DOCSLIB.ORG

Low-Angle Normal Faults and Seismicity: a Review

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Low-Angle Normal Faults and Seismicity: a Review JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 100, NO. B10, PAGES 20,159-20,174, OCTOBER 10, 1995 Low-angle normal faults and seismicity: A review Brian Wernicke Division of Geological and Planetary Sciences,California Institute of Technology,Pasadena Abstract. Although large, low-anglenormal faults in the continentalcrust are widely recognized,doubts persist that they either initiate or slip at shallowdips (<30ø), because (1) globalcompilations of normal fault focal mechanismsshow only a small fraction of eventswith either nodal plane dippingless than 30ø and (2) Andersonianfault mechanics predict that normal faults dippingless than 30ø cannot slip. Geologicalreconstructions, thermochronology,paleomagnetic studies, and seismicreflection profiles, mainly published in the last 5 years,reinforce the view that active low-anglenormal faulting in the brittle crust is widespread,underscoring the paradox of the seismicitydata. For dip-slip faults large enoughto break the entire brittle layer during earthquakes(Mw "• 6.5), considerationof their surfacearea and efficiencyin accommodatingextension as a function of dip 0 suggestsaverage recurrrence intervals of earthquakesR' •c tan 0, assumingstress drop, rigidity modulus,and thicknessof the seismogeniclayer do not vary systematicallywith dip. If the global distributionof fault dip, normalized to total fault length, is uniform, the global recurrenceof earthquakesas a function of dip is shownto be R cr tan 0 sin 0. This relationshippred•icts that the frequencyof earthquakeswith nodalplanes dipping between 30 ø and 60ø•' will exceedthose with planesshallower than 30 ø by a factor of 10, in good agreementwith continentalseismicity, assuming major normal faults dipping more than 60ø are relatively uncommon.Revision of Andersonianfault mechanicsto include rotation of the stressaxes with depth, perhapsas a result of deep crustalshear againstthe brittle layer, would explain both the commonoccurrence of low- angle faults and the lack of large faults dippingmore than 60ø . If correct,this resolution of the paradoxmay indicate significantseismic hazard from large, low-anglenormal faults. Introduction ceeding three decades. Low-angle extensional structures, thoughdocumented by geologicalmapping studies, were inter- It is appropriate for the 75th anniversaryof the American preted as either peculiar thrust faults or surficial landsliding GeophysicalUnion that recognitionbe given to the 50th an- phenomena.Sliding and spreadingof rootless,internally co- niversaryof a paper by Longwell[1945]. Although not the first herent, extended allochthonsalong faults dipping only a few descriptionof suchphenomena [e.g., Ransome et al., 1910],the degrees is well known. It includes caseswhere detachment paper was remarkable in its documentationusing maps, pho- occursalong incompetenthorizons in sedimentssuch as shale tographs,and crosssections of spectacularlyexposed normal or salt, as developed over thousandsof square kilometers in faults in the Las Vegas region,with displacementsof 1-2 km the northern Gulf of Mexico [Worralland Snelson,1989]. How- and dips of 0-30 ø. In one large-scaleexposure, since partly ever, it also includesexamples where the slidingoccurs within drowned beneath the waters of Lake Mead, a fault was ob- competenthorizons, as in the Ordoviciandolostones along the served to flatten downward, from about 30 ø to 5 ø over a cross- Heart Mountain detachment [Pierce, 1957; Hauge, 1990]. sectionaldepth of 600 m. These examplesgenerally involve only the upper few kilome- It is perhaps a measure of a theoreticallybased prejudice ters of the crust and are not accompaniedby coevalextension againstlow-angle normal faults that Longwell[1945] excluded of the underlyingcontinental basement. In contrast,fault sys- regional crustal extensionas a causefor faulting. He instead tems in the Basin and Range, such as those describedby interpreted them to result from extension on the crests of Longwell[1945], clearly involvecontinental basement and are large-scalecompressional anticlines. Mechanical arguments observedin some casesto cut structurallydownward through for downwardflattening (listric) normal faults date back at 10 km or more of the crust. least to McGee [1883], but