Morphological dating of cumulative reverse fault scarps: examples from the Gurvan Bogd fault system, Mongolia

Abstract. The crustal-scale west-vergent San Ramón thrust fault system, which lies at the foot of the main Andean Cordillera in central Chile, is a geologically active structure with manifestations of late Quaternary complex surface rupture on fault segments along the eastern border of the city of Santiago. From the comparison of geophysical and geological observations, we assessed the subsurface structural pattern that affects the sedimentary cover and rock-substratum topography across fault scarps, which is critical for evaluating structural models and associated seismic hazard along the related faults. We performed seismic profiles with an average length of 250 m, using an array of 24 geophones (Geode), with 25 shots per profile, to produce high-resolution seismic tomography to aid in interpreting impedance changes associated with the deformed sedimentary cover. The recorded travel-time refractions and reflections were jointly inverted by using a 2-D tomographic approach, which resulted in variations across the scarp axis in both the velocities and the reflections that are interpreted as the sedimentary cover-rock substratum topography. Seismic anisotropy observed from tomographic profiles is consistent with sediment deformation triggered by west-vergent thrust tectonics along the fault. Electrical soundings crossing two fault scarps were used to construct subsurface resistivity tomographic profiles, which reveal systematic differences between lower resistivity values in the hanging wall with respect to the footwall of the geological structure, and clearly show well-defined east-dipping resistivity boundaries. These boundaries can be interpreted in terms of structurally driven fluid content change between the hanging wall and the footwall of the San Ramón fault. The overall results are consistent with a west-vergent thrust structure dipping ~55° E in the subsurface beneath the piedmont sediments, with local complexities likely associated with variations in fault surface rupture propagation, fault splays and fault segment transfer zones.

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Geomorphic evidence for active, co-seismic slip along a low-angle normal fault: Panamint Valley, California

10.5194/egusphere-egu2020-11523 ◽

2020 ◽

Author(s):

Eric Kirby ◽

Israporn (Grace) Sethanant ◽

John Gosse ◽

Eric McDonald ◽

J Doug Walker

Keyword(s):

Seismic Hazard ◽

Normal Fault ◽

Basin And Range ◽

Detachment Fault ◽

Airborne Lidar ◽

Fault System ◽

Seismic Slip ◽

The Past ◽

Detachment Faults ◽

Fault Scarps

The mechanical feasibility of co-seismic displacement along low-angle normal fault systems remains an outstanding problem in tectonics.&#160; In the southwestern Basin and Range of North America, large magnitude extension during Miocene &#8211; Pliocene time was accommodated along a regionally extensive system of low-angle detachment faults.&#160; Whether these faults remain active today and, if so, whether they rupture during large earthquakes are questions central to understanding the geodynamics of distributed lithospheric deformation and associated seismic hazard.&#160; Here we evaluate the geometric and kinematic relationships of fault scarps developed in Pleistocene &#8211; Holocene alluvial and lacustrine deposits with low-angle detachment faults observed along the western flank of the Panamint Range, in eastern California.&#160; We combine analysis of high-resolution topography generated from airborne LiDAR and photogrammetry with a detailed chronology of alluvial fan surfaces and a calibrated soil chronosequence to characterize the recent activity of the fault system.&#160; The range-front fault system is coincident with a low-angle (15-20&#176;), curviplanar detachment fault that is linked to strike-slip faults at its southern and northern ends. &#160;Fanglomerate deposits in the hanging wall of the detachment are juxtaposed with brecciated bedrock in the footwall across a narrow fault surface marked by clay-rich gouge.&#160; Isochron burial dating of the fanglomerate using the 26Al and 10Be requires displacement in the past ~800 ka.&#160; The degree of soil development in younger alluvial deposits in direct fault contact with the footwall block suggest displacement along the main detachment in the past as ~80-100 ka.&#160; The geometry of recent fault scarps in Holocene alluvium mimic range-scale variations in strike of the curviplanar detachment fault, suggesting that scarps merge with the detachment at depth.&#160; Moreover, fault kinematics inferred from displaced debris-flow levees and from fault striae on the bedrock range front are consistent with slip on a low-angle detachment system beneath the valley.&#160; Finally, paleoseismic results from a trench at the southern end of the fault system suggest 3-4 surface ruptures during past ~4-5 ka, the most recent of which (MRE) occurred ~330-485 cal yr BP.&#160; Scarps related to the MRE can be traced for at least ~50 km northward along the range front and imply surface displacements of 2-4 meters during this event.&#160; Thus, we conclude that ongoing dextral shear along the margin of the Basin and Range is, in part, accommodated by co-seismic slip along low-angle detachment faults in Panamint Valley.&#160; Our results have important implications for the interaction of fault networks and seismic hazard in the region.

