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Peter Bird - One of the best experts on this subject based on the ideXlab platform.
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Neotectonics and long term seismicity in europe and the mediterranean region
Journal of Geophysical Research, 2015Co-Authors: Michele M C Carafa, Salvatore Barba, Peter BirdAbstract:We present a neotectonic model of ongoing lithosphere deformation and a corresponding estimate of long-term shallow seismicity across the Africa-Eurasia plate boundary, including the eastern Atlantic, Mediterranean region, and continental Europe. GPS and stress data are absent or inadequate for the part of the study area covered by water. Thus, we opt for a dynamic model based on the stress equilibrium equation; this approach allows us to estimate the long-term behavior of the lithosphere (given certain assumptions about its structure and physics) for both land and sea areas. We first update the existing plate model by adding five quasirigid plates (the Ionian Sea, Adria, Northern Greece, Central Greece, and Marmara) to constrain the deformation pattern of the study area. We use the most recent data sets to estimate the lithospheric structure. The models are evaluated in comparison with updated data sets of geodetic velocities and the most compressive horizontal principal stress azimuths. We find that the side and basal strengths drive the present-day motion of the Adria and Aegean Sea plates, whereas lithostatic pressure plays a key role in driving Anatolia. These findings provide new insights into the Neotectonics of the greater Mediterranean region. Finally, the preferred model is used to estimate long-term shallow seismicity, which we retrospectively test against historical seismicity. As an alternative to reliance on incomplete geologic data or historical seismic catalogs, these neotectonic models help to forecast long-term seismicity, although requiring additional tuning before seismicity rates are used for seismic hazard purposes.
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kinematic modelling of Neotectonics in the persia tibet burma orogen
Geophysical Journal International, 2008Co-Authors: Zhen Liu, Peter BirdAbstract:SUMMARY We apply a new kinematic modelling technique (program NeoKinema) to estimate neotectonic flow in the Persia‐Tibet‐Burma orogen. The models fit geodetic benchmark velocities, geological fault slip rates and stress directions (seismic moment tensor orientations) using a weightedleast-squares method. Models predict long-term velocities, anelastic strain rates and preferred fault slip rates averaged over timescales of 10 4 ‐10 6 yr. While we find a few regions of low anelastic strain rate, the mean continuum strain rate in the preferred model is 2.2 × 10 −16 s −1 (0.7 per cent Ma −1 ), so the India-Eurasia collision should not be modelled as an interaction between rigid microplates. For most faults, preferred fault slip rates agree with geological slip rates within their uncertainty bounds; this suggests that deformation imaged by geodesy over tens of years is consistent with deformation over 10 4 ‐10 6 yr (given appropriate elastic corrections). We also calculate maps of long-term-average seismicity rate based on model fault slip rates and anelastic strain rates in the continuum, using the seismicity parameters of most comparable type of plate boundary. The pattern is generally in agreement with actual m > 5.67 earthquakes in the CMT catalogue (1977‐2002), except that the Himalayan front, High Zagros and Altyn Tagh zones have been quieter than predicted. The spatial integral of our forecast over the orogen is 371 m > 5.67 earthquakes/25.75 yr, versus 238 which actually occurred. If this discrepancy has high significance, it means that some step(s) in our forecast method are faulty (such as the assumption of equal coupled seismogenic thickness in all continental convergent boundaries). If it is only an artefact of stochastic time-dependence, then this may have occurred in the orogen, in the external calibration region, or in both. Independent evidence suggests that large earthquakes (with many aftershocks) will occur along the Himalayan front in the future, possibly reducing this discrepancy.
