scholarly journals Seismic and Geodetic Crustal Moment-Rates Comparison: New Insights on the Seismic Hazard of Egypt

2021 ◽  
Vol 11 (17) ◽  
pp. 7836
Author(s):  
Rashad Sawires ◽  
José A. Peláez ◽  
Federica Sparacino ◽  
Ali M. Radwan ◽  
Mohamed Rashwan ◽  
...  
Keyword(s):  
Active Regions ◽  
Seismic Source ◽  
Satellite System ◽  
Dead Sea ◽  
Fault System ◽  
Gulf Of Aqaba ◽  
Seismic Sources ◽  
Earthquake Catalog ◽  
Focal Mechanism Solutions ◽  
Rate Ratios

A comparative analysis of geodetic versus seismic moment-rate estimations makes it possible to distinguish between seismic and aseismic deformation, define the style of deformation, and also to reveal potential seismic gaps. This analysis has been performed for Egypt where the present-day tectonics and seismicity result from the long-lasting interaction between the Nubian, Eurasian, and Arabian plates. The data used comprises all available geological and tectonic information, an updated Poissonian earthquake catalog (2200 B.C.–2020 A.D.) including historical and instrumental datasets, a focal-mechanism solutions catalog (1951–2019), and crustal geodetic strains from Global Navigation Satellite System (GNSS) data. The studied region was divided into ten (EG-01 to EG-10) crustal seismic sources based mainly on seismicity, focal mechanisms, and geodetic strain characteristics. The delimited seismic sources cover the Gulf of Aqaba–Dead Sea Transform Fault system, the Gulf of Suez­–Red Sea Rift, besides some potential seismic active regions along the Nile River and its delta. For each seismic source, the estimation of seismic and geodetic moment-rates has been performed. Although the obtained results cannot be considered to be definitive, among the delimited sources, four of them (EG-05, EG-06, EG-08, and EG-10) are characterized by low seismic-geodetic moment-rate ratios (<20%), reflecting a prevailing aseismic behavior. Intermediate moment-rate ratios (from 20% to 60%) have been obtained in four additional zones (EG-01, EG-04, EG-07, and EG-09), evidencing how the seismicity accounts for a minor to a moderate fraction of the total deformational budget. In the other two sources (EG-02 and EG-03), high seismic-geodetic moment-rates ratios (>60%) have been observed, reflecting a fully seismic deformation.

Bathymetry and uplift rate of the Gulf of Aqaba, Dead Sea Fault.

2021 ◽  
Author(s):  
Matthieu Ribot ◽  
Yann Klinger ◽  
Edwige Pons-Branchu ◽  
Marthe Lefevre ◽  
Sigurjón Jónsson
Keyword(s):  
High Resolution ◽  
Tectonic Evolution ◽  
Active Faults ◽  
Major Change ◽  
Dead Sea ◽  
Fault System ◽  
Arabian Plate ◽  
Gulf Of Aqaba ◽  
Uplift Rate ◽  
The Dead

&lt;p&gt;Initially described in the late 50&amp;#8217;s, the Dead Sea Fault system connects at its southern end to the Red Sea extensive system, through a succession of left-stepping faults. In this region, the left-lateral differential displacement of the Arabian plate with respect to the Sinai micro-plate along the Dead Sea fault results in the formation of a depression corresponding to the Gulf Aqaba. We acquired new bathymetric data in the areas of the Gulf of Aqaba and Strait of Tiran during two marine campaigns (June 2018, September 2019) in order to investigate the location of the active faults, which structure and control the morphology of the area. The high-resolution datasets (10-m posting) allow us to present a new fault map of the gulf and to discuss the seismic potential of the main active faults.&lt;/p&gt;&lt;p&gt;We also investigated the eastern margin of the Gulf of Aqaba and Tiran island to assess the vertical uplift rate. To do so, we computed high-resolution topographic data and we processed new series of U-Th analyses on corals from the uplifted marine terraces.&lt;/p&gt;&lt;p&gt;Combining our results with previous studies, we determined the local and the regional uplift in the area of the Gulf of Aqaba and Strait of Tiran.&lt;/p&gt;&lt;p&gt;Eventually, we discussed the tectonic evolution of the gulf since the last major change of the tectonic regime and we propose a revised tectonic evolution model of the area.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Interseismic deformation in the gulf of aqaba from GPS measurements

