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Keywords = intraplate deformation

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34 pages, 4416 KiB  
Article
Strain Localization and Stress Evolution Along the Yangsan Fault: A Geodetic Approach to Seismic Hazard Assessment
by Seung-Jun Lee, Hong-Sik Yun, Dal-Ho Shin and Sang-Hoon Lee
Appl. Sci. 2025, 15(13), 7541; https://doi.org/10.3390/app15137541 - 4 Jul 2025
Viewed by 404
Abstract
This study addresses the lack of detailed geodetic assessments of crustal strain accumulation along the central Yangsan Fault in southeastern Korea, an area of recognized but insufficiently characterized seismic potential. To tackle this, we applied elastic strain tensor analysis to GNSS data from [...] Read more.
This study addresses the lack of detailed geodetic assessments of crustal strain accumulation along the central Yangsan Fault in southeastern Korea, an area of recognized but insufficiently characterized seismic potential. To tackle this, we applied elastic strain tensor analysis to GNSS data from 33 stations, forming 49 triangular elements across the fault zone. From this, we quantified areal strain (Δ), maximum shear strain (γmax), and principal stress orientations (θp, θ_γmax) to map spatial deformation heterogeneity. The results identify several high-strain zones, notably Triangle 10 (2.984 µstrain/yr), Triangle 16 (2.325), and Triangle 31 (2.452), with Triangle 16—located at the Yangsan–Ulsan Fault intersection—exhibiting pronounced shear strain and a sharp angular deviation in stress orientation. These findings reveal localized stress reorganization likely caused by fault–fault interaction. Our analysis highlights the capability of GNSS-based strain tensor modeling to detect subtle intraplate deformation. The proposed methodology offers a practical framework for pinpointing structurally sensitive fault segments with elevated seismic risk in otherwise stable continental interiors, supporting more targeted seismic hazard assessment in Korea and other intraplate regions worldwide. Full article
(This article belongs to the Section Earth Sciences)
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24 pages, 17868 KiB  
Article
Shallow Structural Deformation Reveals Intraplate Seismicity Triggered by Graben Motion in the South China Littoral Fault Zone
by Hu Yi, Wenhuan Zhan, Xiaodong Yang, Jian Li, Xiaochuan Wu, Jie Sun, Yantao Yao, Jiaxian Huang and Zelong Ju
Remote Sens. 2025, 17(13), 2153; https://doi.org/10.3390/rs17132153 - 23 Jun 2025
Viewed by 456
Abstract
High-resolution seismic reflection profiles from the offshore segment of the Littoral Fault Zone (LFZ) near Nan’ao Island were analyzed to investigate fault activity and its potential link to the 1918 M7.3 earthquake. The data reveal a ~19 km-wide graben bounded by seaward- and [...] Read more.
High-resolution seismic reflection profiles from the offshore segment of the Littoral Fault Zone (LFZ) near Nan’ao Island were analyzed to investigate fault activity and its potential link to the 1918 M7.3 earthquake. The data reveal a ~19 km-wide graben bounded by seaward- and landward-dipping normal faults, with fault-propagation folds and growth faults reaching the seafloor. Forward modeling of the fault-propagation fold indicates three discrete episodes of normal dip-slip displacement (~20 m per phase), separated by prolonged quiescent periods, suggesting episodic fault activity and seismic-scale strain accumulation. Despite the regional NW–SE compressional stress regime, active normal faulting is observed, implying vertical stress as the dominant driving force. A gravitational seismic model driven by upper crustal loading is proposed to explain both the fault motion and the down-draw tsunami observed during the 1918 event. These findings offer new insights into intraplate seismogenic mechanisms and associated hazards along the South China coast. Full article
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27 pages, 49480 KiB  
Article
Analyzing Recent Tectonic Activity Along the Karak Wadi Al Fayha Fault System Using Seismic, Earthquake, and Remote Sensing Data
by Mu’ayyad Al Hseinat, Malek AlZidaneen and Ghassan Sweidan
Geosciences 2025, 15(5), 177; https://doi.org/10.3390/geosciences15050177 - 14 May 2025
Viewed by 1102
Abstract
The Karak Wadi Al Fayha Fault (KWF) is a major NW-trending intraplate wrench fault system extending over 325 km from Western Karak in Jordan to Wadi Al Fayha in Saudi Arabia. Structurally linked to the Precambrian Najd Fault System, the KWF has been [...] Read more.