Hafner [1951], citing Longwell's Beginningwith a handful of Basin and Range field studies [1945] observations,showed that certain loading conditions [e.g.,Anderson,1971; Wrightand Troxel,1973; Proffett, 1977], it along the base of an elastic plate induce curvature of stress was not until the late 1970s that ,the numerous documented trajectoriesfavorable for the formation of low-angle normal low-anglenormal faults gained a measureof acceptanceas a faults. direct expressionof large-magnitudecontinental extension. At Despite both observationand theory, the assumptionthat about the same time, it was also realized that many metamor- the least principal stressdirection is horizontal throughoutan phic tectonitesin the Basin and Range previouslythought to extendingcrust [e.g.,Anderson, 1942] held sway for the suc- be Mesozoicor Precambrianin agewere actuallyTertiary [e.g., Davis and Coney, 1979]. In many casesthese rocks lay in the Copyright 1995 by the American GeophysicalUnion. footwalls of regionally extensivelow-angle normal faults or Paper number 95JB01911. "detachments" that could be traced for several tens of kilome- 0148-0227/95/95JB-01911 $05.00 ters parallel to their transportdirections. By 1980, it was clear 20,159 20,160 WERNICKE: LOW-ANGLE NORMAL FAULTS AND SEISMICITY (a) (b) mities have since been documented to be low-angle normal faults(Davis et al. [1980],Gans et al. [1989],and Dokka [1986], B respectively).Similarly, major low-ange fault systemsinterpreted asthrusts by Noble [1941], Misch [1960], and Drewes and Thorman [1978]are now widelyregarded as normalfaults related to Ce- nozoicextension (Wright and Troxel[1984], Miller et al. [1983],and Dickinson[1991], respectively).Reinterpretations currently un- derwayin other mountainbelts are similarlyprofound. These Basinand Rangefield relationsrepresented a classof HISTORIES: geologiccontact that had not been previouslyrecognized as a fundamentaltectonic element. Recognizing them as suchis as Depositionof A Depositionof A basic to accuratehistorical inference in geologyas, for exam- Tilting & erosion Depositionof B Depositionof B Faultingof B on A ple, the knowledge that rocks with igneous texture intrude Erosion Erosion their surroundingsin a molten state. Figure 1. Contrast in geologicalhistory from interpreting a Mechanical Significance contact between older sedimentarysequence A and younger The fact that low-anglenormal faults are not predictedby sequenceB as (a) an unconformityand (b) a low-anglenormal fault. Andersonian theory is also fundamental to interpreting the stressstate and physicalconstitution of the crust.In the 1980s, debate centered on the kinematics of generating the core- complexassociation. Most current modelssuggest asymmetri- that numerous isolated exposuresof detachmentsand their cal denudationalong large normal faults that transectthe up- metamorphicsubstrate formed a nearly continuousbelt from per 15-20 km of the crust at low angle, accompaniedby Sonora, Mexico, to southern British Columbia, referred to as isostaticrebound and flexure of the unloadedfootwall [e.g., the Cordilleranmetamorphic core complexes[Crittenden et al., Wernicke,1981; Howard et al., 1982;Allmendinger et al., 1983; 1980; Armstrong,1982]. It was realized that the footwalls of Spencer,1984; Wernicke,1985; Davis et al., 1986; Wernicke, many exposeddetachments were not stronglymetamorphosed 1992].Recently, controversy has centered on the initial dip and in the Tertiary, raising the possibilitythat low-angle normal subsequentmodification of thesefaults and the roles of foot- faults formed and were active entirely in shallowcrust [e.g., wall metamorphictectonite and magmatism. Wernickeet al., 1985;Spencer, 1985; Dokka, 1986;John, 1987]. This paper addressesthe question: Are brittle low-angle These observations ran counter to Jackson and White's normal faults active while at low dip? A number of authors [1989] descriptivesynthesis of some 56 earthquakeson active have expresseddoubt that shallowlydipping normal faults are continentalnormal faults. They concludedthat (italicstheirs) importantfeatures in the extendingseismogenic crust, pointing to Andersoniantheory and a lack of seismicityon suchfaults Among the most important observationsthat now influencethe debateare... that large earthquakesdo not occuron listtic faults [e.g., Buck, 1988;King and Ellis, 1990]. A large body of liter- that flatten at shallowdepths (as originallythought: e.g. McKen- ature has nonethelessfocused on non-Andersonianexplana- zie, 1978a,b), but on faults that are steepthroughout the seismo- tions for active low-angle normal faulting [e.g., Xiao et al., genic upper crust... 