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finite element modeling of Neotectonics in new zealand
Journal of Geophysical Research, 2002Co-Authors: Zhen Liu, Peter BirdAbstract:[1] Thin-shell finite element methods that incorporate faults, realistic rheology, laterally varying heat flow and topography, and plate velocity boundary conditions have been used to model the Neotectonics of New Zealand. We find that New Zealand's faults have effective friction of ∼0.17, comparable to that found in other Pacific Rim regions. The long-term average slip rate of the Alpine fault varies along strike, generally increasing northeastward until slip is partitioned among the strands of the Marlborough system. The average slip rate, ∼30 mm/yr, when combined with published geodetic results and historical seismicity, strongly suggests a high probability of future large earthquakes. Tectonic deformation of North Island is controlled by a balance between differential topographic pressure and traction from the Hikurangi subduction thrust. The Hikurangi forearc is an independent plate sliver moving relative to the Pacific and Australian plates. There is a complicated zone of slip partitioning in the transition from the Alpine fault to the Puysegur trench. An offshore thrust fault, the southern segment of which may correspond to the Waipounamou fault system, parallels to the SE coast of South Island and needs to be included in seismic hazard estimates.
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thin shell modeling of Neotectonics in the azores gibraltar region
Geophysical Research Letters, 2001Co-Authors: Ivone Jimenezmunt, Peter Bird, Manel FernandezAbstract:We applied the thin-shell neotectonic modeling method to study the Neotectonics of the Africa/Eurasia plate boundary in the Azores-Gibraltar region. The plate boundary consists of a simple fault system running from Azores to the Gorringe Bank where it branches along the Betics and Rift-Tell thrust fronts. Major faults in west Iberia and NW Africa have also been incorporated. Results are compared with seismic strain rates, fault slip rates and stress orientations. The best estimate for the fault friction coefficient is 0.1–0.15 meaning that the plate-boundary is only about 1/4 as strong as the adjacent lithosphere. The largest fault slip rates (>1.5 mm/yr) are obtained along the Gloria fault (strike-slip), and the Betic (transpressive) and Rif-Tell (compressive) thrust systems. Whereas tectonic activity in the Atlas region is comparable to that obtained along the plate boundary, the fault slip rates in the west Iberia fault systems are one order of magnitude less.
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thin plate and thin shell finite element programs for forward dynamic modeling of plate deformation and faulting
Computers & Geosciences, 1999Co-Authors: Peter BirdAbstract:Experiments on deformation of the lithosphere can be performed only in computers. Finite-element codes are best because they can represent lateral strength variations, including faults. Although variations of temperature, strength, and density in the lithosphere must be represented in three dimensions, it is usually suAcient to parameterize the velocity field in two dimensions, giving ‘thin-plate’ or ‘thin-shell’ codes. Four such freeware codes (LARAMY, FAULTS, PLATES and SHELLS) are oAered at ftp://element.ess.ucla.edu. Their capabilities include local neotectonic problems with many faults, global neotectonic problems with many plates and finite strain problems with crust/mantle detachment; the only capability not yet available is finite strain with discrete faults of large oAset. Model predictions include velocities, fault-slip rates, anelastic strain rates and vertically integrated stresses, which can be tested by comparison with data from geologic mapping, seismology and geodesy. # 1999 Elsevier Science Ltd. All rights reserved.
Martin Burkhard - One of the best experts on this subject based on the ideXlab platform.