The Karak Wadi Al Fayha Fault (KWF) is a major NW-trending intraplate wrench fault system extending over 325 km from Western Karak in Jordan to Wadi Al Fayha in Saudi Arabia. Structurally linked to the Precambrian Najd Fault System, the KWF has been previously mapped using field observations, gravity, magnetic, and reflection seismic methods. However, these approaches lacked the vertical resolution necessary to characterize its shallow structure, leaving its influence on recent deposits and surface topography poorly understood. This study employs reflection seismic sections integrated with a Digital Elevation Model to refine terrain analysis and enhance fault mechanism solutions for determining the regional stress field pattern. Our results provide compelling evidence of the KWF’s upward propagation into the surface, as demonstrated by deformation of the uppermost Cretaceous and Cenozoic successions, distinct geomorphic features in the Digital Elevation Model, alignment of earthquake epicenters along the fault, and active landslides associated with its movement. We suggest that the reactivation of the KWF has been influenced by changing stress fields from the Late Cretaceous (Turonian) to the present. The Northwestern Arabian plate has undergone multiple tectonic stress transitions, including WNW–ESE compression associated with the Syrian Arc Fold-Belt system (Turonian–Plio-Pleistocene) and subsequent NNE–SSW extension linked to Red Sea rifting (Neogene–present). The analysis of fault mechanism solutions suggests that the latest fault movements result from the continued activity of the Irbid Rift event (Eocene) and the Dead Sea Transform Fault since the Miocene. Full article
(This article belongs to the Special Issue Applied Geophysics for Geohazards Investigations)
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16 pages, 5610 KiB  
Article
Influence of Digital Elevation Model Resolution on the Normalized Stream Length–Gradient Index in Intraplate Regions: A Case Study of the Yangsan Fault, Korea
by Hyunjee Lim, Sangmin Ha, Sohee Kim, Hee-Cheol Kang and Moon Son
Remote Sens. 2025, 17(9), 1638; https://doi.org/10.3390/rs17091638 - 6 May 2025
Viewed by 724
Abstract
The spatial variability of input parameters plays a crucial role in the interpretation of geomorphic indices, with digital elevation models (DEMs) being the primary data source. However, the influence of DEM resolution on these indices has rarely been investigated. This study investigated the [...] Read more.
The spatial variability of input parameters plays a crucial role in the interpretation of geomorphic indices, with digital elevation models (DEMs) being the primary data source. However, the influence of DEM resolution on these indices has rarely been investigated. This study investigated the influence of DEM resolution on the assessment of tectonic activity using the normalized stream length–gradient (SLk) index, which reflects variations along river profiles. The SLk index is sensitive to changes in river gradients that may result from active faulting or differential uplift, making it a valuable tool for identifying zones of active tectonic deformation. Therefore, understanding the impact of DEM resolution on SLk analysis is critical for accurately detecting and interpreting subtle tectonic signals, particularly in intraplate regions where deformation is slow and geomorphic expressions are faint and discontinuous. By comparing high-resolution LiDAR-derived DEMs (L-DEMs) and low-resolution topographic map-derived DEMs (T-DEMs), we analyzed the SLk index distributions along the Yangsan Fault, Korean Peninsula, an intraplate setting with Quaternary activity. According to the results, SLk anomalies derived from L-DEMs had a continuous distribution along the fault, closely aligning with known surface ruptures and indicating active tectonic deformation. In contrast, SLk anomalies derived from T-DEMs were sporadic and less continuous, especially in low-relief landscapes such as alluvial fans and floodplains, highlighting the limitations of T-DEMs in detecting fault-related features. High-resolution DEMs were better able to capture finer-scale geomorphic features, such as fault scarps, deflected streams, and lineaments associated with active tectonics, providing a more comprehensive view of fault-related deformation. This discrepancy highlights the importance of resolution choice in tectonic assessments, as low-resolution DEMs may underestimate the tectonic activities of intraplate faults by missing subtle topographic variations. While the choice of DEM resolution may depend on study area, scope, and data availability, high-resolution DEMs are critical for identifying tectonic activity in intraplate regions where geomorphic features of faulting due to slow deformation are subtle and dispersed. Full article
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18 pages, 14732 KiB  
Article
Atypical Linear Tectonic Block of the Intraplate Deformation Zone in the Central Indian Ocean Basin
by Vsevolod V. Yutsis, Oleg V. Levchenko, Alexander V. Tevelev, Yulia G. Marinova, Ilia A. Veklich and Abraham Del Razo Gonzalez
J. Mar. Sci. Eng. 2024, 12(12), 2231; https://doi.org/10.3390/jmse12122231 - 5 Dec 2024
Viewed by 1034
Abstract
The Central Indian Ocean Basin (CIOB) is distinguished by unusually high tectonic activity, setting it apart from all other passive oceanic basins. Within the interior of the Indo-Australian lithospheric plate lies a unique area of intraplate deformation. This region is characterized by the [...] Read more.
