scholarly journals Moho beneath Tibet based on a joint analysis of gravity and seismic data

2020 ◽  
Author(s):  
Guangdong Zhao ◽  
Jianxin Liu ◽  
Bo Chen ◽  
Mikhail K. Kaban
Keyword(s):  
Tibetan Plateau ◽  
Gravity Field ◽  
Tarim Basin ◽  
Plate Tectonics ◽  
Moho Depth ◽  
Joint Analysis ◽  
Gravity Inversion ◽  
The Tibetan Plateau ◽  
Gravity Effects ◽  
Moho Depths

<p>The Tibetan Plateau, known as the roof of the Earth, is considered as the “Golden Key” for understanding plate tectonics, continental collisions and continental orogenic formation. A reliable Moho structure is also vital for understanding the deformation mechanism of the Tibetan Plateau.</p><p>In this study, we use improved Parker−Oldenburg’s formulas that include a reference depth into the exponential term and employ a Gauss-FFT method to determine Moho depths beneath the Tibetan Plateau. The synthetic models demonstrate that the improved Parker’s formula has higher accuracy with the maximum absolute error less than 0.25 mGal.</p><p>Two inversion parameters, namely the reference depth and the density contrast are essential for the Moho estimation based on the gravity field, and they need to be determined in advance to obtain correct results. Therefore, the Moho estimates derived from existing seismic studies (Stolk et al., 2013) are used to reduce the non-uniqueness of the gravity inversion and to determine these parameters by searching for the maximum correlation between the gravity-inverted and seismic-derived Moho depths.</p><p>Another critical issue is to remove beforehand the gravity effects of other factors, which affect the observed gravity field. In addition to the topography, the gravity effects of the sedimentary layer and crystalline crust are removed based on existing crustal models, while the upper mantle impact is determined based on the seismic tomography model.</p><p>The inversion results show that the Moho structure under the Tibetan plateau is very complex with the depths varying from about 30 ~ 40 km in the surrounding basins (e.g., the Ganges basin, the Sichuan basin, and the Tarim basin) to 60 ~ 80 km within the plateau. This considerable difference up to 40 km on the Moho depth reveals the substantial uplift and thickening of the crust in the Tibetan Plateau.</p><p>Furthermore, two visible “Moho depression belts” are observed within the plateau with the maximum Moho deepening along the Indus-Tsangpo Suture and along the northern margin of Tibet bounding the Tarim basin with the relatively shallow Moho in central Tibet between them. The southern “belt” is likely formed in compressional environment, where the Indian plate underthrusts northwards beneath the Tibetan Plateau, while the northern one could be formed by the southward underthrust of the Asian lithosphere beneath Tibet.</p><p>Stolk, W., Kaban, M., Beekman, F., Tesauro, M., Mooney, W. D., & Cloetingh, S. (2013). High resolution regional crustal models from irregularly distributed data: Application to Asia and adjacent areas. Tectonophysics, 602, 55-68. https://doi.org/10.1016/j.tecto.2013.01.022</p>

scholarly journals Isostatic Crustal Thickness Under The Tibetan Plateau And Himalayas From Satellite Gravity Gradiometry Data

2015 ◽  
Vol 19 (2) ◽  
pp. 97-106 ◽  
Author(s):  
Robert Tenzer ◽  
Mohammad Bagherbandi ◽  
Lars E Sjöberg ◽  
Pavel Novák
Keyword(s):  
Tibetan Plateau ◽  
Spherical Harmonic ◽  
Crustal Thickness ◽  
Moho Depth ◽  
Gravity Gradient ◽  
The Tibetan Plateau ◽  
Systematic Bias ◽  
Font Size ◽  
Isostatic Gravity ◽  
Vening Meinesz

