Pub Date : 2024-08-29DOI: 10.1134/s001685212470033x
S. F. A. Zaidi, N. Ahsan
Abstract
This research investigates tectonic inversion in rifted continental margins, specifically focusing on the interaction between foreland sediment deposits and fold-and-thrust belts during orogeny. Using numerical modeling with ANSYS-2023 R1 software and a Maxwell-type viscoelastic rheology, the study explores positive inversion in petroleum basins, revealing insights into the evolution of inverted basins. The research emphasizes the role of pre-existing extensional fault systems in controlling thrust faults, delving into the reactivation of faults and uplift of the hanging wall during tectonic compression. The study highlights diverse structural patterns associated with tectonic inversion in sub-thrust regions of fold-and-thrust belts, including anticlines, back-thrusts, fault propagation folds, pop-up, and an inversion-related fracture pattern. Results demonstrate the critical influence of rheological properties in fault reactivation and deformational styles during tectonic inversion. Comparisons with natural case studies, like the Helvetic nappes in Switzerland, validate the predictive capability of numerical models for tectonic inversion structures in different geological settings, including the Kohat-Potwar Fold and Thrust Belt in Pakistan. We find important of understanding interplay between geological structures and rheological properties for accuracy of predicting evolution of inverted basins. The deeply study of tectonic inversion are extending to optimizing exploration efforts and interpreting structural complexities in petroleum exploration, providing valuable insights for reservoir prediction and fold-and-thrust belt structural evolution.
{"title":"The Tectonic Inversion Prediction in Fold-and-Thrust Belts by Using Numerical Modeling","authors":"S. F. A. Zaidi, N. Ahsan","doi":"10.1134/s001685212470033x","DOIUrl":"https://doi.org/10.1134/s001685212470033x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>This research investigates tectonic inversion in rifted continental margins, specifically focusing on the interaction between foreland sediment deposits and fold-and-thrust belts during orogeny. Using numerical modeling with ANSYS-2023 R1 software and a Maxwell-type viscoelastic rheology, the study explores positive inversion in petroleum basins, revealing insights into the evolution of inverted basins. The research emphasizes the role of pre-existing extensional fault systems in controlling thrust faults, delving into the reactivation of faults and uplift of the hanging wall during tectonic compression. The study highlights diverse structural patterns associated with tectonic inversion in sub-thrust regions of fold-and-thrust belts, including anticlines, back-thrusts, fault propagation folds, pop-up, and an inversion-related fracture pattern. Results demonstrate the critical influence of rheological properties in fault reactivation and deformational styles during tectonic inversion. Comparisons with natural case studies, like the Helvetic nappes in Switzerland, validate the predictive capability of numerical models for tectonic inversion structures in different geological settings, including the Kohat-Potwar Fold and Thrust Belt in Pakistan. We find important of understanding interplay between geological structures and rheological properties for accuracy of predicting evolution of inverted basins. The deeply study of tectonic inversion are extending to optimizing exploration efforts and interpreting structural complexities in petroleum exploration, providing valuable insights for reservoir prediction and fold-and-thrust belt structural evolution.</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"3 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-23DOI: 10.1134/s0016852124700109
V. G. Trifonov, S. A. Sokolov, A. N. Ovsyuchenko, S. Yu. Sokolov, Ts. Batsaikhan, S. Demberel, Yu. V. Butanaev, N. G. Koshevoy
Abstract
The active tectonics of northern Central Mongolia is studied between two largest W–E-trending left lateral fault zones: the Khangai Fault and the Tunka–Mondy. These strike-slip zones are part of a single ensemble of active faults in the Mongol–Baikal region, formed under conditions of maximum northeastern compression and maximum northwestern extension. Their ENE-trending Erzin–Agardag and Tsetserleg faults with a dominant sinistral component extend between these zones. A series of the N-trending graben basins (Busiyngol, Darkhat, and Khubsugul) are located between the eastern end of the Erzin–Agardag strike-slip fault and the western part of the Tunka–Mondy strike-slip zone. The basins form a sinistral deformation zone, which is kinematically similar with the strike-slip faults, which follow the latter. In contrast to the largest boundary strike-slip faults, this structural paragenesis formed under conditions of N–S-trending relative compression and N–S-trending extension. A change in the orientation of the axes of the principal normal stress may be caused by the rotation of the block between the boundary faults. The area of graben-shaped basins is located above the top of a vast volume of low-velocity mantle, which we have identified as the Khangai plume. The lithospheric mantle above this rise is reduced; the remaining part of the lithosphere is heated and softened. The large active strike-slip faults are located above areas of subsidence of the low-velocity top of the mantle. Our trenching of the active faults showed that strong earthquakes repeated in the area of graben-shaped basins more often than in the large strike-slip zones, but they were characterized by lower magnitudes.