2021 ◽  
Author(s):  
Nicolás Castro-Perdomo ◽  
Renier Viltres ◽  
Frédéric Masson ◽  
Yann Klinger ◽  
Shaozhuo Liu ◽  
...  
Keyword(s):  
Gulf Coast ◽  
Accumulation Rate ◽  
Slip Rate ◽  
Dead Sea ◽  
Northern Region ◽  
Fault System ◽  
Gulf Of Aqaba ◽  
Dead Sea Transform ◽  
Red Sea Rift ◽  
The Dead

Summary Although the Dead Sea Transform fault system has been extensively studied in the past, little has been known about the present-day kinematics of its southernmost portion that is offshore in the Gulf of Aqaba. Here we present a new GPS velocity field based on three surveys conducted between 2015 and 2019 at 30 campaign sites, complemented by 11 permanent stations operating near the gulf coast. Interseismic models of strain accumulation indicate a slip rate of $4.9^{+0.9}_{-0.6}~mm/yr$ and a locking depth of $6.8^{+3.5}_{-3.1}~km$ in the gulf’s northern region. Our results further indicate an apparent reduction of the locking depth from the inland portion of the Dead Sea Transform towards its southern junction with the Red Sea rift. Our modelling results reveal a small systematic left-lateral residual motion that we postulate is caused by, at least in part, late postseismic transient motion from the 1995 MW7.2 Nuweiba earthquake. Estimates of the moment accumulation rate on the main faults in the gulf, other than the one that ruptured in 1995, suggest that they might be near the end of their current interseismic period, implying elevated seismic hazard in the gulf area.

Exploring the dynamics of the Dead-Sea Transform fault using data-integrated numerical models

2021 ◽  
Author(s):  
Thomas Ulrich ◽  
Alice-Agnes Gabriel ◽  
Yann Klinger ◽  
Jean-Paul Ampuero ◽  
Percy Galvez ◽  
...  
Keyword(s):  
Dead Sea ◽  
Strike Slip ◽  
Fault System ◽  
Gulf Of Aqaba ◽  
Back Projection ◽  
Earthquake Cycle ◽  
Transform Fault ◽  
Dynamic Rupture ◽  
Dead Sea Transform ◽  
The Dead

&lt;p&gt;The Dead-Sea Transform fault system, a 1200 km-long strike-slip fault forming the tectonic boundary between the African Plate and the Arabian Plate, poses a major seismic hazard to the eastern Mediterranean region. The Gulf of Aqaba, which terminates the Dead Sea fault system to the South, results from a succession of pull-apart basins along the Dead-Sea Transform fault system. The complexity of the fault system in the Gulf has been recently evidenced by Ribot et al. (2020), who compiled a detailed map of its fault traces, based on a new multibeam bathymetric survey of the Gulf. Part of the Gulf of Aqaba was ruptured by an Mw 7.3 earthquake in 1995. Teleseismic data analysis suggests that it may have been a multi-segment rupture (Klinger et al., 1999). This event occurred offshore, in a poorly instrumented region, and therefore the exact sequence of faults that ruptured is not precisely known. The detailed fault mapping of Ribot et al. (2020) offers a fresh view of this earthquake. In particular, it identifies many oblique faults between the major strike-slip faults, which may have linked these segments.&lt;/p&gt;&lt;p&gt;Relying on this new dataset, on a new back-projection study, and on 3D dynamic rupture modeling with SeisSol (https://github.com/SeisSol/SeisSol), we revisit the 1995 Aqaba earthquake. Using back projection, we identify 2 strong radiators, which we associate with 2 step-overs. Using 3D dynamic rupture modeling, we propose scenarios of the 1995 earthquake, compatible with the various dataset available. Our modeling allows constraining the regional state of stress in the region, acknowledging transtension, offers constraints on the nucleation location and confirms the role of the oblique faults in propagating the rupture to the North. It offers new constraints on the regional seismic hazard, in particular on the expected maximum moment magnitude.&lt;/p&gt;&lt;p&gt;Finally, we explore the dynamics of the Gulf of Aqaba fault system using earthquake cycle modeling. For that purpose, we rely on QDYN (https://github.com/ydluo/qdyn), a boundary element software, which simulates earthquake cycles under the quasi-dynamic approximation on faults governed by rate-and-state friction and embedded in elastic media. We inform our parameterization of the earthquake cycle modeling using the previously described datasets and modeling results. Recently Galvez et al. (2020) demonstrated the capability of the method to model the dynamics of complex fault system in 3D. Here new code developments are required to adapt the method to the Gulf of Aqaba fault system, e.g. to allow accounting for normal stress changes and for variations in the fault rake.&lt;/p&gt;&lt;p&gt;Overall, we aim to better understand how large earthquakes may nucleate, propagate, and interact across a complex transform fault network. Our findings, e.g. on fault segmentation or the conditions that promote larger earthquakes, will have important implications for other large strike-slip fault systems worldwide.&lt;/p&gt;