The Central Indian Ocean Basin (CIOB) is distinguished by unusually high tectonic activity, setting it apart from all other passive oceanic basins. Within the interior of the Indo-Australian lithospheric plate lies a unique area of intraplate deformation. This region is characterized by the highest recorded intraplate oceanic seismicity, with earthquake magnitudes reaching up to M = 8, abnormally high heat flow—measured to be two to four times higher than background levels for the ancient oceanic lithosphere of the Cretaceous age—and, most notably, intense folding and faulting of sediments and the basement, which are typically associated only with boundary zones of lithospheric plates. This anomalously tectonically active intraplate area was studied during regular research cruises in the 1970s–1980s, after which new conclusions were mainly drawn from satellite data modeling. Substantially new geophysical data were obtained in 2017 after a long gap. Bathymetric surveys using multibeam echosounders during the 42nd cruise of the R/V (Research Vessel) Akademik Boris Petrov and the SO258/2 cruise of the R/V Sonne provided full coverage of a large portion of the intraplate deformation area in the CIOB. This confirmed the mosaic-block structure of the intraplate deformation zone in the Central Indian Ocean Basin, consisting of numerous isometrically deformed tectonic blocks. A linear block at 0.2–0.6° S, which has a branch-like shape in plain view, is morphologically distinct from these blocks. It represents a system of structural elements of different scales (folds, flexures, ruptures), which constitute a structural paragenesis formed in the mechanical environment of a dextral transpressive tectonic setting. Full article
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18 pages, 84736 KiB  
Article
Newly Discovered NE-Striking Dextral Strike-Slip Holocene Active Caimashui Fault in the Central Part of the Sichuan-Yunnan Block and Its Tectonic Significance
by Xin Tan, Kuan Liang, Baoqi Ma and Zhongtai He
Remote Sens. 2024, 16(17), 3203; https://doi.org/10.3390/rs16173203 - 29 Aug 2024
Viewed by 1041
Abstract
The Sichuan-Yunnan block is a tectonically active region in China, with frequent large earthquakes occurring in and around it. Despite most earthquakes being concentrated along boundary faults, intraplate faults also have the potential to generate damaging earthquakes. Remote sensing makes it possible to [...] Read more.