{"title":"Active Faults of Northern Central Mongolia, Their Correlation with Neotectonics and Deep Structure of the Region","authors":"V. G. Trifonov, S. A. Sokolov, A. N. Ovsyuchenko, S. Yu. Sokolov, Ts. Batsaikhan, S. Demberel, Yu. V. Butanaev, N. G. Koshevoy","doi":"10.1134/s0016852124700109","DOIUrl":"https://doi.org/10.1134/s0016852124700109","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The active tectonics of northern Central Mongolia is studied between two largest W–E-trending left lateral fault zones: the Khangai Fault and the Tunka–Mondy. These strike-slip zones are part of a single ensemble of active faults in the Mongol–Baikal region, formed under conditions of maximum northeastern compression and maximum northwestern extension. Their ENE-trending Erzin–Agardag and Tsetserleg faults with a dominant sinistral component extend between these zones. A series of the N-trending graben basins (Busiyngol, Darkhat, and Khubsugul) are located between the eastern end of the Erzin–Agardag strike-slip fault and the western part of the Tunka–Mondy strike-slip zone. The basins form a sinistral deformation zone, which is kinematically similar with the strike-slip faults, which follow the latter. In contrast to the largest boundary strike-slip faults, this structural paragenesis formed under conditions of N–S-trending relative compression and N–S-trending extension. A change in the orientation of the axes of the principal normal stress may be caused by the rotation of the block between the boundary faults. The area of graben-shaped basins is located above the top of a vast volume of low-velocity mantle, which we have identified as the Khangai plume. The lithospheric mantle above this rise is reduced; the remaining part of the lithosphere is heated and softened. The large active strike-slip faults are located above areas of subsidence of the low-velocity top of the mantle. Our trenching of the active faults showed that strong earthquakes repeated in the area of graben-shaped basins more often than in the large strike-slip zones, but they were characterized by lower magnitudes.</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"30 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-23DOI: 10.1134/s0016852124700110
A. A. Kirdyashkin
Abstract
The flow structure created in a viscous medium at a constant angle of inclination of the free surface of an slope of the uplift is analyzed. The velocity field in a high-viscosity slope of the uplift under conditions of a horizontal pressure gradient is determined. This pressure gradient occurs when the slope height decreases with distance from the main ridge. Under a constant dynamic viscosity of the slope of the uplift, the flow velocity in the latter decreases with a distance from the axis of the main ridge. In this case, the slope of the uplift is under conditions of compressive stresses, a consequence of which is development of thrusts and compression folds. Tensile stresses in the slope of the uplift may exist with an increase in the flow velocity in the layer with distance from the axis of the main ridge. The flow velocity increases with decreasing viscosity of the layer with distance from the main ridge. The viscosity distribution at the base of the slope of the uplift with distance from the axis of the main ridge is determined using the tensile condition in the slope of the uplift. Expressions are presented for the forces causing formation of a rupture between blocks of the slope of the uplift. The magnitudes of these forces are estimated. A relation representing the condition for the formation of a disruption between the blocks is obtained. The formation of ruptures is governed by the change in viscosity along the slope of the uplift and the change in the flow velocity in it. When a rupture between the slope of the uplift forms, free vertical boundaries of the blocks appear. The motion of a high-viscosity liquid during the formation of a free vertical boundary of the block has been studied experimentally when the liquid flows from a rectangular vessel. The experiments have revealed two outflow regimes: (i) a regime of constant thickness of the liquid layer; (ii) a regime of decreasing layer thickness. Based on experimental modeling, the time of the first period after formation of the slope rupture and formation of the free volume between blocks is estimated. During this period the height of the layer (slope) is practically constant and the layer length increases. The filling of the free volume between blocks with high-viscosity slope material is considered. As the modeling shows, the filling rate of the free volume between the divergent blocks of the slope of the uplift is much higher than the formation rate of the free volume between these blocks. The parameters of the blocks of the slope of the uplift are determined. Among these parameters are the block viscosity, slope height, flow velocity, and forces acting on the blocks. The time-varying structure of the surface of the slope of the uplift is presented. There is a qualitative correspondence between the modeling results and the profile of the slope of the uplift for the Northwestern Caucasus.
