Eighth GEBCO Science - presentation abstract (original) (raw)
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Tectonophysics, 2020
The cities of Elat, Israel and neighboring Aqaba, Jordan are major economic, cultural, and seaport centers. They are located on the northern shore of the Gulf of Aqaba/Elat (GAE) directly on the Dead Sea Transform. Yet the precise location of the fault trace and its tectonic activity are lacking. The interpretation of seismic reflection profiles across the GAE beach and paleoseismic trench data located 2.2 km north of the shoreline provide evidence that the active offshore mapped Avrona Fault extends onland along the eastern side of the Elat Sabkha (mudflat), where three prominent fault strands crosscut the sedimentary fill. Mismatch of reflector geometry across the faults and flower structures indicate strike-slip faulting with a normal-slip component. Subsurface data from two trenching sites provide evidence for a minimum of two surface ruptures and two paleoliquefaction events. Faulting is constrained by radiocarbon dating for an Event 1 between 897 and 992 CE and Event 2 after 1294 CE. We suggest that the historically documented 1068 CE, and at least one later earthquake in 1458 or 1588 CE, ruptured the Elat Sabkha site. Based on fault mapping, we suggest a minimum value of M 6.6 for the 1068 CE earthquake. Whereas no surface rupture was observed for the 1212 CE historical earthquake, fluidized strata radiocarbon dated to before 1269-1389 CE identified as paleoliquefaction may be attributed to it. Two liquefaction sand-blows mapped in the trench likely formed after 1337 CE and before 1550 CE, which possibly occurred at the same time as in the second faulting event. Our data suggest that no large event occurred along the Avrona segment in the past ~430-550 years. Given a ~ 5 mm/yr slip rate, we conclude that a significant period of time passed since the last surface rupturing on the Avrona Fault, increasing its seismic potential.
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.
DESERT Dead Sea Rift Transect: An interdisciplinary research project to study the Dead Sea Transform
Since the advent of plate-tectonics the Dead Sea Transform (DST) has been considered a prime site to examine geodynamic processes. It has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (~20 My). Large historical earthquakes on the DST with magnitudes up to 7 and the 1995 Nueiba M7.2 event, as well as ongoing micro-seismic activity show that the DST is a seismically active plate boundary. The DST therefore poses a considerable seismic hazard to Palestine, Israel, and Jordan. The DST segment between the Dead Sea and the Red Sea, called Arava/Araba Fault (AF), is studied in DESERT in detail, using a multi-disciplinary and multi-scale approach from the micrometer to the plate-tectonic scale. This volume contains the results of the DESERT project running from 2000 to 2006. It opens with a review paper followed by 33 special papers. Available at http://dx.doi.org/10.2312/GFZ.b103-09084 (open access).
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.
Quaternary tectonic evolution of the Northern Gulf of Elat/Aqaba along the Dead Sea Transform
The northern Gulf of Elat/Aqaba is located in the transition between the deep marine basins of the gulf and the shallow onland basins of the Arava Valley. Interpretation of 500 km of high-resolution seismic reflection data collected across the northern shelf reveals the tectonic structure and evolution of this transition. Six NNE-trending faults and one E-W trending transverse fault are mapped. Slip rates are calculated based on measured offsets and age determination based on a radiocarbon-calibrated sedimentation rate and a Quaternary age model. The most active fault is the Evrona Fault that absorbs most of the left lateral slip within the basin with an average sinistral slip rate of 0.7 ± 0.3 mm/yr through the Late Pleistocene and 2.3–3.4 mm/yr during the Holocene. Two intrabasin faults east of the Evrona Fault that have been inactive for the last several tens of thousands of years were mapped, and motion from these faults has likely transferred to the Evrona Fault. The basin is flanked on the west by the Elat Fault and on the east by the Aqaba Fault. Both faults are marked by large bathymetric escarpments. Based on displaced seismic reflectors, we calculate a Holocene vertical slip rate of 1.0 ± 0.2 and 0.4 ± 0.1 mm/yr for the Elat and Aqaba Faults, respectively. The geometry, slip rates, and slip history of the northern Gulf of Elat/Aqaba faults show that during the Late Pleistocene several intrabasin faults became dominant across the basin but that during the Holocene the Evrona Fault accommodates most of the strike slip.
