Regional Geological Structures Research Articles

A conceptual and numerical model of fluid flow and heat transport in the Topusko hydrothermal system

Comprehensive understanding of hydrothermal systems is often obtained through the integration of conceptual and numerical modelling. This integrated approach provides a structured framework for the reconstruction and quantification of fluid dynamics in the reservoir, thereby facilitating informed decision-making for sustainable utilisation and environmental protection of the hydrothermal system. In this study, an updated conceptual model of the Topusko hydrothermal system (THS; central Croatia) is proposed based on structural, geochemical, and hydrogeological analyses. The stratigraphic sequence and the structural framework of the THS were defined based on geological maps and field investigations. As depicted by hydrochemical and isotope analyses, thermal waters in Topusko (temperatures of up to 65 °C) are of meteoric origin and circulate in a carbonate aquifer. The THS receives diffuse recharge approximately 13 km S from Topusko, where Triassic carbonates crop out. Gravity-driven regional groundwater circulation is favoured by regional thrusts that tectonically uplifted Palaeozoic low permeable rocks. These structures confine the fluid flow in the permeable, fractured and karstified, Triassic carbonates favouring the northward circulation of the water. A regional anticline lifts the aquifer closer to the surface in Topusko. Open fractures in the anticline hinge zone increase the fracturing and permeability field of the aquifer promoting the quick upwelling of the thermal water resulting in the Topusko thermal springs. Numerical simulations of fluid flow and heat transport corroborate the proposed conceptual model. In particular, a thermal anomaly was modelled in the Topusko subsurface with temperature values of 31.3 °C and 59.5 °C at the surface and at the base of the thermal aquifer, respectively, approaching the field observations. These findings showed that the circulation of Topusko thermal water is influenced by regional and local geological structures suggesting that the enhanced permeability field in the discharge area enables the formation of the natural thermal springs.

The Xerias Window near Argos (Peloponnesus) - an example of a regional geological structure of interregional importance

The Argolic-Arcadian border range is built up by rocks of the Tripolitza and the Pindos Zones. Its tectonic architecture is deeply exposed in the area of the Xerias Window. Key structures are worked out in this article. The nappe-shaped superposition of the Tripolitza Zone by the Pindos Zone is obvious in the frame of the Xerias Window. The vergence of the key structures of the latter varies everywhere between W and SW, which proves a relative transport of the Pindos Zone as a whole in that direction. After finishing the nappe transport both Pindos and Tripolitza Zone experienced further, collective deformations, which are brought in a probable chronological order. Round about since Upper Miocene, the compressive stress of the Hellenides was followed by young extensional tectonics, which continues until today. Its influence on the development of the window and on the forming of its frame is described. The most important faults that can be related to the spreading tectonics are called within this investigation as Xerias Faults. Finally, the impacts of the strong regressive erosion, of the numerous landslides, and of the widespread slope waste both on exposing and on covering the tectonic elements are regarded.

Fault Kinematics of the 2023 Mw 6.0 Jishishan Earthquake, China, Characterized by Interferometric Synthetic Aperture Radar Observations

Characterizing the coseismic slip behaviors of earthquakes could offer a better understanding of regional crustal deformation and future seismic potential assessments. On 18 December 2023, an Mw 6.0 earthquake occurred on the Lajishan–Jishishan fault system (LJFS) in the northeastern Tibetan Plateau, causing serious damage and casualties. The seismogenic fault hosting this earthquake is not well constrained, as no surface rupture was identified in the field. To address this issue, in this study, we use Interferometric Synthetic Aperture Radar (InSAR) data to investigate the coseismic surface deformation of this earthquake and invert both ascending and descending line-of-sight observations to probe the seismogenic fault and its slip characteristics. The InSAR observations show up to ~6 cm surface uplift caused by the Jishishan earthquake, which is consistent with the thrust-dominated focal mechanism. A Bayesian-based dislocation modeling indicates that two fault models, with eastern and western dip orientations, could reasonably fit the InSAR observations. By calculating the coseismic Coulomb failure stress changes (∆CFS) induced by both fault models, we find that the east-dipping fault scenario could reasonably explain the aftershock distributions under the framework of stress triggering, while the west-dipping fault scenario produced a negative ∆CFS in the region of dense aftershocks. Integrating regional geological structures, we suggest that the seismogenic fault of the Jishishan earthquake, which strikes NNE with a dip of 56° to the east, may be either the Jishishan western margin fault or a secondary buried branch. The optimal finite-fault slip modeling shows that the coseismic slip was dominated by reverse slip and confined to a depth range between ~5 and 15 km. The released seismic moment is 1.61 × 1018 N·m, which is equivalent to an Mw 6.07 earthquake. While the Jishishan earthquake ruptured a fault segment of approximately 20 km, it only released a small part of the seismic moment that was accumulated along the 220 km long Lajishan–Jishishan fault system. The remaining segments of the Lajishan–Jishishan fault system still have the capability to generate moderate-to-large earthquakes in the future.