{"title":"Theoretical and Experimental Modeling of Geodynamiс Processes in the Slopes of Uplifts","authors":"A. A. Kirdyashkin","doi":"10.1134/s0016852124700110","DOIUrl":"https://doi.org/10.1134/s0016852124700110","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The flow structure created in a viscous medium at a constant angle of inclination of the free surface of an slope of the uplift is analyzed. The velocity field in a high-viscosity slope of the uplift under conditions of a horizontal pressure gradient is determined. This pressure gradient occurs when the slope height decreases with distance from the main ridge. Under a constant dynamic viscosity of the slope of the uplift, the flow velocity in the latter decreases with a distance from the axis of the main ridge. In this case, the slope of the uplift is under conditions of compressive stresses, a consequence of which is development of thrusts and compression folds. Tensile stresses in the slope of the uplift may exist with an increase in the flow velocity in the layer with distance from the axis of the main ridge. The flow velocity increases with decreasing viscosity of the layer with distance from the main ridge. The viscosity distribution at the base of the slope of the uplift with distance from the axis of the main ridge is determined using the tensile condition in the slope of the uplift. Expressions are presented for the forces causing formation of a rupture between blocks of the slope of the uplift. The magnitudes of these forces are estimated. A relation representing the condition for the formation of a disruption between the blocks is obtained. The formation of ruptures is governed by the change in viscosity along the slope of the uplift and the change in the flow velocity in it. When a rupture between the slope of the uplift forms, free vertical boundaries of the blocks appear. The motion of a high-viscosity liquid during the formation of a free vertical boundary of the block has been studied experimentally when the liquid flows from a rectangular vessel. The experiments have revealed two outflow regimes: (i) a regime of constant thickness of the liquid layer; (ii) a regime of decreasing layer thickness. Based on experimental modeling, the time of the first period after formation of the slope rupture and formation of the free volume between blocks is estimated. During this period the height of the layer (slope) is practically constant and the layer length increases. The filling of the free volume between blocks with high-viscosity slope material is considered. As the modeling shows, the filling rate of the free volume between the divergent blocks of the slope of the uplift is much higher than the formation rate of the free volume between these blocks. The parameters of the blocks of the slope of the uplift are determined. Among these parameters are the block viscosity, slope height, flow velocity, and forces acting on the blocks. The time-varying structure of the surface of the slope of the uplift is presented. There is a qualitative correspondence between the modeling results and the profile of the slope of the uplift for the Northwestern Caucasus.</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"18 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-23DOI: 10.1134/s0016852124700122
A. K. Tarasenko, A. K. Alekseeva, Yu. N. Khohlova, N. Yu. Inshakova
Abstract—
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.
{"title":"Tectonic Basis for Oil and Gas Potential in the North Kara Prospective Oil and Gas Region (Western Arctic, Russia)","authors":"A. K. Tarasenko, A. K. Alekseeva, Yu. N. Khohlova, N. Yu. Inshakova","doi":"10.1134/s0016852124700122","DOIUrl":"https://doi.org/10.1134/s0016852124700122","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">\u0000<b>Abstract</b>—</h3><p>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.</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"7 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-30DOI: 10.1134/s0016852124700250
Ya. I. Trikhunkov, H. Ҫelik, V. S. Lomov, V. G. Trifonov, D. M. Bachmanov, Y. Karginoglu, S. Yu. Sokolov
Abstract
The Elbistan (Chardak) earthquake with magnitude Mw = 7.5 or 7.6 happened in Eastern Anatolia on 06.02.2023 at 10:24 UTC, following the strongest in the region of East Anatolian (Pazarcık) earthquake with Mw = 7.8 which occurred on the same day at 1:17 UTC to the south of the region. The Elbistan earthquake activated adjacent segments of the Chardak and Uluova faults with left-lateral strike-slip displacements. The resulting seismic ruptures have a total length of 190 km, of which 148 km are represented by sinistral lateral slip. Their maximum amplitude of 7.84 m was recorded 8 km east of the epicenter. The strike-slip seismic ruptures of the Elbistan and East Anatolian earthquakes represent exposure of their focal zones on the land surface. Both earthquakes exceed average values of these parameters for continental earthquakes of strike-slip type in terms of focal zone sizes and amplitudes of seismic displacements. At the same time, both sources do not propagate deeper than the upper part of the crust (16–20 km). Ophiolite assemblages covering the same depths are widely spread in the area of focal zones of both earthquakes. Two maxima were found in the distribution of seismic strike-slip displacement along the epicentral zone of the Elbistan earthquake (i) amplitudes of 5.7–7.84 m in the Chardak fault zone and (ii) amplitudes of 3.5–5.1 m in the Uluova fault zone. Both maxima coincide with the areas of ophiolites or their contacts with basement rocks. In crystalline basement rocks, the sinistral strike-slip amplitudes are significantly reduced. We attribute the increased values of focal zone sizes and displacement amplitudes of both earthquakes to the rheological features of ophiolites, which increase a possibility rocks slipping during seismic movements. We explain the fact that the sources of both earthquakes cover only the upper part of the crust by the uplift of the top of rocks with reduced P-wave velocities, including the upper mantle and the lower part of the crust, and interpret them as heated rocks with reduced strength.
