Marginal Fault Zone Research Articles

Young geodynamic activity in the marginal fault zone of the Sudetic Block - new data

Young geodynamic activity in the marginal fault zone of the Sudetic Block - new data

Dolomitisation of carbonate platform margins by fault‐controlled geothermal convection: Insights from coupling stratigraphic and reactive transport models

AbstractReactive transport modelling is increasingly deployed to quantitatively evaluate conceptual models of diagenetic processes. However, construction of models of complex systems involves trade‐offs between accuracy and simplification. This tension is explored for models of fault‐associated dolomitisation by sea water convection in a syn‐rift carbonate platform, evaluating the contribution of incorporating stratigraphic growth and fault propagation. Simulations of the high heat flux southern margin of the Derbyshire Platform (Northern England), with heterogeneous matrix permeability that reflects the evolving stratal architecture and burial compaction focusses dolomitisation in more permeable units at all depths. A permeable platform margin fault zone enhances dolomitisation in a broad area on the upper slope and margin, and to a lesser but significant extent, across the interior as platform top waters are entrained and discharge via the fault. Stepwise simulation of flow and reactions during stratigraphic growth suggests that static models over‐predict dolomite abundance in younger sediments and show how regions optimally supplied with reactants and heat to drive dolomite formation migrate vertically and laterally during platform growth. Dolomitisation intensity increases with depth due to greater time for reactions and kinetically favourable temperatures. Adding the fault zone to this model focusses and accelerates flow, giving a more spatially restricted dolostone body and reducing dolomitisation temperature. Changes in fault connectivity with the surface of the evolving platform shift fluid flow pathways and change the rate and temperature of dolomite formation. Results concur with petrographic, isotopic and geochemical observations of the early dolomite on the Derbyshire Platform. This work demonstrates the importance of understanding diagenesis as the product of an evolving set of processes that respond to geological and palaeoenvironmental changes rather than as a sequence of individual diagenetic events. This is particularly critical for reactions, such as dolomitisation by geothermal convection of sea water, which occur over timescales synchronous with platform development.

Estimation of the Slip Rate Along the Unruptured Fault Segment of the M7.2 1896 Rikuu Earthquake, Northeast Japan

AbstractThe Ou Backbone Range (OBR) is one of the most seismically active intraplate regions in northeast Japan. Over the past 200 years, it has been the locus of five large magnitude earthquakes, including the M7.2 1896 Rikuu earthquake, which produced coseismic surface deformation along the northern segment of the Eastern Margin Fault Zone of Yokote Basin (EFZYB), while the southern segment remained unruptured. Despite the extensive paleoseismic investigations along the ruptured segment, the slip rate estimates, and the recurrence interval remained largely unresolved along the southern unruptured segment. This study reports the long‐term slip rate, and recurrence interval along the Higashi Chokai san Fault and the signatures of active faulting along the Kanazawa and Omoriyama Faults. Based on the seismic reflection and borehole survey, we have estimated a vertical displacement of 29.3–36.1 m across the Higashi Chokai san Fault, a long‐term slip rate of 1.6–1.9 mm/yr over the past 35 ka, and a recurrence interval of about 3,800–4,600 years.Combining our results with the already published data along the OBR, revealed two seismic gaps, first along the western margin of the OBR, along the partial rupture zone of the 1970 Akita‐ken earthquake, and second, along the eastern margin of the OBR, north of the 2008 Iwate‐Miyagi Nairiku earthquake (IMEQ) rupture zone. Given most of the slip is released elastically, we propose that these seismic gaps have a potential to produce earthquakes with magnitudes Mw7.1 and Mw7.3, respectively if they were to rupture in a single event.

