Potential earthquake precursors include, among others, electromagnetic fields, gas emissions, Land Surface Temperature (LST), Sea Surface Temperature (SST), and Surface Air Temperature (SAT) anomalies. These observables have been individually studied, before earthquakes, by many researchers. The ionospheric studies concerning earthquakes (EQs) using magnetic data from Low Earth Orbit (LEO) satellites are increasingly being used to detect ionospheric anomalies before large EQs. Also, LST, SST, and SAT values retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua satellites and Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) are considered as physical precursors before EQs. In this work, we jointly analyze magnetic, MODIS, and MERRA-2 data in space and time around the epicenters before the selected EQs in Mexico, Japan, Chile, and Indonesia. Our analyses present interesting findings where anomalies in temperature and magnetic field, preceding the considered EQs, are confirmed through different methods. Particularly, we utilize the Fast Fourier Transform (FFT) and the Discrete Cosine Transform (DCT) for analyzing magnetic data over the designated EQs regions. We use the magnetic data acquired by Swarm satellites in the top side ionosphere along with MODIS and MERRA-2. Five case studies are described to prove the effectiveness of our analyses. Precursory anomalies were observed using these methods in different anomalous days from the considered four regions of interest around the epicenter. It is concluded that these methods could be effective and reliable in detecting anomalies preceding the upcoming EQs.

Egypt is characterized by moderate size seismicity where earthquakes are distributed within several active regions. In the present study, we investigated the source mechanism of earthquakes using the digital waveform data recorded by the Egyptian National Seismic Network (ENSN) during the period from 2004 to 2008. The focal mechanisms are constructed with high reliability based on the polarity of the first motion of P-wave.These solutions are used to examine the mode of tectonic deformation and the present-day stress field pattern affecting on different tectonic provinces in the northern part of Egypt. The results demonstrate mainly a normal faulting mechanism with minor strike slip component generally trending parallel to the northern Red Sea, the Suez rift, Aqaba rift with their connection with the great rift system of the Red Sea and the Gulf of Suez and Cairo-Alexandria trend.The inversion technique scheme is used also in the present study for determining the regional stress field parameters for earthquake focal mechanism solutions based on the grid search method of Gephart and Forsyth (1984). The Results of the stress tensor using focal mechanisms of recent earthquakes show a prevailed tension stress field in N52°E, N41°E and N52°E for the northern Red Sea, Gulf of Suez and Gulf of Aqaba zone respectively

On the 16th June, 2020, a moderate earthquake (Mw = 5.2) hit the Northern Red Sea region, Egypt, that was felt throughout the Hurghada and Sharm El-Sheikh cities and the surrounding areas without any damages. The thermal anomaly before the earthquakes was widely studied with satellite data, such as NOAA/AVHRR and MODIS. The case study aims to monitor and demonstrate the possibility of any variation of the thermal anomaly of sea surface temperature (SST) before and after the 16th June 2020 earthquake and to correlate the results with the previous heat flow study (deep thermal action). The Daytime/Nighttime (SST) data are retrieved from the OBPG serves as a Distributed Active Archive Center (OB. DAAC). The outputs indicated a thermal anomaly on the June 12th, 2020 a few days before the earthquake, covered a large area around the epicenter 60 km impact area, and reached a high value on the 15th June 2020, one day before the earthquake. For the deep thermal action of the entire crust, the earthquake frequency distributions presumed from the reviewed catalogue indicated that the peak of the seismicity is concentrated close to the center of the rift axis in the Northern Red Sea. The heat flow measurements are increased toward the center of the Red Sea rift and decreased toward both sides, generating some partial melt of the rocks and producing crustal subsidence at the center of the Red Sea rift. These results are compatible with the pattern of the seismic activity and heat flow effect around the epicenter. It could be considered as a short-term precursor of the earthquake.