Relevant aspects to the recognition of extensional environments in the field

The understanding of each geological-structural aspect in the field is fundamental to be able to reconstruct the geological history of a region and to give a geological meaning to the data acquired in the outcrop. The description of a brittle extensional environment, which is dominated by normal fault systems, is based on: (I) image interpretation, which aims to find evidence suggestive of an extensional geological environment, such as the presence of scarp lines and fault scarps, horst, graben and/or half-graben, among others, that allow the identification of the footwall and hanging wall blocks; ii) definition of the sites of interest for testing; and iii) analysis of the outcrops, following a systematic procedure that consists of the observation and identification of the deformation markers, their three-dimensional schematic representation, and their subsequent interpretation, including the stereographic representation in the outcrop. This procedure implies the unification of the parameters of structural data acquisition in the field, mentioning the minimum fields necessary for the registration of the data in tables. Additionally, the integration of geological and structural observations of the outcrop allows to understand the nature of the geological units, the deformation related to the extensional environment and the regional tectonic context of the study area.

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New constraints on the exhumation history of the western Tauern Window (European Alps) from thermochronology, thermokinematic modeling, and topographic analysis

International Journal of Earth Sciences ◽

10.1007/s00531-021-02094-w ◽

2021 ◽

Author(s):

Reinhard Wolff ◽

Ralf Hetzel ◽

István Dunkl ◽

Aneta A. Anczkiewicz

Keyword(s):

Hanging Wall ◽

Thermal Relaxation ◽

Slip Rate ◽

Normal Fault ◽

European Alps ◽

Valley Bottom ◽

Topographic Analysis ◽

Tauern Window ◽

History Of ◽

Exhumation History

AbstractThe Brenner normal fault bounds the Tauern Window to the west and accommodated a significant portion of the orogen-parallel extension in the Eastern Alps. Here, we use zircon (U–Th)/He, apatite fission track, and apatite (U–Th)/He dating, thermokinematic modeling, and a topographic analysis to constrain the exhumation history of the western Tauern Window in the footwall of the Brenner fault. ZHe ages from an E–W profile (parallel to the slip direction of the fault) decrease westwards from ~ 11 to ~ 8 Ma and suggest a fault-slip rate of 3.9 ± 0.9 km/Myr, whereas AFT and AHe ages show no spatial trends. ZHe and AFT ages from an elevation profile indicate apparent exhumation rates of 1.1 ± 0.7 and 1.0 ± 1.3 km/Myr, respectively, whereas the AHe ages are again spatially invariant. Most of the thermochronological ages are well predicted by a thermokinematic model with a normal fault that slips at a rate of 4.2 km/Myr between ~ 19 and ~ 9 Ma and produces 35 ± 10 km of extension. The modeling reveals that the spatially invariant AHe ages are caused by heat advection due to faulting and posttectonic thermal relaxation. The enigmatic increase of K–Ar phengite and biotite ages towards the Brenner fault is caused by heat conduction from the hot footwall to the cooler hanging wall. Topographic profiles across an N–S valley in the fault footwall indicate 1000 ± 300 m of erosion after faulting ceased, which agrees with the results of our thermokinematic model. Valley incision explains why the Brenner fault is located on the western valley shoulder and not at the valley bottom. We conclude that the ability of thermokinematic models to quantify heat transfer by rock advection and conduction is crucial for interpreting cooling ages from extensional fault systems.

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Measurable impact of river incision on rift tectonics

10.5194/egusphere-egu21-5193 ◽

2021 ◽

Author(s):

Jean-Arthur Olive ◽

Luca Malatesta ◽

Mark Behn ◽

Roger Buck

Keyword(s):