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Extensional Neotectonics around the bend of the Western/Central Alps: an overview
International Journal of Earth Sciences, 2007Co-Authors: Christian Sue, Bastien Delacou, Jean-daniel Champagnac, Cécile Allanic, Pierre Tricart, Martin BurkhardAbstract:The Western Alps’ active tectonics is characterized by ongoing widespread extension in the highest parts of the belt and transpressive/compressive tectonics along its borders. We examine these contrasting tectonic regimes using a multidisciplinary approach including seismotectonics, numerical modeling, GPS, morphotectonics, fieldwork, and brittle deformation analysis. Extension appears to be the dominant process in the present-day tectonic activity in the Western Alps, affecting its internal areas all along the arc. Shortening, in contrast, is limited to small areas located along at the outer borders of the chain. Strike-slip is observed throughout the Alpine realm and in the foreland. The stress-orientation pattern is radial for σ3 in the inner, extensional zones, and for σ1 in the outer, transcurrent/tranpressional ones. Extensional areas can be correlated with the parts of the belt with the thickest crust. Quantification of seismic strain in tectonically homogeneous areas shows that only 10–20% of the geodesy-documented deformation can be explained by the Alpine seismicity. We propose that, Alpine active tectonics are ruled by isostasy/buoyancy forces rather than the ongoing shortening along the Alpine Europe/Adria collision zone. This interpretation is corroborated by numerical modeling. The Neogene extensional structures in the Alps formed under increasingly brittle conditions. A synthesis of paleostress tensors for the internal parts of the West-Alpine Arc documents major orogen-parallel extension with a continuous change in σ3 directions from ENE–WSW in the Simplon area, to N–S in the Vanoise area and to NNW–SSE in the Briançon area. Minor orogen-perpendicular extension increases from N to S. This second signal correlates with the present-day geodynamics as revealed by focal-plane mechanisms analysis. The orogen-parallel extension could be related to the opening of the Ligurian Sea during the Early-Middle Miocene and to compression/rotation of the Adriatic indenter inducing lateral extrusion.
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extensional Neotectonics around the bend of the western central alps an overview
International Journal of Earth Sciences, 2007Co-Authors: Christian Sue, Bastien Delacou, Jean-daniel Champagnac, Cécile Allanic, Pierre Tricart, Martin BurkhardAbstract:The Western Alps’ active tectonics is characterized by ongoing widespread extension in the highest parts of the belt and transpressive/compressive tectonics along its borders. We examine these contrasting tectonic regimes using a multidisciplinary approach including seismotectonics, numerical modeling, GPS, morphotectonics, fieldwork, and brittle deformation analysis. Extension appears to be the dominant process in the present-day tectonic activity in the Western Alps, affecting its internal areas all along the arc. Shortening, in contrast, is limited to small areas located along at the outer borders of the chain. Strike-slip is observed throughout the Alpine realm and in the foreland. The stress-orientation pattern is radial for σ3 in the inner, extensional zones, and for σ1 in the outer, transcurrent/tranpressional ones. Extensional areas can be correlated with the parts of the belt with the thickest crust. Quantification of seismic strain in tectonically homogeneous areas shows that only 10–20% of the geodesy-documented deformation can be explained by the Alpine seismicity. We propose that, Alpine active tectonics are ruled by isostasy/buoyancy forces rather than the ongoing shortening along the Alpine Europe/Adria collision zone. This interpretation is corroborated by numerical modeling. The Neogene extensional structures in the Alps formed under increasingly brittle conditions. A synthesis of paleostress tensors for the internal parts of the West-Alpine Arc documents major orogen-parallel extension with a continuous change in σ3 directions from ENE–WSW in the Simplon area, to N–S in the Vanoise area and to NNW–SSE in the Briancon area. Minor orogen-perpendicular extension increases from N to S. This second signal correlates with the present-day geodynamics as revealed by focal-plane mechanisms analysis. The orogen-parallel extension could be related to the opening of the Ligurian Sea during the Early-Middle Miocene and to compression/rotation of the Adriatic indenter inducing lateral extrusion.
S A P L Cloetingh - One of the best experts on this subject based on the ideXlab platform.
