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Faris M.,Tanta University | Ahmad F.,University of Jordan | Powell J.H.,Natural Resources Authority NRA
GeoArabia | Year: 2015

The first detailed calcareous nannofossil and planktonic foraminiferal biostratigraphic and integrated lithofacies analyses of the Eocene-Oligocene transition at the Qa' Faydat ad Dahikiya area in the Eastern Desert of Jordan, on the border with Saudi Arabia, is presented. Three calcareous nannofossil zones namely: Discoaster saipanensis (NP17), Chiasmolithus oamaruensis (NP18) and Ericsonia subdisticha (NP21), and three planktonic foraminiferal zones: upper part of Truncorotaloides rohri (E13), Globigerinatheka semiinvoluta (E14) and Cassigerinella chipolensis/ Pseudohastigerina micra (O1) are identified. Calcareous nannofossil bioevents recorded in the present study show numerous discrepancies with the Standard biostratigraphic zonal schemes to detect the Middle/Upper Eocene boundary (e.g. the highest occurrences (HOs) of Chiasmolithus solitus, C. grandis, and lowest occurrences (LOs) of C. oamaruensis, Isthmolithus recurvus are not considered reliable markers for global correlation). The Middle/Upper Eocene boundary occurs in the current study above the extinctions of large muricate planktonic foraminifera (large Acarinina and Truncorotaloides spp.) which coincide within the equivalent calcareous nannofossil NP18 Zone. These microplanktonic bioevents seem to constitute more reliable markers for the base of the Upper Eocene in different provinces. The uppermost portion of the Middle Eocene is characterized by an observed drop in faunal content and, most likely, primarily denotes the effect of the major fall in eustatic sea level. A major unconformity (disconformity) marked by a mineralized hardground representing a lowstand is recorded in the present study at the Eocene-Oligocene transition that reveals an unexpected ca. 2.1 Myr duration, separating Eocene (NP18/E14 zones) from Oligocene (NP21/O1 zones). Furthermore, the microfossil turnover associated with a rapid decline of the microfossil assemblages shows a distinct drop in diversity and abundance towards the Eocene/Oligocene unconformity and is associated with a sharp lithological break marked, at the base, by a mineralized hardground representing a major sequence boundary. These bioevents, depositional sequences and the depositional hiatus correlate well with different parts of the Arabian and African plates, but the magnitude of the faunal break differs from place to place as a result of intraplate deformation during the regional Oligocene regression of Neo-Tethys on the northern Arabian Plate. The presence of the Lower Oligocene shallow-marine calcareous planktonic assemblages in the study area indicate that communication between the eastern and western provinces of the western Neo-Tethys region still existed at this time. Source


Fandi M.,Natural Resources Authority NRA | Alyazjeen T.,Natural Resources Authority NRA
Arabian Journal of Geosciences | Year: 2011

Structural remains of the site refer to clear evidence of large historical earthquakes that strongly affected the site during the last 2,000 years. In this work,we present a study of dynamic behavior of Jabal Al-Qalaasite as well as the dynamic behavior of some archeologicalremaining structures on the site using the free oscillation ofsurface geology and structures. In this study, seven groundrecords were obtained along approximately east – westprofile, crossing the top of the hill zone. Structural recordswere obtained at three selected structures followingadministrative requirements. Allstructural records wereconducted at the top level of each structure using threecomponents seismometer of 2 Hz free oscillation. Horizontalsensors were oriented with respect to the longitudinaland transverse direction of structural horizontal projection.Used orientations are essential for obtaining both structuralfundamental modes in the longitudinal and transversedirections. Moreover, damping factors for each horizontalfundamental mode were calculated based on the obtainedFFTspectrums of each orientation using half-width bandmethod. Analysis shows that all inspected structures in thisstudy areof high frequency. Interesting results of recordsobtained at the Umayyad Alcazar, relatively low dampingfactor as well as sharp fundamental modes in its bothlongitudinal and transverse directions are recorded at thiswell-preserved old historical structure. Free-field recordswere conducted along approximately E-W profile crossingthe top of the hill. The purpose of this methodology is toidentify the variation of H/V amplification along with, andto find out the topographical effect of this convexgeological feature. Obtained H/V ground resonance dominantmodes as well as the site amplification reflect well thetopographical effect of the citadel hill zone. Amplificationgradually increases to reach 4.5 at the top of the hill. © Saudi Society for Geosciences 2011. Source


Fandi M.,Natural Resources Authority NRA | Alyazjeen T.,Natural Resources Authority NRA
Arabian Journal of Geosciences | Year: 2013