Numerical Simulations ◽

Hanging Wall ◽

Normal Fault ◽

Climatic Conditions ◽

Natural Variability ◽

Surface Processes ◽

Tectonic Deformation ◽

Plate Boundaries ◽

River Incision ◽

Half Graben

Models that couple tectonics and surface processes commonly predict that efficient erosion and sedimentation help focus crustal deformation onto fewer, longer-lived faults. However, because their geomorphic parameters are difficult to calibrate against real landscapes, the sensitivity of tectonic deformation to a realistic range of surface process efficiencies remains poorly known. Here we model the growth of structurally simple half-graben structures subjected to fluvial incision of specified efficiency and sedimentation. Numerical simulations predict that infinitely-efficient erosion and deposition (i.e., complete surface leveling) can more than double the maximum offset reached on a master normal fault before crustal strain localizes elsewhere. Further, leveling footwall relief tends to promote the migration of strain towards the hanging wall to form new grabens instead of horsts.&#160;&#160; &#160; &#160; &#160; &#160;To test whether the efficiency of river incision can vary sufficiently across real rifts to exert a control on tectonic styles, we analyze the profiles of rivers draining half-graben footwalls and horst blocks in the Basin & Range, Taupo, Rio Grande, and East African Rift. We adapt the standard methodology of equilibrium river profile analysis to account for spatial variations in uplift expected from crustal flexure in a fault-bounded block. Erosional efficiency (EE) is defined as the inverse of the (dimensionless) slope of uplift- and drainage area-corrected river elevation plots. &#160;Measured EEs range between ~0.1 and ~4, reflecting natural variability in lithology, climate, and uplift rates across sites. Incorporating EEs within this documented range in numerical simulations, we find that increasing EE can increase the maximum throw on half-graben master faults by ~50%. Changing EE also affects the geometry of subsequent faults, with lower EEs favoring the transition from half-graben to horsts. These models predict that rifting in a colder, stronger continental crust is less sensitive to surface processes and requires even lower EE to develop horst structures. Our simulations are consistent with a compilation of EE, crustal strength proxies, and fault characteristics across real rift zones. These results suggest that natural variability in climatic conditions and surface erodibility has a measurable impact on the tectonic makeup of Earth's plate boundaries.

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Termination of a fossil continent-ocean fracture zone imaged with three-dimensional seismic data: The Chain Fracture Zone, eastern equatorial Atlantic

Geology ◽

10.1130/g21530ar.1 ◽

2005 ◽

Vol 33 (8) ◽

pp. 641-644 ◽

Cited By ~ 3

Author(s):

Richard J. Davies ◽

Christopher J. MacLeod ◽

Richard Morgan ◽

Sepribo E. Briggs

Keyword(s):

Oceanic Crust ◽

Fracture Zone ◽

Niger Delta ◽

Three Dimensional ◽

Seafloor Spreading ◽

Spreading Center ◽

Equatorial Atlantic ◽

Half Graben ◽

History Of ◽

Subsequent Phase

Abstract We describe the first three-dimensional imaging of the termination of a continent-ocean fracture zone (COFZ), the Chain Fracture Zone, located offshore of the Niger Delta. The COFZ marks the abrupt transition between extended continental crust, comprising multiple half-graben, and oceanic crust that has a pervasive seafloor-spreading fabric. It preserves a history of continent-continent shearing followed by oceanic crust accretion and continent-ocean shearing during the inception of Atlantic rifting. The termination is marked by steeply dipping faults with sigmoidal planform and thrusts that probably formed as a result of continent-continent or continent-ocean shearing. These are crosscut by the seafloor-spreading fabric that formed during the subsequent phase of oceanic crust accretion. The accreted oceanic crust is cut by listric and planar faults that curve in the direction of the COFZ, where they terminate. The transition from continental to oceanic crust across the COFZ is sharp and resolvable to ∼100–200 m. Complexes of lava flows emanate from volcanoes along the COFZ, bifurcating and trifurcating down the volcano flanks. The volcanoes are 2–5.5 km wide and 1.4 km in height relative to adjacent oceanic crust and were injected at the COFZ, probably as the spreading center migrated along it.

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Imaging Poro-Elastic Effects induced by a Normal Fault Aseismic-to-Seismic Dislocation in Shales

10.5194/egusphere-egu2020-6195 ◽

2020 ◽

Author(s):

Yves Guglielmi ◽

Jens Birkholzer ◽

Jonathan Ajo-Franklin ◽

Christophe Nussbaum ◽

Frederic Cappa ◽

...

Keyword(s):

