scholarly journals Test on the Reliability of the Subsurface Fault Geometry Estimated by Deformed River Terraces Along the Bailang River, North Front of the Qilian Shan (North West China)

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaofei Hu ◽  
Xianghe Ji ◽  
Xilin Cao ◽  
Jiuying Chen ◽  
Baotian Pan
Keyword(s):  
Kinematic Model ◽  
Slip Rate ◽  
Seismic Reflection Profile ◽  
Fault Geometry ◽  
North West ◽  
The North ◽  
River Terraces ◽  
Deformation Kinematics ◽  
Kinematic Models ◽  
Crust Deformation

The subsurface fault geometry is the base for understanding a process of crust deformation and mountain building. Based on kinematic models for fault-related folds, a geomorphic method is recently applied to estimate the subsurface fault geometry, while the validation on its reliability is lacking. In this study, we surveyed a suit of river terrace surfaces across an active fold at the north front of the Qilian Shan. According to the deformation geometry of the terraces, the fold deformation is interpreted by a listric fault fold model, and based on this kinematic model, the fault geometry underlying the fold is estimated. In comparison between the estimated fault geometry and a seismic reflection profile, we found that the decollement depth and the back thrust are highly consistent with each other. Although some small fault bends or internal shearing cannot be estimated solely by the terrace deformation, the overall fault geometry is successfully revealed by the terrace deformation. Using this fault geometry and the terrace dating results, the region deformation kinematics are re-evaluated, which suggest that the dip slip (in a rate of 1.8 ± 0.4 mm/a) along the decollement is mainly accommodated by two structures, one is the blind-back-thrust fault within the piggy basin in a dip-slip rate of 0.9 ± 0.3 mm/a and another is the thrust and fold at the west portion of the Yumu Shan range.

scholarly journals The Subsurface Geology and Landscape Evolution of the Volturno Coastal Plain, Italy: Interplay between Tectonics and Sea-Level Changes during the Quaternary

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3386
Author(s):  
Giuseppe Corrado ◽  
Sabrina Amodio ◽  
Pietro P. C. Aucelli ◽  
Gerardo Pappone ◽  
Marcello Schiattarella
Keyword(s):  
Cross Sections ◽  
Coastal Plain ◽  
Late Quaternary ◽  
Slip Rate ◽  
Tectonic Activity ◽  
Paleoenvironmental Reconstruction ◽  
Sea Level Changes ◽  
Plan View ◽  
North West ◽  
The North

The Volturno alluvial-coastal plain is a relevant feature of the Tyrrhenian side of southern Italy. Its plan-view squared shape is due to Pliocene-Quaternary block-faulting of the western flank of the south-Apennines chain. On the basis of the stratigraphic analysis of almost 700 borehole logs and new geomorphological survey, an accurate paleoenvironmental reconstruction before and after the Campania Ignimbrite (CI; about 40 ky) eruption is here presented. Tectonics and eustatic forcing have been both taken into account to completely picture the evolution of the coastal plain during Late Quaternary times. The upper Pleistocene-Holocene infill of the Volturno plain has been here re-organized in a new stratigraphic framework, which includes seven depositional units. Structural analysis showed that two sets of faults displaced the CI, so accounting for recent tectonic activity. Yet Late Quaternary tectonics is rather mild, as evidenced by the decametric vertical separations operated by those faults. The average slip rate, which would represent the tectonic subsidence rate of the plain, is about 0.5 mm/year. A grid of cross sections shows the stratigraphic architecture which resulted from interactions among eustatic changes, tectonics and sedimentary input variations. On the basis of boreholes analysis, the trend of the CI roof was reconstructed. An asymmetrical shape of its ancient morphology—with a steeper slope toward the north-west border—and the lack of coincidence between the present course of the Volturno River and the main buried bedrock incision, are significant achievements of this study. Finally, the morpho-evolutionary path of the Volturno plain has been discussed.

