Assessing the seismic hazards associated with one of the largest active thrust sheets: the case of the slowly deforming Western Kunlun mountain range (Xinjiang, China).

2020 ◽  
Author(s):  
Martine Simoes ◽  
Christelle Guilbaud ◽  
Jerome van der Woerd ◽  
Laurie Barrier ◽  
Roxane Tissandier ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Active Faults ◽  
Seismic Hazards ◽  
Spatial Gradient ◽  
Mountain Range ◽  
The Tibetan Plateau ◽  
Thrust Sheet ◽  
Fluvial Terraces ◽  
Western Kunlun ◽  
Mountain Front

<p><span lang="EN-US">The Western Kunlun Range (WKR) is a slowly converging orogen located along the northwestern edge of the Tibetan Plateau, facing the Tarim Basin. The recent Mw 6.4 2015 Pishan earthquake along the mountain front recalls that this region remains seismically active, despite little or moderate historical seismicity. Its low deformation rates can be hardly retrieved from current geodetic data, placing limited constraints on the potential interseismic loading of the region. This is particularly critical as recent structural investigations report the existence of an extremely wide (~150-180 km) frontal thrust sheet, whose dimensions would imply the possibility of major M ≥ 8 earthquakes in the case that it is locked and slips during one single seismic event.</span></p> <p><span lang="EN-US">To place further constraints on the seismic hazards of this region, we have conducted morphological and structural analyses of active faults to unravel the geomorphic record of active deformation cumulated other multiple seismic events at specific sites. To do so, field observations, seismic profiles and high-resolution Pléiades images and DEMs were combined together with the dating of fluvial terraces. We find that shortening rates have been of 0.5-2.5 mm/yr, with most probable values of ~2 mm/yr over the last ~300-500 kyr. Our detailed morphological investigations further indicate that this shortening is variably partitioned on one or several blind ramps along the mountain front, and from there is transmitted forward all the way to the deformation front, ~150-180 km further north. As such, this extremely wide single frontal thrust sheet stands most probably as the largest active thrust sheet in the world!</span></p> <p><span lang="EN-US">Finally, previously published GPS velocity fields highlight a 2-3 mm/yr gradient in horizontal velocities across the WKR and southern Tarim basin when combined and expressed in a stable Tarim reference. Such gradient, unseen from previous analyses, is consistent with our morphological results on shortening rates. Most importantly, this spatial gradient in velocities may suggest that the frontal thrust sheet is presently partly locked, questioning the possibility of mega-earthquakes in the region.</span></p>

Investigating lateral variations in the kinematics of active deformation along the Western Kunlun mountain front (Xinjiang, China): structural and morphological analysis of the Hotan anticline

2020 ◽  
Author(s):  
Christelle Guilbaud ◽  
Martine Simoes ◽  
Laurie Barrier ◽  
Jérôme Van der Woerd ◽  
Guillaume Baby ◽  
...  
Keyword(s):  
Morphological Analysis ◽  
Mountain Range ◽  
Thrust Sheet ◽  
Active Deformation ◽  
Fluvial Terraces ◽  
Structural Style ◽  
Western Kunlun ◽  
Mountain Front ◽  
Surface Geology ◽  
Lateral Variations

<p>The Western Kunlun Range is a mountain range located at the northwestern boundary of the Tibetan Plateau, facing the Tarim Basin. Our previous combined structural and morphological investigations of the mountain front, nearby the city of Pishan where a Mw 6.4 earthquake occurred in 2015, revealed the existence of a duplex uplifting Cenozoic strata, in which only the most frontal blind ramp is presently active and slips at a probable rate of 2 to 2.5 mm/yr. Located ~100 km further east along the mountain front, the Hotan anticline seems to present a different structure from surface geology, as older strata from Mesozoic and Paleozoic outcrop. Additionally, some authors proposed that the deformation would be here accommodated by a large blind basement thrust sheet, in clear contrast with the duplexes documented further west.</p><p>To further document potential lateral variations in the structural style and how they may affect the kinematics of active deformation along the mountain front of the Western Kunlun, we carry out a structural and morphological analysis of the Hotan anticline. We build structural cross-sections based on seismic reflection profiles, and calculate the incremental uplift recorded by dated fluvial terraces to quantify shortening rates over the last ~300 kyr. Our analysis reveals that a duplex structure, located below the basement thrust sheet, presently accommodates active deformation at a rate of 0.5 to 2.5 mm/yr, with a preferred rate of ~1.6 to 2.3 mm/yr. In more detail, uplifted terraces reveal that all ramps of the duplex are active in the case of the Hotan anticline, while only the most frontal ramp is documented as active in the case of the Pishan anticline further west. These results indicate that the style and rate of active shortening are rather homogeneous all along the mountain front, in contrast with the first impression provided by surface geology. Moreover, the discrepancy between surface geology and active morphology reveals progressive structural changes over geological times, from a blind basement ramp to duplexes. However, in the details, active deformation still remains segmented as its partitioning on the various ramps of the duplexes is variable along strike.</p>

scholarly journals Kinematics of Active Deformation Across the Western Kunlun Mountain Range (Xinjiang, China) and Potential Seismic Hazards Within the Southern Tarim Basin