Evolution of a salt-rich transtensional rifted margin, eastern North Pyrenees, France

In this field study we reinterpret the narrow eastern North Pyrenean Zone, France, as an inverted salt-rich transtensional rift system based on identification of halokinetic depositional sequences across rift platform to distal rift margin domains with a cumulative throw of >2.8 km on steep Cretaceous faults. The rift platform records extension on detached rotational faults above Triassic evaporites from Jurassic to Aptian with uplift and erosion during the Albian. Transtensional Aptian–Albian minibasins align along the salt-rich rift margin fault zone. In the Aptian–Albian main rift large en echelon synclinal minibasins developed between salt walls, although Jurassic diapiric evolution is likely. Upper Cretaceous units locally record continuing diapirism. The Boucheville and Bas Agly depocentres, altered by synrift HT metamorphism, form the distal rift domain terminating south against the North Pyrenean Fault. The narrowness of the Pyrenean rift, shape of minibasins, en echelon oblique synclinal depocentres and folds coupled with a discontinuous distribution and intensity of HT metamorphism support a transtensional regime along the Iberia–Europe plate margin during late Early and early Late Cretaceous. In this model, the distal European margin comprises deep faults limiting laterally discontinuous crustal domains and ‘hot’ pull-apart basins with mantle rocks directly beneath sedimentary cover. Supplementary material : A table summarizing the stratigraphy of the NE Pyrenees and an interpreted Google Earth view of the Quillan syncline and minibasin are available at https://doi.org/10.6084/m9.figshare.c.5100036

Spatial distribution correlation of soil-gas radon (222Rn) and mercury with leveling deformation in northern margin fault zone of West Qinling, China

This study concerns measurement of 222Rn and mercury concentrations in soil-gas in the northern margin fault zone of West Qinling, Tibet (China). Based on profiles crossing perpendicularly the different segments of the fault at six different locations, the relations between the gas measurements, fault deformation, and seismic activity in each segment of the studied fault were analyzed, determining seismic risks in the fault zone. Soil-gas data are heterogeneous, but appear relatively organized along the three segments of the fault. The detailed multidisciplinary analysis reveals complex interactions between the structural setting, uprising fluids, leveling and seismic activity in different fault segments. The results for both fault soil gas and deformation indicated relatively stronger fault activity in the Wushan segment in the middle-eastern segment of the northern margin fault zone of West Qinling and lower activity in the Zhangxian segment, whereas the fault in the Tianshui segment was relatively locked. Additionally, in the Wushan strike-slip pull-apart area, the active influence of fluid activities facilitated the occurrence of small to medium-sized seismic events, which prevented the occurrence of larger events; in contrast, in the Tianshui segment, the west Zhangxian segment, the weak fluid activities and the corresponding strain rate will probably lead to strong earthquake buildup.

Morphotectonic analysis of Kozani Basin (Western Macedonia, Greece)

Kozani Basin is located in northern-central Greece and constitutes the southernmost of the Plio-Pleistocene basins of western Macedonia. Quantitative and qualitative analysis of morphological slope values, as well as the analysis of the drainage pattern in Kozani Basin confirms that the current topographic relief reflects intense neotectonic activity. Synthetic Morphotectonic Map of the under study area was carried out by means of the combined use of: (a) Digital Elevation Model (DEM), (b) Slope Distribution Map, (c) Morphological Slope Map and (d) Drainage Pattern Map. The composition of the digital modelling in conjunction with the regional geological setting, allows the identification of the main morphological discontinuities and lineaments that result from morphotectonic interpretation. The high morphological slope values indicate well-defined morphotectonic features, which mainly trend NE - SW and, secondarily, NW - SE. Distinct tectonic structures are mostly recognized in the SE margin of Kozani Basin, which is characterized by intense topographic relief. The main large-scale tectonic structure trends NE - SW and corresponds to the major Aliakmonas marginal fault zone that bounds the Kozani basin to the south. On the other hand, the NW margin’s features are indiscernible; thus, the criteria for their recognition are based on the existence of the river terraces, which reflect the tectonic control. The results of our studies are presented on the Morphotectonic Map, which is followed by our 3D model of Kozani Basin.