The Sichuan-Yunnan block is a tectonically active region in China, with frequent large earthquakes occurring in and around it. Despite most earthquakes being concentrated along boundary faults, intraplate faults also have the potential to generate damaging earthquakes. Remote sensing makes it possible to identify these potential earthquake source faults. During an active fault investigation in the Liangshan area, a distinct lithological boundary named Caimashui fault was found. The geometric distribution and kinematic parameter of the fault is crucial for assessing seismic hazards and understanding the deformation pattern within the Sichuan-Yunnan block. The Caimashui fault is mapped with remote sensing interpretation, a field survey, and UAV measurement. Through trenching and Quaternary dating, the Late Quaternary active characteristics of the fault are studied. The fault is a Holocene active dextral strike-slip fault with a reverse component, exhibiting a dextral strike-slip rate of ~0.70 ± 0.11 mm/a. Paleoseismic investigation shows that the last surface rupture event of the Caimashui fault occurred later than 4150 ± 30a BP, with a magnitude of M ≥ 7.0. The fault may act as a secondary splitting fault, absorbing the deformation caused by various sinistral strike-slip rates of the boundary faults and the potential energy from the counterclockwise rotation of the Central Yunnan micro-block. Full article
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20 pages, 10908 KiB  
Article
A Complex Meso–Cenozoic History of Far-Field Extension and Compression: Evidence from Fission Track Analysis in the Helanshan Mountain Tectonic Belt, NW China
by Cheng Wu, Yu Wang, Wanming Yuan and Liyun Zhou
Appl. Sci. 2024, 14(9), 3559; https://doi.org/10.3390/app14093559 - 23 Apr 2024
Cited by 1 | Viewed by 1235
Abstract
The Helanshan Mountain tectonic belt (HTB) is an intraplate deformation belt along the northwestern border of the Ordos Block in the North China Craton. When and why this intracontinental tectonic belt formed, its subsequent uplift and erosion, and the relationships between ranges and [...] Read more.
The Helanshan Mountain tectonic belt (HTB) is an intraplate deformation belt along the northwestern border of the Ordos Block in the North China Craton. When and why this intracontinental tectonic belt formed, its subsequent uplift and erosion, and the relationships between ranges and adjacent basins remain unclear. To better assess the connections between the temporal and structural activity in HTB, apatite fission-track (AFT) and zircon fission-track (ZFT) analyses were conducted in this study. The lack of adequate FT data from the HTB is a source of contention and dispute. This paper collected samples for AFT and ZFT techniques from the central and southern HTB, trying to improve the research. The ZFT and AFT ages could be divided into the following 7 groups: 279 Ma, 222–213 Ma, 193–169 Ma, 151–147 Ma, 130–109 Ma, 92–77 Ma, and 65–50 Ma. The inverse modeling results of AFT indicate 4 fast cooling episodes of 170–120 Ma, 120–95 Ma, 66–60 Ma, and ~10–8 Ma to the present. Combining the results of FT analysis with radial plot and inverse modeling of AFT, the following eight age groups are believed to reveal the distinct tectonic activities in HTB: the first age group of 279 Ma mainly represented the back-arc extension of the southern HTB; the age group of 222–213 Ma was bounded with NNE-SSE trending contraction between the South China block and North China Craton; the event of 193–169 Ma responded to the post-orogenic collapse followed after the second event; the 151–147 Ma group was interpreted as the eastward extrusion induced by the subduction between Qiangtang and Lhasa blocks; the Early Cretaceous (130–109 Ma) group was not only affected by the rollback of the Pacific Plate, but also denoted the collapse of the thickened lithosphere formed in the Late Jurassic; the Late Cretaceous (92–77 Ma) group was attributed to long-distance impact from the subduction of the Pacific Plate beneath the Eurasian Plate; the event during 65–50 Ma was a correspondence to far-field effect of the onset collision between the Eurasian and Indian Plates; and from 10–8 Ma to the present, the progressive collision of the Indian and Eurasian Plates have a significant impact on the HTB and the northeastern Tibetan Plateau. Full article
(This article belongs to the Special Issue New Advances, Challenges, and Illustrations in Applied Geochemistry)
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42 pages, 8069 KiB  
Review
Definitions, Classification Schemes for Active Faults, and Their Application
by Zhonghai Wu and Mengmeng Hu
Geosciences 2024, 14(3), 68; https://doi.org/10.3390/geosciences14030068 - 4 Mar 2024
Cited by 8 | Viewed by 6790
Abstract
Active faults are generally defined as faults that have moved in the past and will continue to be active in the future. They are expected to cause deformation and potential disasters if they are localized close to human activities. The definition and classification [...] Read more.
