Remote sensing and geophysical studies for groundwater exploration in Osmania University campus, Hyderabad, India: A case study

With the increasing resolution of satellite sensors, it is possible to fruitfully exploit the special advantages of image analysis for a wide range of geological environments. With this view, a LISS-III and PAN merged image of the 1600 acre (approximately 6.5 sq km) Osmania University (OU) campus taken from IRS-ID in the month of May (a fairly representative month in terms of minimum annual drainage/vegetation cover) was acquired. The image was then digitally processed and visually interpreted for potential groundwater resource regions. Since occurrence of groundwater in crystalline rocks, the host rocks for the entire Hyderabad region, is generally associated with secondary porosity, the accent was on determining and establishing lineaments of considerable surface extent. This was then augmented with maps of subsurface features as obtained from geophysical studies for the southern part of 0 U campus and available bore well/open well information. Subsequently, information from the three sources was integrated for a better understanding of the geological situation and the interrelationship of its various constituents to determine possible locations of groundwater resources. The significant findings comprised the identification of three major dykes, two running E-W and the third running NE-SW. A major N-S linear exposure of granitic rocks, as also several criss-crossing fractures in the southern side of the campus, along with the prevailing drainage pattern for the entire campus area were mapped. Based on these findings and supporting geophysical/hydrogeological data, a geological/lithological map of Osmania University campus was prepared and prospective groundwater zones have been identified.

What Would Happen If the M 7.3 (1721) and M 7.4 (1780) Historical Earthquakes of Tabriz City (NW Iran) Occurred Again in 2021?

Tabriz is located in the northwest of Iran. Two huge earthquakes with magnitudes of 7.4 and 7.3 occurred there in 1780 and 1721. These earthquakes caused considerable damage and casualties in Tabriz. Using the method of scenario building, we aim to investigate what would happen if such earthquakes occurred in 2021. This scenario building was carried out using deterministic and GIS-oriented techniques to find the levels of damage and casualties that would occur. This procedure included two steps. In the first step, a database of factors affecting the destructive power of earthquakes was prepared. In the next step, hierarchical analysis was used to weigh the data, and then the weighted data were combined with an earthquake intensity map. The obtained results were used to predict the earthquake intensity in Tabriz. According to our results, the earthquake with a magnitude of 7.3 that occurred in 1721 caused huge destruction in the north of Tabriz, as this earthquake occurred inside the site. However, this earthquake caused minimal damage to the south of the city owing to the geological situation of this area of Tabriz. The earthquake with a magnitude of 7.3 that occurred in 1780 caused less damage because of its distance from the site. In the third step of this analysis, the vulnerability of buildings and the population were examined. According to the estimates, District 4 would experience the highest damage rate in the earthquake of 1721, with 15,477 buildings destroyed, while this area would have a lower damage rate in the earthquake that occurred in 1780. The total casualties in Tabriz would number 152,092 and 505 people in the earthquakes of 1721 and 1780, respectively.

Deflection Laws of Gas Drainage Boreholes in Interbedded Soft and Hard Seams: A Case Study at Xinzheng Coal Mine, China

Coal and gas outbursts can lead to serious disasters in coal mines. The drilling of boreholes to predrain the gas is an effective measure for preventing such accidents. However, due to the complexity of the geological situation, the drilling trajectory often deviates from the design trajectory, resulting in poor gas extraction. To solve the problem of gas drainage borehole deflection, an analytic hierarchy process (AHP) model is established based on geological factors, technical factors, and human factors. The AHP model is used to rank the weights of various influencing factors, and the analysis is combined with a drilling model and engineering examples. Finally, the results show that soft and hard interlayers are the most important factors affecting the deflection of the borehole. The rock drilling model is mainly affected by the formation forces. The regularity of the change in the azimuth angle during drilling is not obvious when the angle of the encountered layer is less than some critical value. When the borehole is skewed downward, the deflection angle ranges from 0 to 4°, and the deflection of the borehole occurs mainly at the interface of the rock layers. When the angle of the encountered layer is greater than the critical value, the borehole is skewed upward, with a deflection angle of 0–6°, and the deflection occurs at the rock interface. The trajectory curve obtained by theoretical predictions from field data is found to be consistent with that of an actual project.