{"title":"Geological Position, Structural Manifestations of the Elbistan Earthquake and Tectonic Comparison of Two Strongest 06.02.2023 Seismic Events in Eastern Turkiye","authors":"Ya. I. Trikhunkov, H. Ҫelik, V. S. Lomov, V. G. Trifonov, D. M. Bachmanov, Y. Karginoglu, S. Yu. Sokolov","doi":"10.1134/s0016852124700250","DOIUrl":"https://doi.org/10.1134/s0016852124700250","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The Elbistan (Chardak) earthquake with magnitude <i>M</i><sub>w</sub> = 7.5 or 7.6 happened in Eastern Anatolia on 06.02.2023 at 10:24 UTC, following the strongest in the region of East Anatolian (Pazarcık) earthquake with <i>M</i><sub>w</sub> = 7.8 which occurred on the same day at 1:17 UTC to the south of the region. The Elbistan earthquake activated adjacent segments of the Chardak and Uluova faults with left-lateral strike-slip displacements. The resulting seismic ruptures have a total length of 190 km, of which 148 km are represented by sinistral lateral slip. Their maximum amplitude of 7.84 m was recorded 8 km east of the epicenter. The strike-slip seismic ruptures of the Elbistan and East Anatolian earthquakes represent exposure of their focal zones on the land surface. Both earthquakes exceed average values of these parameters for continental earthquakes of strike-slip type in terms of focal zone sizes and amplitudes of seismic displacements. At the same time, both sources do not propagate deeper than the upper part of the crust (16–20 km). Ophiolite assemblages covering the same depths are widely spread in the area of focal zones of both earthquakes. Two maxima were found in the distribution of seismic strike-slip displacement along the epicentral zone of the Elbistan earthquake (i) amplitudes of 5.7–7.84 m in the Chardak fault zone and (ii) amplitudes of 3.5–5.1 m in the Uluova fault zone. Both maxima coincide with the areas of ophiolites or their contacts with basement rocks. In crystalline basement rocks, the sinistral strike-slip amplitudes are significantly reduced. We attribute the increased values of focal zone sizes and displacement amplitudes of both earthquakes to the rheological features of ophiolites, which increase a possibility rocks slipping during seismic movements. We explain the fact that the sources of both earthquakes cover only the upper part of the crust by the uplift of the top of rocks with reduced <i>P</i>-wave velocities, including the upper mantle and the lower part of the crust, and interpret them as heated rocks with reduced strength.</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"11 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141872520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-30DOI: 10.1134/s0016852124700249
N. Mahmoudi, R. Azizi
Abstract
In this paper we use a multidisciplinary approach including field observations, geological mapping and stress analysis to investigate the structural evolution of the NE-trending Sfina Basin, which located in the foreland basin of the Alpine chain (Maghrebides) in Tunisia. The Sfina Basin structure is the Neogene pull-apart basin, forming along the NE-trending Zaghouan fault, it located in Tunisian Atlas domain and formed in a NE‒SW-trending dextral strike-slip fault systems. Our result has shown that this NE-trending basin is limited in both northern and southern edges by two NE-trending dextral fault segments. During the Late Cretaceous‒Middle Miocene, under NE‒SW extensional regime, the NE-trending transtensional fault segments constituted the boundaries of the Sfina Basin that developed as a dextral releasing stepover. During the Late Miocene‒Early Quaternary, Sfina Basin was inverted under a regional NW‒SE-to-NNW‒SSE compressional event in response to the Africa‒Eurasia convergence with continental collision process. The inversion occurred mainly along Sfina Basin sidewalls by reactivation of the pre-existing NE‒SW-trending weaknesses as right-lateral transpressional shears and led to formation of the NE‒SW-trending major folds structures in the Sfina area.