PRESENT DAY DEFORMATION IN THE EAST VIETNAM SEA AND SURROUNDING REGIONS

This paper presents velocities of present-day tectonic movement and strain rate in the East Vietnam Sea (South China Sea) and surroundings determined from GPS campaigns between 2007 and 2010. We determine absolute velocities of GPS stations in the ITRF05 frame. The result indicates that GPS stations in the North of East Vietnam Sea move eastwards with the slip rate of 30 - 39 mm/yr, southwards at the velocities of 8 - 11 mm/yr. Song Tu Tay offshore moves eastwards at the rate of ~24 mm/yr and southwards at ~9 mm/yr. GPS stations in the South of East Vietnam Sea move to the east at the rate of ~22 mm/yr and to the south at the velocities of 7 - 11 mm/yr. The effect of relative movement shows that the Western Margin Fault Zone activates as left lateral fault zone at the slip rate less than 4 mm/year.In Western plateau, the first result from 2012 - 2013 GPS measurement shows that the velocities to the east vary from 21.5 mm/yr to 24.7 mm/year. The velocities to the south vary from 10.5 mm/yr to 14.6 mm/year. GPS solutions determined from our campaigns are combined with data from various authors and international projects to determine the strain rate in the East Vietnam Sea. Principal strain rate changes from 15 nanostrain/yr to 9 nanostrain/yr in the East Vietnam Sea. Principal strain rate and maximum shear strain rate along the Red River Fault Zone are in order of 10 nanostrain/year. East Vietnam Sea is considered to belong to the Sunda block.

Tectonic phase separation applied to the Sudetic Marginal Fault Zone (NE part of the Czech Republic)

This study emphasizes the advantage of tectonic phase separation in determination of a tectonic evolution of complicated fault zones. The research focused on the Sudetic Marginal Fault Zone (SMFZ) −a 250 km long active fault zone with documented intraplate seismicity situated on the NE margin of the Bohemian Massif (the Czech Republic). The tectonic history of the SMFZ as well as its kinematic development has been rather complicated and not quite understood. A field structural investigation was carried out in extensive surroundings of the fault zone. The fault-slip data were collected in a number of natural outcrops and quarries with the aim at establishing a robust and field-constrained model for local brittle structural evolution of the studied area. A paleostress analysis was calculated using the collected fault-slip data inversion. The T-Tecto software was utilized for semiautomatic separation of the paleostress phases. Simultaneously three methods of data separation were employed: (1) the Gauss inverse method, (2) the Visualization of Gauss object Function, and (3) the frequency analysis. Within the fault zone multiphase movements were observed on various types of faults as well as wide range of the kinematic indicators orientations. The frequency analysis confirmed the multiphase history of the SMFZ. The calculated tectonic phases were divided according to their relative age as constrained by cross cutting relationships and, where observed, multiple striations on a single fault plane and classified from the oldest to the younger. Data separation and inversion using T-Tecto software with the Gauss inverse method revealed four different stress phases which are 3 strike-slip stress regimes and one compressional regime. The strike-slip regimes are characterized by σ1 trending NW-SE (43), NNE-SSW (18), ENE-WSW (76) and the compressional one by σ1 trending W-E (26). First, compression occurred parallel to the SMFZ supposedly during the Variscan period. Second, compression at an angle of 60° to general direction of the SMFZ yielded right-lateral movement along the fault zone. This is considered to have occurred during the late-Variscan and post-Variscan period. Third, compression in the W-E direction with almost vertical extension led to reverse movement along the fault zone. This is considered to have occurred during Cenozoic. Fourth, compression almost perpendicular to the SMFZ led to left-lateral transpression along the SMFZ. This is considered to have occurred during Quaternary.

Tectonic geomorphology and subsurface structure based on seismic reflection profiling of the western marginal fault zone of the Kitakami lowland

Tectonic geomorphology and subsurface structure based on seismic reflection profiling of the western marginal fault zone of the Kitakami lowland

Northeastern Extension of the New Madrid North Fault, New Madrid Seismic Zone, Central United States