Local CMP stacking improvement technique for better traceability of separate reflection horizon

В последние годы всё больше объектов сейсморазведочных работ относится к проблемным территориям, характеризующимся неблагоприятными поверхностными условиями и сложной геологической обстановкой. Получение качественных сейсмических изображений при обработке в таких случаях входит в число приоритетных направлений современной сейсморазведки. Одним из путей решения проблем ухудшения прослеживаемости сейсмических горизонтов в сложных условиях является оптимизированное суммирование общей средней точки (ОСТ), учитывающее качество входных сейсмических данных. Цель исследования. Настоящая работа посвящена созданию и тестированию гибкой, универсальной методики оптимизации суммирования ОСТ на конечной стадии полевой или камеральной обработки сейсмических данных метода отражённых волн общей глубинной точки (МОВ-ОГТ 2D/3D) для улучшения прослеживаемости отражающих горизонтов. При создании такой методики важным требованием являлась возможность реализации в существующем программном обеспечении (ПО), в том числе, отечественном. Методы исследования. Для исследования влияния сложных геологических объектов на распределение энергии в выборках ОСТ было выполнено построение иллюминационной модели по целевому горизонту, расположенному под эрозионным врезом. Оценка влияния рассеивающих аномалий верхней части разреза (ВЧР) проводилась с помощью двумерного лучевого моделирования с получение синтетических сейсмограмм ОПВ по горизонтально-слоистому модельному разрезу, содержащему участок палеокарста. Чтобы оценить потенциал применения предлагаемой методики были генерированы синтетические данные, содержащие сильные помехи различной природы, а также зону падения амплитуды полезного сигнала. По этим данным были разными способами получены и оценены суммарные трассы. Предлагаемая методика также была опробована на реальных данных метода общей глубинной точки (МОГТ-2D). Оценка результатов работы различных вариантов суммирования выполнялась визуально, а также количественно (с помощью атрибутного анализа). Результаты работы. Выполненное исследование показало недостаточную эффективность стандартного суммирования ОСТ для сложных сейсмических данных. Польза от применения существующих методик улучшения суммирования ОСТ очевидна, но они имеют недостатки: нарушение естественной динамики волновой картины, невозможность локального применения, необходимость реализации в специальном ПО. Предлагаемая авторами методика оптимизации суммирования даёт высокую гибкость и маневренность работы и позволяет справиться с вышеуказанными проблемами. Свободный выбор критериев взвешивания интервалов трасс на основе анализа пользовательского набора атрибутов открывает широкие возможности тонкой настройки процедуры, вводит интерпретационную составляющую в процесс оптимизации суммирования, делая его более осмысленным в геолого-геофизическом отношении. Предлагаемая методика не требует написания и опробования нового специального ПО и может быть реализована в уже имеющихся сейсмических пакетах, включая и российские программные комплексы Today increasingly more objects of prospecting seismology belong to problem areas characterized by unfavorable surface conditions and complex geological situation. Acquiring of high-quality seismic images by processing in these cases is a part of priority directions of modern prospecting seismology. One of the way to overcome the problem of seismic horizon traceability worsening in hard conditions is optimized CMP stacking, considering the quality of input seismic data. Aim. This work is devoted to generation and examination of flexible universal technique of optimized stacking on the last stage of field or final processing of 2D/3D reflection seismic data for seismic horizon traceability improvement. Creating this technique assumed important condition of embodiment ability in existing software (including Russian). Methods. Illumination model building was performed for target horizon, located beneath the erosive cut for studying of complex geological objects influence on energy distribution in CMP gathers. Scattering superficial anomalies influence was estimated by means of 2D ray tracing and synthetic shot records generation on horizontally layered model sectionconsisting near surface ancient karst spot. Synthetic data with different kinds of noise and signal amplitude decay zone war generated to appreciate implementation potential of introducing technique. Stacked traces were obtained and evaluated on this data with different methods. The introduced technique was tested on real 2D seismic data too. Evaluation of results of different kinds of stacking was performed by sight and with quantitative (attribute) analysis. Results. Performed research showed insufficient efficiency convenience CMP stacking for complex seismic data. The advantages of existing CMP stacking improvement methods are obvious but there are drawbacks too: natural wave field dynamic violation, disability of local implementation, need of special software development. Offered technique of stacking optimization gives high flexibility and mobility in work and allow overcoming the aforementioned problems. Easy choice of trace range weighting criteria based on customer attribute set analysis gives wide opportunities of fine-tuning for this procedure, bringing in interpretation term of stack optimization process and making it more sensible in geological-geophysical relation. This technique need not new software development and testing, it could be embodied in existing seismic software suites, including Russian complexes