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Rock bursts and associated neotectonic forms at Minnipa Hill, northwestern Eyre Peninsula, South Australia

Environmental and Engineering Geoscience ◽

10.2113/gseegeosci.6.2.129 ◽

2000 ◽

Vol 6 (2) ◽

pp. 129-140 ◽

Cited By ~ 27

Author(s):

C. R. Twidale ◽

J. A. Bourne

Keyword(s):

Compressive Stress ◽

South Australia ◽

Reverse Fault ◽

Rock Bursts ◽

Fault Scarps

Abstract Disturbance of the surface of Minnipa Hill Southeast, a low granite dome located on the northwestern Eyre Peninsula, on 19 January 1999, coincided with a shallow earth tremor, and it is suggested that the two events are causally related. The disturbance, which affected an area 170X100 m, took the form of rock bursts, reverse fault scarps, low angle planes of dislocation and overriding sheets, A-tents, dislocated slabs and blocks and widespread surficial flaking. Evidence of two earlier disturbances was noted. The event directly confirms the association of A-tents and dislocated slabs with compressive stress and by implication links bornhardts and sheet fractures with similar strain environments.

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Mineralization and Structural Controls of the AB-Bid Carbonate-Hosted Pb-Zn (±Cu) Deposit, Tabas-Posht e Badam Metallogenic Belt, Iran

Minerals ◽

10.3390/min12010095 ◽

2022 ◽

Vol 12 (1) ◽

pp. 95

Author(s):

Abdorrahman Rajabi ◽

Carles Canet ◽

Pura Alfonso ◽

Pouria Mahmoodi ◽

Ali Yarmohammadi ◽

...

Keyword(s):

Middle Jurassic ◽

Structural Data ◽

Wall Rock ◽

Fault System ◽

Current Evidence ◽

Mining District ◽

Sulfur Source ◽

Reverse Fault ◽

Sulfide Mineralization ◽

Metallogenic Belt

The Ab-Bid deposit, located in the Tabas-Posht e Badam metallogenic belt (TPMB) in Central Iran, is the largest Pb-Zn (±Cu) deposit in the Behadad-Kuhbanan mining district. Sulfide mineralization in the Ab-Bid deposit formed in Middle Triassic carbonate rocks and contains galena and sphalerite with minor pyrite, chalcopyrite, chalcocite, and barite. Silicification and dolomitization are the main wall-rock alteration styles. Structural and textural observations indicate that the mineralization occurs as fault fills with coarse-textured, brecciated, and replacement sulfides deposited in a bookshelf structure. The Ab-Bid ore minerals precipitated from high temperature (≈180–200 °C) basinal brines within the dolomitized and silicified carbonates. The sulfur isotope values of ore sulfides suggest a predominant thermochemical sulfate reduction (TSR) process, and the sulfur source was probably Triassic-Jurassic seawater sulfate. Given the current evidence, mineralization at Ab-Bid resulted from focusing of heated, over-pressurized brines of modified basinal origin into an active fault system. The association of the sulfide mineralization with intensely altered wall rock represents a typical example of such features in the Mississippi Valley-type (MVT) metallogenic domain of the TPMB. According to the structural data, the critical ore control is a bookshelf structure having mineralized dextral strike-slip faults in the northern part of the Ab-Bid reverse fault, which seems to be part of a sinistral brittle shear zone. Structural relationships also indicate that the strata-bound, fault-controlled Ab-Bid deposit was formed after the Middle Jurassic, and its formation may be related to compressive and deformation stages of the Mid-Cimmerian in the Middle Jurassic to Laramide orogenic cycle in the Late Cretaceous-Tertiary.