The nature of the Albstadt Shear Zone, Germany

2020 ◽  
Author(s):  
Sarah Mader ◽  
Klaus Reicherter ◽  
Joachim Ritter ◽  
the AlpArray Working Group
Keyword(s):  
Shear Zone ◽  
Seismic Velocity ◽  
Active Regions ◽  
Velocity Model ◽  
Strike Slip ◽  
Fault System ◽  
Earthquake Catalog ◽  
Depth Range ◽  
Study Region ◽  
The Town

&lt;p&gt;&lt;span&gt;The region around the town of Albstadt, SW Germany, is one of the most seismically active regions in Central Europe. In the last century alone three earthquakes with a magnitude greater than five happened and caused major damage. The ruptures occur along the Albstadt Shear Zone (ASZ), an approx. 20-30 km long, N-S striking fault with left-lateral strike slip. As there is no evidence for surface rupture the nature of the Albstadt Shear Zone can only be studied by its seismicity.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;To characterize the ASZ we &lt;/span&gt;&lt;span&gt;continuously&lt;/span&gt;&lt;span&gt; complement the earthquake catalog of the &lt;/span&gt;&lt;span&gt;State Earthquake Service&lt;/span&gt;&lt;span&gt; of Baden-W&amp;#252;rttemberg with additional seismic phase onsets. For the latter we use the station network of AlpArray as well as &lt;/span&gt;&lt;span&gt;5 &lt;/span&gt;&lt;span&gt;additional, &lt;/span&gt;&lt;span&gt;in 2018/2019&lt;/span&gt;&lt;span&gt; installed seismic stations from the KArlsruhe BroadBand Array. &lt;/span&gt;&lt;span&gt;W&lt;/span&gt;&lt;span&gt;e invert&lt;/span&gt;&lt;span&gt;ed&lt;/span&gt;&lt;span&gt; for &lt;/span&gt;&lt;span&gt;a &lt;/span&gt;&lt;span&gt;new minimum 1D &lt;/span&gt;&lt;span&gt;seismic &lt;/span&gt;&lt;span&gt;velocity model&lt;/span&gt; &lt;span&gt;of the study region. &lt;/span&gt;&lt;span&gt;We use this seismic velocity model to relocalize the complemented catalog&lt;/span&gt; &lt;span&gt;and to calculate focal mechanisms&lt;/span&gt;&lt;span&gt;. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;The majority of the seismicity happens between the towns T&amp;#252;bingen and Albstadt at around 9&amp;#176;E in a depth range of &lt;/span&gt;&lt;span&gt;about 1.5 to 16 km &lt;/span&gt;&lt;span&gt;and aligns &lt;/span&gt;&lt;span&gt;n&lt;/span&gt;&lt;span&gt;orth-&lt;/span&gt;&lt;span&gt;s&lt;/span&gt;&lt;span&gt;outh&lt;/span&gt;&lt;span&gt;. &lt;/span&gt;&lt;span&gt;Additionally, we see &lt;/span&gt;&lt;span&gt;a &lt;/span&gt;&lt;span&gt;cluster&lt;/span&gt;&lt;span&gt;ing of events at the town&lt;/span&gt;&lt;span&gt;s&lt;/span&gt;&lt;span&gt; Hechingen and Albstadt.&lt;/span&gt;&lt;span&gt; The dominating focal mechanism is strike-slip, &lt;/span&gt;&lt;span&gt;but we also observe &lt;/span&gt;&lt;span&gt;minor components of &lt;/span&gt;&lt;span&gt;normal and reverse faulting.&lt;br&gt;&lt;/span&gt;&lt;span&gt;Our results image the ASZ by its mainly micro-seismic activity b&lt;/span&gt;&lt;span&gt;etween&lt;/span&gt;&lt;span&gt; 2011 &lt;/span&gt;&lt;span&gt;and&lt;/span&gt;&lt;span&gt; 2018 &lt;/span&gt;&lt;span&gt;confirming the N-S striking character, but also indicating a more complex fault system.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;We thank the &lt;/span&gt;&lt;span&gt;State Earthquake Service&lt;/span&gt;&lt;span&gt; in Freiburg for using their data (Az. 4784//18_3303). &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Formation of the Red Sea Depression