Tectonic Basis for Oil and Gas Potential in the North Kara Prospective Oil and Gas Region (Western Arctic, Russia)

—Russia’s Arctic shelf and, in particular, the Kara Sea shelf, is one of the unique regions in the world with enormous hydrocarbon potential; however, due to the harsh climate conditions, it has been studied unevenly. The lack of deep and parametric drilling data in the northern Kara Sea leads to numerous uncertainties in regional geological structure models and, as a consequence, in assessing the resource potential of this Arctic region. A vast number of 2D CDP seismic explorations were carried out in the northern Kara Sea. The results of these studies made it possible to refine the geological structure of the Kara Plate, substantiate the boundaries of the North Kara independent prospective oil and gas region and promising areas within it, and assess hydrocarbon resources.

Identifying Dominant Structural Pattern of Semarang City Using Digital Elevation Model and Landsat 8-OLI Imagery

Semarang City is an area in the northern part of Java Island, administratively the Capital of Central Java Province. Because Semarang City is the provincial capital, Semarang City has a relatively dense population. Geologically, the city of Semarang is an area that consists of various types of lithology and is traversed by various regional geological structures. In this case, understanding the existence and distribution of geological structures in the city of Semarang is essential, considering that geological structures are one of the controllers for natural disasters such as landslides and earthquakes. This study analyzed the existence and distribution of geological structures in the city of Semarang based on the lineaments observed from digital elevation models and satellite imagery. This study aims to identify the dominant structural pattern in Semarang City, determine the relationship between fault fracture density (FFD) with regional geological structure and lithology, and determine the fault zone area in Semarang City based on FFD & lineament analysis. The method used in this analysis is to process DEM data and Landsat 8-OLI imagery, then interpret the lineaments in the form of rosset diagrams and the density in the form of FFD maps. The results of the rosset diagram analysis show that Semarang City has various structural lineament patterns, namely: North–South, Northeast–Southwest, and Northwest–Southeast, with the North–South pattern as the dominant pattern. Based on the results of the lineament density distribution on the FFD map, it is known that the area traversed by the Semarang regional geological structure has a high lineament density value which is interpreted that the area is a weak zone with high structural intensity. From this study, it can also be seen that there is no significant relationship between the type of lithology and the density value on the FFD map. The distribution of lineament density is not affected by the type of lithology, except in the northern and northeastern parts of Semarang city, which consist of alluvium. Based on these results, it can be interpreted that the fault zone area is associated with areas that have high-density values on the FFD map. Distribution of the fault zone area of Semarang City is spreading over the Banyumanik, Gunungpati, and Mijen Districts, which are relatively in the southern and central parts of Semarang City.

Gravimetric and morpho-structural analyses in the superhot geothermal system Los Humeros: an example from central Mexico

The influence of deep and regional geological structures is becoming increasingly important in superhot geothermal systems due to their proximity to the transition between brittleness and ductility. In the Los Humeros geothermal field in Mexico, where subsurface fluids reach temperatures of over 350 °C, the surface structures resulting from the collapse of calderas have so far only been interpreted at the local scale. The aim of this work is to place the recent tectonic and volcano-tectonic geomorphologic evolution and structures in the Los Humeros volcanic area in a regional context. NE- and NW-striking dominant structures resulting from a morpho-structural analysis on a regional scale are confirmed by negative and positive anomalies, respectively, after Butterworth filtering of gravity field data with different wavelengths over a local area of about 1000 km2. By analyzing the slip and dilation trends of the observed directions, we show the relevance of the regional context for reservoir exploration. The magnitudes of the principal stresses we estimate indicate a trans-tensional fault regime, a combination of strike-slip and normal faulting. The structures derived from the gravity and morpho-structural analyses, which are parallel to the maximum horizontal stress, have the highest potential for tensile and shear failure. Therefore, the corresponding negative gravity anomalies could be related to fracture porosity. Consequently, we hypothesize that these structures near the transition between brittleness and ductility control fluid flow in the Los Humeros geothermal field.