Active faults are generally defined as faults that have moved in the past and will continue to be active in the future. They are expected to cause deformation and potential disasters if they are localized close to human activities. The definition and classification of active faults are important bases for evaluating the risk. This paper summarizes and compares the history, status, and progress of their definition and classification schemes used in representative countries and regions, as well as in some relevant standards, in active fault mapping, in the construction of spatial databases, and in some other aspects. It is concluded that the current geodynamic setting, existing technical means, geological operability, application purpose, and social acceptability of active faulting hazard in a specific area comprehensively determine the selection of the definition and classification. The key parameter in defining active faults is the time limit. It usually involves four time scales, i.e., Neotectonic (post-Neogene), Quaternary, Late Quaternary, and Holocene. The definition using a short time scale, such as Late Quaternary and Holocene, is usually suitable for the plate boundary zone, which has a high strain rate, but active faults in the intraplate deformation region and stable continental region should be defined with a long time scale, such as the Quaternary and Neotectonics. In addition, the magnitude standard can determine the activity intensity of active faults, which most generally includes three classes, namely, M ≥ 5.0 damaging earthquakes, M ≥ 6.0 strong earthquakes, and M ≥ 6.5 earthquakes that may produce surface displacement or deformation. The M ≥ 5.0 earthquake is generally applicable to regional earthquake prevention and risk mitigation in many countries or regions, but the M ≥ 6.5 earthquake magnitude benchmark is generally used as the standard in rules or regulations regarding active fault avoidance. The most common classification schemes in many countries or regions are based on fault activity, which is reflected mainly by the fault slip rate and fault recurrence interval (FRI), as well as by the last activation time. However, when determining the specific quantitative parameters of the different activity levels of faults, it is necessary to comprehensively consider the differences in activity and ages of the faults in the study region, as well as the amount and validity of existing data for the purpose of classifying different active levels of faults effectively. Full article
(This article belongs to the Special Issue Active Tectonics and Earthquakes)
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24 pages, 5343 KiB  
Article
Archeoseismic Study of Damage in Medieval Monuments around New Delhi, India: An Approach to Understanding Paleoseismicity in an Intraplate Region
by Sambit Prasanajit Naik, Klaus Reicherter, Miklos Kázmér, Jens Skapski, Asmita Mohanty and Young-Seog Kim
GeoHazards 2024, 5(1), 142-165; https://doi.org/10.3390/geohazards5010007 - 14 Feb 2024
Cited by 1 | Viewed by 3053
Abstract
The seismic shaking observed around Delhi and the surrounding region due to near-field and far-field earthquakes is a matter of concern for the seismic safety of the national capital of India, as well as the historical monuments of the region. Historical seismicity indicates [...] Read more.
The seismic shaking observed around Delhi and the surrounding region due to near-field and far-field earthquakes is a matter of concern for the seismic safety of the national capital of India, as well as the historical monuments of the region. Historical seismicity indicates that the Delhi region has been affected by several damaging earthquakes originating from the Himalayan region as far-field events, as well as due to near-field earthquakes with epicenters close to Delhi. The historical records, along with recent archeoseismological studies, suggest that Qutab Minar, a UNESCO World Heritage Site, was damaged by the earthquake of 1803 CE. This event represents the only evidence of seismic damage from the region, as there has been no detailed study of other historical monuments in the area or earthquakes that have caused damage. In this context, the earthquake damage to other monuments might have been overlooked to some extent around the Qutab Minar due to the lack of proper earthquake damage surveys and documentation in historical times. The main goal of this study is to identify evidence of earthquake archeological effects around the Qutab Minar and to shed new light on the occurrence and characteristics of ancient earthquakes while providing data to inform seismic risk assessment programs. With this aim, we describe different earthquake-related damage (EAE, earthquake archeological effects) at the Isa Khan Tomb and Humayun’s Tomb, built between 1548 CE and 1570 CE, respectively, as well as the older Tomb of Iltutmish (built in 1235 CE) along with the Qutab Minar, which was built between 1199 CE and 1220 CE. The damage was probably caused by seismic events with intensities between VIII and IX on the European Macroseismic Scale (EMS). Based on the methodology of paleo ShakeMaps, it is most likely that the 1803 CE earthquake was the causative earthquake for the observed deformation in the Isa Khan Tomb, Tomb of Iltutmish, and Humayun’s Tomb. More detailed regional paleoseismological studies are required to identify the responsible fault. In conclusion, the impressive cultural heritage of Delhi city and the intraplate region is constantly under seismic threats from near-field earthquakes and far-field Himalayan earthquakes. Full article
(This article belongs to the Special Issue Active Faulting and Seismicity)
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32 pages, 23485 KiB  
Article
Late Cenozoic to Present Kinematic of the North to Eastern Iran Orogen: Accommodating Opposite Sense of Fault Blocks Rotation
by Ahmad Rashidi, Majid Shahpasandzadeh and Carla Braitenberg
Remote Sens. 2022, 14(16), 4048; https://doi.org/10.3390/rs14164048 - 19 Aug 2022
Cited by 6 | Viewed by 2617
Abstract
The opposite-sense fault block rotation across the continental strike-slip faulting plays an important role in accommodating crustal deformation in the north of the East Iran orogen. This research constrains the post-Neogene kinematics of the NW-SE to E-W left-lateral transpressional zones at the northern [...] Read more.