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Fault and vein relationships in a reverse fault system at the Centenary orebody (Darlot gold deposit), Western Australia: Implications for gold mineralisation

Journal of Structural Geology ◽

10.1016/j.jsg.2006.11.004 ◽

2007 ◽

Vol 29 (4) ◽

pp. 712-735 ◽

Cited By ~ 1

Author(s):

Shane Kenworthy ◽

Steffen G. Hagemann

Keyword(s):

Gold Deposit ◽

Western Australia ◽

Fault System ◽

Reverse Fault

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Comparison of morphological dating models for cumulative reverse fault scarps

Journal of Geophysical Research Atmospheres ◽

10.1029/2000jb000028 ◽

2002 ◽

Vol 107 (B10) ◽

pp. ETG 4-1-ETG 4-16 ◽

Cited By ~ 5

Author(s):

S. Carretier ◽

F. Lucazeau ◽

J.-F. Ritz ◽

H. Philip

Keyword(s):

Reverse Fault ◽

Fault Scarps

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Recent Activity and Kinematics of the Bounding Faults of the Catanzaro Trough (Central Calabria, Italy): New Morphotectonic, Geodetic and Seismological Data

Geosciences ◽

10.3390/geosciences11100405 ◽

2021 ◽

Vol 11 (10) ◽

pp. 405

Author(s):

Claudia Pirrotta ◽

Graziella Barberi ◽

Giovanni Barreca ◽

Fabio Brighenti ◽

Francesco Carnemolla ◽

...

Keyword(s):

Scaling Laws ◽

Normal Fault ◽

Historical Earthquakes ◽

Fault System ◽

Normal Faults ◽

The North ◽

Seismological Data ◽

Geomorphic Features ◽

Half Graben ◽

Fault Scarps

A multidisciplinary work integrating structural, geodetic and seismological data was performed in the Catanzaro Trough (central Calabria, Italy) to define the seismotectonic setting of this area. The Catanzaro Trough is a structural depression transversal to the Calabrian Arc, lying in-between two longitudinal grabens: the Crati Basin to the north and the Mesima Basin to the south. The investigated area experienced some of the strongest historical earthquakes of Italy, whose seismogenic sources are still not well defined. We investigated and mapped the major WSW–ENE to WNW–ESE trending normal-oblique Lamezia-Catanzaro Fault System, bounding to the north the Catanzaro Trough. Morphotectonic data reveal that some fault segments have recently been reactivated since they have displaced upper Pleistocene deposits showing typical geomorphic features associated with active normal fault scarps such as triangular and trapezoidal facets, and displaced alluvial fans. The analysis of instrumental seismicity indicates that some clusters of earthquakes have nucleated on the Lamezia-Catanzaro Fault System. In addition, focal mechanisms indicate the prevalence of left-lateral kinematics on E–W roughly oriented fault plains. GPS data confirm that slow left-lateral motion occurs along this fault system. Minor north-dipping normal faults were also mapped in the southern side of the Catanzaro Trough. They show eroded fault scarps along which weak seismic activity and negligible geodetic motion occur. Our study highlights that the Catanzaro Trough is a poliphased Plio-Quaternary extensional basin developed early as a half-graben in the frame of the tear-faulting occurring at the northern edge of the subducting Ionian slab. In this context, the strike-slip motion contributes to the longitudinal segmentation of the Calabrian Arc. In addition, the high number of seismic events evidenced by the instrumental seismicity, the macroseismic intensity distribution of the historical earthquakes and the scaling laws relating to earthquakes and seismogenic faults support the hypothesis that the Lamezia-Catanzaro Fault System may have been responsible for the historical earthquakes since it is capable of triggering earthquakes with magnitude up to 6.9.

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RECENT SEISMIC STUDIES UPGRADE THE PETROLEUM PROSPECTS OF THE TOKO SYNCLINE, GEORGINA BASIN

The APPEA Journal ◽

10.1071/aj78005 ◽

1979 ◽

Vol 19 (1) ◽

pp. 30

Author(s):

P.L. Harrison

Keyword(s):