Pore Pressure ◽

Fault Zone ◽

Hanging Wall ◽

Three Dimensional ◽

Normal Fault ◽

Fault Reactivation ◽

Foot Wall ◽

Fault Activation ◽

Strain Monitoring ◽

Receiver Array

Understanding fault reactivation as a result of subsurface fluid injection in shales is critical in geologic CO2 sequestration and in assessing the performance of radioactive waste repositories in shale formations. Since 2015, two semi-controlled fault activation projects, called FS and FS-B, have been conducted in a fault zone intersecting a claystone formation at 300 m depth in the Mont Terri Underground Research Laboratory (Switzerland). In 2015, the FS project involved injection into 5 borehole intervals set at different locations within the fault zone. Detailed pressure and strain monitoring showed that injected fluids can only penetrate the fault when it is at or above the Coulomb failure criterion, highlighting complex mixed opening and slipping activation modes. Rupture modes were strongly driven by the structural complexity of the thick fault. An overall normal fault activation was observed. One key parameter affecting the reactivation behavior is the way the fault&#8217;s initial very low permeability dynamically increases at rupture. Such complexity may also explain a complex interplay between aseismic and seismic activation periods. Intact rock pore pressure variations were observed in a large volume around the rupture patch, producing pore pressure drops of ~4 10-4 MPa up to 20 m away from the ruptured fault patch. Fully coupled three-dimensional numerical analyses indicated that the observed pressure signals are in good accordance with a poro-elastic stress transfer triggered by the fault dislocation.&#160;In 2019, the FS-B experiment started in the same fault, this time activating a larger fault zone volume of about 100 m extent near (and partially including) the initial FS testbed. In addition to the monitoring methods employed in the earlier experiment, FS-B features time-lapse geophysical imaging of long-term fluid flow and rupture processes. Five inclined holes were drilled parallel to the Main Fault dip at a distance of about 2-to-5m from the fault core &#8220;boundary&#8221;, with three boreholes drilled in the hanging wall and two boreholes drilled in the foot wall. An active seismic source-receiver array deployed in these five inclined boreholes allows tracking the variations of p- and s-wave velocities during fault leakage associated with rupture, post-rupture and eventually self-sealing behavior. The geophysical measurements are complemented by local three-dimensional displacements and pore pressures measurements distributed in three vertical boreholes drilled across the fault zone. DSS, DTS and DAS optical fibers cemented behind casing allow for the distributed strain monitoring in all the boreholes. Twelve acoustic emission sensors are cemented in two boreholes set across the fault zone and close to the injection borehole. Preliminary results from the new FS-B fault activation experiment will be discussed.

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Earthquake effects and insights on fault activity at the Beatrice Cenci cave (Abruzzo, Central Apennines)

Annals of Geophysics ◽

10.4401/ag-8571 ◽

2021 ◽

Vol 64 (4) ◽

pp. SE435

Author(s):

Laura Leonilde Alfonsi ◽

Francesca Romana Cinti

Keyword(s):

Central Italy ◽

Normal Fault ◽

Fault Activity ◽

Central Apennines ◽

Regional Tectonic ◽

Cave Environment ◽

History Of ◽

Tectonic Lineament ◽

Earthquake Effects ◽

Past Activity

he focus of this study is the analysis of a cave in Central Italy, the Beatrice Cenci cave, in order to point out and constrain evidence of possible past earthquakes and of fault activity in the area. We performed a survey of seismic related damages within the cave. This included the analysis of broken/collapsed speleothems, the recognition of structural collapse, of tilting/growth alteration in the speleothems, and the mapping of fractures, joints and/or faults. To timely set the occurrence of the recognized damage, organic sediments were dated with 14C radiocarbon method. The results merged toward the recognition of two distinct seismic shaking events affecting the cave environment, one older than 30 kyr and another around 7 kyr. The deformation observed within the cave led us to the hypothesis that the events of damage were possibly linked to the activity of the regional tectonic lineament that crosses the cave, i.e., the Liri normal fault. The morphology and the evolution of the cave appear controlled by the fault zone. These speleoseismological results provided a new contribution on the knowledge of the past activity of the Liri fault and on the earthquake history of this sector of Central Apennines.

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AlphaFold-Predicted Structures of KCTD Proteins Unravel Previously Undetected Relationships among the Members of the Family

Biomolecules ◽

10.3390/biom11121862 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1862

Author(s):

Luciana Esposito ◽

Nicole Balasco ◽

Giovanni Smaldone ◽

Rita Berisio ◽

Alessia Ruggiero ◽

...

