251 ISSN 0016-8521, Geotectonics, 2019, Vol. 53, No. 2, pp. 251–259. © Pleiades Publishing, Inc., 2019. Study of the Relationship between Recently Induced Earthquakes and Water Level at the Northwestern Side of Lake Nasser in Aswan Region, Egypt 1 Kh. A. Omar a, *, E. M. El-Amin a , S. A. Dahy a , and M. O. Ebraheem b a National Research Institute of Astronomy and Geophysics, Helwan, Egypt b Geology Department, Faculty of Science, New Valley Branch of Assiut University, Assiut, 71515 Egypt *e-mail: khaled.abdellah@nraig.sci.eg Received July 27, 2018; revised November 22, 2018; accepted November 27, 2018 Abstract—Lake Nasser is situated in an area with a very non-recurring earthquake, and revealed the history of Egypt registered 5000 years ago. After seventeen years of filling the Aswan High Dam reservoir began a long series of earthquakes caused. The main shock, Ms. = 5.6, occurred on November 14, 1981, preceded by sev- eral factions, followed by a large number of aftershocks. Thirty-three years later, seismic activity remains, but is much lower in frequency and volume. The aim of this paper is to study the effect of the reservoir on the induced seismic and determine the coordination mechanism of some earthquakes that occurred in the north- western part of High Dam reservoir. These investigations indicate that seismic activity occurred mainly along the Kalabsha fault and small parallel sectors, and there is a range of activities in the Khor al-Ramla area, about 40 km southwest of the High Dam. From 1982 to the end of 2017, seventy-five earthquakes with a mag- nitude of 3.5 ≤ M < 4.0 and 13 earthquakes of magnitude greater than or equal to 4.0 have occurred. It also shows that these earthquakes occurred during loading and unloading periods. This shows that the effect of the reservoir itself does not produce earthquakes, and there is no direct relationship between changing the daily rate and the magnitude of earthquakes. So it can’t be used as a predictor in the case of the Aswan reservoir, which is a unique reservoir in its behavior. The focused coordination mechanism of four different seismic zones in the west of Lake Nasser shows errors in striking the strike with a simple natural element. The P (pres- sure) and T (tension) stress axes are trending ESE–WNW and NNE–SSW, respectively. Keywords: pressure, tension, Kalabsha fault, composite focal mechanism DOI: 10.1134/S0016852119020067 INTRODUCTION The main objective of seismic monitoring in the reservoir is to detect the start of any seismic activity and follow its progress, both in space and time. Seis- mic earthquakes refer to earthquakes caused by human activities which, changes stress and strains in the earth’s crust. Induced earthquakes are of very low magnitude, and in many cases human activity is just the trigger of an earthquake that would naturally occur anyway. There are a number of ways in which induced earthquakes occur and from these manners, the mass of water in the reservoir changes the pressure in the rocks below, which can lead to earthquakes. Seismic events caused by the reservoir can be relatively large compared to other forms of induced earthquakes. There are few small-scale earthquakes occurring in the vicinity of artificial water reservoirs. It should also be noted that a large number of these sites exist in stable continental areas [12]. It is worth noting in this regard: Quinna (India), Kiribah (Zambia and Zimbabwe bor- der), Hsinfengkiang (China), Aswan (Egypt), etc. Lake Nasser or Aswan High Dam is a large indus- trial lake in southern Egypt and northern Sudan. It extends for 500 km along the Nile and covers the area between 20.45° and 23.97° N and from 30.17° to 33.25° E; to the west Desert of the Sahara Desert, and the Eastern Desert on the eastern side stretching to the Red Sea. On November 14, 1981, a 5.6-magnitude earthquake struck the Kalabshah area, along the Kalabshah fault, 70 km southwest of Aswan [21]. This earthquake is a very important event, because it is located away from the Aswan High Dam. Follow- ing this earthquake, many studies have already been published on seismic properties in the areas surround- ing the Aswan reservoir [5, 8, 10, 13, 14, 21, 22, 27].This sequence of earthquakes has raised many questions about the potential future activity of the local earth- quake, in particular the proximity of this activity to the Aswan reservoir. 1 The article is published in the original.