<p>The global gravity and crustal models are used in this study to determine the regional Moho model. For this </span><span style="font-size: 9.000000pt; font-family: 'TimesNewRomanPSMT';">purpose, we solve the Vening Meinesz-Moritz’s (VMM) inverse problem of isostasy de ned in terms of the </span><span style="font-size: 9.000000pt; font-family: 'TimesNewRomanPSMT';">isostatic gravity gradient. The functional relation between the Moho depth and the second-order radial derivative </span><span style="font-size: 9.000000pt; font-family: 'TimesNewRomanPSMT';">of the VMM isostatic potential is formulated by means of the (linearized) Fredholm integral equation of the rst kind. Methods for a spherical harmonic analysis and synthesis of the gravity eld and crustal structure models </span><span style="font-size: 9.000000pt; font-family: 'TimesNewRomanPSMT';">are applied to evaluate the gravity gradient corrections and the respective corrected gravity gradient, taking into consideration major known density structures within the Earth’s crust (while mantle heterogeneities are disregarded). The resulting gravity gradient is compensated isostatically based on applying the VMM scheme. The VMM inverse </span><span style="font-size: 9.000000pt; font-family: 'TimesNewRomanPSMT';">problem for finding the Moho depths is solved iteratively. The regularization is applied to stabilize the ill-posed </span><span style="font-size: 9.000000pt; font-family: 'TimesNewRomanPSMT';">solution. The global geopotential model GOCO-03s, the global topographic/bathymetric model DTM2006.0 and the global crustal model CRUST1.0 are used to generate the VMM isostatic gravity gradient with a spectral resolution complete to a spherical harmonic degree of 250. The VMM inverse scheme is used to determine the regional isostatic crustal thickness beneath the Tibetan Plateau and Himalayas (compiled on a 1x1 arc-deg grid). The differences between the isostatic and seismic Moho models are modeled and subsequently corrected for by applying the non-isostatic correction. Our results show that the regional gravity gradient inversion can model realistically the relative Moho geometry, while the solution contains a systematic bias. We explain this bias by more localized </span><span style="font-size: 9.000000pt; font-family: 'TimesNewRomanPSMT';">information on the Earth’s inner structure in the gravity gradient eld compared to the potential or gravity fields. </span></p><p><span style="font-size: 9.000000pt; font-family: 'TimesNewRomanPSMT';"><br /></span></p><p><span style="text-decoration: underline;"><strong><span style="font-family: TimesNewRomanPSMT; font-size: 11pt;">Espesor isostático de la corteza bajo la meseta tibetana y los Himalayas a partir de datos satelitales de gradiente gravitatoria </span></strong></span></p><p><span style="font-family: TimesNewRomanPSMT; font-size: 11pt;"><br /></span></p><p><strong><span style="font-family: TimesNewRomanPSMT; font-size: 11pt;">Resumen</span></strong></p><p><span style="font-family: TimesNewRomanPSMT;"><span style="font-size: 14.6667px;">Este estudio utiliza los modelos globales de gravedad y de espesor de la corteza para determinar un modelo regional de la discontinuidad de Mohorovičić (Moho). Con este  fin se resolvió el problema inverso de isostasia Vening Meinesz-Moritz (VMM) de nido en términos de gradiente gravitatoria isostática. La relación funcional entre la profundidad de la Moho y la derivación radial de segundo orden del potencial isostático VMM fue formulado a través de la ecuación integral Fredholm de primera clase. Se aplicaron métodos para el análisis esférico armónico y para la síntesis del campo gravitacional, y los modelos de estructura de corteza para evaluar las correcciones de gradiente gravitatoria y el respectivo gradiente gravitatorio corregido, considerando el conocimiento de las principales densidades de la estructura al interior de la corteza de la Tierra (las heterogenidades del manto fueron ignoradas). El gradiente gravitatorio resultante se compensó isostáticamente con la aplicación del esquema VVM. Se resolvió reiterativamente el problema inverso VVM para encontrar las profundidades de la discontinuidad Moho. Se aplicó la regularización para estabilizar la solución planteada. El modelo geopotencial global GOCO-03s, el modelo global topográfico/batimetrico DTM2006.0 y el modelo global de la corteza CRUST 1.0 permitieron generar el gradiente gravitacional isostático VVM con una resolución espectral completa a un grado esférico armonioso de 250. A través del esquema inverso VMM se determinó el espesor isostático regional bajo la meseta Tibetana y los Himalayas (compilada en una cuadrícula de 1x1 grados sexagesimales). Las diferencias entre los modelos isostático y sísmico de la Moho fueron modeladas y corregidas con la aplicación de la corrección no isostática. Los resultados muestran que la inversión del gradiente gravitatorio puede modelar realísticamente la geometría de la Moho, a pesar que la solución contiene una desviación sistemática. Esta inclinación se explica por la información estructural interna de la Tierra en el campo del gradiente gravitatorio comparado con el potencial gravitatorio.</p>

Modelling the Moho depth and Flexure parameters across the Indo-Burma subduction zone.

