# GIS-Analysis for Active Tectonics Assessment of Wadi Al-Arish, Egypt
## 2 Study Area  
The Wadi Al-Arish catchment is in northern Egypt and covers most of the Sinai Peninsula. It flows northward to the Mediterranean Sea (Figure 1). The mouth of Wadi Al-Arish is occupied by Al-Arish City. The Wadi Al-Arish catchment is located between 29\({}^{\circ}\)00\({}^{\prime}\) and 31\({}^{\circ}\)00\({}^{\prime}\) N and 33\({}^{\circ}\)05\({}^{\prime}\) and 34\({}^{\circ}\)45\({}^{\prime}\) E, covers \(\sim\)23,300 km\({}^{2}\), and occupies \(\sim\)36% of the total area of the Sinai Peninsula. Mostly, water tributaries come from Sinai (\(\sim\)91%) and a few drain from the neighboring El-Naqp Desert [15; 16; 17]. Wadi Al-Arish drains the central highlands of the Peninsula and its upstream courses come from El-Egma and El-Teeh plateaus [16]. The geology of the Sinai Peninsula has been investigated, defined, and mapped by many researchers [18; 19; 20; 21]. The local lithology of Wadi Al-Arish has been remapped based on previous works and geological maps of Egypt prepared by Conoco and General Petroleum Corporation of Egypt [18] (Figure 2). The oldest exposed surface lithology in Wadi Al-Arish belongs to the Jurassic age, represented by Safa and Masajid Formations and made up of coal-bearing continental plastics with some marine carbonates with a few fossils, and marine shelf limestone with shale intercalations at the base. The Lower Cretaceous age is represented by the Risan' Aneiza Formation, which is composed of basal sandstone and conglomerate overlain by interbedded clastic and carbonate. The Upper Cretaceous is represented from the oldest to the youngest by undifferentiated deposits; the Raha Formation, Matulla Formation, and Suder Formation, respectively. The basal unit of the Upper Cretaceous is made up of clastic and biogenetic carbonate comprising Raha, Wata, Matulla, Qusier, and Duwi Formations. The Raha Formation consists of fossiliferous limestone with shale intercalations and oyster beds. The Matulla Formation consists of marine sandstone, marl, and shale. The Suder Formation was recognized as the youngest lithology of the Upper Cretaceous age, and consists of uniform marine chalk with thin shale intercalations. In Wadi Al-Arish, the Tertiary is represented by three units. They are arranged from base to top as the Esna Formation, which is composed of greenish-grey open marine shale, the Thebes Group (Egma Formation) that consists of bedded marine chalky limestone with a chert band, and the Plio-Pleistocene deposits comprising the Shagara and Marsa Alam Formations. The Quaternary deposits of the Wadi Al-Arish are represented by undifferentiated Quaternary deposits, stabilized dunes, wadi deposits, and sand dunes from the base to top, respectively. Figure 2 illustrates the geology of the entire study area. Historical and instrumental seismicity of the Sinai Peninsula have been investigated by many researchers [22; 23; 24; 25; 26; 27]. Twenty-five seismic events have been reported between 95 BC and 1910 AD at various localities with different intensities [28]. The reported intensities were based on recorded damage, which indicates heterogeneous behavior in space or time (Figure 3). Instrumentally, earthquakes have been reported in Egypt since 1903, and seismographs have been used since 1962 by the installing an observation station in the Helwan area, south of Cairo [24]. In the Sinai Peninsula, signals of earthquakes were recorded from 1900 to 1997 from a number of seismological stations. The main earthquakes of Sinai and surrounding areas are illustrated in Figure 3.  
Figure 3: Distribution of historical and instrument-monitored earthquakes that have affected Sinai. The focal mechanisms are illustrated for each earthquake. The red polygon indicates Wadi Al-Arish area. Figure 2: Detailed lithological map of the study area overlain by classified catchments/sub-catchments, modified after Reference in [18]. Tectonically, the Sinai sub-plate is a triangular continental block bounded between the African and Arabian plates and the Anatolian microplate [13; 29; 30; 31].