Geological and structural characteristics of the zengjiacun copper deposit in jinggu, southern yunnan: A comprehensive analysis of three-dimensional ore-controlling structures

The Zengjiacun copper deposit is situated in the northeastern part of the Minle copper deposit, located in Jinggu County, Yunnan Province. It is one of the typical deposits in southern Yunnan. In this paper, we employ the theory and method of ore field tectonics to elucidate the formation mechanism of ore bodies and their structural controls on hosting spaces. The regional geological structure exerts control over lithofacies paleogeography and magmatic activity within this area, directly influencing the formation and distribution of various endogenetic and exogenetic minerals such as Songjiapo, Nanwenghe, Wengkongba, and Dadutian. Under the combined influence of regional crustal uplift and nearly east-west compression stress during the Yanshanian period, strata within this region underwent folding and interlaminar sliding processes. Notably, due to differences in rigidity between limestone and sand mudstone lithologies, limestone formations became brittle and prone to fracturing. This resulted in the development of interlaminar fracture zones that provided pathways for tectonic hydrothermal fluids to migrate and accumulate, ultimately leading to the formation of a reformed copper deposit. Tectonic stress variations have led to increased complexity within strata and ore bodies present in the northern section where local closed folds have formed. However, the stratum and copper body in the south part are inclined to the East in a gentle wave shape due to relatively small tectonic stress. Overall, understanding these structural controls on mineralization is crucial for guiding exploration efforts both at depth as well as around periphery areas surrounding this deposit.

A constrained 3D gravity inversion for complex density distributions: Application to Brazil rifted continental margin

Gravity inversion is a highly effective method for investigating regional geological structures, and this paper proposes an optimization scheme for constrained three-dimensional (3D) gravity inversion to obtain a 3D density model, utilizing prior geological and geophysics information. Specifically, the proposed method enhances deep structural imaging resolution and minimizes false structures by progressively inverting deep and shallow-density structures using long and short-wavelength signals of gravity anomaly with prior information. The scheme is applied in the southeast passive continental margin of Brazil, and the results show that the density model is consistent with the previous reflection and refraction seismic data. Moreover, the 3D density model reveals several insights: (i) The Abimael Ridge (AR) and the São Paulo Plateau (SPP) exhibit thin crustal thickness (∼5–7 km) indicative of proto-oceanic crust. The SPP and AR area crustal thinning may be related to an aborted opposing rift propagator pair. (ii) The rifting modes of Santos and Campos Basins differ significantly. Campos Basin exhibits a depth-dependent lithospheric stretching model with a relatively intact upper crust. In contrast, Santos Basin shows a highly brittle upper crust that is partially thinned and, in some regions, even absent under the far-field effect of spreading failed rifts, while the lower crust remains relatively intact. Moreover, the upper crustal stretching factor is about five to ten higher than the lower crustal. Thus, the constrained 3D gravity inversion scheme provides a new avenue for continental rifted margin geological structure studies.

Unmanned Aerial Vehicle Aeromagnetic Analyses Reveal the Causative Faults and Seismogenic Mechanism of the 2021 Ms 6.0 Luxian, China, Earthquake

Abstract On 16 September 2021, an Ms 6.0 earthquake occurred in Luxian, Sichuan, China, breaking the historical record of no earthquake with magnitude ≥ M 6 along the Huaying Mountain fault belt. The regional geological structure is primarily controlled by the northeast-striking fault belt, but the long axis of the isoseismic line, distribution of early aftershocks and coseismic rupture plane all strike northwest, posing challenges to the seismogenic mechanism. To investigate this, we conducted a 400 km2 unmanned aerial vehicle (UAV) aeromagnetic survey near the epicenter, with a line spacing of 1 km. Through aeromagnetic analyses, combined with the spatial distribution of relocated foreshocks and aftershocks, we outline potential basement causative faults and a change in the structural trend between the shallow and deep portions of the seismic zone. We conjecture that the Luxian earthquake was triggered by the hydrofracturing-driven reactivation of a pre-existing northwest-striking and southwest-dipping basement fault, of which the upward propagation induced extrusion and dislocation at the hypocenter within the sedimentary layer. The special structural configurations for the focal area could contribute to the stress concentration and occurrence of large earthquakes.