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Neotectonics and intraplate continental topography of the northern alpine foreland
Earth-Science Reviews, 2006Co-Authors: S A P L Cloetingh, T Cornu, P A Ziegler, F BeekmanAbstract:Research on Neotectonics and related seismicity has hitherto been mostly focused on active plate boundaries that are characterized by generally high levels of earthquake activity. Current seismic hazard estimates for intraplate domains are mainly based on probabilistic analyses of historical and instrumental earthquake catalogues. The accuracy of such hazard estimates is limited by the fact that available catalogues are restricted to a few hundred years, which, on geological time scales, is insignificant and not suitable for the assessment of tectonic processes controlling the observed earthquake activity. More reliable hazard prediction requires access to high quality data sets covering a geologically significant time span in order to obtain a better understanding of processes controlling on-going intraplate deformation. The Alpine Orogen and the intraplate sedimentary basins and rifts in its northern foreland are associated with a much higher level of neotectonic activity than hitherto assumed. Seismicity and stress indicator data, combined with geodetic and geomorphologic observations, demonstrate that deformation of the Northern Alpine foreland is still on-going and will continue in the future. This has major implications for the assessment of natural hazards and the environmental degradation potential of this densely populated area. We examine relationships between deeper lithospheric processes, Neotectonics and surface processes in the northern Alpine Foreland, and their implications for tectonically induced topography. For the Environmental Tectonics Project (ENTEC), the Upper and Lower Rhine Graben (URG and LRG) and the Vienna Basin (VB) were selected as natural laboratories. The Vienna Basin developed during the middle Miocene as a sinistral pull-apart structure on top of the East Alpine nappe stack, whereas the Upper and Lower Rhine grabens are typical intracontinental rifts. The Upper Rhine Graben opened during its Late Eocene and Oligocene initial rifting phase by nearly orthogonal crustal extension, whereas its Neogene evolution was controlled by oblique extension. Seismic tomography suggests that during extension the mantle-lithosphere was partially decoupled from the upper crust at the level of the lower crust. However, whole lithospheric folding controlled the mid-Miocene to Pliocene uplift of the Vosges–Black Forest Arch, whereas thermal thinning of the mantle–lithosphere above a mantle plume contributed substantially to the past and present uplift of the Rhenish Massif. By contrast, oblique crustal extension, controlling the late Oligocene initial subsidence stage of the Lower Rhine Graben, gave way to orthogonal extension at the transition to the Neogene. The ENTEC Project integrated geological, geophysical, geomorphologic, geodetic and seismological data and developed dynamic models to quantify the societal impact of Neotectonics in areas hosting major urban and industrial activity concentrations. The response of Europe's intraplate lithosphere to Late Neogene compressional stresses depends largely on its thermo-mechanical structure, which, in turn, controls vertical motions, topography evolution and related surface processes.
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Neotectonics of the netherlands a review
Quaternary Science Reviews, 2005Co-Authors: R T Van Balen, R F Houtgast, S A P L CloetinghAbstract:Abstract Earthquakes and vertical land movements inferred from geodetic levelling results demonstrate that the Netherlands is situated on a tectonically active part of the Earth's surface. Tectonic subsidence analyses of the sedimentary records in the basins and the history of tectonic uplift inferred from Meuse river terraces show that the current tectonic activity is part of a deformation phase which began in the late Early Miocene, which we take as the start of the neotectonic period. The neotectonic faulting mode is normal-slip. This is in accordance with the present-day orientation of the maximum horizontal stress, and the vertical orientation of the maximum stress. However, the neotectonic fault zones are reactivated Variscan or older wrench faults. These faults have been reactivated repeatedly during the Mesozoic and Cenozoic in normal and wrenching modes, and therefore represent fundamental crustal weakness zones. As a result, the surficial neotectonic fault pattern resembles the inherited wrenching fault pattern, although the faulting mode is normal-slip. This is illustrated for the area where normal faults have displaced the Meuse fluvial terrace system in the southeastern part of the Netherlands. The neotectonic vertical motions in and around the Roer Valley Rift System have affected the courses of the Rhine and Meuse rivers from Pliocene times until the present. In addition, a fluvial terrace staircase developed along the Meuse river in response to the uplift of the Ardennes-Rhenish Massif and its foreland, for example near Maastricht. Furthermore, small fault scarps are present along segments of the bounding fault zones of the Roer Valley Graben: the Peel Boundary Fault Zone and the Feldbiss Fault Zone. In other parts of the Netherlands the neotectonic vertical motions have no direct expression in the morphology. Examples of possible indirect control on the morphology in these areas occur in glacial landscapes, the Zuiderzee Basin and the coastal zone.