Neogene Exhumation History along TRANSALP: Insights from Low Temperature Thermochronology and Thermo-Kinematic Models

2020 ◽  
Author(s):  
Paul R. Eizenhöfer ◽  
Christoph Glotzbach ◽  
Lukas Büttner ◽  
Jonas Kley ◽  
Todd A. Ehlers
Keyword(s):  
Low Temperature ◽  
Kinematic Model ◽  
Eastern Alps ◽  
European Alps ◽  
Eastern European ◽  
Tauern Window ◽  
The North ◽  
Late Neogene ◽  
Kinematic Models ◽  
Exhumation Rates

<p>Many convergent orogens such as the eastern European Alps display an asymmetric doubly-vergent wedge geometry. Loci of deepest exhumation are located above the overriding retro-wedge, whereas increased fault activity occurs in the pro-wedge on the subducting plate. The main drainage divide separates steeper from more gently sloping topography on the two wedges of different critical taper. We performed apatite and zircon (U-Th)/He analyses densely spaced along the TRANSALP geophysical transect in combination with thermo-kinematic models based on cross-section balancing. Our new low temperature thermochronology data and thermo-kinematic model results underline (i) deepest levels of exhumation across the Tauern Window until the Pliocene and (ii) higher Late Neogene exhumation rates south of the Periadriatic Fault relative to the north, while seismic activity is focussed across the Southern Alps. Our proposed mantle-to-surface link positions the retro-wedge north of the Periadriatic Fault subsequent to subduction polarity reversal during continental collision. Present-day drainage divide migration trends and imaged locations of mantle-lithospheric slabs beneath TRANSALP suggest ongoing, slow slab reversal since Adriatic indentation in the Eastern Alps. </p>

Kinematics of Subduction Processes during the Earthquake Cycle in Central Chile

2019 ◽  
Author(s):  
Leonardo Aguirre ◽  
Klaus Bataille ◽  
Camila Novoa ◽  
Carlos Peña ◽  
Felipe Vera
Keyword(s):  
Subduction Zones ◽  
Slip Rate ◽  
Convergent Margins ◽  
Earthquake Cycle ◽  
Central Chile ◽  
The North ◽  
The Future ◽  
Maule Earthquake ◽  
Kinematic Models ◽  
Inversion Techniques

ABSTRACT Subduction processes at convergent margins produce complex temporal and spatial crustal displacements during different periods of the earthquake cycle. Satellite geodesy observations provide important clues to constrain kinematic models at subduction zones. Here, we analyze geodetic observations in central Chile, where two large earthquakes occurred: 2010 Mw 8.8 Maule and 2015 Mw 8.3 Illapel. We propose a model that considers the motion along both interfaces of the brittle subducting slab as the sources responsible for the movement of the crust in the different periods of the earthquake cycle. Using standard inversion techniques, we provide a consistent framework of the kinematic displacement during each period of the earthquake cycle. We show that during the interseismic period prior to the Maule and Illapel earthquakes, two patches of slip rate on the lower interface are determined. These patches are located just below the future hypocenters. Because the interseismic period corresponds to the loading process and the coseismic to the unloading process, it is interesting to note that the area where loading is stronger corresponds to the area where unloading is also strong. Furthermore, we show that the Maule earthquake causes a significant displacement on the lower interface, just below the epicenter of the future Illapel earthquake to the north, a few years later. We speculate that the interaction between motions along both interfaces is the key to understanding the evolution of stress and the occurrence of earthquakes at subduction zones. This framework improves the understanding of the observed loading and unloading processes and potential triggering between subduction earthquakes.