2017 ◽  
Vol 122 (12) ◽  
pp. 10,398-10,426 ◽  
Author(s):  
Christelle Guilbaud ◽  
Martine Simoes ◽  
Laurie Barrier ◽  
Amandine Laborde ◽  
Jérôme Van der Woerd ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Seismic Hazards ◽  
Mountain Range ◽  
Active Deformation ◽  
Kunlun Mountain ◽  
Western Kunlun

Kinematics of Cenozoic shortening across the foothills of the Western Kunlun Range (Xinjiang, China): the case of the Hotan anticline

2021 ◽  
Author(s):  
Guillaume Baby ◽  
Martine Simoes ◽  
Laurie Barrier ◽  
Christelle Guilbaud ◽  
Jérôme Van der Woerd ◽  
...  
Keyword(s):  
Cross Sections ◽  
Large Scale ◽  
The Tibetan Plateau ◽  
Seismic Profiles ◽  
Growth Strata ◽  
Subsequent Decrease ◽  
Western Kunlun ◽  
Mountain Front ◽  
Shortening Rate ◽  
Seismic Reflectors

<p>Quantitative constraints on the Cenozoic deformation of the northwestern edge of the Tibetan Plateau remain limited, in particular in terms of shortening rates and of their possible evolution over time. This is indeed the case for the Western Kunlun Range, along the southwestern rim of the Tarim Basin, even though surface geological data and an extensive database of seismic profiles allow to explore the sedimentary record of Cenozoic deformation. Here, we take advantage of these data to document the structural geometry and Cenozoic kinematics of the large scale east-west striking Hotan anticline along the mountain front. Four balanced cross-sections are constructed, and the temporal evolution of deformation is deciphered from the exceptionally seismically well imaged growth strata on the forelimb of the anticline.</p><p>The fold results from a broad unfaulted basement ramp anticline, subsequently deformed by a duplex structure that developed in the footwall units. The total shortening of the Hotan thrust system is relatively constant along strike, from ~40 to ~32 km. The shortening accommodated by the duplex varies laterally from west to east, from ~50-40 % to 0 % of the total shortening. </p><p>Two distinct successive patterns of growth strata are recognised in the forelimb, and are interpreted to be representative of deformation on the basement ramp, followed by deformation related to the growth of the underlying duplex. Deformation on the basement ramp initiated by ~17 Ma, when calibrating growth seismic reflectors on surface magnetostratigraphic sections. Deformation of the underlying duplex began at ~12 Ma to the west and subsequently propagated eastward.</p><p>From these results on shortening and timing of deformation, we determine a shortening rate of 4-3 mm/yr from ~17 to ~7 Ma across the Hotan anticline. We find a significant subsequent decrease in shortening rates, possibly down to <0.5 mm/yr since the uppermost Miocene. These rates are compared to existing values and their regional significance is discussed.</p>

Quantifying active deformation within the Southwestern Foothills of Taiwan, from incised fluvial terraces and sedimentary data

2020 ◽  
Author(s):  
Philippe Steer ◽  
Valentine Lefils ◽  
Martine Simoes ◽  
J. Bruce H. Shyu ◽  
Magali Rizza ◽  
...  
Keyword(s):  
Coastal Plain ◽  
Active Faults ◽  
Active Regions ◽  
Sedimentary Facies ◽  
Tectonic Uplift ◽  
Mountain Range ◽  
Active Deformation ◽  
Fluvial Terraces ◽  
Base Level ◽  
Shortening Rate