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geothermics of the pannonian basin and its bearing on the Neotectonics
Stephan Mueller Special Publication Series, 2001Co-Authors: Laszlo Lenkey, Peter Dovenyi, F Horvath, S A P L CloetinghAbstract:Different aspects of the geothermics of the Pannonian basin are investigated from the viewpoint of Neotectonics. A heat flow map of the basin and the surrounding region is presented. It is shown that the high heat flow of the Pannonian basin, the subsidence and maturation history of the Neogene sediments can be explained in general by Middle Miocene extension and thinning of the lithosphere. To obtain fit to the observed vitrinite reflectance data in the peripheral areas uplift and erosion had to be assumed, which started in the Late Pliocene. For the same time period a thermo-mechanical extensional model would predict thermal subsidence, therefore, the observation of this late stage uplift suggests that the thermal subsidence has been overprinted by tectonic forces, like an increase of intraplate stress. Groundwater flow in porous sedimentary rocks or in fractured rocks disturbs the geothermal field making difficult the interpretation of the heat flow in terms of simple conductive models. However, from the viewpoint of tectonics the occurrence of thermal springs is helpful, because most of the thermal springs occur along faults. Almost half of the thermal springs in Hungary are found along faults, which have been active during the Late Pliocene through Quaternary period. The relationship between the geothermics and the seismicity of the Pannonian basin has also been investigated. It is shown that the seismicity can be understood in terms of collision of the Adriatic microplate with Europe and differences in thermal state of the lithosphere. The tectonically less active Bohemian Massif, Ukrainian and Moesian Platforms form a cold rigid frame of the Pannonian basin. The Pannonian basin and the Dinarides comprise a complex seismotectonic unit. The Pannonian basin, which is characterized by high heat flow, has low to moderate seismic activity, with earthquakes occurring in the upper crust. The Dinarides, which are characterized by low heat flow, have high seismic activity and the focal depth of the earthquakes reaches 40 km. Rheological profiles constructed for the region show that in the Pannonian basin only the upper 10–14 km thick Correspondence to: L. Lenkey (lenl@freemail.hu) part of the crust has brittle strength, as opposed to the Dinarides where the brittle part of the crust is 20–24 km thick, and there is a mechanically strong layer also in the upper mantle.
Christian Sue - One of the best experts on this subject based on the ideXlab platform.
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Extensional Neotectonics around the bend of the Western/Central Alps: an overview
International Journal of Earth Sciences, 2007Co-Authors: Christian Sue, Bastien Delacou, Jean-daniel Champagnac, Cécile Allanic, Pierre Tricart, Martin BurkhardAbstract:The Western Alps’ active tectonics is characterized by ongoing widespread extension in the highest parts of the belt and transpressive/compressive tectonics along its borders. We examine these contrasting tectonic regimes using a multidisciplinary approach including seismotectonics, numerical modeling, GPS, morphotectonics, fieldwork, and brittle deformation analysis. Extension appears to be the dominant process in the present-day tectonic activity in the Western Alps, affecting its internal areas all along the arc. Shortening, in contrast, is limited to small areas located along at the outer borders of the chain. Strike-slip is observed throughout the Alpine realm and in the foreland. The stress-orientation pattern is radial for σ3 in the inner, extensional zones, and for σ1 in the outer, transcurrent/tranpressional ones. Extensional areas can be correlated with the parts of the belt with the thickest crust. Quantification of seismic strain in tectonically homogeneous areas shows that only 10–20% of the geodesy-documented deformation can be explained by the Alpine seismicity. We propose that, Alpine active tectonics are ruled by isostasy/buoyancy forces rather than the ongoing shortening along the Alpine Europe/Adria collision zone. This interpretation is corroborated by numerical modeling. The Neogene extensional structures in the Alps formed under increasingly brittle conditions. A synthesis of paleostress tensors for the internal parts of the West-Alpine Arc documents major orogen-parallel extension with a continuous change in σ3 directions from ENE–WSW in the Simplon area, to N–S in the Vanoise area and to NNW–SSE in the Briançon area. Minor orogen-perpendicular extension increases from N to S. This second signal correlates with the present-day geodynamics as revealed by focal-plane mechanisms analysis. The orogen-parallel extension could be related to the opening of the Ligurian Sea during the Early-Middle Miocene and to compression/rotation of the Adriatic indenter inducing lateral extrusion.