The opposite-sense fault block rotation across the continental strike-slip faulting plays an important role in accommodating crustal deformation in the north of the East Iran orogen. This research constrains the post-Neogene kinematics of the NW-SE to E-W left-lateral transpressional zones at the northern termination of the N-S striking right-lateral Neh fault system in the East Iran orogen. Using two case studies, we analyzed the NW-SE Birjand splay and the E-W Shekarab transpression zone by analysis of satellite images, structural features, fault geometry and kinematics, GPS (Global Positioning System) velocities, fault- and earthquake-slip stress inversion, and paleomagnetic data. Our results show two distinctive regions of opposite-sense fault block rotations and with different rotation rates. As an asymmetric arc, the Birjand splay displays a transition from the prevailing N-S right lateral shear in the east to NW-SE left lateral transpression in the middle and E-W left lateral shear in the west. In the east, with clockwise fault block rotation, the N-S right lateral faults and the NW-SE oblique left-lateral reverse faults constitute push-ups through the restraining fault bends. In the west, with counterclockwise fault block rotation, the Shekarab transpression zone is associated with the duplex, pop-up, and shear folds. Our suggested kinematic model reveals that the N-S right-lateral shear is consumed on the left-lateral transpressional zones through the vertical axis fault block rotation. This led to an E-W shortening and N-S along-strike lengthening in the East Iran orogen. This research improves our understanding of how opposite fault block rotations accommodate India- and Eurasia-Arabia convergence in the north of the East Iran orogen. The suggested model has implications in the kinematic evolution of intra-plate strike-slip faulting through continental collision tectonics. Full article
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31 pages, 11666 KiB  
Article
Intraplate Strike-Slip Corridor within South America (NE Border of the Paraná Basin) Unveiled by Structural Analysis of Faults and Fracture Swarms
by Paola Cianfarra, Marcos Roberto Pinheiro, Fernando Nadal Junqueira Villela and Francesco Salvini
Geosciences 2022, 12(2), 101; https://doi.org/10.3390/geosciences12020101 - 21 Feb 2022
Cited by 11 | Viewed by 4614
Abstract
We present the effect of neotectonics in intracratonic settings as revealed by the surface, brittle deformation associated to a regionally-sized shear corridor, which affects Southeastern Brazil. The deformation zone is characterized by the presence of nearly orthogonal fracture sets, interpreted as systematic and [...] Read more.
We present the effect of neotectonics in intracratonic settings as revealed by the surface, brittle deformation associated to a regionally-sized shear corridor, which affects Southeastern Brazil. The deformation zone is characterized by the presence of nearly orthogonal fracture sets, interpreted as systematic and non-systematic joints often cutting Quaternary deposits. An original methodology of fault and joint inversion by the Monte Carlo converging approach is used to infer multiple paleostress fields. The method provides the best orientation of the principal paleo-stresses responsible for the observed fracturing. At each step of the inversion process, structures are uniquely associated to the stress tensor that provides the lowest error. The results showed the poly-phased tectonic history of the shear corridor studied and paleostresses compatible with a regional strike-slip motion. Specifically, an E-W, left-lateral shear was followed by an E-W, right-lateral kinematics related to the post-Paleogene drifting of South American Plate and its clockwise rotation. The latter tectonic event is presently responsible for brittle deformation observed in Quaternary deposits. The proposed deformation corridor may represent the Cenozoic reactivation of an ancient weakness zone. We speculate that the described intraplate strike-slip deformation belt represents the continental prosecution of the Rio de Janeiro fracture zone. Full article
(This article belongs to the Special Issue Landscape Evolution in Tectonically Active Regions)
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16 pages, 6053 KiB  
Article
Brittle Deformation in the Neoproterozoic Basement of Southeast Brazil: Traces of Intraplate Cenozoic Tectonics
by Marcos Roberto Pinheiro and Paola Cianfarra
Geosciences 2021, 11(7), 270; https://doi.org/10.3390/geosciences11070270 - 27 Jun 2021
Cited by 8 | Viewed by 3389
Abstract
The basement of southeast Brazil is traditionally interpreted as the result of Neoproterozoic and early Paleozoic orogenic cycles. Wide regions of the Atlantic Plateau (southeast Brazil) are characterized by rocks and tectonic structures of Precambrian age. According to the classical literature, these regions [...] Read more.