<p>The Taiwan mountain range stands as one of the most active regions on Earth. With an overall shortening rate of ~40 mm/yr and an average erosion rate of ~4 mm/yr, this mountain range appears ideal to better understand the interactions between tectonics and surface processes, and how these shape active landscapes. Here we explore the geomorphic and sedimentary record of active deformation within the Southwestern Foothills of Taiwan, and we quantify from there the kinematics of active faults. In particular, we investigate the downstream portion of the meandering Tsengwen river - one of the largest rivers of this region - where we identify and correlate remnants of 7 terrace levels, progressively abandoned over the last ~5 kyr. The incision of these terraces is interpreted as being controlled to the first-order by folding and uplift related to underlying active faults. The evolution of the river is reconstructed from correlated terrace remnants, and our results indicate that the overall river sinuosity and gradient did not vary significantly during the past ~5 kyr in response to tectonics. Incremental tectonic uplift is retrieved from terrace incision corrected for sedimentation at the mountain front, and is used to derive the incremental shortening since terrace abandonment. Downstream, within the Coastal Plain, the Tsengwen river reaches its base level and aggrades. Sedimentary facies within boreholes of the Coastal Plain record vertical displacements relative to sea level, spatially consistent with potential blind active faults. When corrected for eustatic variations, these data allow for quantifying tectonic uplift rates within the Coastal Plain over the last ~20 kyr. Taken altogether, our quantitative analysis of the Tsengwen river record, from terrace incision to dowsntream aggradation, reveals that the most frontal active faults absorb a shortening rate of at least ~35 mm/yr, that is most of - if not all -  the shortening rate to the absorbed across the whole mountain range.</p>

scholarly journals Atmospheric brown clouds reach the Tibetan Plateau by crossing the Himalayas

2015 ◽  
Vol 15 (11) ◽  
pp. 6007-6021 ◽  
Author(s):  
Z. L. Lüthi ◽  
B. Škerlak ◽  
S.-W. Kim ◽  
A. Lauer ◽  
A. Mues ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Weather Prediction ◽  
Mountain Range ◽  
The Tibetan Plateau ◽  
Pollution Transport ◽  
Synoptic Scale ◽  
Gangetic Plain ◽  
Dark Light ◽  
Air Masses ◽  
Pollution Episode

Abstract. The Himalayas and the Tibetan Plateau region (HTP), despite being a remote and sparsely populated area, is regularly exposed to polluted air masses with significant amounts of aerosols including black carbon. These dark, light-absorbing particles are known to exert a great melting potential on mountain cryospheric reservoirs through albedo reduction and radiative forcing. This study combines ground-based and satellite remote sensing data to identify a severe aerosol pollution episode observed simultaneously in central Tibet and on the southern side of the Himalayas during 13–19 March 2009 (pre-monsoon). Trajectory calculations based on the high-resolution numerical weather prediction model COSMO are used to locate the source regions and study the mechanisms of pollution transport in the complex topography of the HTP. We detail how polluted air masses from an atmospheric brown cloud (ABC) over South Asia reach the Tibetan Plateau within a few days. Lifting and advection of polluted air masses over the great mountain range is enabled by a combination of synoptic-scale and local meteorological processes. During the days prior to the event, winds over the Indo-Gangetic Plain (IGP) are generally weak at lower levels, allowing for accumulation of pollutants and thus the formation of ABCs. The subsequent passing of synoptic-scale troughs leads to southwesterly flow in the middle troposphere over northern and central India, carrying the polluted air masses across the Himalayas. As the IGP is known to be a hotspot of ABCs, the cross-Himalayan transport of polluted air masses may have serious implications for the cryosphere in the HTP and impact climate on regional to global scales. Since the current study focuses on one particularly strong pollution episode, quantifying the frequency and magnitude of similar events in a climatological study is required to assess the total impact.

scholarly journals Μορφοτεκτονική μελέτη της ευρύτερης περιοχής Θεσ/νίκης για τη χαρτογράφηση νεοτεκτονικών ρηγμάτων.

2005 ◽  
Vol 38 ◽  
pp. 30 ◽  
Author(s):  
Α. ΖΕΡΒΟΠΟΥΛΟΥ ◽  
Σ. ΠΑΥΛΙΔΗΣ
Keyword(s):  
Drainage Basin ◽  
Digital Elevation Models ◽  
Active Faults ◽  
Gradient Index ◽  
Stream Length ◽  
Drainage Patterns ◽  
Digital Elevation ◽  
Mountain Front ◽  
Morphotectonic Indices

At this paper studied the neotectonic active faults of the broader area of Thessaloniki with morphotectonic criteria. We have studied three main faults of Anthemounta, Asvestophori and Pylaia - Panorama with the contribution of cartography, digital elevation models, drainage patterns, and the morphotectonic indices like drainage basin asymmetry, mountain front sinuosity, knick points and stream length-gradient index. Those faults show elements of activity.