Abstract Analysis of electric and geologic logs of 517 shallow wells (91 m, 300 ft deep) in southeastern Missouri has revealed a subsurface structural high (herein called the Charleston Uplift) trending N46°E from near New Madrid, Missouri, to Cairo, Illinois, that juxtaposes Paleocene Flour Island Formation against Eocene Claiborne Group. The Charleston Uplift is 30 km (19 miles) long, 7.2 km (4.5 miles) wide, and has a relief of 36 m (120 ft) at the unconformity surface between the Paleogene and Quaternary sections. Two seismic‐reflection soundings, one conducted north of the uplift, and the second conducted within the uplift indicate 60 m (198 ft) of apparent structural relief on the underlying top of the Paleozoic, 47 m (155 ft) on the top of the Late Cretaceous, and 19 m (63 ft) on a Tertiary reflector. The Charleston Uplift is interpreted to be the northeastern extension of the New Madrid North fault of the New Madrid seismic zone and locally the western margin fault zone of the Reelfoot rift. Although no surface faulting has been mapped along the Charleston Uplift, the uplift appears to have influenced the Holocene course of the Mississippi River and displaced the Paleocene/Quaternary unconformity, thus indicating Quaternary displacement of the Charleston Uplift across southeastern Missouri, which may continue beneath the Ohio River valley into adjacent Illinois and Kentucky. Thus, the Charleston Uplift strongly suggests Quaternary structural continuity between the Reelfoot rift and Rough Creek graben of Kentucky. Although currently seismically quiet, the 12 February 2012 M 3.9 earthquake and probably the 31 October 1895 ∼ M 6.6 Charleston earthquake occurred on this structure, thereby illustrating the seismic potential of this structure and extending the New Madrid North fault system at least 30 km (19 miles).

北上低地西縁断層帯・上平断層群南端付近の断層変位地形と断層露頭

北上低地西縁断層帯・上平断層群南端付近の断層変位地形と断層露頭

Fault discontinuity of the western marginal fault zone of Fukushima basin around Iizaka Town in northeast Japan

Fault discontinuity of the western marginal fault zone of Fukushima basin around Iizaka Town in northeast Japan

テクトニックな沈降域における沿岸河口低地の地層形成

There have been fewer studies on strata formation in tectonically subsiding areas than in tectonically stable and uplifting areas. In this study, (1) 1000 year scale sediment stacking patterns, (2) seismic subsidence and meltwater pulse (MWP) 1B, and (3) event stratigraphy derived from seismic subsidence are revealed on the basis of sedimentary facies and 162 radiocarbon dating of three sediment cores obtained from the latest Pleistocene to Holocene Shinano River incised-valley fill (Alluvium) in the Echigo Plain. Aggradation is dominant in sediment stacking patterns of the incised-valley fill due to tectonic subsidence from the Nagaoka Plain Western Margin Fault Zone. Two continuous layers with abundant marine diatoms and rapid sediment accumulation rates are identified in transgressive salt marsh sediments. These layers may be due to seismic subsidence, but the latter layer (11.2-11.6 cal kyr BP) coincides with MWP 1B. If MWP 1B exists, the thickness of the latter layer indicates that the magnitude of the relative sea-level jump is less than 4 m. The event stratigraphy derived from seismic subsidence in salt marsh sediments is characterized by grading, dominant marine diatoms, and intense sediment accumulation rates. The presence of this event stratigraphy in the Echigo Plain suggests that seismic events strongly affect strata formation in tectonically subsiding areas in Japan.

Sediment accumulation patterns in a tectonically subsiding incised valley: Insight from the Echigo Plain, central Japan

Abstract The Echigo Plain is on the Japan Sea coast of the island of Honshu and is bounded to the west by the Echigo Plain Western Margin Fault Zone. The Shinano River incised valley lies east of the bounding fault zone and runs seaward, approximately parallel to it. The incised valley deepens to more than 160 m below mean sea level near the coast, deeper than sea-level fall during the Last Glacial Maximum, because of subsidence governed by the fault zone. In this study, we examined the sediment stacking patterns of the incised-valley fill at 1000-year scale by analyzing sedimentary facies and radiocarbon ages from three sediment cores from the Echigo Plain. The latest Pleistocene to Holocene Shinano River incised-valley fill sediments unconformably overlie a basement of late Pleistocene flood plain sediments that contain Aira-Tn (AT) tephra dated at 25,120 ± 220 BP (ca. 30 cal kyr BP). The fill sequence comprises sediments of meandering river (> 12 cal kyr BP), estuarine (13–9 cal kyr BP), and barrier–lagoon (9–0 cal kyr BP) systems, in ascending order. Thousand-year isochrons based on radiocarbon ages show that the meandering river and estuarine systems were deposited aggradationally and retrogradationally and the barrier–lagoon system was deposited progradationally and aggradationally. These sediment stacking patterns resemble those of other incised-valley fill sequences in East and Southeast Asia, which indicates that the last deglacial eustasy was a major factor controlling sediment stacking patterns of incised-valley fill in these regions. However, aggradational sedimentation in all three depositional systems is only observed in the Echigo Plain and suggests that long-term subsidence at 2.7–3.8 mm/yr is an important factor controlling the 1000-year scale sediment stacking pattern in this tectonically subsiding incised valley.