Modeling Crustal Structure in West Sumatera Using Teleseismic Receiver Function

Indonesia is located between three significant plate confluences that play a role in creating a subduction zone. Sumatra, one of Indonesia’s provinces, is located near the collision of the Eurasian Plate, the Indo-Australian Plate, and the Pacific Plate. The Semangko Fault, the Mentawai Islands, a chain of non-volcanic forearc islands, and active faults that induce earthquakes and landslides are all produced by subduction zones on Sumatra Island. The receiver function approach was developed to identify the discontinuity limits of the Earth’s structures, such as the crust and mantle, from teleseismic events. The information in this study comes from 25 temporal and 1 permanent station in West Sumatra and the time period between 2007 and 2009 from the IRIS data station. The earthquake data was taken from teleseismic earthquakes from the three components of seismic stations using criteria arc distances between 30° and 90° and magnitudes ranging from 6.0 to 10.0. This research aims to determine how crustal thickness is distributed and what effect regional geological structure has on crustal thickness. According to the early results of the study, the estimated range of crustal thickness in the research region is 27.11–32.48 km, and the range of Vp/Vs ratio values is 1.70–2.19. The direction of crustal thickness thickening in the area was likewise East-South.

Estimation Method for an In Situ Stress Field along a Super-Long and Deep-Buried Tunnel and Its Application

Aiming at some stress-induced failure phenomena in surrounding rock that occur during the construction of super-long and deep-buried tunnels, a method for estimating the in situ stress in the tunnels based on multivariate information integration is proposed, which uses a small amount of in situ stress measurement, stereographic projection technology, and a numerical simulation method. Firstly, by conducting a macroscopic analysis of the regional geological structure, topography, and pre-excavated small tunnels (such as exploration of adits and pilot tunnels), the strength of the tectonic stress field and the orientation of the principal stresses in the tunnel sections are preliminarily determined. Secondly, the reliability of the in situ stress measurement data were analyzed using full-space stereographic projection and the plane stress projection method. Then, some representative measurement points that reflected the distribution characteristics of in situ stress in the project area, on the whole, were determined. Thirdly, the finite difference (FDM) and multiple regression analysis (MRA) methods were used to inverse the in situ stress field in the project area. The proposed method was applied to a super-long and deep-buried tunnel project in Qinling, and the in situ stress distribution characteristics of the tunnel sections at different mileages were obtained. The results show that both the calculated principal stress values and the azimuth angle of the maximum horizontal principal stress are in good agreement with the measured ones, indicating that the method used in this study is reasonable. Finally, the typical surrounding rock failure phenomena encountered during the excavation of the project were investigated, and targeted treatment measures were proposed. The research results can provide references for support design and disaster management of surrounding rock in deep-buried long tunnels.

Pemetaan Daerah Potensi Longsor Menggunakan Analisis Fault Fracture Density Pada Data DEMNAS Di Wilayah Cisarua, Kabupaten Bandung Barat, Jawa Barat

The Cisarua area is located in the northern part of Bandung City and is one of the sub-districts in West Bandung Regency and has steep topography in several locations, giving rise to the potential for landslides. The eastern region is part of the Lembang Fault which is still active in the North Bandung area. The potential for landslides related to the geological structure in this area can be identified by looking at the lineament patterns of the valleys, the presence of lithological offsets and others. The geological structure that developed in the Cisarua area was identified based on the results of analysis of satellite imagery data and the National Digital Elevation Model (DEMNAS) to identify the presence of geological structures and determine the direction of the dominant force. This study aims to determine the distribution of potential landslides in the Cisarua area using the Fault Fracture Density (FFD) method. Linearity analysis is estimated using the Fault Fracture Density (FFD) method. This method produces an analysis based on the straightness of the ridges and valleys around Cisarua which is then processed using a rosette diagram and interpreted as the dominant lineament trending west-east and northeast- southwest, this dominant lineament corresponds to the direction of the Lembang Fault. The lineament density level value describes a weak zone in the rock which creates the potential for landslide hazard. The weak zone in red indicates that the study area has a high landslide hazard potential, which is red, and the light green color indicates that the study area has a low landslide hazard potential. The potential for landslides in the study area is spread more in areas close to regional geological structures such as faults when compared to other areas. This pattern indicates that the presence of geological structures has an influence on the occurrence of landslides in potential areas.