The basement of southeast Brazil is traditionally interpreted as the result of Neoproterozoic and early Paleozoic orogenic cycles. Wide regions of the Atlantic Plateau (southeast Brazil) are characterized by rocks and tectonic structures of Precambrian age. According to the classical literature, these regions have not been affected by tectonics since the Miocene, despite the fact that they rest close to Cenozoic basins, which have suffered recent tectonic deformation. The objective of this research is to evaluate the role of neotectonics in the Atlantic Plateau. This task is accomplished through a multiscalar approach which includes lineament domain analysis from regionally sized digital elevation models and structural geology field surveys. Lineaments are automatically detected and statistically analyzed. Azimuthal analyses of data on faults and fractures by a polynomial Gaussian fit enables the identification of the main structural trends. Fault-slip direct inversion by means of the original Monte Carlo approach allows one to compute the multiple paleostresses that produced the measured fault population. The results show the presence of a principal ENE–WSW lineament domain, related to an old shear zone possibly reactivated since the Miocene. One of the paleostresses computed from fault-slip inversion is in agreement with the neotectonic stress-field proposed by other authors. Full article
(This article belongs to the Special Issue Landscape Evolution in Tectonically Active Regions)
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25 pages, 12295 KiB  
Article
Basement Structure and Styles of Active Tectonic Deformation in Central Interior Alaska
by Nilesh C. Dixit and Catherine Hanks
Geosciences 2021, 11(3), 127; https://doi.org/10.3390/geosciences11030127 - 10 Mar 2021
Cited by 4 | Viewed by 4040
Abstract
Central Interior Alaska is one of the most seismically active regions in North America, exhibiting a high concentration of intraplate earthquakes approximately 700 km away from the southern Alaska subduction zone. Seismological evidence suggests that intraplate seismicity in the region is not uniformly [...] Read more.
Central Interior Alaska is one of the most seismically active regions in North America, exhibiting a high concentration of intraplate earthquakes approximately 700 km away from the southern Alaska subduction zone. Seismological evidence suggests that intraplate seismicity in the region is not uniformly distributed, but concentrated in several discrete seismic zones, including the Nenana basin and the adjacent Tanana basin. Although the location and magnitude of the seismic activity in both basins are well defined by a network of seismic stations in the region, the tectonic controls on these intraplate earthquakes and the heterogeneous nature of Alaska’s continental interior remain poorly understood. We investigated the crustal structure of the Nenana and Tanana basins using available seismic reflection, aeromagnetic and gravity anomaly data, supplemented by geophysical well logs and outcrop data. We developed nine new two-dimensional forward models to delineate internal geometries and the crustal structure of Alaska’s interior. The results of our study demonstrates a strong crustal heterogeneity beneath both basins. The Tanana basin is a relatively shallow (up to 2 km) asymmetrical foreland basin with its southern, deeper side controlled by the northern foothills of the Central Alaska Range. Northeast-trending left lateral strike-slip faults within the Tanana basin are interpreted as a zone of clockwise crustal block rotation. The Nenana basin has a fundamentally different geometry. It is a deep (up to 8 km), narrow transtensional pull-apart basin that is deforming along the left-lateral Minto Fault. This study identifies two distinct modes of current tectonic deformation in Central Interior Alaska and provides a basis for modeling the interplay between intraplate stress fields and major structural features that potentially influence the generation of intraplate earthquakes in the region. Full article
(This article belongs to the Special Issue Satellite/Airborne Gravity and Magnetic Investigations)
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26 pages, 3695 KiB  
Article
New Insights into Long-Term Aseismic Deformation and Regional Strain Rates from GNSS Data Inversion: The Case of the Pollino and Castrovillari Faults
by Gabriele Cambiotti, Mimmo Palano, Barbara Orecchio, Anna Maria Marotta, Riccardo Barzaghi, Giancarlo Neri and Roberto Sabadini
Remote Sens. 2020, 12(18), 2921; https://doi.org/10.3390/rs12182921 - 9 Sep 2020
Cited by 5 | Viewed by 2819
Abstract
We present a novel inverse method for discriminating regional deformation and long-term fault creep by inversion of GNSS velocities observed at the spatial scale of intraplate faults by exploiting the different spatial signatures of these two mechanisms. In doing so our method provides [...] Read more.