Keyword(s):

Structural Information ◽

Three Dimensional ◽

Structural Data ◽

Protein Family ◽

General Sequence ◽

Btb Domain ◽

The Family ◽

Three Dimensional Models ◽

Definition Of ◽

Sequence Similarities

One of the most striking features of KCTD proteins is their involvement in apparently unrelated yet fundamental physio-pathological processes. Unfortunately, comprehensive structure–function relationships for this protein family have been hampered by the scarcity of the structural data available. This scenario is rapidly changing due to the release of the protein three-dimensional models predicted by AlphaFold (AF). Here, we exploited the structural information contained in the AF database to gain insights into the relationships among the members of the KCTD family with the aim of facilitating the definition of the structural and molecular basis of key roles that these proteins play in many biological processes. The most important finding that emerged from this investigation is the discovery that, in addition to the BTB domain, the vast majority of these proteins also share a structurally similar domain in the C-terminal region despite the absence of general sequence similarities detectable in this region. Using this domain as reference, we generated a novel and comprehensive structure-based pseudo-phylogenetic tree that unraveled previously undetected similarities among the protein family. In particular, we generated a new clustering of the KCTD proteins that will represent a solid ground for interpreting their many functions.

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Extension of the Kinematics-Based Method for Predicting the Motion of Proteins

Volume 5A: 38th Mechanisms and Robotics Conference ◽

10.1115/detc2014-34576 ◽

2014 ◽

Author(s):

Keisuke Arikawa

Keyword(s):

Computational Cost ◽

Three Dimensional ◽

Structural Data ◽

Data Bank ◽

Serial Manipulators ◽

Protein Model ◽

The Matrix ◽

Basic Equations ◽

Definition Of ◽

Structural Compliance

On the basis of an analogy between the kinematic structures of proteins and robotic mechanisms, we have so far developed methods for predicting the internal motion of proteins from three-dimensional structural data in the protein data bank (PDB). With these methods, we model proteins as serial manipulators constrained by springs, and calculate the structural compliance of the protein model. In this study, toward more practical purposes, we reformulate and extend the existing methods by broadening the definition of structural compliance and reducing the number of variables for expressing the conformation of the model. The broadening is performed by separating the parts whose deformations are evaluated from those where forces are applied. This separation allows the calculation of the effective forces causing deformation in other specified parts. We also reduce the number of conformation variables from the consideration based on the algebraic structure of the basic equations. The size of the matrix whose inverse must be calculated is thus minimized, and the computational cost is reduced. We verify the effectiveness of these extensions by analyzing the PDB data of some proteins.

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Using UAV and drilling to detect Quaternary activity of the Zhuozishan West Piedmont Fault, provides insight into the structural development of the Wuhai Basin and Northwestern Ordos Block, China

10.5194/egusphere-egu2020-12617 ◽

2020 ◽

Author(s):

Kuan Liang ◽

Baoqi Ma ◽

Qinjian Tian

Keyword(s):

Hanging Wall ◽

Slip Rate ◽

Normal Fault ◽

Fault System ◽

Structural Development ◽

Slip Rates ◽

Ordos Block ◽

Elevation Data ◽

Northwestern Margin ◽

Regional Tectonic

The Wuhai Basin is in the northwestern corner of the Ordos Block. Analyzing the geometry, and kinematic and dynamic characteristics of the boundary fault, the Zhuozishan West Piedmont Fault (ZWPF), will elucidate the regional tectonic environment and guide earthquake prevention and disaster reduction projects. Six presentative sites were selected for topographic measurements, from northern, middle and southern parts. Displacements of the ZWPF were calculated by measuring the top surface elevation of a widely distributed lacustrine layer in the footwall from outcrops at the sites (using UAV), and in the hanging wall from boreholes. The vertical slip rate of the ZWPF was then calculated based on the displacement and age of the lacustrine layer. Three to four normal fault-controlled terraces have developed on the footwall of the ZWPF, and the top surface of the lacustrine layer is at 1092&#8211;1132 m elevation. Data from boreholes showed that the top surface of the lacustrine layer is at an elevation of 1042&#8211;1063 m in the hanging wall. Vertical slip rates since 70 ka were estimated as 0.5&#177;0.2 to 1.0&#177;0.2 mm/a. The highest rate of vertical slip was observed at Fenghuang Ridge, in the central part of the fault system, and the vertical slip rate reduced to the south. In the northern Wuhai Basin, normal faulting still controls the piedmont landscape. However, NW-SE trending reverse faults and secondary folding have resulted from dextral strike-slip movement of the fault. The Wuhai Basin developed as a dextral-tensional negative flower structure. This study indicated that stress conditions of the northwestern margin of the Ordos Block include NE&#8211;SW compression and NW&#8211;SE extension, and an S-shaped rift zone has dominated the scale, structure, and evolution of the Yinchuan, Wuhai and Hetao Basins, and the active mode of faulting in these basins.