Geological hazards in the Oujiang estuary in the Zhejiang Province, China: type, distribution, and origin

Introduction: As our understanding of the ocean and its uses continues to advance, countries worldwide with ocean access are implementing new marine strategies. For example, understanding marine geological disasters can help develop the use of ocean resources and oceanic engineering.Methods: Therefore, this study used recent data from the Oujiang Estuary, a nearshore area in China, to determine its geological hazards.Results: The geological hazards were classified as active or restricted based on topography, geomorphology, shallow seismic profile, single-channel seismic profile, and geological drilling data. Active geological hazards primarily include shallow gas and active sand waves, whereas restrictive geological hazards include irregularly buried bedrock, erosion channels, steep submarine slopes, and buried paleochannels. We also evaluated the distribution characteristics and scope, such as the vertical distribution of shallow gas based on the seismic profiles, drilling rock facies, methane, and carbon dioxide contents in the top air, and the isotope values. We found that shallow gas was vertically distributed among multiple layers. The main gas-bearing layers were the clayey silt and sandy (silt) clay layers of the early Holocene and late Pleistocene strata. The shallow gas content was relatively low in the coarse sediment layer at the bottom of the late Pleistocene succession. Generally, the Holocene and late Pleistocene deposits do not contain gas, and the gas content in the middle and late Pleistocene strata (at greater depths) is relatively low.Discussion: The combined effects of the regional geological structure, sea level changes, modern hydrodynamics, and human activities have formed the geological environment of the Oujiang Estuary.

Characterizing groundwater and surface water interaction using geological, environmental tracers (222Rn, EC, δ18O, and δ2H) and baseflow index methods for part of the Upper Awash and the adjacent Blue Nile Basin, Ethiopia

Characterization of groundwater-surface water interaction using a combined approach of geological, environmental tracers (222Rn, EC, δ18O, and δ2H) and baseflow index in a complex geological environment was carried out for part of the Upper Awash and adjacent Blue Nile Basins. In this work, total measurements of 59 water samples were used (52 from different reaches of main Rivers and tributaries, 4 from springs, and 3 from boreholes) for 222Rn analysis in dry and wet seasons, along with recent 8–20 years of daily stream flow records from 11-gauge stations. For sub-surface inference, regional geological structures and lineament density zones were determined using Kriging interpolation techniques. 222Rn values for the river and streams show 2.7–468 Bq/m3 during the rainy season and 17.1–1467 Bq/m3 for the non-rainy season. The credible justification related to moderate to high seasonal 222Rn values (100–400 Bq/m3) in the upstream parts of the two Basins, including areas falling along the surface water divide between the two adjacent Basins, shows a link between groundwater and surface water systems. In the same area, a very high mean annual baseflow index (BFI >0.5) is dominantly associated with high lineament density (0.9 < LD < 3.0), regional faults, and geologic units of highly permeable scoriaceous basalt, rift basalt, and fractured ignimbrite units. Relatively, low 222Rn (<100 Bq/m3) in both seasons and low baseflow index (BFI <0.35) values mainly in the central part of the Upper Awash basin are attributed to existing impervious superficial deposits (alluvial, tuff and ash). This, in turn, shows the poor connection between the groundwater and surface water systems in the central plain part of the Upper Awash Basin and, as also evidenced by the storage of floodwater for an extended time after the end of the rainy season, prove poor connectivity between groundwater and surface water systems. The very high 222Rn (400–1467 Bq/m3) with varied mean annual baseflow index (0.35 < BFI <0.5) at different stations in the extreme southern and southeastern parts of the Upper Awash Basin show Awash River is gaining from the aquifer system through highly fractured basalt and fractured ignimbrite geologic units. Evidence from analysis of measured electrical conductivity and stable isotopes (δ18O, δ2H) generally agree with the observed 222Rn value and baseflow analysis.