摘要 本文采用野外观测、地质测绘和应力分析等多学科方法，对位于突尼斯阿尔卑斯山脉（马格里布山脉）前缘盆地的东北向斯菲娜盆地的构造演化进行了研究。斯菲娜盆地的构造是新近纪的拉裂盆地，沿 NE 走向的扎古安断层形成，位于突尼斯阿特拉斯域，在 NE-SW 走向的右旋走向滑动断层系统中形成。我们的研究结果表明，这一 NE 走向盆地的南北边缘受到两个 NE 走向右旋断层段的限制。在晚白垩世-中新世中期，在 NE-SW 延伸机制下，NE 走向的横断断层段构成了 Sfina 盆地的边界，该盆地发展为右旋释放阶地。在中新世晚期-第四纪早期，斯菲娜盆地在非洲-欧亚大陆辐合与大陆碰撞过程的作用下，发生了区域性的西北-东南向-西北-东南向的压缩性倒转。这种倒转主要发生在斯菲娜盆地侧壁，是由于原先存在的东北-西南走向的薄弱环节被重新激活，形成了右侧转压剪切，并导致斯菲娜地区形成了东北-西南走向的主要褶皱结构。
{"title":"Pre-Existing Structures and Stress Evolution Controlling a Pull-Apart Basin in the Tunisian Atlas Domain (Siliana Area): Geodynamic Implication","authors":"N. Mahmoudi, R. Azizi","doi":"10.1134/s0016852124700249","DOIUrl":"https://doi.org/10.1134/s0016852124700249","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>In this paper we use a multidisciplinary approach including field observations, geological mapping and stress analysis to investigate the structural evolution of the NE-trending Sfina Basin, which located in the foreland basin of the Alpine chain (Maghrebides) in Tunisia. The Sfina Basin structure is the Neogene pull-apart basin, forming along the NE-trending Zaghouan fault, it located in Tunisian Atlas domain and formed in a NE‒SW-trending dextral strike-slip fault systems. Our result has shown that this NE-trending basin is limited in both northern and southern edges by two NE-trending dextral fault segments. During the Late Cretaceous‒Middle Miocene, under NE‒SW extensional regime, the NE-trending transtensional fault segments constituted the boundaries of the Sfina Basin that developed as a dextral releasing stepover. During the Late Miocene‒Early Quaternary, Sfina Basin was inverted under a regional NW‒SE-to-NNW‒SSE compressional event in response to the Africa‒Eurasia convergence with continental collision process. The inversion occurred mainly along Sfina Basin sidewalls by reactivation of the pre-existing NE‒SW-trending weaknesses as right-lateral transpressional shears and led to formation of the NE‒SW-trending major folds structures in the Sfina area.</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"171 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141872518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1134/s0016852124700158
C. P. Simha, K. M. Rao, R. K. Dumka
Abstract
Identifying pre-seismic atmospheric and ionospheric anomalies is of research importance but also meets difficulties, especially for earthquakes with varying magnitudes, focal depths and focal mechanisms. In this paper, atmospheric‒ionospheric disturbances associated with earthquakes in Nepal (April 25, 2015, M = 7.8 and May 12, 2015, M = 7.3) are investigated using atmospheric and ionospheric parameters. Ionospheric (vertical total electron content (VTEC)) and atmospheric (outgoing long wave radiation (OLR), cloud mask, vertical temperature gradient (VTG)) parameters are archived from IGS GPS stations and INSAT 3D data from Indian Meteorological Department (IMD) of Ministry of Earth Sciences, Government of India. The abnormal VTEC signal was noticed 3 days and 10 days prior to April 25, 2015 event and 2 days and 6 days prior to the May 12, 2015 event. Inter-quartile range (IQR) and associated running median over one day were determined as the upper limit reference to a signature of VTEC for the 51-days period of the Nepal earthquake, it can be clearly observed that the total electron content (TEC) has increased from the limits of UB (upper bound) at the stations closest to the earthquake epicentre such as LCK-4, LHAZ than the far stations such as IISC, HYDE, SGOC and URUM. Prior to these earthquakes, UB observed a 54‒60% increase in relative amplitude of VTEC. The overall geomagnetic storm condition was thoroughly examined using the global planetary index (Kp) and storm time disturbance index (Dst) over the 51-days period. The IQR range method was used to analyse its abnormal positive and negative signals. We found no geomagnetic signatures caused by geomagnetic storms during the seismic regime The OLR varied from 240 to 340 watts/m2 observed 4 days before the event. The vertical temperature gradient varied from 4.3 to 23.2 K. Daily variations of 51 days for the OLR showed good anomalous atmospheric responses a few days before the event. The shallow depth of the earthquake gives the best coupling, releasing a large amount of energy from the seismic zones, and could be a causal factor in the enhancement of anomalous VTEC patterns.