1991;Forsyth, 1992;Axen, 1992; Parsons and Thompson,1993]. If low-anglenormal faults are indeed activein the seismogenic Whether or not this conclusionis correctis a first-orderproblem crust, why are there so few, if any earthquakesobserved on in understandingthe structureand dynamicsof the lithosphere. them? Evidence summarizedbelow, mostly publishedin the Geological Significance last 5 years,tends to reinforcethis paradox.A simplemechan- ical model relating fault dip to earthquake recurrenceis de- The recognition of low-angle normal faults and the core veloped that may provide an explanation. complex tectonic associationis now global and includesoce-
Load more

Recommended publications
  • GEO 2008 Conference Abstracts, Bahrain GEO 2008 Conference Abstracts
    GEO 2008 conference abstracts, Bahrain GEO 2008 Conference Abstracts he abstracts of the GEO 2008 Conference presentations (3-5 March 2008, Bahrain) are published in Talphabetical order based on the last name of the first author. Only those abstracts that were accepted by the GEO 2008 Program Committee are published here, and were subsequently edited by GeoArabia Editors and proof-read by the corresponding author. Several names of companies and institutions to which presenters are affiliated have been abbreviated (see page 262). For convenience, all subsidiary companies are listed as the parent company. (#117804) Sandstone-body geometry, facies existing data sets and improve exploration decision architecture and depositional model of making. The results of a recent 3-D seismic reprocessing Ordovician Barik Sandstone, Oman effort over approximately 1,800 square km of data from the Mediterranean Sea has brought renewed interest in Iftikhar A. Abbasi (Sultan Qaboos University, Oman) deep, pre-Messinian structures. Historically, the reservoir and Abdulrahman Al-Harthy (Sultan Qaboos targets in the southern Mediterranean Sea have been the University, Oman <[email protected]>) Pliocene-Pleistocene and Messinian/Pre-Messinian gas sands. These are readily identifiable as anomalousbright The Lower Paleozoic siliciclastics sediments of the amplitudes on the seismic data. The key to enhancing the Haima Supergroup in the Al-Haushi-Huqf area of cen- deeper structure is multiple and noise attenuation. The tral Oman are subdivided into a number of formations Miocene and older targets are overlain by a Messinian- and members based on lithological characteristics of aged, structurally complex anhydrite layer, the Rosetta various rock sequences.
    [Show full text]
  • Part 3: Normal Faults and Extensional Tectonics
    12.113 Structural Geology Part 3: Normal faults and extensional tectonics Fall 2005 Contents 1 Reading assignment 1 2 Growth strata 1 3 Models of extensional faults 2 3.1 Listric faults . 2 3.2 Planar, rotating fault arrays . 2 3.3 Stratigraphic signature of normal faults and extension . 2 3.4 Core complexes . 6 4 Slides 7 1 Reading assignment Read Chapter 5. 2 Growth strata Although not particular to normal faults, relative uplift and subsidence on either side of a surface breaking fault leads to predictable patterns of erosion and sedi­ mentation. Sediments will fill the available space created by slip on a fault. Not only do the characteristic patterns of stratal thickening or thinning tell you about the 1 Figure 1: Model for a simple, planar fault style of faulting, but by dating the sediments, you can tell the age of the fault (since sediments were deposited during faulting) as well as the slip rates on the fault. 3 Models of extensional faults The simplest model of a normal fault is a planar fault that does not change its dip with depth. Such a fault does not accommodate much extension. (Figure 1) 3.1 Listric faults A listric fault is a fault which shallows with depth. Compared to a simple planar model, such a fault accommodates a considerably greater amount of extension for the same amount of slip. Characteristics of listric faults are that, in order to maintain geometric compatibility, beds in the hanging wall have to rotate and dip towards the fault. Commonly, listric faults involve a number of en echelon faults that sole into a low­angle master detachment.