Adaptive vertical-deformation field estimation and current tectonic deformation significance analysis in Shanxi rift valley

The Shanxi rift valley is a continental rift system that is characterized by mantle uplift, crustal thinning, and tectonic deformation. A continuous, vertical crustal-deformation field can elucidate the constraints for understanding the mechanisms currently driving the deformation of the rift. Accordingly, we acquired and processed data from 250 continuous and mobile GPS stations located in the Shanxi rift valley and its surrounding region. Accounting for the influence of fault activity, we established the vertical crustal-deformation field of the Shanxi rift valley as a continuous function of space, using an adaptive least-squares collocation method. The main research findings are stated as follows: 1) the adaptive least-squares model yielded a reliable interpolation prediction results with adequate robustness, even for relatively sparse actual observation data. 2) The current general deformation pattern of the Shanxi rift valley exhibits an uplift of the mountainous regions on both sides and subsidence of the central basin. The average uplift rate of the mountain area is 2–3 mm/a, and the subsidence rate of the basin is not uniform and is positively correlated with the spatial distribution of the Cenozoic sediment thickness. However, in certain areas, a high subsidence rate of 10–30 mm/a is associated with human activities such as groundwater exploitation. 3) In summary, the current vertical crustal deformation occurring in the Shanxi rift valley correlates with the pattern over a time scale of millions of years. Overall, it is controlled by regional geological structure pattern, and is influenced by nonstructural factors in the shallow crust, exhibiting both complex and orderly characteristics in its spatial distribution.

Seismic anisotropy in the upper crust around the north segment of Xiaojiang faults in the SE margin of Tibetan Plateau

The Xiaojiang faults located in the SE margin of the Tibetan Plateau is a fault system of left-lateral strike-slip, striking NS, between the 2nd-order Sichuan-Yunnan block and the 1st-order South China block. The Xiaojiang faults and the surrounding areas are characterized by strong tectonic movements and intense seismic activities. Using seismic data from January 2013 to November 2020 recorded at the stations of the temporary QiaoJia seismic Array (QJ Array), deployed by the Institute of Geophysics, China Earthquake Administration, this study investigates the upper crustal anisotropy by the shear-wave splitting analysis on small local earthquakes, discusses the deformation patterns in the upper crust in the north segment of the Xiaojiang faults, evaluates the stress distribution in the study area, and analyzes its relationship with the regional tectonic structure. Adopting the data processing technique of shear-wave splitting, a total of 875 effective records were obtained at 50 stations. The mean direction of polarizations of fast shear-wave (PFS) is 162° ± 44° in the study areaand the mean normalized time-delay is 4.96 ± 2.38 ms/km. Based on the spatial distribution of the PFS and the regional geologic structure, the study area is divided into two zones: the zone N and the zone S. The PFS in the zone N is scattered, but the dominant PFS direction is in NNW, which is consistent with the direction of the regional maximum principal compressive stress. In the zone N, there are a few smaller local areas (i.e., subzones A, B, C, and D) in which the orientations of the PFS are quite different from the surrounding area. In the zone S, the dominant directions at most stations are in nearly NS, consistent with the strike of the Xiaojiang fault. It reveals the detailed spatial distribution of seismic anisotropy in the upper crust, as well as in situ principal compressive stress, indicating the influence of the regional stress, the complex tectonic environment, and maybe also the impact of the South China block. It also reveals that there also might be an upper-crust scale of tectonic line at near 26°20′N under Xiaojiang faults, which coincides with the north-south tectonic boundary in the lithospheric anisotropy.

Assessment of basin-scale geomorphic processes based on the analysis of longitudinal profiles: A case study of the Dwarkeswar river, Eastern India

ABSTRACT The longitudinal profile of the river bears geomorphic signature of long-term fluvial adjustment to tectonic, structure, lithology, and climate. Therefore, analysis of the longitudinal profile can be helpful in understanding the fluvial process and the response of the river to regional geodynamics. The present study uses longitudinal profiles and related geomorphic indices, including the Stream Length-Gradient Index (SL Index) of the Dwarkeswar river and its nine major tributaries, to understand the role of regional geological structure and lithology on the landscape evolution of the basin and the stage of river-valley development. Four mathematical functions were used in the present study to fit the curves of the profiles, on the basis of which the sequence of evolution was estimated. The exponential function is the best fit, followed by the linear function for each river, indicating a dynamic equilibrium condition. Moreover, profile concavity and hypsometric integral were used in the present study to understand sediment generation and transportation dynamics. The lower concavity index in Arkasa, Beko river, and Debkhal rivers indicate that sediment production and transportation balance each other. All the indices and the shape of Hack’s profile indicate that the rivers are in non-graded condition. The concavity of the profile reveals that Dwarkeswar rivers is an energy-limited river with a lower sediment delivery ratio (SDR)(0.47). Other rivers of the basin have moderate to high SDR (0.61–0.78). The integration of the results with the geological data indicates that the segments with anomalously high values of the SL index correspond to the fault lines, lineaments, and lithological discontinuities.

