Global electromagnetic induction constraints on transition-zone water content variations

Nature ◽  
2009 ◽  
Vol 460 (7258) ◽  
pp. 1003-1006 ◽  
Author(s):  
Anna Kelbert ◽  
Adam Schultz ◽  
Gary Egbert
Keyword(s):  
Water Content ◽  
Transition Zone ◽  
Electromagnetic Induction ◽  
Zone Water

Predicting seed-zone water content for summer fallow in the Inland Pacific Northwest, USA

2011 ◽  
Vol 115-116 ◽  
pp. 94-104 ◽  
Author(s):  
Prabhakar Singh ◽  
Markus Flury ◽  
William F. Schillinger
Keyword(s):  
Water Content ◽  
Pacific Northwest ◽  
Seed Zone ◽  
Summer Fallow ◽  
Zone Water

Determination of water content in drying soils: incorporating transition from liquid phase to vapour phase

Soil Research ◽  
2004 ◽  
Vol 42 (1) ◽  
pp. 1 ◽  
Author(s):  
F. Konukcu ◽  
A. Istanbulluoglu ◽  
I. Kocaman
Keyword(s):  
Water Content ◽  
Transition Zone ◽  
Sandy Loam ◽  
Vapour Phase ◽  
Coarse Sand ◽  
Arid Environments ◽  
Evaporation Front ◽  
Matric Potential ◽  
Silty Loam

In arid and semi-arid environments, soil profiles often exhibit a liquid–vapour displacement known as evaporation front characterised by a critical matric potential (ψme) or water content (θe) located somewhere inside the unsaturated zone above a watertable (WT). The objective of this study was to determine the θe including the range of water content (θ) in the transition zone from liquid to vapour both theoretically and experimentally for different soil textures under saline and non-saline WTs. Characteristic shapes of water content and salt concentration profiles were the criteria to obtain θe experimentally, and the θ–diffusivity relationship was used to compute the θe and θ range in the transition zone. Measured θe values of 0.05 and 0.12 m3/m3 under non-saline WT and 0.07 and 0.15 m3/m3 under saline WT were in agreement with the computed values of 0.05 and 0.10 m3/m3 for sandy loam and clay loam soils, respectively. The model calculates roughly the same θe for saline and non-saline conditions. Besides experimental soils, θe and range of θ in the transition zone were calculated for silty loam and coarse sand. The lighter the soil texture, the smaller is θe and the steeper the transition zone. The results were further compared with those calculated by different authors.

Electrical conductivity in the mantle transition zone beneath Eastern China derived from L1-Norm C-responses

2020 ◽  
Vol 221 (2) ◽  
pp. 1110-1124 ◽  
Author(s):  
Yanhui Zhang ◽  
Aihua Weng ◽  
Shiwen Li ◽  
Yue Yang ◽  
Yu Tang ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Objective Function ◽  
Water Content ◽  
Transition Zone ◽  
Regularization Parameter ◽  
Eastern China ◽  
Bfgs Method ◽  
L1 Norm ◽  
Mantle Transition Zone ◽  
Dehydration Reactions

SUMMARY Constraining the distribution of water in different regions of the mantle remains one of the significant challenges to comprehend the global deep water cycle. Geomagnetic depth soundings can provide such constraint through the electrical conductivity structure. Hence, this study aims to propose a regularization technique that can estimate previously unavailable C-response. In the method, the objective function comprised an L1-norm measured data prediction error and a spectral smoothness constraint term. We used the data error of C-response to weight the predicted error. The L-BFGS method was introduced to determine the minimum point of the objective function, and the regularization parameter decreased adaptively during inversion. Thus, the geomagnetic data processed yielded high-quality C-responses in 31 stations in Eastern China. In addition, we obtained 1-D electrical conductivity profiles in the mantle transition zone (MTZ) beneath Eastern China from C-responses using the L-BFGS method. Compared with the global 1-D model, the conductivity–depth profiles revealed that the MTZ beneath Eastern China is more conductive in the east but more resistive in the west. The conversion of these conductivities to water content based on the mineral physics suggested that the MTZ beneath Eastern China is characterized by a high water concentration, approximately 0.2 and 1 wt per cent in the upper and lower MTZ, respectively. Owing to the inclusion of more stations, the water-rich region could be constrained roughly to the east of the North–South Gravity Lineament (NSGL). Further considering seismic images in the same area, this water content distribution pattern suggested that the front of the stagnant Pacific Plate in the lower MTZ might have reached the NSGL. However, the dehydration reactions in the stagnant slab were more active in the eastern part. Perhaps, some of these fluids migrated into the upper MTZ and could be the source of the trapped water found in the xenoliths from the deep upper mantle beneath Eastern China.

