Abstract. We study the sedimentary record of past tsunamis along the coastal area west of Alexandria (NW Egypt) taking into account the occurrence of major historical earthquakes in the eastern Mediterranean. The two selected sites at Kefr Saber (∼32 km west of Marsa-Matrouh city) and ∼ 10 km northwest of El Alamein village are coastal lagoons protected by 2–20 m-high dunes parallel to the shoreline. Field data were collected by (1) coastal geomorphology along estuaries, wedge-protected and dune-protected lagoons; and (2) identification and spatial distribution of paleotsunamis deposits using five trenches (1.5 m-depth) at Kefr Saber and twelve cores (1 to 2.5 m-depth) at El Alamein. Detailed logging of sedimentary sections was conducted using X-rays, grain size and sorting, total organic and inorganic matter, bulk mineralogy, magnetic susceptibility, and radiocarbon dating to identify past tsunamis records. Generally of low energy, the stratigraphic succession made of coastal lagoon and alluvial deposits includes intercalated high-energy deposits made of mixed fine and coarse sand with broken shells, interpreted as catastrophic layers correlated with tsunami deposits. Radiocarbon dating of 46 samples consist in mixed old (>13 000 BP) and young (<5500 BP), dated charcoal and shells in sedimentary units correlate with the 24 June AD 1870 (Mw 7.5), 8 August AD 1303 (Mw ∼ 8) and 21 July AD 365 (Mw 8–8.5) large tsunamigenic earthquakes that caused inundation along the Alexandria and northern Egyptian shoreline. Our results point out the size and recurrence of past tsunamis and the potential for future tsunami hazards on the Egyptian coastline and the eastern Mediterranean regions.
Ethiopia began constructing the Grand Ethiopian Renaissance Dam (GERD) in 2011 on the Blue Nile near the borders of Sudan for electricity production. The dam was constructed as a roller-compacted concrete (RCC) gravity-type dam, comprising two power stations, three spillways, and the Saddle Dam. The main dam is expected to be 145 m high and 1780 m long. After filling of the dam, the estimated volume of Nile water to be bounded is about 74 billion m3. The first filling of the dam reservoir started in July 2020. It is crucial to monitor the newly impounded lake and its size for the water security balance for the Nile countries. We used remote sensing techniques and a geographic information system to analyze different satellite images, including multi-looking Sentinel-2, Landsat-9, and Sentinel-1 (SAR), to monitor the changes in the volume of water from 21 July 2020 to 28 August 2022. The volume of Nile water during and after the first, second, and third filling was estimated for the Grand Ethiopian Renaissance Dam (GERD) Reservoir Lake and compared for future hazards and environmental impacts. The proposed monitoring and early warning system of the Nile Basin lakes is essential to act as a confidence-building measure and provide an opportunity for cooperation between the Nile Basin countries.
Abstract. We study the sedimentary record of past tsunamis along the coastal area west of Alexandria (NW Egypt) taking into account the occurrence of major historical earthquakes in the eastern Mediterranean. The two selected sites at Kefr Saber (~ 32-km west of Marsa-Matrouh city) and ~ 10 km northwest of El Alamein village are coastal lagoons protected by 2 to 20-m-high dunes parallel to the shoreline. Field data were collected by: (1) Coastal geomorphology along estuaries, wedge-protected and dune-protected lagoons, and (2) identification of paleotsunamis deposits and their spatial distribution using five trenches (1.5-m-depth) at Kefr Saber and twelve cores (1 to 2.5-m-depth) at El Alamein. Detailed logging of sedimentary sections were analysed using X rays, grain size and sorting, total organic and inorganic matter, bulk mineralogy, magnetic susceptibility and radiocarbon dating necessary for the identification of past tsunamis records. Generally of low energy, the stratigraphic succession made of marine and alluvial deposits includes intercalated high-energy deposits made of mixed fine and coarse sand with broken shells, interpreted as catastrophic layers correlated with tsunami deposits. Although the radiocarbon dating of 46 samples consist in mixed old (> 13 000 year BP) and young (
Large earthquakes have affected Gulf of Aqaba with magnitudes ranging from 6 to 7.3 as examples in years 1068, 1212, 1588 AD during historical records. In recent seismicity, a large earthquake occurred on 22 November 1995, of Mw 7.3 that triggered a small tsunami that affected the port of Nuweiba in Egypt, Eilat and Aqaba beaches. The epicenter of this earthquake has been occurred between the Aragonese and Eilat basin at the central part of the Gulf of Aqaba. The long low seismicity, especially for significant events at the southern Arnona fault, manifested its act as possible seismic gap with an expected a future rupture of Mw 7.2 earthquake. This event will affect the three countries Egypt, Saudi Arabia, Jordon Israel coastal cities using two scenarios. We used Mirone version 3.10 software to calculate the maximum wave height at the Gulf of Aqaba cities. The main two tested scenarios depend on the 22 November 1995 which was earthquake located at the Aragonese fault and the 1068 or 1839 AD earthquake with epicenters at Arnona fault at Aqaba basins. The Nov.,1995 scenario will produce a maximum wave height of 2.10 meters in the Nuweiba and 0.5 meters at Dahab coastal cities and 0.7 meters at Eilat city. The Arnona fault second scenario will produced a maximum wave height of 1.2 m Dahab, 1.8 m Nuweiba coastal cites at Egypt and 2.10 meters at Magna Saudi Arabia with less wave height to 1.2 m at Eilat city and Aqaba at Israel and Jordon respectively.
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