The potential to destroy any structure during earthquakes depends on the structural design, vulnerability rating, percentage of structural elongation as compared with the natural quiet conditions, the dynamic characteristics of structure itself, as well as the dynamic characteristics of the site. Thus, factors related to the dynamic characteristics of structure and the dynamic characteristics of the site are necessary in the design of resistant structures against earthquakes. In this study, recordings of free oscillation were made directly on 18 selected structures in the urban city of Aqaba, which represent the structural culture of the city and the whole Jordan in general. Ground ambient vibration records were conducted at 18 nearby location at a few meters away from each structure. Records were conducted during the maximal cultural activities using three-component seismometer of 2 Hz free oscillation. Analytical results of records obtained on structures, has given the following equation: f = 18/N, where f, is the fundamental mode of structure and N, is the number of stories. All structural records were conducted at the top level of each structure except at Shmesani 4 and 7. Horizontal sensors were oriented with respect to the longitudinal and transverse direction of structural horizontal projection. Damping factors for each structural longitudinal and transverse fundamental mode were calculated based on the obtained FFT spectrums of each orientation using half-width band method. Analysis of obtained records on structures in Aqaba show that most of them are of short periodic structures except a few multi-story tall buildings. Most of the results obtained on structures refer to damping factors that range between 0. 05 and 0. 208. Mathematical relation derived from this study above, in addition to the actual calculated damping factor, refers to non-compliance with the standards of earthquake-resistant design. Results of ground records analysis indicate to the westward and north-westward decrease of dominant frequency relative to the eastern and southeastern part of the study area, where the crystalline granite bedrock is much shallower reflecting the actual condition of surface geology. Striking that the H/V amplification was relatively higher in the scope of areas where the thicknesses of soft surface deposits in the eastern and southeastern part are much shallower relative to the western and north-western part of the study area. This can be interpreted as a result of much higher impedance contrast in the eastern and southeastern part relative to the western and northwestern parts of the study area. © 2011 Saudi Society for Geosciences. Source


Braeuer B.,German Research Center for Geosciences | Asch G.,German Research Center for Geosciences | Hofstetter R.,Geophysical Institute of Israel GII | Haberland C.,German Research Center for Geosciences | And 4 more authors.
Geophysical Journal International | Year: 2012

Local earthquake data from a dense temporary seismological network in the southern Dead Sea area have been analysed within the project DESIRE (Dead Sea Integrated Research Project). Local earthquakes are used for the first precise image of the distribution of the P-wave velocity and the v P/v S ratios. 65 stations registered 655 local events within 18 months of observation time. A subset of 530 well-locatable events with 26730 P- and S-arrival times was used to calculate a tomographic model for the v P and v P/v S distribution. Since the study area is at first-order 2-D, a gradual approach was chosen, which compromised a 2-D inversion followed by a 3-D inversion. The sedimentary basin fill is clearly imaged through high v P/v S ratios and low v P. The basin fill shows an asymmetric structure with average depth of 7 km at the western boundary and depth between 10 and 14 km at the eastern boundary. This asymmetry is reflected by the vertical strike-slip eastern border fault, and the normal faulting at the western boundary, caused by the transtensional deformation within the last 5 Myr. Within the basin fill the Lisan salt diapir is imaged through low v P/v S ratios, reflecting its low fluid content. The extensions were determined to 12 km in E-W and 17 km in N-S direction while its depth is 5-6 km. The thickness of the pre-basin sediments below the basin fill cannot be derived from the tomography data-it is estimated to less than 3 km from former investigations. Below the basin, down to 18 km depth very low P-wave velocities and low v P/v S ratios are observed-most likely caused by fluids from the surrounding crust or the upper mantle. © 2012 The Authors Geophysical Journal International © 2012 RAS. Source


Braeuer B.,German Research Center for Geosciences | Asch G.,German Research Center for Geosciences | Hofstetter R.,Geophysical Institute of Israel GII | Haberland C.,German Research Center for Geosciences | And 4 more authors.
Geophysical Journal International | Year: 2012

While the Dead Sea basin has been studied for a long time, the available knowledge about the detailed seismicity distribution in the area, as well as the deeper structure of the basin, is limited. Therefore, within the framework of the international project DESIRE (DEad Sea Integrated REsearch project), a dense temporary local seismological network was operated in the southern Dead Sea area. We use 530 local earthquakes, having all together 26730 P- and S-arrival times for a simultaneous inversion of 1-D velocity models, station corrections and precise earthquake locations. Jackknife tests suggest an accuracy of the derived hypocentre locations of about 1 km. Thus, the result is the first clear image of the absolute distribution of the microseismicity of the area, especially in depth. The seismicity is concentrated in the upper crust down to 20 km depth while the lower limit of the seismicity is reached at 31 km depth. The seismic events at the eastern boundary fault (EBF) in the southern part of the study area represent the northward transform motion of the Arabian Plate along the Dead Sea Transform. North of the Boqeq fault the seismic activity represents the transfer of the motion in the pull-apart basin from the eastern to the western boundary. We find that from the surface downward the seismic events are tracing the boundary faults of the basin. The western boundary is mapped down to 12 km depth while the EBF reaches about 17 km depth, forming an asymmetric basin. One fifth of the data set is related to a specific cluster in time and space, which occurred in 2007 February at the western border fault. This cluster is aligned vertically, that is, it is perpendicular to the direction of the dominating left-lateral strike-slip movement at the main transform fault. © 2012 The Authors Geophysical Journal International © 2012 RAS. Source

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