Sharpness of the 410-km discontinuity from the P410s and P2p410s seismic phases

2019 ◽  
Author(s):  
Lev Vinnik ◽  
Yangfan Deng ◽  
Grigoriy Kosarev ◽  
Sergey Oreshin ◽  
Zhou Zhang ◽  
...  
Keyword(s):  
Transition Zone ◽  
Southern Africa ◽  
Amplitude Ratio ◽  
Southern China ◽  
Broad Band ◽  
Receiver Functions ◽  
P Wave ◽  
Seismic Model ◽  
Yangtze Craton ◽  
Zone Water

Summary Sharpness of the 410-km boundary is of interest because it is sensitive to water content in the transition zone. We evaluate the width of the 410-km discontinuity with a new seismic method. Our estimates are inferred from the amplitude ratio of the P2p410s and P410s seismic phases that are detected in P-wave receiver functions. We applied this method to seismic recordings from arrays of broad-band stations deployed in central Fennoscandia, southern Africa and southern China. The obtained estimates of width of the 410-km discontinuity range from 10 to 22 km and always exceed the width of 7 km which is expected for anhydrous conditions. The enlarged width may be interpreted in terms of hydrous conditions, but we have found only one region (the eastern Yangtze Craton in China) where the broad 410-km discontinuity, as expected, is accompanied by a broad transition zone. Water in the transition zone may be a kind of a global phenomenon, but evidence of the enlarged width of the transition zone may be missing in most of our data because the reference seismic model is affected by water, as well.

Simulation of soil water content on a small reclaimed watershed in northern Alberta using the Root Zone Water Quality Model (RZQWM)

2006 ◽  
Vol 86 (4) ◽  
pp. 675-690 ◽  
Author(s):  
E. Mapfumo ◽  
D S Chanasyk ◽  
C. L.A. Chaikowsky
Keyword(s):  
Water Quality ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Model Evaluation ◽  
Root Zone ◽  
Weather Data ◽  
Quality Model ◽  
D Values ◽  
Zone Water

A study was conducted at Syncrude Canada Ltd., Alberta, to evaluate the simulation of soil volumetric water content from the reclaimed slopes of the Southwest Sand Storage Facility using the Root Zone Water Quality Model (RZWQM). Soil water content measurements were conducted every 2 wk using a neutron moisture meter in 2001 (dry year) and 2002 (wet year). Two types of calibration and evaluation were performed: first, calibration using 2001 weather data (dry year) and evaluation using 2002 weather data (wet year) (herein referred to as method 1); second, calibration using 2002 weather data (wet year) and evaluation using 2001 weather data (dry year) herein referred to as (method 2). Results from the method 1 calibration for each tube indicated modeling efficiencies (EF) between −0.27 and 0.90, coefficients of determination (r2) between 0.13 and 0.97, and deviation (D, as %) of simulated from measured values of less than 5%. The model evaluation by tube location following method 1 calibration indicated EF values between −3.80 and 0.56, whereas r2 values ranged between 0.08 and 0.82. Although five out of eight tubes had D values > 5%, all except for one tube had D values < 20%. Method 2 calibration results for each tube indicated EF values of −0.34 to 0.85, r2 values of 0.07 to 0.85 and all D values < 5%. Results of the method 2 model evaluation by tube location indicated EF values of −10.15 to 0.75 (overall EF = −0.84), r2 values of 0.04 to 0.96 (overall r2 = 0.39) and D values of 2.6 to 48.6% (overall D = 19.8). Method 2 model evaluation results indicated EF values of −1.69, −3.85 and −0.01, for depths of 15, 25 and 35 cm, respectively. The D values were 27, 20 and 13%, respectively. Graphical displays indicated that during the evaluation process, the model generally tended to slightly under-estimate the wetter moisture conditions, regardless of whether data for a wet year or a dry year were used during the calibration process. Key words: Modeling, calibration method, soil water, land reclamation

Sign in / Sign up

Export Citation Format

Share Document