Reply to comment of Pirazzoli and Evelpidou

The Echigo Plain is on the Japan Sea coast of the island of Honshu and is bounded to the west by the Echigo Plain Western Margin Fault Zone. The Shinano River incised valley lies east of the bounding fault zone and runs seaward, approximately parallel to it. The incised valley deepens to more than 160 m below mean sea level near the coast, deeper than sea-level fall during the Last Glacial Maximum, because of subsidence governed by the fault zone. In this study, we examined the sediment stacking patterns of the incised-valley fill at 1000-year scale by analyzing sedimentary facies and radiocarbon ages from three sediment cores from the Echigo Plain. The latest Pleistocene to Holocene Shinano River incised-valley fill sediments unconformably overlie a basement of late Pleistocene flood plain sediments that contain Aira-Tn (AT) tephra dated at 25,120 ± 220 BP (ca. 30 cal kyr BP). The fill sequence comprises sediments of meandering river (> 12 cal kyr BP), estuarine (13–9 cal kyr BP), and barrier–lagoon (9–0 cal kyr BP) systems, in ascending order. Thousand-year isochrons based on radiocarbon ages show that the meandering river and estuarine systems were deposited aggradationally and retrogradationally and the barrier–lagoon system was deposited progradationally and aggradationally. These sediment stacking patterns resemble those of other incised-valley fill sequences in East and Southeast Asia, which indicates that the last deglacial eustasy was a major factor controlling sediment stacking patterns of incised-valley fill in these regions. However, aggradational sedimentation in all three depositional systems is only observed in the Echigo Plain and suggests that long-term subsidence at 2.7–3.8 mm/yr is an important factor controlling the 1000-year scale sediment stacking pattern in this tectonically subsiding incised valley.

The application of electrical resistivity tomography and gravimetric survey as useful tools in an active tectonics study of the Sudetic Marginal Fault (Bohemian Massif, central Europe)

This paper presents the results of two separate geophysical investigations undertaken across the Sudetic Marginal Fault zone in the Bohemian Massif. This fault zone represents one of the most important tectonic features in central Europe. The first, preliminary, investigation used electrical resistivity tomography (ERT) to define the exact position of the main fault at two localities (Kamenička & Bílá Voda). Both profiles revealed a resistivity gradient that divided a complex of crystalline rocks with high resistivities from sedimentary deposits with low resistivities. From these data, sites were selected for palaeoseismic trenching. This trenching provided detailed information regarding the surveyed structures and lithologies. The second, more extensive, investigation used electrical resistivity tomography and gravimetric survey in order to extend the previously recognised features both laterally and to depth. The fault is displayed by the presence of an expressive resistivity gradient, even on profiles undertaken in more homogeneous lithologies. Finally, the most intensive investigations were conducted at Bílá Voda, where highly detailed ERT was undertaken on the floor of the trench. From this, it was possible to trace approximately logged geological structures to far greater depths and assess sedimentary thicknesses. A gravimetric survey was also undertaken adjacent to the trench. From modelling the gravitational effects of the fault zone, it is shown that the fault dips about 75° NE and that the vertical offset of Miocene vs. bedrock on the fault is approximately 200 m. The presented study has demonstrated the value of undertaking two phases of geophysical exploration separated by a trenching investigation. It is considered that this methodology is particularly suitable for the study of active tectonics in analogous intraplate settings where fault slip-rate is low.

