuth of the phase velocity is the same for all layers of the package. In general, however, the azimuth of the ray velocity differs from the azimuth of the phase velocity. The ray azimuth depends on the layer properties and may be different for each layer. In this case, the use of the Dix equation requires projection of the moveout velocity of each layer on the phase plane. We derive an accurate equation for hyperbolic and high‐order terms of the normal moveout, relating the traveltime to the surface offset, or alternatively, to the subsurface reflection angle. We relate the azimuth of the surface offset to its magnitude (or to the reflection angle), considering short and long offsets. We compare the derived approximations with analytical ray tracing.  相似文献   

Model calculations of the total electron content for the system of GPS satellites     

V. A. Surotkin  V. V. Klimenko  Yu. N. Koren’kov 《Geomagnetism and Aeronomy》2011,51(5):681-687

The numerical global self-consistent model of the Earth’s thermosphere, ionosphere and protonosphere (GSM TIP), which makes it possible to calculate all the main parameters of the near-Earth plasma, is used to calculate the total electron content (TEC). Calculations have been performed along the radiosignal propagation trajectory between a surface receiving point and a GPS satellite. The TEC value calculated from the satellite data have been compared with such a “true model” TEC value for magnetically quiet conditions of the spring equinox and moderate solar activity. The relative errors in determining the satellite data-based TEC for two European (Troms have been calculated. It has been indicated that an increase in the number of satellites not always results in an increase in accuracy of the TEC value measured on satellites.  相似文献   

Formation of continental flood volcanism — The perspective of setting of melting     

Zvi Garfunkel   《Lithos》2008,100(1-4):49-65

Models of continental flood basalt (CFB) formation are evaluated by examining their implications for the setting, mainly temperature and depth, of melting which is assumed to result from adiabatic decompression. Most attractive is the model of melting in upwelling bodies (probably plume heads) rising to the base of the continental lithosphere. This constrains the melting to 120–150 km or deeper (continental lithospheric thickness) and thus the plume potential temperatures to ≥ 300 °C higher than ambient mantle. The primary melts should be hot, MgO-rich, modified during ascent, and assimilate components of the lithosphere, which can provide the continental-like geochemical signature of many CFB. Circulation within the upwellings and presence of eclogite patches also influence magma generation and composition. Dehydration melting when plumes heat the lowermost lithosphere can generate CFB only if the source region contains ca. 15% hydrous minerals beneath the entire area covered by flood volcanics, which is difficult to justify. On the other hand, assimilation of “continental” chemical components from large parts of the lithosphere does not require such extreme metasomatism. Decompression melting under strongly thinned rifted lithosphere requires lower potential temperatures of the rising material and lesser modification of the primary magmas than the plume head model of CFB formation. Available observations do not support the contemporaneity of flood volcanism with rifts having the required sizes and histories, but more information is needed to further test this model. On the other hand, magma production can assist rift initiation and lithospheric rupture, so subsequent thinning can explain the common formation of volcanic rifted margins immediately following CFB emplacement. Ancient LIP should record the same processes as seen in young CFB.  相似文献   

An analysis of type III burst occurrence in spotless regions     

C. Zanelli  P. Zlobec  U. Koren 《Solar physics》1980,65(2):387-396

An analysis has been carried of the correlation of the occurrence of type III bursts and flares in spotless regions over the past ten years. As a comparison, the same study has been performed also for flares covering major sunspot umbrae (i.e. in magnetic conditions presumably opposite to the above).The results show a very low correlation of the former flares with type III bursts (8%) and a higher than average value for the latter flares (36% against the normally accepted 25%). Thus an important role of the ambient magnetic field on the generation of type III events seems well established.The effect of the presence of surges and of rapid brightness rises (flash-phases) on the correlation with these bursts has been examined: both features appear to improve the correlation.Some considerations regarding the results of other researches as compared to this one are outlined.  相似文献