    [Show full text]
  • The Origin and Evolution of the Southern Snake Range Decollement, East Central Nevada Allen J
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by University of Dayton University of Dayton eCommons Geology Faculty Publications Department of Geology 2-1993 The Origin and Evolution of the Southern Snake Range Decollement, East Central Nevada Allen J. McGrew University of Dayton, [email protected] Follow this and additional works at: https://ecommons.udayton.edu/geo_fac_pub Part of the Geology Commons, Geomorphology Commons, Geophysics and Seismology Commons, Glaciology Commons, Hydrology Commons, Other Environmental Sciences Commons, Paleontology Commons, Sedimentology Commons, Soil Science Commons, Stratigraphy Commons, and the Tectonics and Structure Commons eCommons Citation McGrew, Allen J., "The Origin and Evolution of the Southern Snake Range Decollement, East Central Nevada" (1993). Geology Faculty Publications. 29. https://ecommons.udayton.edu/geo_fac_pub/29 This Article is brought to you for free and open access by the Department of Geology at eCommons. It has been accepted for inclusion in Geology Faculty Publications by an authorized administrator of eCommons. For more information, please contact [email protected], [email protected]. TECTONICS, VOL. 12, NO. 1, PAGES 21-34, FEBRUARY 1993 THE ORIGIN AND EVOLUTION OF INTRODUCTION THE SOUTHERN SNAKE RANGE The origin,kinematic significance and geometrical evolu- DECOLLEMENT, EAST CENTRAL tion of shallowlyinclined normal fault systemsare NEVADA fundamentalissues in extensionaltectonics. Regionally extensivefaults that juxtapose nonmetamorphic sedimentary Allen J. McGrew1 rocksin theirhanging walls againstplastically deformed Departmentof Geology,Stanford University, Stanford, crystallinerocks in their footwallscommand special California attentionbecause they offer rare opportunitiesto characterize kinematiclinkages between contrasting structural levels. Thesefaults, commonly known as detachmentfaults, are the Abstract.Regional and local stratigraphic, metamorphic, subjectsof muchcontroversy.
