Structure of the earth's crust in Jordan from potential field data (original) (raw)
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A crustal structure study of Jordan derived from seismic refraction data
Tectonophysics, 1987
El-Isa, Z., Mechie, J., Prodehl, C., Makris, J. and Rihm, R., 1987. A crustal structure study of Jordan derived from seismic refraction data. Tectonophysics, 138: 235-253. The interpretation of a deep seismic refraction study in Jordan, performed in May 1984, shows that much of the country is underlain by continental crust, 32-35 km thick, and normal mantle with a velocity of 8.0-8.2 km/s. In the Aqaba region, southwest and central Jordan, east of Wadi Araba, the crustal thickness is of the order of 32-35 km, while in the Amman region it is not less than 35 km. In southeast Jordan the crust thickens to at least 37 km in what is probably the transition to the Arabian Shield type of crust. The boundaries between the upper and lower crust at about 20 km depth and the lower crust and uppermost mantle are probably transition zones. The upper crystalline crust has velocities of 5.8-6.5 km/s while the lower crust has velocities greater than or around 6.65 km/s. While the crystalline basement is exposed in southwest Jordan and is at a depth of 2-2.5 km north of Amman, it is at a depth of not less than 5 km in central Jordan. A comparison of the crustal type and structure of Jordan and the adjacent Dead Sea rift with that of the Black Forest and the Rhine valley yields a striking resemblance. The situation of the Jordan-Dead Sea rift is explained in terms of the continental crust of Arabia rifting in preference to the thin (?oceanic) crust of the Mediterranean Sea.
Geophysical investigations in Jordan
Tectonophysics, 1990
A mnnber of geophysical investigations have been undertaken in the Hashemite Kingdom of Jordan to provide data for understanding the tectonic framework, the pattern of seismicity, earthquake hazards and geothermal resources of the country. Both the historical seismic record and the observed recent seismicity point to the dominance of the Dead Sea Rift as the main locus of seismic activity but significant branching trends and gaps in the seismicity pattern are also seen. A wide variety of focal plane solutions are observed emphasizing the complex pattern of fault activity in the vicinity of the rift zone. Geophysical ~v~t~tions directed towards the geothermal assessment of the prominent thermal springs of Zerga Ma'in and Zara are not supportive of the presence of a crustal magmatic source.
CRUSTAL THICKNESS AND VP/VS VARIATIONS IN JORDAN INFERRED FROM TELESEISMIC P-RECEIVER FUNCTIONS
Crustal structure of Jordan was previously studied using deep sounding refraction profiles which led to deducing average crustal structure and Vp/Vs ratios. Other attempts employed different geophysical methods were mainly focused on crustal structure along Dead-Sea Transform Fault which is the main tectonic element in this area. The present work elucidates detailed crustal structure of Jordan using Pwave receiver functions technique. The RF method is applied for the first time to teleseismic earthquakes data from 15 broadband permanent stations that are covering the whole of Jordan and along the Eastern side of Northern part of Arabian plate boundary. The results indicate varying Moho depths beneath selected stations near the main fault and to the east of it, and reveal a thick crust under northern stations (about 35 ± 1 km) with Vp/Vs ratio of about 1.8. In the northeastern part of Jordan, three stations show deeper Moho depths with varying Vp/Vs ratios ranging from 1.76-1.79, they are situated in the area of basaltic extrusions that can be interpreted as more mafic crustal content in average. The thinnest crust of ~30.5 km occurs in the southern Dead-Sea basin along the Transform Fault and near the Gulf of Aqaba (~30.4 km) with Vp/Vs ratios ranging from 1.83 to 1.79, respectively. The crust in Jordan is thickening toward north and northeast. Finally, a 3D topographic map of the Moho discontinuity was constructed.
A Review of Gravity and Magnetic Studies in the Jordan Dead Sea Transform Zone
2020
1. Introduction The Dead Sea Transform, also known as the Dead Sea rift, is a major continental fracture zone that separates the Arabian plate and the Sinai-Palestine plate (Figure 1). It extends over a distance of more than 1000 km, linking the Zagros-Taurus convergence zone in the north with the Red Sea in the south, where seafloor spreading takes place (Garfunkel, 1981). The geology and tectonics of the transform fault are largely affected and controlled by the geodynamic processes acting in the Red Sea region which have resulted in its opening (Girdler, 1990 and references therein). Continental transform faults, such as the Dead Sea fault system, involve complex structural and sedimentary regimes related to the active transform displacement along fault segments (
Geochemistry Geophysics Geosystems, 2006
[1] A detailed three-dimensional (3-D) gravity model of upper crustal structures was created for the Dead Sea Transform in the Araba/Arava Valley, located some 80 km south of the Dead Sea Basin. The density model covers an area of 30A^30kmandincorporatesresultsfromseveralrecentgeophysicalexperimentsperformedinthisregion.Themodelpresentedisalocaldensitymodelthatfocusesontheuppermostcrustallayerstoadepthof30 Â 30 km and incorporates results from several recent geophysical experiments performed in this region. The model presented is a local density model that focuses on the uppermost crustal layers to a depth of 30A^30kmandincorporatesresultsfromseveralrecentgeophysicalexperimentsperformedinthisregion.Themodelpresentedisalocaldensitymodelthatfocusesontheuppermostcrustallayerstoadepthof5 km. Therefore, in order to separate the effect of regional structures (such as the crust-mantle boundary) from that of local structures within the crust, a residual anomaly was computed from a newly compiled Bouguer gravity anomaly database. In contrast to the Bouguer anomaly, which is negative across the entire study area, the residual gravity field contains both positive and negative values. The 3-D structural image of the upper crust reveals that the basement east and west of the Dead Sea Transform is vertically offset by 1.5 to 2.8 km. Considering the 105 km of sinistral displacement of the Dead Sea Transform, this result confirms the findings of other geophysical measurements that show an abrupt change in the physical parameters and geometry of the two lithological blocks that are juxtaposed along the Dead Sea Transform. Additionally, analysis of the calculated gravity gradients suggests that the Dead Sea Transform and the neighboring Zofar fault could be offset at depth with respect to the present-day traces at the surface.