Elevation of the Gangdese Mountains and Their Simulated Impacts on Asian Climate during the Late Cretaceous

2021 ◽  
Author(s):  
Jian Zhang ◽  
Yonggang Liu ◽  
Xiaomin Fang ◽  
Tao Zhang ◽  
Chenguang Zhu ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Early Stage ◽  
Aridity Index ◽  
Mountain Range ◽  
The Tibetan Plateau ◽  
Dry Land ◽  
Climate Indicators ◽  
Community Earth System Model ◽  
Paleoenvironmental Evolution ◽  
High Topography

<p>The Tibetan Plateau has a significant impact on the Asian climate due to its high topography. However, its uplift history, especially the uplift of the Gangdese Mountains in its early stage, is under intense debate. Most quantitative reconstructions are done for the Cenozoic only, impeding our understanding of the geodynamic and paleoenvironmental evolution during the Cretaceous. How high would the Gangdese Mountains be then, and what effects would they have on Asian climate? In order to explore these two questions, here we model the impacts of the Gangdese Mountains on the Asian climate during the Late Cretaceous by employing the Community Earth System Model version 1.2.2. It is found that the extent of dry land in East Asia is sensitive to the altitude of the Gangdese Mountains; it expands eastwards and southwards with the rise of the mountain range, which is due to the fact that the Gangdese Mountains can significantly reduce the precipitation over the low- to mid-latitude Asia. We then attempt to constrain their paleoaltitude using the available climate indicators in the sediments. The aridity index is further calculated for this region, and its comparison with the climate records suggests that Gangdese Mountains should be higher than 1 km but lower than 3 km during the Late Cretaceous, most likely ~2 km.</p>

scholarly journals Summer Atmospheric Heat Sources over the Western–Central Tibetan Plateau: An Integrated Analysis of Multiple Reanalysis and Satellite Datasets

2019 ◽  
Vol 32 (4) ◽  
pp. 1181-1202 ◽  
Author(s):  
Zhiling Xie ◽  
Bin Wang
Keyword(s):  
Tibetan Plateau ◽  
Integrated Analysis ◽  
Mountain Range ◽  
The Tibetan Plateau ◽  
Heat Sources ◽  
Central Tibetan Plateau ◽  
New Finding ◽  
Highly Correlated ◽  
Atmospheric Heat ◽  
Heat Released

Multiple bias-corrected top-quality reanalysis datasets, gauge-based observations, and selected satellite products are synthetically employed to revisit the climatology and variability of the summer atmospheric heat sources over the Tibetan Plateau (TP). Verification-based selection and ensemble-mean methods are utilized to combine various datasets. Different from previous works, this study pays special attention to estimating the total heat source (TH) and its components over the data-void western plateau (70°–85°E), including the surface sensible heat (SH), latent heat released by precipitation (LH), and net radiation flux (RD). Consistent with previous studies, the climatology of summer SH (LH) typically increases (decreases) from southeast to northwest. Generally, LH dominates TH over most of the TP. A notable new finding is a minimum TH area over the high-altitude region of the northwestern TP, where the Karakoram mountain range is located. We find that during the period of 1984–2006, TH shows insignificant trends over the eastern and central TP, whereas it exhibits an evident increasing trend over the western TP that is attributed to the rising tendency of LH before 1996 and to that of RD after 1996. The year-to-year variation of TH over the central–eastern TP is highly correlated with that of LH, but that is not the case over the western TP. It is also worth noting that the variations of TH in each summer month are not significantly correlated with each other, and hence study of the interannual variation of the TP heat sources should consider the remarkable subseasonal variations.

scholarly journals Onset of permanent Taklimakan Desert linked to the mid-Pleistocene transition

Geology ◽  
2020 ◽  
Vol 48 (8) ◽  
pp. 782-786
Author(s):  
Weiguo Liu ◽  
Zhonghui Liu ◽  
Jimin Sun ◽  
Chunhui Song ◽  
Hong Chang ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Sand Dunes ◽  
Western China ◽  
Taklimakan Desert ◽  
The Tibetan Plateau ◽  
Mountain Glaciers ◽  
Long Period ◽  
Carbonate Carbon ◽  
Eolian Sand ◽  
Desert Landscape

Abstract The initial occurrence of desert landscape or eolian sand dunes is thought to have occurred long before the Pleistocene, and desertification was subsequently enhanced under cold, dusty glacial conditions. However, when and how the desert landscape persisted during both glacial and interglacial periods, defined as “permanent” desert here, remain elusive. Here, we present carbonate carbon isotope and grain-size records from the Tarim Basin, western China, revealing a detailed desertification history for the Taklimakan Desert. Our records demonstrate that after desiccation of episodic lakes at ca. 4.9 Ma, alternations of eolian sand dunes and fluvial and playa-like conditions persisted for a long period until 0.7 Ma in the Tarim Basin. The onset of permanent desert landscape around 0.7–0.5 Ma occurred concurrently with the climatic reorganization across the mid-Pleistocene transition. The occurrence of mountain glaciers on the Tibetan Plateau and atmospheric circulation changes may have controlled the formation and extreme aridification of the permanent desert in inland Asia since the mid-Pleistocene transition.

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