{"title":"Observation of Atmospheric and Ionospheric Anomalies before the Nepal Earthquakes on 25th April and 12th May 2015","authors":"C. P. Simha, K. M. Rao, R. K. Dumka","doi":"10.1134/s0016852124700158","DOIUrl":"https://doi.org/10.1134/s0016852124700158","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Identifying pre-seismic atmospheric and ionospheric anomalies is of research importance but also meets difficulties, especially for earthquakes with varying magnitudes, focal depths and focal mechanisms. In this paper, atmospheric‒ionospheric disturbances associated with earthquakes in Nepal (April 25, 2015, <i>M</i> = 7.8 and May 12, 2015, <i>M</i> = 7.3) are investigated using atmospheric and ionospheric parameters. Ionospheric (vertical total electron content (VTEC)) and atmospheric (outgoing long wave radiation (OLR), cloud mask, vertical temperature gradient (VTG)) parameters are archived from IGS GPS stations and INSAT 3D data from Indian Meteorological Department (IMD) of Ministry of Earth Sciences, Government of India. The abnormal VTEC signal was noticed 3 days and 10 days prior to April 25, 2015 event and 2 days and 6 days prior to the May 12, 2015 event. Inter-quartile range (IQR) and associated running median over one day were determined as the upper limit reference to a signature of VTEC for the 51-days period of the Nepal earthquake, it can be clearly observed that the total electron content (TEC) has increased from the limits of UB (upper bound) at the stations closest to the earthquake epicentre such as LCK-4, LHAZ than the far stations such as IISC, HYDE, SGOC and URUM. Prior to these earthquakes, UB observed a 54‒60% increase in relative amplitude of VTEC. The overall geomagnetic storm condition was thoroughly examined using the global planetary index (K<sub>p</sub>) and storm time disturbance index (D<sub>st</sub>) over the 51-days period. The IQR range method was used to analyse its abnormal positive and negative signals. We found no geomagnetic signatures caused by geomagnetic storms during the seismic regime The OLR varied from 240 to 340 watts/m<sup>2</sup> observed 4 days before the event. The vertical temperature gradient varied from 4.3 to 23.2 K. Daily variations of 51 days for the OLR showed good anomalous atmospheric responses a few days before the event. The shallow depth of the earthquake gives the best coupling, releasing a large amount of energy from the seismic zones, and could be a causal factor in the enhancement of anomalous VTEC patterns.</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"8 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141506494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1134/s0016852124700134
Sh. Shahzad, M. A. F. Miraj, N. Ahsan
Abstract
Potwar Basin is one of the hydrocarbon prolific basins but pertains complex deformational style. Maximum production has been taken from Paleocene and Eocene carbonates but deeper reservoirs like Cambrian (Khewra sandstone) and Permian (Tobra formation) are also well producing. Geology of the Northern Potwar deformed zone (NPDZ) is mainly controlled by Pre-Cambrian salt, gently dipping basement and its warp. As we move towards south, salt thickness decreases near the axis of Soan syncline, north of Dhurnal structure. Eastern part of NPDZ is buried one while an emergent fold and thrust front (fault propagating fold) in the western part of NPDZ. Eastern NPDZ has duplex structure with initiation of roof thrust from the Murree Formation and sole thrust from Pre-Cambrian salt. The Southern Potwar platform zone (SPPZ) is less disturbed in comparison with NPDZ in which Pre-Cambrian salt acts as a decollement/lubricating surface over which the Cambrian to Pliocene sequence slides as a single thrust sheet. Due to the combined effect of thick overburden of ~3‒5 km and the decollement, folding and thrusting is significant in the Potwar Basin. In the eastern SPPZ, pop-up and fault propagating folds are prominent while in the western SPPZ, triangular zones, pop-up or detachment folds are significant.
