Contributions to Geophysics and Geodesy

Investigation into potential TEC changes due to 9 seismic tremors of 2021–2022

Kunvar S. YADAV — 2024-04-01

This research document delves into the analysis of alterations in Total Electron Content (TEC) as identified through GPS observations leading up to nine earthquakes that transpired between the late months of 2021 and 2022. The comprehensive study investigates the TEC variations and provides a detailed examination of heat maps centred around the earthquake epicentres. These heat maps, characterized by diverse latitudes and longitudes, play a pivotal role in validating the precise locations of the earthquake epicentres. Notably, the examination of these maps unveils discernible GPS TEC variations several days before the occurrence of each earthquake. In addition to the TEC analysis, the research sheds light on the fluctuations in solar magnetic parameters. The study elucidates instances where TEC peaks surpassed normal values, particularly during periods characterized by minimal solar radiation effects. This correlation between solar magnetic parameters and TEC fluctuations adds a nuanced layer to the understanding of the complex interplay of factors leading to seismic events. The cumulative findings derived from the investigation point towards a compelling conclusion: GPS TEC observations and the analysis of heat maps serve as indispensable indicators for identifying precursory signs that precede an impending earthquake. This multidimensional approach enhances our comprehension of the temporal and spatial aspects of seismic activity and underscores the potential significance of solar magnetic parameters in influencing such geophysical events.

Regular observations of the geomagnetic field at the Ógyalla observatory (present-day Hurbanovo) near the turn of the 20th century, including magnetic storms accompanied by auroras in March 1894, September 1898, and October 1903

Fridrich VALACH — 2024-04-01

From 1893 to 1905, the values of the geomagnetic field recorded three times a day are available from the Ógyalla magnetic observatory. We introduce these unique records, and at the same time, we provide an analysis of three noteworthy magnetic storms from this period, namely the events on 30 March 1894, 9 September 1898, and 31 October 1903. In addition to violent magnetic variations, remarkable auroras were observed in Central Europe during these events. The analysed events indicate that the source of the most intense, potentially dangerous geomagnetic disturbances can be the electric currents of the auroral oval or the field-aligned currents connected to the auroral oval.

Exploring carbonate reservoirs potential, north Egypt

Mohamed Said RADWAN — 2024-04-01

Carbonate reservoirs contain a significant portion of the world's oil reserves. The Middle East is home to many of these reservoirs. Carbonate reservoirs can be found in a few very large oil fields, including Egypt's Zohr field, the largest conventional gas field in Egypt. In this article, we present a couple of successful tertiary carbonate reservoirs that are bearing hydrocarbon in the Egyptian Western Desert and Gulf of Suez provinces, they are distributed across Egypt's subsurface, and they are characterized by heterogeneous porosity and permeability. These heterogeneities are caused by the wide spectrum of tectonostratigraphic environments in which carbonates are deposited and by subsequent diagenetic alteration of the original rock fabric. The structural analysis of the study areas based on the interpretation of both geophysical and geological data, in JD, Abu Sennan, and the North Amer areas in the Western Desert and offshore Gulf of Suez respectively showed that tectonostratigraphic history during tertiary time affected a great extent carbonate reservoir quality. Major fault trends formed secondary fracture porosity possibly allowing hydrothermal solutions to pass through the reservoirs and form secondary vuggy porosity. These characteristics are considered important factors of promising carbonate reservoirs. In this study, several carbonate reservoirs have been outlined. The study workflow helped us better identify carbonate prospects with high fractured density.

Comparison of anomalies in the VLF spectrum of the natural electromagnetic field with data from the seismometer in a landslide-affected area

Michal HOFFMAN — 2024-04-01

The data from a permanent monitoring station, based on a sound card as an AD/DA converter and a magnetic loop antenna for continuous recording of electromagnetic field intensities in the Very Low Frequency (VLF) range, were recorded and compared with data from a seismic station based on Raspberry Pi located in a landslide-affected area. The stations operated 24/7 and were placed in a room below ground level. Correlations were observed between seismic signals in the frequency spectrum from 0.1 Hz to 10 Hz (some extending beyond 20 Hz) and anomalies in the electromagnetic field in the VLF range. These anomalies are likely associated with micro-fracturing, piezo-electromagnetic, and triboelectric phenomena within the landslide body, producing relatively weak VLF emissions and a faint seismic signal. A single-component 4.5 Hz 395 Ohm vertical Racotech RGI-20DX geophone with electronic extension to lower frequencies (< 1 Hz) was used with a sampling rate of 100 sps (samples per second). VLF emissions cover almost the entire spectrum from 6 kHz with a peak at 14 kHz to 18 kHz. The received spectrum was divided into following sections: VLF band 4 kHz – 6 kHz; 6 kHz – 8 kHz; 8 kHz – 10 kHz; 10 kHz – 12 kHz; 12 kHz – 14 kHz; 14 kHz – 16 kHz; 16 kHz – 18 kHz. Simultaneously, there were changes in these sections analysed and compared with the seismic record within the same time interval.

Probabilistic forecast of next earthquake event in Makran subduction zone using Weibull distribution

Adil REHMAN — 2024-04-01

Earthquake is the most lethal type of natural disaster. Researchers have been working to develop precise earthquake prediction methods to save lives. A statistical investigation is an effective earthquake prediction method because they offer more details about the seismic risk or hazard issue. This study utilizes seismic data from the Makran subduction zone from 1934 to 2017. Probability distributions may be employed to assess the risk of seismic events and earthquake occurrence probability. This work estimates the probability of the next major event in the Makran subduction zone through Weibull distribution by considering strong earthquakes with a magnitude (M_w ≥ 6) in the intervals (in years) between two consecutive earthquakes. The probabilities of the forthcoming seismic event have been estimated based on the previous earthquake record, pictorially. The calculated parameters of the Weibull distribution for the Makran subduction zone may help to forecast the probabilities of a strong earthquake and describe the pattern of earthquake average return time. The calculated probability for the Weibull distribution reaches 0.92 after ten years since the last strong earthquake in 2021, indicating that the Weibull distribution within and around the present research area in 2031 will be 92%.

Evaluation of the air quality in arid climate megacities (Case study: Greater Cairo)

Mohammed Mahmoud A. HWEHY — 2024-04-01

The accelerated urbanization in the last decade and population growth in developing countries in the Middle East and North Africa (MENA) region have increased the count of humans exposed to air pollution. This work aims to provide an insight into air quality in the Greater Cairo (GC) area which is one of the largest megacities in the MENA region and is classified as its most polluted city according to the reports of the World Health Organization (WHO). Exploratory data analysis and cluster analysis were used to assess the pollutants data and meteorological data to understand the impacts of weather factors on air quality in GC. According to the results, GC suffers from particle matter of 10 micrometres or less (PM10) pollutants. The annual averages ranged from 97 ± 10 to 203 ± 42 μg/m³. Though short-term exposure to gaseous pollutants did not exceed the limits, the long-term exposures exceeded those in some congested traffic areas. The annual averages ranged from 20 ± 5 to 63 ± 24 μg/m³ for Nitrogen dioxide (NO₂) and from 9 ± 3 to 21 ± 5 μg/m³ for sulphur dioxide (SO₂). Also, the terrain affects the spatial variation of pollutants observation. There is a negative correlation between the monitoring site elevation and the pollutant concentration.