Dead Sea Transform Fault System: Reviews
Modern Approaches in Solid Earth Sciences, 2014
Volcanism is common along the northern segments of the Dead Sea Transform (DST). In this paper we review its distribution and composition and conclude that this tectono-magmatic association has mainly to do with the magma migration toward the surface and less with magma generation, namely: some volcanic activity concentrated along the DST due to better magma channeling and not due to an enhanced mantle partial melting along this lineament. The volcanism along the DST is clearly part of the western Arabia magmatism, and the early phases of this volcanism probably have to do with Red Sea-related extension during the Early to Middle Miocene. Nevertheless, the DST does play a role in the emplacement of lithospheric mantle domains with different compositions next to each other, which is refl ected in the derived lavas. Keywords Dead Sea Transform • Volcanism • Red Sea • Harrat Ash Shaam • Azraq-Sirhan 4.1 Introduction Volcanic landscapes are very common along the northern part of the Dead Sea Transform fault (hereafter DST; Figs. 4.1 and 4.2a). This mainly includes the northwestern edge of the Harrat Ash Shaam (Early Miocene to Pleistocene, Fig. 4.2a, b),
Seismic behaviour of the Dead Sea fault along Araba valley, Jordan
Geophysical Journal International, 2000
The Dead Sea fault zone is a major left-lateral strike-slip fault. South of the Dead Sea basin, the Wadi Araba fault extends over 160 km to the Gulf of Aqaba. The Dead Sea fault zone is known to have produced several relatively large historical earthquakes. However, the historical events are unequally distributed along the fault and only four events have been reported in the Araba valley over the last few thousands of years. Magnitudes estimated from the historical record are probably slightly smaller than that of the Mwy7.3 earthquake that struck the Gulf of Aqaba in 1995. The fault cuts straight across Pleistocene to Holocene alluvium and shows morphologic evidence for essentially pure strike-slip motion. Regional seismic monitoring reveals little microseismicity along the fault except around the Dead Sea and Gulf of Aqaba, where the fault splays into complex pull-apart basin fault systems. We have investigated the fault zone at several sites selected from SPOT images and the study of aerial photography. At the site of the now destroyed Tilah Castle, a well-preserved wall, dated to be about 1200 yr BP (14 C age on charcoal), is cut by the fault and offset by 2.2 m. Comparison with offset gullies at a nearby site 3 km to the north and at three other sites, respectively 25, 50 and 65 km to the south, reveals that this speci®c fault displacement is probably related to the last seismic event that ruptured that fault segment, possibly in AD 1458. Moreover, the offset gullies suggest a characteristic slip behaviour with recurring slip of about 1.5 m on average. Given the 4t2 mm yr x1 slip rate derived for this fault segment, we infer that the fault should produce Mwy7 earthquakes along some segment in the Araba valley about every 200 years. The historical period, with only four welldocumented large earthquakes in AD 1068, AD 1212, AD 1293 and AD 1458, thus appears to have been relatively quiescent, with a 20 per cent de®cit of Mwy7 earthquakes. However, our data do not exclude the possibility of larger Mwy7.6 earthquakes or time clustering of earthquakes over longer timespans. An alternative seismic behaviour involves Mwy 7.6 earthquakes about every 6000 years and Mwy 7 earthquakes about every 250 years. The historical catalogue would then appear to be complete for Mwy7 earthquakes.
2007
In a high-resolution small scale seismic experiment we investigated the shallow structure of the Wadi Araba Fault (WAF), the principal fault strand of the Dead Sea Transform System between the Gulf of Aqaba/Eilat and the Dead Sea. The experiment consisted of 8 sub-parallel 1 km long seismic lines crossing the WAF. The recording station spacing was 5 meters and the source point distance was 20 m. The first break tomography yields insight into the fault structure down to a depth of about 200 m. The velocity structure varies from one section to the other which were 1 to 2 km apart, but distinct velocity variations along the fault are visible between several profiles. The reflection seismic images show positive flower structures and indications for different sedimentary layers at the two sides of the main fault. Often the superficial sedimentary layers are bent upward close to the WAF. Our results indicate that this section of the fault (at shallow depths) is characterized by a transpressional regime. We detected a 100 to 300 m wide heterogeneous zone of deformed and displaced material which, however, is not characterized by low seismic velocities at a larger scale. At greater depth the geophysical images indicate a blocked cross-fault structure. The structure revealed, fault cores not wider than 10 m, are consistent with scaling from wear mechanics and with the low loading to healing ratio anticipated for the fault.