    [Show full text]
  • Crossing the Several Scales of Strain-Accomplishing Mechanisms in the Hinterland of the Central Andean Fold±Thrust Belt, Bolivia
    Journal of Structural Geology 24 02002) 1587±1602 www.elsevier.com/locate/jstrugeo Crossing the several scales of strain-accomplishing mechanisms in the hinterland of the central Andean fold±thrust belt, Bolivia Nadine McQuarriea,b,*, George H.Davis a aDepartment of Geosciences, University of Arizona, Tucson, AZ 85721, USA bDivision of Geological andPlanetary Science, California Institute of Technology, Pasadena, CA 91125, USA Received 14 November 2000; revised 28 October 2001; accepted 29 October 2001 Abstract Depictions of structures at outcrop, regional and tectonic scales enforce horizontal shortening and vertical thickening as the predominant style of deformation at all scales within the hinterland of the central Andean fold±thrust belt.Outcrop-scale structures document a progression of strain that created: 01) ¯exural-slip folds, 02) fold ¯attening via axial-planar cleavage, 03) vertical stretching via boudinage and late-stage faulting and, ®nally, 04) kink folding.These examples of intraformational deformation are generally concentrated just beyond the tip lines of thrust faults, where fault-propagation folds and related structures are well developed.Fault-propagation folding accommo- dated the accrual of strain indicated by outcrop-scale structures while the structures themselves indicate how deformation developed within each individual fold.Fault-propagation fold geometries at a regional scale emerge from the construction of regional balanced cross-sections. The sections were drawn with careful attention to: 01) known map relationships,
    [Show full text]
  • Systematic Variation of Late Pleistocene Fault Scarp Height in the Teton Range, Wyoming, USA: Variable Fault Slip Rates Or Variable GEOSPHERE; V
    Research Paper THEMED ISSUE: Cenozoic Tectonics, Magmatism, and Stratigraphy of the Snake River Plain–Yellowstone Region and Adjacent Areas GEOSPHERE Systematic variation of Late Pleistocene fault scarp height in the Teton Range, Wyoming, USA: Variable fault slip rates or variable GEOSPHERE; v. 13, no. 2 landform ages? doi:10.1130/GES01320.1 Glenn D. Thackray and Amie E. Staley* 8 figures; 1 supplemental file Department of Geosciences, Idaho State University, 921 South 8th Avenue, Pocatello, Idaho 83209, USA CORRESPONDENCE: thacglen@ isu .edu ABSTRACT ously and repeatedly to climate shifts in multiple valleys, they create multi­ CITATION: Thackray, G.D., and Staley, A.E., 2017, ple isochronous markers for evaluation of spatial and temporal variation of Systematic variation of Late Pleistocene fault scarp height in the Teton Range, Wyoming, USA: Variable Fault scarps of strongly varying height cut glacial and alluvial sequences fault motion (Gillespie and Molnar, 1995; McCalpin, 1996; Howle et al., 2012; fault slip rates or variable landform ages?: Geosphere, mantling the faulted front of the Teton Range (western USA). Scarp heights Thackray et al., 2013). v. 13, no. 2, p. 287–300, doi:10.1130/GES01320.1. vary from 11.2 to 37.6 m and are systematically higher on geomorphically older In some cases, faults of known slip rate can also be used to evaluate ages landforms. Fault scarps cutting a deglacial surface, known from cosmogenic of glacial and alluvial sequences. However, this process is hampered by spatial Received 26 January 2016 Revision received 22 November 2016 radionuclide exposure dating to immediately postdate 14.7 ± 1.1 ka, average and temporal variability of offset along individual faults and fault segments Accepted 13 January 2017 12.0 m in height, and yield an average postglacial offset rate of 0.82 ± 0.13 (e.g., Z.
    [Show full text]
  • Geology of the Earthquake Source: an Introduction
    Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021 Geology of the earthquake source: an introduction A˚ KE FAGERENG1* & VIRGINIA G. TOY2 1Department of Geological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa 2Department of Geology, University of Otago, PO Box 56, Dunedin 9054, New Zealand *Corresponding author (e-mail: [email protected]) Abstract: Earthquakes arise from frictional ‘stick–slip’ instabilities as elastic strain is released by shear failure, almost always on a pre-existing fault. How the faulted rock responds to applied shear stress depends on its composition, environmental conditions (such as temperature and pressure), fluid presence and strain rate. These geological and physical variables determine the shear strength and frictional stability of a fault, and the dominant mineral deformation mechanism. To differing degrees, these effects ultimately control the partitioning between seismic and aseismic defor- mation, and are recorded by fault-rock textures. The scale-invariance of earthquake slip allows for extrapolation of geological and geophysical observations of earthquake-related deformation. Here we emphasize that the seismological character of a fault is highly dependent on fault geology, and that the high frequency of earthquakes observed by geophysical monitoring demands consider- ation of seismic slip as a major mechanism of finite fault displacement in the geological record. Rick Sibson has, throughout his career, pointed out the geological and physical parameters likely to that earthquakes occur in rocks (e.g. Sibson 1975, control their prevalence discussed. The mechanisms 1977, 1984, 1986, 1989, 2002, 2003). This simple by which rocks were deformed can be inferred from fact implies that fault rocks exert a critical control their textures (Knipe 1989); these relationships for on earthquake nucleation and propagation, and the typical fault rocks encountered in exhumed should contain an integrated record of earthquakes.