The GPS velocity field of the Aegean. New observations, contribution of the earthquakes, crustal blocks model

2021 ◽  
Author(s):  
Pierre Briole ◽  
Athanassios Ganas ◽  
Panagiotis Elias ◽  
Dimitar Dimitrov
Keyword(s):  
Time Series ◽  
Kinematic Model ◽  
Relaxation Times ◽  
North Anatolian Fault ◽  
Postseismic Deformation ◽  
Boundary Line ◽  
Localized Deformation ◽  
Series Length ◽  
North West ◽  
The North

Summary We calculate and analyse the coordinate time series of 282 permanent GPS stations located in Greece and 47 in surrounding countries. The studied period is 2000–2020. The average GPS time series length is 6.5 years. The formal velocity uncertainties are rescaled to be consistent with the velocity scatters measured at 110 pairs of stations separated by less 15 km. We remove the effect of the crustal earthquakes of Mw ≥ 5.3. We quantify and model the postseismic deformations. Two relaxation times are usually needed, one short of some weeks, one long of one year or more. For the large Mw = 6.9 events of Samothraki 2014 and Methoni 2008, the postseismic deformation equals or exceeds the coseismic one. We detect at three stations a deformation transient in May 2018 that may correspond to a slow earthquake beneath Zakynthos and north-west Peloponnese, with equivalent magnitude 5.8. The density and accuracy of the velocities make it possible to better quantify several characteristics of the deformation in the Aegean, in particular: (a) the transition from the Anatolian domain, located in the south-east, to the European domain through the western end of the North Anatolian fault; (b) the north-south extension in the western Aegean; (c) the east-west extension of the western Peloponnese; (d) the clockwise rotation of the Pindos; (e) the north-south extension in central Macedonia. Large parts of the central Aegean, eastern Peloponnese and western Crete form a wide stable domain with internal deformation below 2 nstrain yr−1. We build a kinematic model comprising ten crustal blocks corresponding to areas where the velocities present homogeneous gradients. The block boundaries are set to fit with known localized deformation zones, e.g. the rift of Corinth, the North Anatolian fault, the Katouna fault. When the velocities steps are clear but not localized, e.g. through the Peloponnese, the boundary line is arbitrary and represents the transition zone. The model fits the velocities with a root mean square deviation of ± 0.9 mm yr−1. At the boundaries between blocks we compare the predicted and observed deformations. We find shear rates of 7.4 and 9.0 mm yr−1 along the Movri and Katouna faults, 14.9 and 8.7 mm yr−1 along the North Anatolian fault near Lemnos and near Skopelos respectively, extension of 7.6, 1.5 and 12.6 mm yr−1 across the Gulf of Patras, the Trichonis Lake and the Ambracian Gulf. The compression across western Epirus is 3.7 mm yr−1. There is a dextral transtensional movement of 4.5 mm yr−1 between the Amorgos and Astypalea islands. Only the Ionian Islands region shows evidence of coupling along the subduction interface.

SEM and TEM observations of sperm development in the testis of the freshwater fish Oreochromis mossambicus

1990 ◽  
Vol 48 (3) ◽  
pp. 58-59
Author(s):  
Daryl A. Cornish ◽  
George L. Smit
Keyword(s):  
Morphological Characteristics ◽  
Oreochromis Mossambicus ◽  
Breeding Cycle ◽  
Limited Information ◽  
North West ◽  
The North ◽  
Sem And Tem ◽  
Sperm Development ◽  
Ultrastructural Characteristics ◽  
The University

Oreochromis mossambicus is currently receiving much attention as a candidater species for aquaculture programs within Southern Africa. This has stimulated interest in its breeding cycle as well as the morphological characteristics of the gonads. Limited information is available on SEM and TEM observations of the male gonads. It is known that the testis of O. mossambicus is a paired, intra-abdominal structure of the lobular type, although further details of its characteristics are not known. Current investigations have shown that spermatids reach full maturity some two months after the female becomes gravid. Throughout the year, the testes contain spermatids at various stages of development although spermiogenesis appears to be maximal during November when spawning occurs. This paper describes the morphological and ultrastructural characteristics of the testes and spermatids.Specimens of this fish were collected at Syferkuil Dam, 8 km north- west of the University of the North over a twelve month period, sacrificed and the testes excised.

The North West Passage

2014 ◽  
Author(s):  
Roald Amundsen ◽  
Godfred Hansen
Keyword(s):  
North West ◽  
The North
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