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Development of surface ruptures by hanging-wall extension over a thrust ramp along the Ragged Mountain fault, Katalla, Alaska, USA: Applications of high-resolution three-dimensional terrain models

Geosphere ◽

10.1130/ges02097.1 ◽

2021 ◽

Author(s):

Sarah N. Heinlein ◽

Terry L. Pavlis ◽

Ronald L. Bruhn

Keyword(s):

High Resolution ◽

Hanging Wall ◽

Three Dimensional ◽

Active Tectonics ◽

Normal Fault ◽

Fault Slip ◽

The South ◽

The North ◽

Terrain Models ◽

Surface Ruptures

High-resolution three-dimensional terrain models are used to evaluate the Ragged Mountain fault kinematics (Katalla, Alaska, USA). Previous studies have produced contradictory interpretations of the fault’s kinematics because surface ruptures along the fault are primarily steeply dipping, uphill-facing normal fault scarps. In this paper, we evaluate the hypothesis that these uphill-facing scarps represent extension above a buried thrust ramp. Detailed geomorphic mapping along the fault, using 20-cm-resolution aerial imagery draped onto a 1-m-resolution lidar (light detection and ranging) elevation model, was used to produce multiple topographic profiles. These profiles illustrate scarp geometries and prominent convex-upward topographic surfaces, indicating significant disturbance by active tectonics. A theoretical model is developed for fault-parallel flow over a thrust ramp that shows the geometric relationships between thrust displacement, upper-plate extension, and ramp dip. An important prediction of the model for this study is that the magnitude of upper-plate extension is comparable to, or greater than, the thrust displacement for ramps with dips greater than ~45°. This model is used to analyze profile shapes and surface displacements in Move software (Midland Valley Ltd.). Analyses of scarp heights allow estimates of hanging-wall extension, which we then use to estimate slip on the underlying thrust via the model. Assuming a low-angle (30°) uniformly dipping thrust and simple longitudinal extension via normal faulting, variations in extension along the fault would require a slip gradient from ~8 m in the north to ~22 m in the south. However, the same north-south variation in extension with a constant slip of 8–10 m may infer an increase in fault dip from ~30° in the north to ~60° in the south. This model prediction has broader implications for active-fault studies. Because the model quantifies relationships between hanging-wall extension, fault slip, and fault dip, it is possible to invert for fault slip in blind thrust ramps where hanging-wall extension is the primary surface manifestation. This study, together with results from the St. Elias Erosion and Tectonics Project (STEEP), clarifies the role of the Ragged Mountain fault as a contractional structure within a broadly sinistral shear system in the western syntaxis of the St. Elias orogeny.

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THE FIRST PALEOSEISMIC TRENCH DATA FROM ACIPAYAM FAULT, FETHİYE BURDUR FAULT ZONE, SW TURKEY

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11703 ◽

2017 ◽

Vol 50 (1) ◽

pp. 75 ◽

Cited By ~ 4

Author(s):

A. Kürçer ◽

E. Özdemir ◽

Ç. Uygun Güldoğan ◽

T.Y. Duman

Keyword(s):

Fault Zone ◽

Active Fault ◽

Three Dimensional ◽

Normal Fault ◽

Structural Data ◽

14C Dating ◽

Sw Turkey ◽

Active Tectonic ◽

Step Over ◽

Tectonic Features

The Acıpayam Fault is an active fault segment which is located on the central part of Fethiye Burdur Fault Zone in SW Turkey. According to the Active Fault Map of Turkey published by MTA (Turkey), it is described as a Quaternary fault. Acıpayam Fault extends from Acıpayam at northeast to Akköprü Dam at southwest. The general strike of fault is N 35°E, approximately 60 km long and it’s a normal fault with minor sinistral strike-slip component. The fault is composed of three fault section, which are named as Örenköy, Olukbaşı and Yolçatı, seperated from each other by step-over zones. In this study, active tectonic features of Acıpayam fault are investigated and paleoismological trench surveys are perfomed at the Örenköy fault section. Two cross trenches were excavated along the fault. The samples collected from the trenches were dated using the 14C dating method. Örenköy trenches were photographed using the Paleoseismological Three Dimensional Virtual Photography Method, which is a new tecnique for paleoseismology. According to the trench microstratigraphy, structural data and dating results, Acıpayam fault is described as a Holocene fault. The date of last event that occurred on the Acıpayam fault is between 3030 ± 30 BP and 2410 ± 30 BP.

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