The Relationship between Lineament Patterns and Mass Movements in the Municipality of Vitória (Espírito Santo, Southeast Brazil)

The main objective of this research is to analyze and relate lineament patterns to the occurrence of mass movements in the municipality of Vitória (Espírito Santo, Brazil). The methodology used consists of cabinet and field analyses. In a cabinet, Lineament Maps were made from the manual extraction technique, using ArcGIS 10.5 tools, on a Digital Elevation Model (DEM) with different artificial lighting (scale 1:110000) and Digital Orthophotos (scale 1:25000) and orientation rosettes generated. In the field, the geological structures were identified and analyzed from the lineaments identified in the cabinet, and their orientations were measured (Brunton compass). These data were integrated and analyzed from the Municipal Civil Defense mass movements records, referring to the period between 2006 and 2020. It was possible to verify the orientation patterns of dominant geological structures in the area (NNW-SSE and NW-SE, followed by NE-SW), including all measured fractures. At the regional scale, more mass movements occurred near NNW-SSE, NW-SE, and NE-SW orientation lineaments. At the local scale, these processes occurred more frequently in the vicinity of NNW-SSE, NNE-SSW, and NE-SW orientation lineaments. Data analysis demonstrates the important relationship between lineaments and occurrences of mass movements with regional geological structures and neotectonic events of the Espírito Santo in altered rocks of the Precambrian basement and Cenozoic deposits. The data revealed an association between the density of geological structures and the occurrence of mass movements since the increase in density is directly proportional to these processes, except for the Very High -density class, which presented little area representation.

Present-day state of tectonic stress and tectonization in coastal gold mine area near Laizhou Gulf, North China

AbstractTo investigate the present-day state of tectonic stress and tectonization in a coastal gold mine area near the Laizhou Gulf, North China, overcoring, anelastic strain recovery, and hydraulic fracturing stress measurement campaigns were performed, and a total of 49 groups of stress data were determined. The results indicate that horizontal tectonic stress plays a predominant role in the present-day stress field, which is a typical tectonic stress field. The stress fields are characterized by σH>σh>σv (σH, σh and σv are the maximum horizontal, minimum horizontal and vertical principal stresses, respectively) and σH>σv>σh, which appear to favor thrust and strike-slip faulting, respectively. The stress level is relatively high and is not conducive to the stability of underground excavations. σH is oriented in the WNW−ESE or approximately E−W directions, which is in accord with that indicated by focal mechanism solutions and regional geological structure analysis. The contemporary stress field is the result of dynamic action and tectonic movement in various geological periods; the contemporary stress field generally inherited the characteristics of the third stage tectonic stress field (Himalayan movement period) while partially retaining the characteristics of the second stage tectonic stress field (Yanshanian period), and finally evolved into the tectonic stress field characterized by nearly E−W extrusion.

EXTENSIONAL TECTONIC INVESTIGATION BASED ON GRAVITY AND MAGNETIC DATA ANALYSIS IN THE GULF OF TOMINI, INDONESIA

The enigmatic genesis of Sulawesi Island remains a debate among earth scientists up to the present day. The Northern Arm of Sulawesi is designated as a volcanic province, while the Eastern Arm is identified as an ophiolite zone along with several micro continental fragments. However, the tectonic relationship in the marine area between these two arms is not clearly defined. The existence of isolated volcanic islands, namely the Una-Una and Togian islands increases the complexity of the area. A regional study utilizing gravity and magnetic methods is needed in the Gulf of Tomini, North Sulawesi, Indonesia. Therefore, a comprehensive analysis was conducted, involving 3D inverse modelling and Moho depth estimation based on the Parker-Oldenburg algorithm using 3D Euler deconvolution to obtain the average depth of causative bodies. As a result, the presence of extensional tectonics were revealed and identified as multiple parallel dextral strike-slip faults across the study area. All of these faults show northwest-southeast lineaments consistent with the existing seismic sections. The extensional tectonic mechanism triggers crustal thinning and rifting, leading to the build-up of graben structures such as the Gorontalo, Tomini, and Poso basins. Additionally, it influences volcanic activity around the Togian and Una-Una islands. The major axes of the inferred opening area are oriented in the northeast-southwest direction, perpendicular to the lineaments of these faults. The opening area coincides with the orientation of Lalanga and Togian ridges. Finally, a regional geological structure is proposed across the Gulf of Tomini linking both the Northern and Eastern arms of Sulawesi.