Joint Analysis as an Important Tool for an Optimizing Block Extraction of Natural Stones

The steadily increasing demand on the natural stone market is accompanied by a predominantly poor economic balance in the extraction of the raw material "ornamental stone". Thus, the net production of raw blocks is far too low in relation to the resulting overburden, which is often the result of insufficient geoscientific input and evaluation of the deposit itself and the deposit-controlling factors.Under these conditions, the investigation pursued the goal of capturing an essential part of the geological conditions with the analytical observation of the fractures systems, in order to contribute to an optimized stone extraction. Only by critically derived constraints on the quarrying process based on the geological situation can the economic viability of natural stone deposits be maintained or increased in the long term, and this from an environmentally friendly point of view.Profitable dimensional stone production mainly depends on the number of extracted blocks. Compared to statistical approaches the application of the 3D-BlockExpert computer code is based on modelling the block sizes on the discontinuity system such as fracture spacing and fracture orientation. The assessment of all joint and fracture systems provides a forwards-looking approach for sustainable quarry management. It is essential to make the best possible use of high-quality material and to minimize the impact of quarrying activities to nature. Investigations were carried out in quarry areas of different lithologies in Germany and Spain like sandstones, limestones, slate and granites. The block sizes, the irregularity of acute-angled blocks and the waste to block ratio controls the economic success by avoiding time- and cost-consuming procedures based on geoscientific considerations.

Research on Pseudo-2D Joint Inversion of TEM and CSAMT Based on Well Log Constraint

The transient electromagnetic method (TEM) and controlled-source audio-frequency magnetotellurics method (CSAMT) are commonly used in detecting water abundance of rock formation and faults in coal mines. However, these methods show low accuracy, given the multiplicity of their inversion results, especially for areas with minor differences in lithology and electrical property. To improve the accuracy of electromagnetic exploration, a pseudo-2D joint inversion is performed. The objective function of this pseudo-2D joint inversion is established, and the joint inversion process is constrained by resistivity logging data. Afterward, the symmetric successive over-relaxation (SSOR) is used to realize the pseudo-2D joint inversion calculation of TEM and CSAMT with well log constraint. The effectiveness of joint inversion is verified by combining synthetic and field data. Results show that the pseudo-2D joint inversion results of TEM and CSAMT with well log constraint correspond to the actual geological situation. Compared with either TEM or CSAMT, joint inversion has a significantly better capability of reflecting water abundance in rock formation and faults.

Integrated land and water-borne geophysical surveys shed light on the sudden drying of large karst lakes in southern Mexico