    [Show full text]
  • Deformation Pattern During Normal Faulting: a Sequential Limit Analysis
    Originally published as: Yuan, X., Maillot, B., Leroy, Y. M. (2017): Deformation pattern during normal faulting: A sequential limit analysis. ‐ Journal of Geophysical Research, 122, 2, pp. 1496—1516. DOI: http://doi.org/10.1002/2016JB013430 Journal of Geophysical Research: Solid Earth RESEARCH ARTICLE Deformation pattern during normal faulting: 10.1002/2016JB013430 A sequential limit analysis Key Points: • New 2-D mechanically balanced X. P. Yuan1,2 , B. Maillot3, and Y. M. Leroy1,4 model of formation and evolution of half-grabens above low-angle normal 1Laboratoire de Géologie, CNRS UMR, École Normale Supérieure, Paris, France, 2Now at Helmholtz Centre Potsdam, detachment 3 • Tectonic extensional and gravitational German Research Center for Geosciences (GFZ), Potsdam, Germany, Laboratoire Géosciences et Environnement Cergy, 4 modes of deformation in frictional Université de Cergy-Pontoise, Cergy-Pontoise, France, Now at Total, CSTJF, Pau, France wedges are well captured • Fault weakening and sedimentation control number of fault-bounded Abstract We model in 2-D the formation and development of half-graben faults above a low-angle blocks in hanging wall normal detachment fault. The model, based on a “sequential limit analysis” accounting for mechanical equilibrium and energy dissipation, simulates the incremental deformation of a frictional, cohesive, and Supporting Information: fluid-saturated rock wedge above the detachment. Two modes of deformation, gravitational collapse and • Supporting Information S1 tectonic collapse, are revealed which compare well with the results of the critical Coulomb wedge theory. •MovieS1 •MovieS2 We additionally show that the fault and the axial surface of the half-graben rotate as topographic •MovieS3 subsidence increases. This progressive rotation makes some of the footwall material being sheared and •MovieS4 entering into the hanging wall, creating a specific region called foot-to-hanging wall (FHW).
    [Show full text]
  • Along-Strike Growth of a Crustal Fault Controls the Modern Corinth Rift
    Geophysical Research Abstracts Vol. 20, EGU2018-12264, 2018 EGU General Assembly 2018 © Author(s) 2018. CC Attribution 4.0 license. Along-strike growth of a crustal fault controls the modern Corinth Rift David Fernández-Blanco, Gino de Gelder, Robin Lacassin, and Rolando Armijo Sorbonne Paris Cité, Univ Paris Diderot, CNRS, Institut de Physique du Globe de Paris, Lithosphere Tectonics and Mechanics, Paris, France ([email protected]) The Corinth Rift is the worldwide fastest-extending subaerially-exposed continental region, and thus an outstand- ing natural laboratory for research on fault and young rift mechanics. Here we address two of the rift’s most foundational and discrepant questions: whether the Corinth Rift formed; (i) as a “long” lived feature (∼5 Ma) by basinward fault migration, or as a short-lived feature (<1 Ma) by a single fault system; and by (ii) a north-dipping low angle detachment fault in the upper-to-middle crust or a steep normal fault affecting the entire crust. We re- assess available data and integrate it into a new map of the rift and use DEM-based analysis together with key concepts of fault mechanics and fluvial geomorphology to unravel the evolution of the master fault from onset to present. Footwall relief denotes that the master fault, composed at the surface of several segments, is at depth a single fault system >90 km in length. This finding implies that the Corinth Rift master fault reaches at least basal crustal depths. This crustal master fault initiated around the present rift centre and grew laterally by linkage and inclusion of younger individual fault segments along strike and has very high slip (and derived uplift) rates all along its strike.