We present a novel inverse method for discriminating regional deformation and long-term fault creep by inversion of GNSS velocities observed at the spatial scale of intraplate faults by exploiting the different spatial signatures of these two mechanisms. In doing so our method provides a refined estimate of the upper bound of the strain accumulation process. As case study, we apply this method to a six year GNSS campaign (2003–2008) set up in the southern portion of the Pollino Range over the Castrovillari and Pollino faults. We show that regional deformation alone cannot explain the observed deformation pattern and implies high geodetic strain rate, with a WSW-ENE extension of 86±41×109/yr. Allowing for the possibility of fault creep, the modelling of GNSS velocities is consistent with their uncertainties and they are mainly explained by a shallow creep over the Pollino fault, with a normal/strike-slip mechanism up to 5 mm/yr. The regional strain rate decrease by about 70 percent and is characterized by WNW-ESE extension of 24±28×109/yr. The large uncertainties affecting our estimate of regional strain rate do not allow infering whether the tectonic regime of the area is extensional or strike-slip, although the latter is slightly more likely. Full article
(This article belongs to the Special Issue Ground Deformation Patterns Detection by InSAR and GNSS Techniques)
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61 pages, 37292 KiB  
Review
Paleoliquefaction Studies and the Evaluation of Seismic Hazard
by Martitia P. Tuttle, Ross Hartleb, Lorraine Wolf and Paul W. Mayne
Geosciences 2019, 9(7), 311; https://doi.org/10.3390/geosciences9070311 - 13 Jul 2019
Cited by 55 | Viewed by 11141
Abstract
Recent and historical studies of earthquake-induced liquefaction, as well as paleoliquefaction studies, demonstrate the potential usefulness of liquefaction data in the assessment of the earthquake potential of seismic sources. Paleoliquefaction studies, along with other paleoseismology studies, supplement historical and instrumental seismicity and provide [...] Read more.
Recent and historical studies of earthquake-induced liquefaction, as well as paleoliquefaction studies, demonstrate the potential usefulness of liquefaction data in the assessment of the earthquake potential of seismic sources. Paleoliquefaction studies, along with other paleoseismology studies, supplement historical and instrumental seismicity and provide information about the long-term behavior of earthquake sources. Paleoliquefaction studies focus on soft-sediment deformation features, including sand blows and sand dikes, which result from strong ground shaking. Most paleoliquefaction studies have been conducted in intraplate geologic settings, but a few such studies have been carried out in interplate settings. Paleoliquefaction studies provide information about timing, location, magnitude, and recurrence of large paleoearthquakes, particularly those with moment magnitude, M, greater than 6 during the past 50,000 years. This review paper presents background information on earthquake-induced liquefaction and resulting soft-sediment deformation features that may be preserved in the geologic record, best practices used in paleoliquefaction studies, and application of paleoliquefaction data in earthquake source characterization. The paper concludes with two examples of regional paleoliquefaction studies—in the Charleston seismic zone and the New Madrid seismic zone in the southeastern and central United States, respectively—which contributed to seismic source models used in earthquake hazard assessment. Full article
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