Earth, Planets and Space, 2013
The present study deals with the analysis of data from a ground magnetic survey that was conducted in the Abu-Rodaym area of the Southwestern Sinai Peninsula, Egypt. This survey was carried out to delineate the subsurface structural framework, and to identify the thickness of the sedimentary basin of the study area. Locating these structures, and determining the localities of maximum sedimentary thicknesses that consist mainly of sandstone, serves as a preliminary process in exploring the confined aquifer beneath the surface of the Abu-Rodaym area. This will greatly benefit Bedouins who suffer greatly from a lack of water in the driest region in the country. The processing, analysis, and interpretation, of the total intensity magnetic data shows that there are three sets of faults striking mainly in the N-S, NW-SE, and NE-SW, directions. The depth to the basement surface was found to fluctuate from about 45 m, to more than 100 m, beneath the ground surface. It was also found that the variations in magnetic observations were produced by the striking structures that are mainly responsible for the variations in thicknesses of the sedimentary rocks in the area.
Marine and Petroleum Geology, 2006
Interpretation of recently released seismic reflection lines from the Shuna (Eastern Jericho) Basin combined with re-analysis of the lithologic logs of the deep JV-1 and JV-2 boreholes provide new insights into the structure of the sedimentary basin that formed along the Dead Sea Transform fault north of the Dead Sea in Jordan. We identified four major seismic boundaries in the reflection profiles. The upper two were correlated with borehole stratigraphy. These reflection boundaries include the top of the pan-African basement (R4), the base of the Mesozoic (R3), the base of the Cretaceous (R2), and the base of the post-Eocene section (R1). The latter records sedimentation during the Dead Sea Transform tectonic regime. The total thickness attained by the older sedimentary units (Late Cretaceous through Cambrian) is apparently less than 2 km. We identified a subsurface structure, a faulted monocline, with a N-S trend, sub-parallel to the strike of the Dead Sea Transform, that is named here Al Kharrar monocline. The Al Kharrar structural ensemble is buried by syntectonic lacustrine and fluviatile sediments of the Jordan Valley Group. The structure formed as part of the Dead Sea Transform deformation overprinting the Late Cretaceous Syrian arc folds. Continued tectonic deformation is evident from the prominent unconformity at the base of post-Eocene syntectonic deposits that dip NW, W and S away from the structural high. Along the NW-flank of the Al Kharrar monocline syntectonic sediment thickness is generally less than 0.5 km while along the SW-flank it thickens rapidly to nearly 1 km at the southern end of the interpreted seismic lines. This rapid southern subsidence probably continues into the north end of the Dead Sea Basin the lake's shoreline being located less than 3 km to the south. Young bifurcating faults with reverse slip components cutting the eastern part of the Al-Kharrar monocline are attributed to a positive flower structure. This pattern suggests strike slip with localized active compression northeast of the Dead Sea. It may result from local transpression between fault strands that appear to be a northward continuation of the eastern boundary fault of the Dead Sea Basin.
Geophysical Surveys at Khirbat Faynan, an Ancient Mound Site in Southern Jordan
Faynan in Jordan contains the largest copper ore resource zone in the southern Levant (Israel, Jordan, Palestinian territories, Lebanon, Syria, and the Sinai Peninsula). Located 50 km southeast of the Dead Sea, it is home to one of the world's best-preserved ancient mining and metallurgy districts encompassing an area of ca. 400 km 2 . During the past three decades, archaeologists have carried out numerous excavations and surveys recording hundreds of mines and sites related to metallurgical activities that span the past 10 millennia. Khirbat Faynan (Biblical Punon), is situated in the main Faynan Valley and is the largest (ca. 15 ha) settlement site in the region and has remained unexcavated until 2011. As Jordan's most southern mound site with indications of widespread ancient architecture, we employed a suite of noninvasive geophysical survey methods to identify areas suitable for excavation. Earlier geophysical surveys were carried out in the Faynan region by our team in the late 1990s when only EMI (electromagnetic induction) proved successful, but with relatively poor resolution. As reported here, by 2011, improvements in data processing software and 3D ERT (electrical resistivity tomography) sampling protocols made it possible to greatly improve the application of noninvasive geophysical surveying in this hyperarid zone.
The Hammam Faroun has a particular importance due to its geothermal activity which constitutes the main geothermal resource of Egypt. The area is located on the Sinai Peninsula, a subplate bounded by two seismically active structural zones along the Gulf of Suez and Gulf of Aqaba. High-resolution ground-based gravity and magnetic data are available for the entire Hammam Faroun area, acquired as part of a national project to explore for mineral, geothermal, and hydrocarbon resources. Gravity and magnetic data were analyzed using Source Edge Detection and Source Parameter Imaging (SPI) techniques to image subsurface structures. These analyses show that the area is characterized by a set of northwest-striking faults lying parallel to the Gulf of Suez. Orthogonal patterns are also present, possibly related to rifting of the Gulf of Suez. Depth analysis using the SPI method indicates that surface faults extend to 5-km depth. Analysis of potential-field data elucidates the structurally complex subsurface structure of the Hammam Faroun area.