    [Show full text]
  • Evolving Flexure Recorded in Continental Rift Uplifting Landscapes - Corinth Rift, Greece
    [Non Peer-Reviewed Earth ArXiv Preprint – Originally submitted to Geology, preparing resubmission to GRL] Evolving flexure recorded in continental rift uplifting landscapes - Corinth Rift, Greece David Fernández-Blanco1, Gino de Gelder1, Sean Gallen2, RoBin Lacassin1 & Rolando Armijo1 1 Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ Paris Diderot, UMR 7154 CNRS, F-75005 Paris, France 2 GeoloGical Institute, Swiss Federal Institute of TechnoloGy (ETH), 8092 Zü rich, Switzerland Abstract Elastic flexure of the lithosphere is commonly used to model crustal mechanics, rheoloGy and dynamics. However, accurate characterizations of flexure in nature at the spatiotemporal scale of active continental riftinG (tens of km; 104-106 yr) are scant. We use exceptionally preserved Geomorphic evidence in the asymmetric, younG and fast-extendinG Corinth Rift, central Greece, to document the combined effect of proGressive uplift and footwall flexure throuGhout its upliftinG marGin. Across the rift marGin, footwall lonGitudinal river profiles and topoGraphy define uplift increasinG exponentially towards the boundinG fault. AlonG the rift marGin, geomorphic proxies for fault’s footwall relief, slip rate and uplift rate show parabolic distributions decayinG alonG strike away from the fault center. Conspicuous drainage reversals where the topoGraphic expression of elastic flexure is most prominent similarly suGGest that maximum slip rates occur at the rift center. Overall, the geomorphic evidence for flexure implies disruptive Middle Pleistocene onset of a highly-localized, master fault system of crustal scale controllinG the Growth of the modern Corinth Rift. Similar hiGhly-localized strain and associated elastic flexure of the lithosphere may have occurred elsewhere, includinG old and/or slow-extendinG rifts and areas of intracontinental extension lackinG adequate Geomorphic evidence.
    [Show full text]
  • Faulted Joints: Kinematics, Displacement±Length Scaling Relations and Criteria for Their Identi®Cation
    Journal of Structural Geology 23 (2001) 315±327 www.elsevier.nl/locate/jstrugeo Faulted joints: kinematics, displacement±length scaling relations and criteria for their identi®cation Scott J. Wilkinsa,*, Michael R. Grossa, Michael Wackera, Yehuda Eyalb, Terry Engelderc aDepartment of Geology, Florida International University, Miami, FL 33199, USA bDepartment of Geology, Ben Gurion University, Beer Sheva 84105, Israel cDepartment of Geosciences, The Pennsylvania State University, University Park, PA 16802, USA Received 6 December 1999; accepted 6 June 2000 Abstract Structural geometries and kinematics based on two sets of joints, pinnate joints and fault striations, reveal that some mesoscale faults at Split Mountain, Utah, originated as joints. Unlike many other types of faults, displacements (D) across faulted joints do not scale with lengths (L) and therefore do not adhere to published fault scaling laws. Rather, fault size corresponds initially to original joint length, which in turn is controlled by bed thickness for bed-con®ned joints. Although faulted joints will grow in length with increasing slip, the total change in length is negligible compared to the original length, leading to an independence of D from L during early stages of joint reactivation. Therefore, attempts to predict fault length, gouge thickness, or hydrologic properties based solely upon D±L scaling laws could yield misleading results for faulted joints. Pinnate joints, distinguishable from wing cracks, developed within the dilational quadrants along faulted joints and help to constrain the kinematics of joint reactivation. q 2001 Elsevier Science Ltd. All rights reserved. 1. Introduction impact of these ªfaulted jointsº on displacement±length scaling relations and fault-slip kinematics.