1968 ◽  
Vol 105 (3) ◽  
pp. 231-246 ◽  
Author(s):  
A. J. Whiteman
Keyword(s):  
Red Sea ◽  
Large Scale ◽  
Dead Sea ◽  
Morphological Data ◽  
Fault System ◽  
Gulf Of Aqaba ◽  
Fault Line ◽  
Basement Complex ◽  
Early Palaeozoic ◽  
Sea Area

SUMMARYVarious views have been expressed about the origin of the Red Sea Depression. Many earth scientists favour large-scale crustal separation and rotation of Arabia with respect to Africa—the paar theory; whereas a minority believe in a simple tensional origin. In the writer's view the almost “timeless” models presented by Drake & Girdler (1964) and Laughton (1966) are unacceptable because little of the available stratigraphic, structural and geo-morphological data was utilized in their construction. A tension system may have existed in the Red Sea area in late Pre-Cambrian and early Palaeozoic times. A depression existed in the northern part of the region in Carboniferous times and during Cretaceous times a tongue of Tethys occupied the northern and central portions of the depression. In Miocene times an extensive evaporite basin developed occupying most of the depression. The sill was situated in the Gulf of Suez Ayun Musa area.The main and central troughs developed as a result of tension in Pliocene and later times. The Gulf of Aqaba Depression was formed by a fault system continuous with Dead Sea System which originated in (?) early Cretaceous times. The northern and central parts of the gulf were invaded by the sea in Pleistocene times.The escarpments which bound the Red Sea Depression are in very few places fault or fault line scarps. Primarily they appear to be erosional features developed by pediplanation across the downwarped margins of the depression. In places, the shoulders and flanks were faulted later. In this way the uncon-formable nature of the contact, between the Mesozoic-Tertiary sediments and the Basement Complex (mainly Pre-Cambrian) which occurs at the foot of the escarpments, is best explained.

A Ground-Motion Database for Israel with Its Corresponding Point-Source Parameters, for Engineering Seismology Applications

2021 ◽  
Author(s):  
Gony Yagoda-Biran ◽  
Soumya K. Maiti ◽  
Nadav Wetzler ◽  
Ran N. Nof ◽  
Yona Pashcur ◽  
...  
Keyword(s):  
Ground Motion ◽  
Attenuation Factor ◽  
Source Parameters ◽  
Dead Sea ◽  
Fault System ◽  
Earthquake Catalog ◽  
Joint Effort ◽  
Near Surface ◽  
Anelastic Attenuation ◽  
Main Components

Abstract The seismic activity in Israel and its surrounding neighbors originates mainly from the active Dead Sea fault system. The historical and archeological records suggest a recurrence interval of approximately 102 and 103  yr for earthquakes of M 6 and 7, respectively. Despite the existing hazard, local advancements on this topic have been slow and incremental, partly due to inherent challenges, such as the limited number of significant recorded earthquakes and a limited azimuthal coverage resulting from geopolitical constraints. Annual earthquake bulletins and an earthquake catalog have been published over the years by the Geophysical Institute of Israel, which operated the network until January 2020. In this article, we summarize a joint effort aimed at standardizing the catalog and creating the first of its kind, publicly available ground-motion database for Israel, which is open to the scientific and engineering communities. The database is composed of three main components: event database, ground-motion recording database, and site database. Once compiled, we use this database to derive and calibrate the source, path, and site parameters required to execute ground-motion simulations, namely, the regional stress drop, anelastic attenuation factor Q, geometrical spreading, and the near-surface high-frequency attenuation, kappa. The parameters are optimized to fit the measurement database, and once they do, a synthetic dataset can be simulated, which will compensate for the lack of measurements in the large-magnitude range.

New structural model of strike-slip tectonics of the Gulf of Aqaba, southern Dead Sea Transform

2020 ◽  
Author(s):  
Jakub Fedorik ◽  
Abdulkader Afifi
Keyword(s):  
Dead Sea ◽  
Strike Slip ◽  
Fault System ◽  
Gulf Of Aqaba ◽  
Normal Faults ◽  
Dead Sea Transform ◽  
Internal Fault ◽  
Riedel Shear ◽  
The One ◽  
Riedel Shears

