Geophysical investigations in Jordan (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.
The Tectonic Geomorphology and the Archeoseismicity of the Dead Sea Transform in Jordan Valley
2007
The continuous record of large surface-rupturing earthquakes along the Dead Sea fault brings unprecedented insights for paleoseismic and archaeoseismic research. In most recent studies, paleoseismic trenching documents the late Holocene faulting activity, while tectonic geomorphology addresses the long-term behavior (> 10 ka), with a tendency to smooth the effect of individual earthquake rupture events (M w > 7). Here, we combine historical, archaeological, and paleoseismic investigations to build a consolidated catalog of destructive surface-rupturing earthquakes for the last 14 ka along the left-lateral Jordan Valley fault segment. The 120km-long fault segment limited to the north and the south by major pull-apart basins (the Hula and the Dead Sea, respectively) is mapped in detail and shows five subsegments with narrow stepovers (width < 3 km). We conducted quantitative geomorphology along the fault, measured more than 20 offset drainages, excavated four trenches at two sites, and investigated archaeological sites with seismic damage in the Jordan Valley. Our results in paleoseismic trenching with 28 radiocarbon datings and the archaeoseismology at Tell Saydiyeh, supplemented with a rich historical seismic record, document 12 surface-rupturing events along the fault segment with a mean interval of ∼1160 yr and an average 5 mm=yr slip rate for the last 25 ka. The most complete part of the catalog indicates recurrence intervals that vary from 280 yr to 1500 yr, with a median value of 790 yr, and suggests an episodic behavior for the Jordan Valley fault. Our study allows a better constraint of the seismic cycle and related short-term variations (late Holocene) versus long-term behavior (Holocene and late Pleistocene) of a major continental transform fault.
Seismicity of Jordan and Conterminous Countries
SYNO~~~~ An up-to-date seismic hazard maps for Jordan and conterminous areas have been develped based on probabilistic approach: Such maps are intended to show the Peak Ground Acceleration (PGA) with 90% probability of not being exceeded in a life time of 50, 100, and 200 years, respectively. The computer program FRISK was used for estimating the PGA. A Suitable attenuation equation reported in the literature, along with up-to-date earthquake catalogue including all the earthquake events that occurred in Jordan and neighboring countries, were considered in this study. Altogether, ten seismic zones as potential of earthquake activities are identified in the assessment of the assessment of the seismic hazard maps. These are Aqaba Gulf fault, Wadi Araba fault, Dead Sea fault, Northern fault, SE-Medlterranean fault, Farah and Carmel faults, Wadi Sirhan fault, Karak-Fayha fault, Suez Gulf fault, and Cyprus zone fault.
Historical seismicity of the Jordan Dead Sea Transform region and seismotectonic implications
Arabian Journal of Geosciences, 2014
Based on all available files, catalogs, and previous compilations, it is found that 96 historical earthquakes (M≥6.0) were felt along the Jordan Dead Sea Transform region during the last 2,000 years. More than 50 % of these occurred in the form of sequences and swarms that lasted for different periods, some of which were volcanic related. The largest assigned magnitude is 7.6 with 667 years recurrence period, while the maximum possible future magnitude is 7.8±0.2 with 1,000± 80 years recurrence period. Quiescent periods, with a duration of up to 200 and 400 years and characterized by reduced levels of seismicity, are punctuated by active periods of tens of years when a few large earthquakes occurred. The historical seismicity indicates that all tectonic elements of the study region are presently active. Our results indicate that previous studies overestimate the level of seismicity in this region. Not less than 25 earthquakes, most of which had M≥7.0, are erroneously related to the transform. It is probable that most of these are located within the East Mediterranean region and/or along intraplate faults, rather than the Jordan Dead Sea Transform. This is evidenced by (i) frequency-magnitude results, (ii) moderatelarge East Mediterranean tsunamis, (iii) an apparent higher seismicity of the northernmost three segments compared with the southern three, (iv) relatively high annual seismic slip rate as calculated from the compiled historical seismicity, and (v) overdependence of some previous compilations on secondary rather than primary sources. The revised historical seismicity implies an annual seismic slip rate of about 0.68 cm/year, which indicates that not less than 30 % of the tectonic movements along the regional structures of the study region are aseismic. This is in agreement with results obtained from prehistoric and instrumental data.