    [Show full text]
  • The Callovian Unconformity and the Ophiolite Obduction Onto the Pelagonian Carbonate Platform of the Internal Hellenides
    Δελτίο της Ελληνικής Γεωλογικής Εταιρίας, τόμος L, σελ. 144-152 Bulletin of the Geological Society of Greece, vol. L, p. 144-152 Πρακτικά 14ου Διεθνούς Συνεδρίου, Θεσσαλονίκη, Μάιος 2016 Proceedings of the 14th International Congress, Thessaloniki, May 2016 THE CALLOVIAN UNCONFORMITY AND THE OPHIOLITE OBDUCTION ONTO THE PELAGONIAN CARBONATE PLATFORM OF THE INTERNAL HELLENIDES Scherreiks R.1, Meléndez G.2, Bouldagher-Fadel M.3, Fermeli G.4 and Bosence D.5 1Bayerische Staaatssammlung, Department of Geology, University of Munich, Luisenstr. 33, 80333 Munich, Germany, [email protected] 2Departamento de Geologia (Paleontologia), Universidad de Zaragoza, 50009 Saragossa, Spain, [email protected] 3Earth Sciences, University College London, Gower Street, London WC1E6BT, UK, [email protected] 4Department of Historical Geology and Paleontology, University of Athens, Panepistimioupolis, Zographou, 15784 Athens, Greece, [email protected] 5Department of Earth Sciences, Royal Holloway University of London, Egham TW20 0EX, UK, [email protected] Abstract The carbonate-platform-complex and the oceanic formations of the central Pelagonian zone of the Hellenides evolved in response to a sequence of plate-tectonic episodes of ocean spreading, plate convergence and ophiolite obduction. The bio- stratigraphies of the carbonate platform and the oceanic successions, show that the Triassic-Early Jurassic platform was coeval with an ocean where pillow basalts and radiolarian cherts were being deposited. After convergence began during late Early- Jurassic - Middle Jurassic time, the oceanic leading edge of the Pelagonian plate was subducted beneath the leading edge of the oceanic, overriding plate. The platform subsided while a supra-subduction, volcanic-island-arc evolved.
    [Show full text]
  • Mechanics, Structure and Evolution of Fault Zones
    Pure appl. geophys. 166 (2009) 1533–1536 Ó Birkha¨user Verlag, Basel, 2009 0033–4553/09/101533–4 DOI 10.1007/s00024-009-0509-y Pure and Applied Geophysics Mechanics, Structure and Evolution of Fault Zones YEHUDA BEN-ZION and CHARLES SAMMIS 1. Introduction The brittle portion of the Earth’s lithosphere contains a distribution of joints, faults and cataclastic zones that exist on a wide range of scale-lengths and usually have complex geometries including bends, jogs, and intersections. The material around these complexities is subjected to large stress concentrations, which lead during continuing deformation to the generation of new fracture and granular damage with an associated evolution of the elasticity, permeability and geometry of the actively deforming regions. The evolving material and geometrical properties within and around the fault zone can lead, in turn, to evolution of various aspects of earthquake and fault mechanics. The geometrical complexity, material heterogeneities and wide range of effective space-time scales make the quantification of properties and processes associated with fault zones extremely challenging. Many fundamental questions concerning the mechanics, structure and evolution of fault zones remain unanswered despite consider- able research spanning over 100 years. The fourteen papers in this volume provide recent theoretical and observational perspectives on fault zones. Topics include damage and breakage rheologies, development of instabilities, fracture and friction, dynamic rupture experiments, analysis of geodetic data, and geological and laboratory characterizations of fault traces, fault surfaces, fracture zones, and particles in rock samples from fault zone environments. FINZI et al. present computer simulations of the evolution of geometrical and elastic properties of large strike-slip fault zones and associated deformation fields, using a model with a seismogenic upper crust governed by a continuum damage rheology.
    [Show full text]