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extensional Neotectonics around the bend of the western central alps an overview
International Journal of Earth Sciences, 2007Co-Authors: Christian Sue, Bastien Delacou, Jean-daniel Champagnac, Cécile Allanic, Pierre Tricart, Martin BurkhardAbstract:The Western Alps’ active tectonics is characterized by ongoing widespread extension in the highest parts of the belt and transpressive/compressive tectonics along its borders. We examine these contrasting tectonic regimes using a multidisciplinary approach including seismotectonics, numerical modeling, GPS, morphotectonics, fieldwork, and brittle deformation analysis. Extension appears to be the dominant process in the present-day tectonic activity in the Western Alps, affecting its internal areas all along the arc. Shortening, in contrast, is limited to small areas located along at the outer borders of the chain. Strike-slip is observed throughout the Alpine realm and in the foreland. The stress-orientation pattern is radial for σ3 in the inner, extensional zones, and for σ1 in the outer, transcurrent/tranpressional ones. Extensional areas can be correlated with the parts of the belt with the thickest crust. Quantification of seismic strain in tectonically homogeneous areas shows that only 10–20% of the geodesy-documented deformation can be explained by the Alpine seismicity. We propose that, Alpine active tectonics are ruled by isostasy/buoyancy forces rather than the ongoing shortening along the Alpine Europe/Adria collision zone. This interpretation is corroborated by numerical modeling. The Neogene extensional structures in the Alps formed under increasingly brittle conditions. A synthesis of paleostress tensors for the internal parts of the West-Alpine Arc documents major orogen-parallel extension with a continuous change in σ3 directions from ENE–WSW in the Simplon area, to N–S in the Vanoise area and to NNW–SSE in the Briancon area. Minor orogen-perpendicular extension increases from N to S. This second signal correlates with the present-day geodynamics as revealed by focal-plane mechanisms analysis. The orogen-parallel extension could be related to the opening of the Ligurian Sea during the Early-Middle Miocene and to compression/rotation of the Adriatic indenter inducing lateral extrusion.
Chuanchou Shen - One of the best experts on this subject based on the ideXlab platform.
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travertine deposits constraining transfer zone Neotectonics in geothermal areas an example from the inner northern apennines bagno vignoni val d orcia area italy
Geothermics, 2020Co-Authors: Andrea Brogi, Enrico Capezzuoli, Paola Francesca Matera, Sandor Kele, Tsailuen Yu, Domenico Liotta, Giovanni Ruggieri, Michele Soligo, Paola Tuccimei, Chuanchou ShenAbstract:Abstract Studying travertine deposits and the network of banded calcite veins that form their roots in the substratum can place important constraints on neotectonic activity and the seismotectonic settings of geothermal areas. In this paper, we present the results of integrated studies of a geothermal area located in the inner Northern Apennines (Bagno Vignoni area, Italy), where low magnitude (M 3 km) formed by two orthogonal faults systems, NE- and NW-striking, characterised by oblique-slip to normal kinematics, respectively; these faults belong to a tract of the so-named “Grosseto-Pienza” transfer zone, crossing the southern Tuscany from the sea-cost to the outer Apennines belt. The Grosseto-Pienza transfer zone formed with extensional tectonics that have been affecting the inner Northern Apennines since the middle Miocene. U-Th dating of travertine and banded calcite veins indicates that faulting enhanced the hydrothermal fluid circulation since the middle Pleistocene, in an unvaried tectonic setting, as indicated by the δ18O signature and temperature of the hydrothermal fluids, which remained stable through time. The activity of the faults continued until the Holocene and still produces seismicity. Finally, our findings permit to define the seismo-tectonic setting of this sector of the inner Northern Apennines, demonstrating more broadly the utility of travertine deposits in reconstructing the Neotectonics in geothermal areas.