Tectonics, 2012
1] The Dead Sea strike-slip fault accommodates the northward motion of Arabia relative to Sinai at a rate of 5mm/yr.Thesouthernsegmentofthefault,theWadiArabafault,runsalongavalleyblanketedinQuaternarysediments.Wefirstfocusedonunderstandingtherelativeandabsolutetimingofemplacementofthealluvialsurfaces.WethendeterminedtheprobablesourceofthesedimentsbeforeassessingtheirlateraloffsettoconstrainthelatePleistocenefaultsliprate.Sevensuccessivemorphostratigraphiclevelswereidentified.Attwosites,werecognizedanalluvialsequenceoffivetosevensuccessivelevelswithagesgettingyoungernorthward,apatternconsistentwiththewesternblockmovingsouthwardrelativetotwofixedfeedingchannelslocatedtotheeast.Surfacesampleswerecollectedfor10Becosmogenicradionuclidedating.FansF3andF5werefoundtobesynchronousfromsitetosite,at102AE26kaand324AE22ka,respectively,whileF4couldbedatedat163AE19kaatonesiteonly.Theseareminimumages,assumingnoerosionofthealluvialsurfaces.Atleasttwooftheseperiodsarecorrelatedwithwetperiodsthatareregionallywelldocumented.Furtheranalysesoftectonicoffsetsareaffectedinmostcasesbylargeuncertaintiesduetotheconfigurationofthesites.Theyindicatemaximumoffsetsof5 mm/yr. The southern segment of the fault, the Wadi Araba fault, runs along a valley blanketed in Quaternary sediments. We first focused on understanding the relative and absolute timing of emplacement of the alluvial surfaces. We then determined the probable source of the sediments before assessing their lateral offset to constrain the late Pleistocene fault slip rate. Seven successive morphostratigraphic levels were identified. At two sites, we recognized an alluvial sequence of five to seven successive levels with ages getting younger northward, a pattern consistent with the western block moving southward relative to two fixed feeding channels located to the east. Surface samples were collected for 10 Be cosmogenic radionuclide dating. Fans F3 and F5 were found to be synchronous from site to site, at 102 AE 26 ka and 324 AE 22 ka, respectively, while F4 could be dated at 163 AE 19 ka at one site only. These are minimum ages, assuming no erosion of the alluvial surfaces. At least two of these periods are correlated with wet periods that are regionally well documented. Further analyses of tectonic offsets are affected in most cases by large uncertainties due to the configuration of the sites. They indicate maximum offsets of 5mm/yr.Thesouthernsegmentofthefault,theWadiArabafault,runsalongavalleyblanketedinQuaternarysediments.Wefirstfocusedonunderstandingtherelativeandabsolutetimingofemplacementofthealluvialsurfaces.WethendeterminedtheprobablesourceofthesedimentsbeforeassessingtheirlateraloffsettoconstrainthelatePleistocenefaultsliprate.Sevensuccessivemorphostratigraphiclevelswereidentified.Attwosites,werecognizedanalluvialsequenceoffivetosevensuccessivelevelswithagesgettingyoungernorthward,apatternconsistentwiththewesternblockmovingsouthwardrelativetotwofixedfeedingchannelslocatedtotheeast.Surfacesampleswerecollectedfor10Becosmogenicradionuclidedating.FansF3andF5werefoundtobesynchronousfromsitetosite,at102AE26kaand324AE22ka,respectively,whileF4couldbedatedat163AE19kaatonesiteonly.Theseareminimumages,assumingnoerosionofthealluvialsurfaces.Atleasttwooftheseperiodsarecorrelatedwithwetperiodsthatareregionallywelldocumented.Furtheranalysesoftectonicoffsetsareaffectedinmostcasesbylargeuncertaintiesduetotheconfigurationofthesites.Theyindicatemaximumoffsetsof5.5 km for the oldest, possibly $1 Ma old, surfaces. They lead to bracketing of the fault slip rate between 5 and 12 mm/yr, with preferred values of 5-7 mm/yr, for the last 300 ka. Citation: Le Béon, M., Y. Klinger, A.-S. Mériaux, M. Al-Qaryouti, R. C. Finkel, O. Mayyas, and P. Tapponnier (2012), Quaternary morphotectonic mapping of the Wadi Araba and implications for the tectonic activity of the southern Dead Sea fault, Tectonics, 31, TC5003,
Active tectonics along the Wadi Araba-Jordan Valley transform fault
Journal of Geophysical Research, 1999
A geological study has been carried out along the 200 km long Wadi Araba following the transform fault that separates the Arabian and Sinai-African Plates. Recent movements along this structure affect upper Pleistocene-Holocene deposits and archaeological sites. Kinematic indicators show sinistral strike-slip and oblique movements, in agreement with the relative motion between the two plates. Other evidence of recent horizontal displacement exists along the Jordan Valley Fault, both on the Dead Sea-Lake Tiberias segment and on the segment north of Lake Tiberias. A minimum horizontal slip rate of 1 cm yr-• has been estimated for both the southern segment of the Wadi Araba Fault and for the southern Jordan River Fault. The two faults can be roughly subdivided into at least four segments: two in the Wadi Araba (80 km long each), one from the Dead Sea to Lake Tiberias (130 km), and one from Lake Tiberias to the Hula graben (>30 km). Faulting may also occur along shorter subsegments, as shown by bends in the Wadi Araba-Jordan River Fault and by the growth of local compression and extension features. Instrument-recorded seismicity appears to be mainly concentrated along some of these subsegments. A comparison between the observed seismic and field-determined slip rates across the fault indicates possible strain accumulation during the last 2000 years.