{"title":"Comparative Structural Analysis of the Northern Potwar Deformed Zone and the Southern Potwar Platform Zone, NW‒Himalayas, Pakistan","authors":"Sh. Shahzad, M. A. F. Miraj, N. Ahsan","doi":"10.1134/s0016852124700134","DOIUrl":"https://doi.org/10.1134/s0016852124700134","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Potwar Basin is one of the hydrocarbon prolific basins but pertains complex deformational style. Maximum production has been taken from Paleocene and Eocene carbonates but deeper reservoirs like Cambrian (Khewra sandstone) and Permian (Tobra formation) are also well producing. Geology of the Northern Potwar deformed zone (NPDZ) is mainly controlled by Pre-Cambrian salt, gently dipping basement and its warp. As we move towards south, salt thickness decreases near the axis of Soan syncline, north of Dhurnal structure. Eastern part of NPDZ is buried one while an emergent fold and thrust front (fault propagating fold) in the western part of NPDZ. Eastern NPDZ has duplex structure with initiation of roof thrust from the Murree Formation and sole thrust from Pre-Cambrian salt. The Southern Potwar platform zone (SPPZ) is less disturbed in comparison with NPDZ in which Pre-Cambrian salt acts as a decollement/lubricating surface over which the Cambrian to Pliocene sequence slides as a single thrust sheet. Due to the combined effect of thick overburden of ~3‒5 km and the decollement, folding and thrusting is significant in the Potwar Basin. In the eastern SPPZ, pop-up and fault propagating folds are prominent while in the western SPPZ, triangular zones, pop-up or detachment folds are significant.</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"477 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141506497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1134/s001685212470016x
C. P. Simha, K. M. Rao
Abstract
Gujarat region (India) was struck by an earthquake of magnitude 5.3 on June 14, 2020 at 14:43 UTC near Bhachau city in Kachchh district in the state of Gujarat, with a depth of 20 km at the epicentre of 23.38° N, 70.36° E. In order to study the earthquake precursors for this event, data from the Induction Coil Magnetometer (LEMI-30) installed at the Badargadh Multi-Parameter Geophysical Observatory (MPGO) was analyzed for the period from January 1 to June 16, 2020. This station is located ~20 km from the epicentre of this earthquake. We observed that a clear geomagnetic burst was identified in the raw data of the Bx and By components in the LEMI-30 data before this earthquake. Geomagnetic amplitude bursts were identified 6 to 18 days and 2 days before this earthquake with a frequency of 0.01 to 0.02 Hz. Polarization ratio (PR) analysis revealed an anomalous signal on June 11, 2020 with PR values increasing to 1.4. The planetary index (Kp) and disturbance storm time index (Dst) due to the Sun‒Earth interaction are also very low (Kp = 0.3 and Dst = –6 nT) from June 10 to 16, 2020. In order to understand the dynamics of seismic processes, fractal dimensional analysis is also applied to magnetic data. Fractal dimension values also corroborate with the results of PR analysis, which showed a similar anomaly on June 11, 2020. The ULF geomagnetic data was further analyzed by applying the band-pass filtered data instead of the raw data in the period range from 10 to 45 seconds and derived the Z/X amplitude ratio in the Pc3 band. We found an upward trend and a downward trend from June 10, 2020. Enhanced polarization ratios were detected in the reconstructed components using the EMD technique which are linked to the current earthquake. It has been clearly demonstrated that the EMD method can be used to isolate noise and thus improve the identification of simultaneous short-term geomagnetic variations/anomalies. Therefore, in our study, we have clearly differentiated their origin, whether external (the Sun‒Earth interactions) or internal (local changes in conductivity in the area of the preparation).