Mineral Resources ◽

Seismic Survey ◽

Fault System ◽

Reverse Fault ◽

Middle Cambrian ◽

Middle Ordovician ◽

Upper Cambrian ◽

Marine Carbonate ◽

Potential Reservoir ◽

Northeastern Flank

The Georgina Basin covers an area of 325,000 sq km in the Northern Territory and Queensland. Most of the basin contains less than 500m of Palaeozoic sediments, but the Toko Syncline, in Queensland, contains up to 5000m of Middle Cambrian to Middle Ordovician shallow marine carbonate, sandstone and shale. The syncline is bounded on its western margin by the Toomba-Craigie Fault systemHydrocarbon shows are known within the Middle Cambrian to Middle Ordovician strata and some of the rocks have fair source rock potential. Potential reservoir rocks are vuggy dolostones and sandstone. Ordovician siltstones and shales may provide cap-rocks. The southern, deepest part of the syncline appears to have been protected from flushing. AOD Ethabuka-I well, drilled in the southern part, encountered gas in the Ordovician, but drilling problems prevented penetration of the deeper section.A Bureau of Mineral Resources (BMR) seismic survey in 1977, linked lines shot on earlier surveys, tied to wells and examined the Toomba Fault system. The results show that two previously unidentified reflectors represent the top of Upper Cambrian Georgina Limestone and the base of the Middle Cambrian section. Substantial thickening of Ordovician and slight thinning of Middle and Upper Cambrian strata occurs southeast along the axis of the syncline. Southeast progradation of some Middle Cambrian strata and possible bioherms were observed. The Toomba Fault is a high-angle reverse fault and several possible anticlines are present in the adjacent folded and faulted zone. The two largest ones, the Ethabuka and Mirrica Structures, were partially outlined by Alliance Oil Development (AOD). They are shown to lie within a larger structure which has a minimum vertical closure of 700m over a minimum area of 130 sq km. Possible stratigraphic traps are located on the northeastern flank and along the axis of the syncline.The seismic work has better defined the prospective section and confirmed closure on a large structure. The next step in exploration should be to drill the Mirrica-Ethabuka Structure, where about 1500m of section remains to be tested.

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Analysing landforms, borehole logs, and geophysics, for localization and assessment of active faults in the central Vienna Basin (Austria)

10.5194/egusphere-egu2020-18834 ◽

2020 ◽

Author(s):

Michael Weissl ◽

Decker Kurt ◽

Adrian Flores-Orozco ◽

Matthias Steiner

Keyword(s):

Active Faults ◽

Fault System ◽

Tectonic Activity ◽

Fluvial Sediments ◽

River Channels ◽

Vienna Basin ◽

Geothermal Resources ◽

Near Surface ◽

Growth Strata ◽

Fault Scarps

The formation of pull apart basins and normal faulting at splays along the Vienna Basin strike-slip fault system resulted in the dissection of the Pleistocene river terraces of the Danube. Displacements of terrace segments are visible on the surface as fault scarps or dells what allows mapping the system of active faults. Furthermore displacement rates can be estimated from the elevation of the basis and the thickness of Quaternary fluvial sediments.With regard to the prospective utilization of geothermal resources in the area of Vienna a research group was built (Geotief Explore 3D, funded by Wien Energie and FFG) with the objective to identify, map, and assess, Quaternary faults, because such rupture zones are not suitable for the reinjection of thermal water in view of the hazard of triggered earthquakes.Normal splay faults define the eastern and western margins of Pleistocene Danube terraces north of Vienna. The bodies of these terraces are built up of coarse sandy gravel and sand whereas their surfaces are covered with aeolian and alluvial sediments of the last glacial. Tectonic displacements during the Pleistocene left distinct marks in the late glacial landform configuration of the terraces. Therefore many fault scarps and fault related valleys are clearly cognizable in high resolution LiDAR and satellite images.During the last decade three distinct fault scarps of the Vienna Basin Transform Fault situated at the terrace edges could be investigated by trenching and transect analysis. Actual research has the objective to model the 3D geometry of the base of the Quaternary strata (horizon Base Quaternary) from a compilation of shallow drillings and the construction of a regional isopach map showing the thickness of Quaternary (growth-) strata.In the course of research it becomes apparent that within the tectonically subsided areas evidence of neotectonics is overprinted by fluvial sediments and alluvium what hinders accurate localization of faults. However, the sinuosity of palaeochannels in the Danube floodplain seems to be related to tectonics and therefore the pattern of former river channels can be used as sign for tectonic activity during the Pleistocene. In places where signs for active faulting are completely overprinted by fluvial sedimentation and cryoturbation the approved methods for the localization and the assessment of active faults are electrical resistivity tomography and near-surface seismics.

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