Geothermal Investigations in the Dead Sea Rift Zone, Israel: Implications for Petroleum Geology
Journal of Petroleum Geology, 1996
Thermal surveys of the Dead Sea-Arava Valley area have been conducted in order to investigate the present-day geothermul characteristics of the sedimentary cover. Horizontal geothermal gradients have been assessed, and heat-absorbing and heat-radiating intervals have been identijied. The second temperature versus depth derivative is used as an index of the thermal state of the sedimentary cover. Average vertical gradients are low, and vary between 20" and 3O"Ckm. Horizontal geothermal gradients in the study area do not usually exceed I" C k m , although they are higher within the major Dead Sea graben fault zone. Horizontal gradients may cause excess pressures, which influence the direction of fluidflow within the sedimentary cover. Basaltic intrusions may also cause the migration of overheated waters. Analytical methods based on those applied in magnetic prospecting are used for the quantitative interpretation of temperature anomalies, and these methods may contribute to the location of faults and salt domes.
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.
Lithospheric structure of the Jordan-Dead Sea transform from earthquake data
Tectonophysics, 1990
P-wave travel times from 89 shallow earthquakes (M < 6) recorded at the Jordan University Seismological Station (UNJ) from epicentral distances in the range (140 km 6 x < 1308 km) are utilized in the derivation of a lithosphetic model for the Jordan-Dead Sea transform region. The selected events are of high signal/noise ratio. For most events, the standard deviation of the origin time is in the range 0.1-1.2 s. One-dimensional ray tracing is used to model the P-wave travel times. Results indicate that an average crustal thickness of about 35 km beneath the station, as derived from explosion data, is confirmed by the earthquake data. The P,,-velocity for the uppermost mantle is 8.07 f 0.02 km/s. The first upper mantle refractor below the Moho occurs at a depth of about 54 km, with an apparent velocity (at this discontinuity) of 8.4 f 0.06 km/s being measured. The thickness of the layer below this discontinuity appears to be of the order of only 2-3 km. Below this, the data are interpreted to represent a low-velocity zone where the velocity gradually decreases to a minimum of about 8.1 km/s at a depth of 80 km and increases thereafter at a constant rate of 0.02 s-l down to a depth of 105 km. At this depth, the next refractor occurs, producing a constant velocity of 8.6 f 0.04 km/s. The layer below this refractor seems to extend to a depth of not less than 150 km.
The thermal structure of Israel and the Dead Sea Fault
Tectonophysics, 2013
In this paper we analyze temperature data from all the available oil and water wells in Israel and compare the results with seismicity depth and with heat flux estimation from xenoliths. We show that the average heat flux in Israel is 40-45 mW/m 2 , consistent with measurements of the Arabian Shield. A heat flux anomaly exists in Northern Israel and Jordan. This could be attributed to groundwater flow or young magmatic activity (~100,000 years) that is common in this area. A higher heat flux exists in Southern Israel and Jordan, probably reflecting the opening of the Red Sea and the Gulf of Eilat (Gulf of Aqaba) and does not represent the average value present in the Arabian Shield. The temperature gradient at the Dead Sea basin is relatively low, resulting in low heat flux (b 40 mW/m 2 ) and a relatively deep seismicity extending to lower crustal depths, in agreement with earthquake depths (b 25-30 km). Higher heat fluxes at the Sea of Galilee (70 mW/m 2 ) and at the Gulf of Eilat (65 mW/m 2 ) results with shallower seismicity (b 10-12 km). The steep geothermal gradients yielded by xenoliths (>80 mW/m 2 ) could be the result of local heating by magmas or by lithospheric necking and shear heating.
Tectonic Analysis of the Tall Al Qarn Pressure Ridge, Dead Sea Transform Fault, Jordan
Iraqi geological journal, 2023
Jordan's Dead Sea Transform is made up of three morphotectonic elements: Wadi Araba, Dead Sea Basin, and Jordan Valley. A few pressure ridges and depressions exist in the Jordan Valley Fault. Among these, the Tall Al Qarn pressure ridge is one of the active Dead Sea Transform's morphotectonic features. Stratigraphically, the Waqqas (Miocene), Ghor Al Katar (Early Pleistocene), and Lisan (Late Pleistocene) Formations constitute the rock outcrops in the study area. The ridge was created when the sinistral strike-slip fault of the Jordan Valley bent rightward. The major structures include the Waqqas and Ghor Al Katar inclined beds, the NW-SE oriented normal and NE-SW reverse faults and the ESE-WNW oriented dextral strike-slip faults. Faults and folds indicate a local NW-SE compressional stress caused by the sinistral Jordan Valley Fault's right bending. The steeply dipping Ghor Al Katar strata, which are overlain by the horizontal Lisan beds, display a prominent angular unconformity. Many horizontal Lisan beds exhibit abundant synsedimentary deformational features, indicating the energetic seismic activity at that time.