{"title":"Anomalous ULF Geomagnetic Anomalies Associated with the June 14, 2020 Earthquake (M = 5.3) in Kachchh, Gujarat Region (India)","authors":"C. P. Simha, K. M. Rao","doi":"10.1134/s001685212470016x","DOIUrl":"https://doi.org/10.1134/s001685212470016x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Gujarat region (India) was struck by an earthquake of magnitude 5.3 on June 14, 2020 at 14:43 UTC near Bhachau city in Kachchh district in the state of Gujarat, with a depth of 20 km at the epicentre of 23.38° N, 70.36° E. In order to study the earthquake precursors for this event, data from the Induction Coil Magnetometer (LEMI-30) installed at the Badargadh Multi-Parameter Geophysical Observatory (MPGO) was analyzed for the period from January 1 to June 16, 2020. This station is located ~20 km from the epicentre of this earthquake. We observed that a clear geomagnetic burst was identified in the raw data of the B<sub>x</sub> and B<sub>y</sub> components in the LEMI-30 data before this earthquake. Geomagnetic amplitude bursts were identified 6 to 18 days and 2 days before this earthquake with a frequency of 0.01 to 0.02 Hz. Polarization ratio (PR) analysis revealed an anomalous signal on June 11, 2020 with PR values increasing to 1.4. The planetary index (K<sub>p</sub>) and disturbance storm time index (D<sub>st</sub>) due to the Sun‒Earth interaction are also very low (K<sub>p</sub> = 0.3 and D<sub>st</sub> = –6 nT) from June 10 to 16, 2020. In order to understand the dynamics of seismic processes, fractal dimensional analysis is also applied to magnetic data. Fractal dimension values also corroborate with the results of PR analysis, which showed a similar anomaly on June 11, 2020. The ULF geomagnetic data was further analyzed by applying the band-pass filtered data instead of the raw data in the period range from 10 to 45 seconds and derived the Z/X amplitude ratio in the Pc3 band. We found an upward trend and a downward trend from June 10, 2020. Enhanced polarization ratios were detected in the reconstructed components using the EMD technique which are linked to the current earthquake. It has been clearly demonstrated that the EMD method can be used to isolate noise and thus improve the identification of simultaneous short-term geomagnetic variations/anomalies. Therefore, in our study, we have clearly differentiated their origin, whether external (the Sun‒Earth interactions) or internal (local changes in conductivity in the area of the preparation).</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"67 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141506540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1134/s0016852124700146
S. A. S. Araffa, M. I. Mohamaden, M. F. Abu-Hashesh, A. N. H. Galal, M. S. Takey, N. M. Hassan
Abstract
El-Hammam area is situated along the northwest coastal region of Egypt, which is a tight strip of ground between the Mediterranean and the vast deserts outside of the delta agricultural region on the west. A digital elevation model (DEM) and Landsat-8 image with a 30 m resolution were used. Also, the data were utilized in the geomorphological analysis and interpretations of the geology of the El Hammam area. The processed Landsat ETM + satellite imageries were used to interpret and construct the geological map. The digital data of the DEM has been utilized to extract the structural lineaments map. The main geomorphic properties of the El Hammam area were delineated by the geomorphological analysis. Gravity data are utilized to determine the subsurface features (faults and basins) and the depth of the basement, where are used processing and filtering techniques to outline the dominant structure. The interpretation of the gravity data reveals that directions of the major structures are aligned in NW‒SE and NE‒SW whereas the small structures are alignment in E‒W, WNW‒ESE, ENE‒WSW, NNE‒SSW, N‒S, and NNW–SSE directions. The findings of depth in order to estimate the basement rocks by 2D and 3D modeling ranges from 1254 m at the SW and western parts to 5650 m at the SE and eastern parts of the study area.
{"title":"Geophysical and Remote Sensing Data for Delineating Structural Elements at El Hammam Area, Northern Part of Western Desert, Egypt","authors":"S. A. S. Araffa, M. I. Mohamaden, M. F. Abu-Hashesh, A. N. H. Galal, M. S. Takey, N. M. Hassan","doi":"10.1134/s0016852124700146","DOIUrl":"https://doi.org/10.1134/s0016852124700146","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>El-Hammam area is situated along the northwest coastal region of Egypt, which is a tight strip of ground between the Mediterranean and the vast deserts outside of the delta agricultural region on the west. A digital elevation model (DEM) and Landsat-8 image with a 30 m resolution were used. Also, the data were utilized in the geomorphological analysis and interpretations of the geology of the El Hammam area. The processed Landsat ETM + satellite imageries were used to interpret and construct the geological map. The digital data of the DEM has been utilized to extract the structural lineaments map. The main geomorphic properties of the El Hammam area were delineated by the geomorphological analysis. Gravity data are utilized to determine the subsurface features (faults and basins) and the depth of the basement, where are used processing and filtering techniques to outline the dominant structure. The interpretation of the gravity data reveals that directions of the major structures are aligned in NW‒SE and NE‒SW whereas the small structures are alignment in E‒W, WNW‒ESE, ENE‒WSW, NNE‒SSW, N‒S, and NNW–SSE directions. The findings of depth in order to estimate the basement rocks by 2D and 3D modeling ranges from 1254 m at the SW and western parts to 5650 m at the SE and eastern parts of the study area.</p>","PeriodicalId":55097,"journal":{"name":"Geotectonics","volume":"187 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141506541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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