2021 ◽  
Author(s):  
Anirban Biswas ◽  
Srinivasa Rao Gangumalla
Keyword(s):  
Subduction Zone ◽  
Ocean Circulation ◽  
Active Regions ◽  
Indian Plate ◽  
Moho Depth ◽  
Gravity Inversion ◽  
Stress Regime ◽  
Moho Interface ◽  
Moho Depths ◽  
Vertical Gravity

&lt;p&gt;Indo-Burma subduction zone is one of the seismically active regions in India where the Indian plate is underthrusting the Burmese arc. However, the nature of the slab subduction in this region and its associated stress-regime are less understood due to the lack of deep crustal information. In the present study, we analyze the vertical gravity component of the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) and topography data to model the Moho depth interface and flexure parameters of the Indo-Burmese subduction region. Here, Moho depths are obtained by performing the non-linear gravity inversion using tesseroids in spherical coordinates. It is observed that the Moho interface in the Bay of Bengal (Indian plate) lies at a depth of 20-30 km and then deepens to a depth of 50-60 km towards the Burmese region. Beneath the Shan Plateau, Moho depth varies gently from 35 to 40 km and shows an eastward dip at Sagaing fault.&amp;#160; We also constructed eight profiles across the subduction zone to model the flexure parameters such as effective elastic thickness (Te), forebulge, and bending moments (Mo). The modelling results indicate that both Te (15-55 km) and Mo (1.12&amp;#215;10-19 to 2.84&amp;#215;10-19 N.m) values vary significantly along the subduction zone and show correlation with slab depth. Larger values of Te (55 km) and Mo (2.84&amp;#215;10-19 N.m) are noticed in the central Indo-Burmese subduction zone, where the slab depth is around 110-120 km. Whereas the lowest values of Te (15 km) and Mo (1.12&amp;#215;10-19 N.m) are inferred for the profiles lying in the southern Indo-Burmese subduction.&lt;/p&gt;

Geophysical subsurface modelling based on the updated, enhanced regional gravity field solution in Antarctica

2021 ◽  
Author(s):  
Theresa Schaller ◽  
Mirko Scheinert ◽  
Philipp Zingerle ◽  
Roland Pail ◽  
Martin Willberg
Keyword(s):  
Gravity Field ◽  
Gravity Data ◽  
Average Density ◽  
Weddell Sea ◽  
Moho Depth ◽  
Gravity Inversion ◽  
Satellite Gravity ◽  
German Research Foundation ◽  
Field Solution ◽  
Gravity Disturbances

&lt;p&gt;The gravity field reflects mass inhomogeneities (mostly) inside the Earth. Therefore, gravity inversion and geophysical gravity field modelling are important tools to study the Earth's inner structure and tectonic evolution. In Antarctica, it is extremely challenging to carry out geoscientific studies due to its harsh environment and difficult logistics. Additionally, the continent is covered by an up to 5 km thick ice sheet. However, in the framework of IAG Subcommission 2.4f &amp;#8220;Gravity and Geoid in Antarctica&amp;#8221; (AntGG) a large database of airborne, shipborne and ground based gravity data has been compiled. Especially airborne data have been acquired during recent years, among others in the area of the polar gap of satellite gravity data. Now, in a joint project funded by the German Research Foundation (DFG) all existing and new gravity data were processed to infer an enhanced gravity field solution for Antarctica (see contribution by Scheinert et al., session G1.5). Processed data e.g. gravity disturbances on the ground or a constant height and other functionals will be provided on a regular grid with 5 km grid spacing. Subsequently, the new Antarctic gravity field solution can now be used for further geophysical and tectonic studies. We use the newly calculated gravity disturbances to study subglacial topography, sediment thickness and Moho depth and to improve respective existing models in Antarctica. For this, we apply 2D Parker-Oldenburg inversion in combination with results from other gravity based studies and further constraining data (e.g. seismic data and ice penetrating radar). We investigate how the higher resolution (5 km) of the new Antarctic gravity field solution facilitates the study of smaller regions in more detail, specifically parts of Wilkes Land, Dronning Maud Land and the Weddell Sea. Additionally, we will infer accuracy estimates for the resulting boundaries in terms of the used inversion parameters (density contrast, average density and filter wavelengths) and their respective gravity signal. Thus, the challenges of gravity field inversion in Antarctica will be discussed in detail and first results of the subsurface modelling will be presented.&lt;/p&gt;