Tectonic landform and fault outcrop of the Nanshozan active fault group, in the northern part of the western margin fault zone of the Kitakami lowland, northeast Japan

Tectonic landform and fault outcrop of the Nanshozan active fault group, in the northern part of the western margin fault zone of the Kitakami lowland, northeast Japan

A tectonic pressure pulse and increased geodynamic activity recorded from the long-term monitoring of faults in Europe

This paper presents the results of a long-term monitoring study undertaken during the period 2002–2007. The study recorded the displacement of various widely-distributed tectonic structures along the generally aseismic Bohemian Massif (Czech Republic) and specifically along the Sudeten Marginal Fault Zone. The derived results were compared with data recorded over the same time period in the Upper Rhine Graben (Germany), Central Apennines (Italy), and the Gulf of Corinth (Greece). It is clear that a tectonic pressure pulse initiated a period of increased geodynamic activity across central and southern Europe during the course of our monitoring. Within the Bohemian Massif, the pressure pulse was first recorded in mid 2003 and the ensuing period of increased geodynamic activity lasted for nearly three years. This period is associated with compression along the Sudeten Marginal Fault Zone. The southern flank was repeatedly downthrust beneath the northern flank, which caused the latter to continually uplift and subside. The period of increased geodynamic activity was terminated by two strong local earthquakes. Consequently, it is considered that this period induced earthquake activity within the Bohemian Massif. When taken together, the presented data provides robust evidence for the reconfiguration of stress and strain relationships within central and southern Europe. Whilst it is possible that tectonic activity in the Alps produced a north-verging pressure pulse that affected central Europe (e.g. in the Bohemian Massif and Upper Rhine Graben), it cannot account for the pressure pulse recognised to the south (e.g. in the Central Apennines and the Gulf of Corinth). Due to the predominance of vertical movements, it is suggested that this reconfiguration results from deep seated processes within the lithosphere–asthenosphere. However, the influence of horizontal movements transmitted from the compressional zone between Africa and Europe cannot be discounted.

Determining the Relative Age of Fault Activity through Analyses of Gouge Mineralogy and Geochemistry: A Case Study from Vápenná (Rychleby Mts), Czech Republic

The relative age of fractures can be determined through structural analyses in the field or through the detailed mineralogical (XRD) and chemical analyses (AAS method, volumetric, and gravimetric analysis) of fault gouge in the laboratory. The aim of this work was to compare these approaches. It was hypothesised that the two methods would yield consistent results. The studied faults were located in the Rychleby Mts, part of the Sudetic Marginal Fault Zone. The relative age of the faults was determined in the field through the application of the intersection law. The fault gouges were sampled in a crystalline limestone quarry near the village of Vápenná. The mineralogical composition of the fault gouges has been established by XRD analysis of powder samples and analysis of preferentially oriented clay minerals. From our result, it is clear that these two approaches yielded consistent results with regard to the relative age of the faults.

The sea-level record of the last deglacial in the Shinano River incised-valley fill, Echigo Plain, central Japan

The Echigo Plain, on the Japan Sea coast, is in a sedimentary basin governed by subsidence controlled by the Echigo Plain Western Margin Fault Zone. The glacial incised valley in the Echigo Plain filled with the sediment discharge of the Shinano River as the sea level rose during the last deglacial. The incised-valley fill allows us to reconstruct the detailed sea-level record, because the plain is still interseismically subsiding at a rate of about 3 mm/yr and the present tidal range along the Japan Sea coast is less than 0.3 m. In this study, we reconstructed a centennial-scale sea-level record for the deglacial period (12,000–9000 cal BP) on the basis of the sedimentary facies and 54 radiocarbon dates from a sediment core obtained from the Echigo Plain near the Western Margin Fault Zone. In this core, the interval from 95 to 55 m below the present sea level consists of floodplain and salt marsh sediments deposited aggradationally during 11,600–9000 cal BP as a result of transgression. Taking into account the Holocene subsidence rate of 2.7 mm/yr at the core site, the relative sea-level rise during the period of core deposition can be divided into the periods of rapid and slow rates. Sea level rose rapidly (> 23 mm/yr) during 11,600–11,100 cal BP, followed by a slow rate of sea-level rise (2 mm/yr) during 11,200–10,300 cal BP. Another period of rapid sea-level rise (11 mm/yr) during 10,500–9400 cal BP was followed by a slow rate of rise (2 mm/yr) during 9600–9000 cal BP. This record of relative sea-level rise indicates that the rapid rate of sea-level rise during 11,600–11,100 cal BP is consistent with meltwater pulse 1B.