&lt;p&gt;The Dead Sea Transform is an active left lateral, strike-slip plate boundary. The Gulf of Aqaba corresponds to its southern segment, where the largest amount of opening is observed. The gulf itself is deformed by a set of en echelon faults which are bounded by normal faults. These en echelon faults show structural styles of Riedel shears which are typically observed in strike-slip tectonics. However, their orientation is the opposite to the one observed in well described models or natural cases. In this study, we compare a compiled dataset to analogue models which simulate the displacement in various strike-slip systems. This comparison to a sandbox model highlights the importance of the tectonic load in a strike-slip fault system. The model is composed of two base plates with only one straight velocity discontinuity. X-Ray Computed Tomography is used as a technique to carry out a 4D analysis of internal fault structures of the model. The 10&amp;#176;-transtensional model generates a set of Riedel shear faults, which merge during the later stages of deformation. The 30&amp;#176;-transtensional tectonic load shows two major steep bounding faults with a dip-slip component and a set of en echelon faults - opposite Riedel shears in between them. A higher amount of transtension rotates the classic Riedel shear faults to the opposite position. This fault pattern is very similar to the one observed in the Gulf of Aqaba, where the internal fault system is composed of opposite Riedel shears bounded by normal faults. These observations can increase the understanding of the structural styles seen in the Gulf of Aqaba. Moreover, our study describes a new strike-slip fault system.&lt;/p&gt;

scholarly journals Midyan Peninsula, northern Red Sea, Saudi Arabia: Seismic imaging and regional interpretation

GeoArabia ◽  
2014 ◽  
Vol 19 (3) ◽  
pp. 165-184
Author(s):  
Robert E. Tubbs ◽  
Hussein G. Aly Fouda ◽  
Abdulkader M. Afifi ◽  
Nickolas S. Raterman ◽  
Geraint W. Hughes ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
Red Sea ◽  
Seismic Data ◽  
Field Studies ◽  
Dead Sea ◽  
Strike Slip ◽  
Fault System ◽  
Gulf Of Aqaba ◽  
Geologic History ◽  
Angular Unconformity

ABSTRACT The Midyan Peninsula of northwest Saudi Arabia offers an exceptional opportunity to observe a complex interplay of rifting, salt tectonics, and strike-slip faulting. Recently onshore 3-D, transition zone 2-D, and offshore 2-D seismic data have been acquired in the area. In addition, ongoing fieldwork and an active drilling program have provided new insights into the geologic history of the region. The initial stages of continental rifting began during the Early Oligocene (ca. 33 Ma) and often utilized pre-existing basement fault trends. The early syn-rift sedimentary record is typified by formation of deep half-grabens filled with thick wedges of primarily continental sediments, with lesser amounts of evaporitic and marine deposits. Seismic data show a distinct break in deposition occurred ca. 21 Ma characterized by a persistent angular unconformity near the basin-bounding fault, before a shift to marine and offshore deposits of the Lower Miocene Burqan Formation. Post-Burqan a second angular unconformity termed the mid-clysmic event is evident away from the basin edge. This surface exhibits significant relief created by re-activation of older EW-trending faults and lower Maqna Group sediments display substantial thickening across these faults. Overall, the Maqna section transitions from normal marine sedimentation to more restricted basin conditions before being succeeded by the thick-layered evaporite sequence of the Mansiyah Formation. Approximately 15–12 Ma active strike-slip faults appeared in the Red Sea and shifted the extension from rift normal to highly oblique directed at N15°–20°E, parallel to the Gulf of Aqaba. During this transition the composition of the rift-fill changed as well from basin-wide precipitates to thick siliciclastic wedges of the Ghawwas Formation. Seismic images of the Ghawwas show abrupt thickness changes and stratal geometries that date deposition as coincident with both the growth of Mansiyah Formation diapirs and the movement of a large detachment at the base of the Mansiyah. Roughly five million years ago, organized seafloor spreading began in the southern Red Sea and strike-slip motion intensified as deformation began to focus along the Dead Sea/Aqaba strike-slip fault system. Adjacent to Midyan, a pull-apart basin in the Gulf of Aqaba has opened over 26 km perpendicular to the strike-slip system resulting in significant footwall uplift. The positive interference of the Aqaba/Dead Sea and Red Sea footwall uplifts has uniquely exposed the full syn-rift stratigraphic section from basement to Upper Miocene at Midyan, making the area an ideal locality for field studies. Presence of the complete Miocene section on the Aqaba shoulder uplift clearly indicates the uplift occurred after the Miocene. Salt-filled pull-apart basins in the same orientation as the Gulf of Aqaba are also observed on 3-D seismic data in the Ifal Basin.

scholarly journals Active faults' geometry in the Gulf of Aqaba, southern Dead Sea fault, illuminated by multi beam bathymetric data

2020 ◽  
Author(s):  
Matthieu Ribot ◽  
Yann Klinger ◽  
Sigurjón Jónsson ◽  
Ulas Avsar ◽  
Edwige Pons-Branchu ◽  
...  
Keyword(s):  
Active Faults ◽  
Dead Sea ◽  
Gulf Of Aqaba ◽  
Bathymetric Data
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