Spring Dust Mass Flux over the Tibetan Plateau during 2007–19 and Connections with North Atlantic SST Variability

2020 ◽  
Vol 33 (22) ◽  
pp. 9691-9703
Author(s):  
Chao Xu ◽  
Yaoming Ma ◽  
Jiehua Ma ◽  
Chao You ◽  
Huijun Wang
Keyword(s):  
Tibetan Plateau ◽  
North Atlantic ◽  
Tarim Basin ◽  
Mass Flux ◽  
The Tibetan Plateau ◽  
Indian Peninsula ◽  
The North ◽  
Dust Mass ◽  
The North Atlantic ◽  
Spring Dust

AbstractDust is the major aerosol type over the Tibetan Plateau (TP), and the TP plays an important role in forming the spring dust belt across the Northern Hemisphere in the upper troposphere. Estimated spring dust mass flux (DMF) showed a significant declining trend over the TP during 2007–19. The total spring DMF across the TP (TDMFTP) was mainly affected by DMFs over the Tarim Basin, while the spring DMF across the TP in the midtroposphere was also connected with DMFs over the northwest Indian Peninsula and central Asia. Interannual variability of spring TDMFTP was strongly correlated with the North Atlantic winter sea surface temperature (SST) tripole. A cold preceding winter induced by the North Atlantic winter SST tripole over midlatitude Eurasia promotes dust activities in the subsequent spring. The North Atlantic winter SST tripole anomalies persist into the subsequent spring and induce a corresponding atmosphere response. Enhanced atmospheric baroclinicity develops over northwest China and the northern Indian Peninsula during spring, which is attributed to surface thermal forcing induced by the positive winter SST tripole phase. A strong positive North Atlantic winter SST tripole anomaly strengthens the upper-level westerly jets, enhancing airflow toward the TP midtroposphere; together, these circulation patterns cause anomalous cyclonic conditions in the lower troposphere, especially over the Tarim Basin, via the eastward propagation of a Rossby wave train. These atmospheric circulation conditions are likely to increase the frequency of dust occurrence and promote the transport of dust onto the TP.

The impacts of the summer plateau monsoon over the Tibetan Plateau on the rainfall in the Tarim Basin, China

2015 ◽  
Vol 126 (1-2) ◽  
pp. 265-272 ◽  
Author(s):  
Yong Zhao ◽  
Anning Huang ◽  
Yang Zhou ◽  
Qing Yang
Keyword(s):  
Tibetan Plateau ◽  
Tarim Basin ◽  
The Tibetan Plateau

scholarly journals GNSS Imaging of Strain Rate Changes and Vertical Crustal Motions over the Tibetan Plateau

2021 ◽  
Vol 13 (23) ◽  
pp. 4937
Author(s):  
Yunfei Xiang ◽  
Hao Wang ◽  
Yuanyuan Chen ◽  
Yin Xing
Keyword(s):  
Tibetan Plateau ◽  
Strain Rate ◽  
Tarim Basin ◽  
Three Dimensional ◽  
Indian Plate ◽  
The Tibetan Plateau ◽  
Eurasian Plate ◽  
Himalayan Belt ◽  
Low Altitude ◽  
Main Factor