Karst water resources play an important role in drinking water supply but are highly vulnerable to even slight changes in climate. Thus, solid and spatially dense geological information is needed to model the response of karst hydrological systems to such changes. Additionally, environmental information archived in lake sediments can be used to understand past climate effects on karst water systems. In the present study, we carry out a multi-methodological geophysical survey to investigate the geological situation and sedimentary infill of two karst lakes (Metzabok and Tzibaná) of the Lacandon Forest in Chiapas, southern Mexico. Both lakes present large seasonal lake-level fluctuations and experienced an unusually sudden and strong lake-level decline in the first half of 2019, leaving Lake Metzabok (maximum depth ∼25 m) completely dry and Lake Tzibaná (depth ∼70 m) with a water level decreased by approx. 15 m. Before this event, during a lake-level high stand in March 2018, we collected water-borne seismic data with a sub-bottom profiler (SBP) and transient electromagnetic (TEM) data with a newly developed floating single-loop configuration. In October 2019, after the sudden drainage event, we took advantage of this unique situation and carried out complementary measurements directly on the exposed lake floor of Lakes Metzabok and Tzibaná. During this second campaign, we collected time-domain induced polarization (TDIP) and seismic refraction tomography (SRT) data. By integrating the multi-methodological data set, we (1) identify 5–6 m thick, likely undisturbed sediment sequences on the bottom of both lakes, which are suitable for future paleoenvironmental drilling campaigns, (2) develop a comprehensive geological model implying a strong interconnectivity between surface water and karst aquifer, and (3) evaluate the potential of the applied geophysical approach for the reconnaissance of the geological situation of karst lakes. This methodological evaluation reveals that under the given circumstances, (i) SBP and TDIP phase images consistently resolve the thickness of the fine-grained lacustrine sediments covering the lake floor, (ii) TEM and TDIP resistivity images consistently detect the upper limit of the limestone bedrock and the geometry of fluvial deposits of a river delta, and (iii) TDIP and SRT images suggest the existence of a layer that separates the lacustrine sediments from the limestone bedrock and consists of collapse debris mixed with lacustrine sediments. Our results show that the combination of seismic methods, which are most widely used for lake-bottom reconnaissance, with resistivity-based methods such as TEM and TDIP can significantly improve the interpretation by resolving geological units or bedrock heterogeneities, which are not visible from seismic data. Only the use of complementary methods provides sufficient information to develop comprehensive geological models of such complex karst environments

Risk assessment of water and mud inrush in a tunnel in Chongqing based on analytic hierarchy process

Water and mud inrush is one of the typical geological hazards during tunnel construction in karst area. In weight of water or mud inrush risks of karst tunnels are studied and the index system for water and mud inrush risk evaluation is established based on analytic hierarchy process. The analysis shows that geological structure, formation lithology and groundwater level are the main control ingredients of water or mud inrush risk；geographic and geomorphic conditions, attitude of rock formation are the minor significant factors；surrounding rock mass classification , rainfall are the least important elements. Aiming at a tunnel in Chongqing, combining with the actual geological situation of the tunnel site, the evaluation model is used to evaluate the risk of water and mud inrush in each section, which provides a certain theoretical basis for the prevention and control of water and mud inrush disaster during the tunnel construction.

TYPES OF RIVERS FEEDING SEDIMENTARY BASINS ON THE SOUTHEASTERN EDGE OF THE SIBERIAN PLATFORM DURING THE RIPHEAN: SKETCH OF RECONSTRUCTION

Some geochemical features of fine-grained clastic/clay rocks of a number of Riphean formations of the Yudoma-Maya region of southeastern Yakutia are considered. A comparison of the distribution character of the data points of individual and average samples of clay rocks in the (La/Yb)N–Eu/Eu* and (La/Yb)N–Th diagrams, which show the composition of the bottom sediments of the estuarine parts of modern rivers of various categories, allowed us to make a number of conclusions. Thus, individual data points on the (La/Yb)N–Eu/Eu* diagram are concentrated mainly in the fields of bottom sediments of rivers feeding on erosion products of mainly sedimentary (categories 1 and 2) and volcanic rocks (category 4), as well as their overlapping zones. The average data point of the clay rocks of the Trekhgorka Formation in this diagram is located in the field of bottom sediments of rivers draining magmatic/metamorphic terranes (category 3). The average data points of shales of the Dim, Talyn, and Svetly formations are located in the zone of overlapping fields of bottom sediments of rivers of categories 1, 2, and 3, i.e., they contain erosion products of both sedimentary formations and magmatic and metamorphic complexes. This is quite well consistent with the real geological situation. At the same time, in the composition of clayey rocks of higher stratigraphic levels of Riphean, erosion products of magmatic/metamorphic terranes are either absent or their proportion is very small. On the (La/Yb)N–Th graph, most of the individual data points of Riphean clayey rocks tend to be in the fields 1, 2, and 4. Their average data points are mainly confined to the overlapping zone of the fields of bottom sediments of rivers of categories 1 and 2. The average data point of clay rocks of Ust-Kirba Formation is located in the field of bottom sediments of rivers that feed on products of erosion from rocks of volcanic provinces. It also does not contradict the real geological situation.