## 1 Introduction  
Saudi Vision 2030 sets a target to transform from an oil-based economy to a diversified economy based on renewable and sustainable energy to offer a supply of 9.5 GW by 2030 [1]. Thus, the Saudi government introduced several initiatives for investment in renewable energy such as wind, solar, and geothermal [2; 3; 4; 5]. Saudi Arabia has a series of hot springs (hydrothermal systems) and volcanic basaltic fields along the Red Sea coast that can be used for conventional geothermal systems. These resources are associated with tectonic (or volcanic) heating, which is related to the opening of the Red Sea/Gulf of Aqaba [6; 7]. An excellent ridge of hot dry rock (e.g., high-heat-generating granites) is also recognized in the Arabian shield and northwestern parts, which can be considered to be hot dry rocks (HDRs) that are good for enhanced geothermal systems (EGSs). EGSs, sometimes called hot dry rocks (HDRs), have been verified for 40 years [8]. The idea of an EGS is the use of hydraulic fracturing to create an artificial geothermal reservoir at deep depths (3-5 km). The technology of EGSs has been verified and is still under development all over the world. A total number of 18 sites of EGSs around the world (e.g., United States, Australia, the EU, South Korea, and Japan) are operating and under development [9]. The advantages of EGSs are that these technologies can function as baseload resources that produce power 24 h/day and they are available anywhere in the world. Good locations are over deep granite covered by a 3-5 km layer of insulating sediments that slow heat loss. An EGS plant is expected to have an economical lifetime of 20-30 years using current technology [10]. A global review of EGSs can be found in [9]. Worldwide, many authors have investigated geothermal resources, including EGSs, using a variety of geological, geochemical, and geophysical techniques in the last few years [11; 12; 13; 14]. More specifically, geophysical methods such as gravity, electromagnetic, and magnetotelluric have been regionally applied to explore geothermal HDRs at different basins in the world such as the Cooper Basin, Australia, and the Gonghe Basin, China. The geophysical resistivity method is one of the methods that can be used to explore and investigate geothermal resources. It provides information about the rock properties (e.g., porosity and permeability) and the degree of hydrothermal alteration, which can be used to determine the geometry and depths of geothermal reservoirs and to locate the fracture zones by means of resistivity contrasts [15; 16]. The electrical resistivity of geothermal reservoir rocks is associated with porosity, water, and the exchange capacity, and is strongly controlled by temperature. Therefore, exploring low-resistivity areas by geophysical methods based upon electric resistivities plays a significant role in identifying high-temperature zones related to geothermal reservoirs [11; 17]. One of the most important geophysical methods to map resistivity is the audio magnetotelluric (AMT) method. It is a natural source method that uses a frequency range from 1 Hz to 20 kHz (audio frequencies) and higher. It is commonly used in geothermal exploration. On the other hand, the gravity method, based on measuring the differences in the Earth's gravitational field at different locations, is usually used to understand the subsurface geological features on various scales [18]. The density models obtained from gravity data are non-unique solutions. However, gravity information can be successfully used in conjunction with AMT data by using integrated inversion procedures [19]. The final geological models represent the solution of a joint minimization process of both datasets. Geophysical exploration methods have contributed to the development of geothermal energy in Australia. One of the first successful projects for the exploration of HDRs using geophysical techniques was that undertaken by Geodynamics Limited (GDY) in the Cooper Basin in South Australia [20].