In this paper, we perform a comprehensive analysis of contemporary three-dimensional crustal deformations over the Tibetan Plateau. Considering that the coverage of continuous GNSS sites in the Tibetan Plateau is sparse, a newly designed method that mainly contains Spatial Structure Function (SSF) construction and Median Spatial Filtering (MSF) is adopted to conduct GNSS imaging of point-wise velocities, which can well reveal the spatial pattern of vertical crustal motions. The result illustrates that the Himalayan belt bordering Nepal appears significant uplift at the rates of ~3.5 mm/yr, while the low-altitude regions of Nepal and Bhutan near the Tibetan Plateau are undergoing subsidence. The result suggests that the subduction of the Indian plate is the driving force of the uplift and subsidence in the Himalayan belt and its adjacent regions. Similarly, the thrusting of the Tarim Basin is the main factor of the slight uplift and subsidence in the Tianshan Mountains and Tarim Basin, respectively. In addition, we estimate the strain rate changes over the Tibetan Plateau using high-resolution GNSS horizontal velocities. The result indicates that the Himalayan belt and southeastern Tibetan Plateau have accumulated a large amount of strain rate due to the Indian-Eurasian plate collision and blockage of the South China block, respectively.

scholarly journals In-situ observation of warm atmospheric layer and the contribution of suspended dusts over the Tarim Basin

2021 ◽  
Author(s):  
Chenglong Zhou ◽  
Yuzhi Liu ◽  
Qingzhe Zhu ◽  
Qing He ◽  
Tianliang Zhao ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Heat Source ◽  
Tarim Basin ◽  
Regional Climate ◽  
Dust Particles ◽  
Taklimakan Desert ◽  
In Situ Observation ◽  
Average Intensity ◽  
The Tibetan Plateau ◽  
Atmospheric Layer

Abstract. Basing on the radiosonde observations in the spring and summer during 2016–2017, an anomalous warm atmospheric layer is verified and the contribution of suspended dusts over the Tarim Basin (TB) is quantified. The result indicates a warm atmospheric layer between 300 hPa and 500 hPa with an average intensity of 2.53 K and 1.39 K in the spring and summer, respectively. Over the TB, where the world’s second largest moving desert, the Taklimakan Desert (TD) is distributed, large amounts of dust particles are emitted from the TD and suspended over the TB. Using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data, we found the dusts can be lifted to the upper atmospheric layer between 2.5 and 5.5 km above mean sea level over the TB. Consequently, the suspended dusts can exert a maximum heating effect of approximately +0.45 K and +0.25 K in spring and summer, respectively. The contribution of dust heating to the anomalous warm atmospheric layer over the TB is 13.77 % and 10.25 % in spring and summer, respectively. In view of the topographical feature, the TB is adjacent to the Tibetan Plateau (TP) which acts as an elevated heat source in spring and summer. The warm atmospheric layer over the TB seems a northward extension of Tibet heat source, the concept of which is proposed in this study. Such a northward extension of the elevated heating by the Tibetan Plateau could induce some profound impacts on the regional climate, especially on the western section of the “Silk Road Economic Belt”, and therefore demands more attention.

scholarly journals Physical Mechanisms of Summer Precipitation Variations in the Tarim Basin in Northwestern China

2015 ◽  
Vol 28 (9) ◽  
pp. 3579-3591 ◽  
Author(s):  
Wei Huang ◽  
Song Feng ◽  
Jianhui Chen ◽  
Fahu Chen
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
Central Asia ◽  
Tarim Basin ◽  
Arabian Sea ◽  
Summer Precipitation ◽  
Teleconnection Pattern ◽  
Central China ◽  
Northwestern China ◽  
The Tibetan Plateau

Abstract The Tarim basin (TB) in northwestern China is one of the most arid regions in the middle latitudes, where water is scarce year-round. This study investigates the variations of summer precipitation in the TB and their association with water vapor fluxes and atmospheric circulation. The results suggest that the variations of summer precipitation in the TB are dominated by the water vapor fluxes from the south and east, although the long-term mean water vapor mostly comes from the west. The anomalous water vapor fluxes are closely associated with the meridional teleconnection pattern around 50°–80°E and the zonal teleconnection pattern along the Asian westerly jet in summer. The meridional teleconnection connects central Asia and the tropical Indian Ocean; the zonal teleconnection resembles the “Silk Road pattern.” The two teleconnections lead to negative height anomalies in central Asia and positive height anomalies in the Arabian Sea and India and in northern central China. The anomalous pressure gradient force, caused by these height anomalies, leads to anomalous ascending motion in the TB and brings low-level moisture along the eastern periphery of the Tibetan Plateau and water vapor from the Arabian Sea passing over the Tibetan Plateau to influence precipitation development in the study region.

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