Imaging of Vp, Vs, and Poisson’s ratio anomalies beneath Kyushu, southwest Japan: Implications for volcanism and forearc mantle wedge serpentinization

2008 ◽  
Vol 31 (4-6) ◽  
pp. 404-428 ◽  
Author(s):  
Mohamed K. Salah ◽  
Tetsuzo Seno
Keyword(s):  
Poisson’S Ratio ◽  
Mantle Wedge ◽  
Poisson's Ratio ◽  
Southwest Japan ◽  
Forearc Mantle

scholarly journals The fate of fluids released from subducting slab in northern Cascadia

2011 ◽  
Vol 3 (2) ◽  
pp. 943-962 ◽  
Author(s):  
K. Ramachandran ◽  
R. D. Hyndman
Keyword(s):  
Poisson’S Ratio ◽  
Subduction Zones ◽  
Poisson's Ratio ◽  
Crustal Layer ◽  
Collision Tectonics ◽  
Significant Addition ◽  
Increasing Temperature ◽  
Lower Crustal ◽  
Forearc Region ◽  
Forearc Mantle

Abstract. Large amounts of water carried down in subduction zones are driven upward into the overlying forearc upper mantle and crust as increasing temperature and pressure dehydrate the subducting crust. Through seismic tomography velocities we show that, (a) the overlying forearc mantle in Northern Cascadia is hydrated to serpentinite, and (b) the low Poisson's ratio at the base of the forearc lower crust that may represent silica deposited from the rising fluids. From the velocities observed in the forearc mantle, the volume of serpentinite estimated is ~30 %. This mechanically weak hydrated forearc region has important consequences in limits to great earthquakes and to collision tectonics. An approximately 10 km thick lower crustal layer of low Poisson's ratio (σ = 0.22) in the forearc is estimated to represent a maximum addition of ~14 % by volume of quartz (σ = 0.09). If this quartz is removed from rising silica-saturated fluids over long times it represents a significant addition of silica to the continental crust and an important contributor to its average composition.

scholarly journals The fate of fluids released from subducting slab in northern Cascadia

Solid Earth ◽  
2012 ◽  
Vol 3 (1) ◽  
pp. 121-129 ◽  
Author(s):  
K. Ramachandran ◽  
R. D. Hyndman
Keyword(s):  
Poisson’S Ratio ◽  
Subduction Zones ◽  
Poisson's Ratio ◽  
Crustal Layer ◽  
Collision Tectonics ◽  
Significant Addition ◽  
Lower Crustal ◽  
Subducting Slab ◽  
Forearc Region ◽  
Forearc Mantle

Abstract. Large amounts of water carried down in subduction zones are driven upward into the overlying forearc upper mantle and crust as increasing temperatures and pressure dehydrate the subducting crust. Through seismic tomography velocities we show (a) the overlying forearc mantle in northern Cascadia is hydrated to serpentinite, and (b) there is low Poisson's ratio at the base of the forearc lower crust that may represent silica deposited from the rising fluids. From the velocities observed in the forearc mantle, the volume of serpentinite estimated is ∼30 %. This mechanically weak hydrated forearc region has important consequences in limits to great earthquakes and to collision tectonics. An approximately 10 km thick lower crustal layer of low Poisson's ratio (σ = 0.22) in the forearc is estimated to represent a maximum addition of ∼14 % by volume of quartz (σ = 0.09). If this quartz is removed from rising silica-saturated fluids over long times, it represents a significant addition of silica to the continental crust and an important contributor to its average composition.

scholarly journals Role of warm subduction in the seismological properties of the forearc mantle: An example from southwest Japan

2021 ◽  
Vol 7 (28) ◽  
pp. eabf8934
Author(s):  
Changyeol Lee ◽  
YoungHee Kim
Keyword(s):  
Subduction Zones ◽  
Mantle Wedge ◽  
Numerical Models ◽  
Thermal Structure ◽  
Free Fluid ◽  
Southwest Japan ◽  
Seismic Properties ◽  
Delay Times ◽  
Forearc Mantle ◽  
Nonvolcanic Tremors

A warm slab thermal structure plays an important role in controlling seismic properties of the slab and mantle wedge. Among warm subduction zones, most notably in southwest Japan, the spatial distribution of large S-wave delay times and deep nonvolcanic tremors in the forearc mantle indicate the presence of a serpentinite layer along the slab interface. However, the conditions under which such a layer is generated remains unclear. Using numerical models, we here show that a serpentinite layer begins to develop by the slab-derived fluids below the deeper end of the slab-mantle decoupling interface and grows toward the corner of the mantle wedge along the interface under warm subduction conditions only, explaining the large S-wave delay times in the forearc mantle. The serpentinite layer then allows continuous free-fluid flow toward the corner of the mantle wedge, presenting possible mechanisms for the deep nonvolcanic tremors in the forearc mantle.

The Model for Calculating Elastic Modulus and Poisson's Ratio of Coal Body

2013 ◽  
Vol 6 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Ai Chi ◽  
Li Yuwei
Keyword(s):  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Fractured Rock ◽  
Rock Block ◽  
Poisson's Ratio ◽  
Linear Elastic ◽  
Study Results ◽  
The Face ◽  
Block Face ◽  
Coal Rock

Coal body is a type of fractured rock mass in which lots of cleat fractures developed. Its mechanical properties vary with the parametric variation of coal rock block, face cleat and butt cleat. Based on the linear elastic theory and displacement equivalent principle and simplifying the face cleat and butt cleat as multi-bank penetrating and intermittent cracks, the model was established to calculate the elastic modulus and Poisson's ratio of coal body combined with cleat. By analyzing the model, it also obtained the influence of the parameter variation of coal rock block, face cleat and butt cleat on the elastic modulus and Poisson's ratio of the coal body. Study results showed that the connectivity rate of butt cleat and the distance between face cleats had a weak influence on elastic modulus of coal body. When the inclination of face cleat was 90°, the elastic modulus of coal body reached the maximal value and it equaled to the elastic modulus of coal rock block. When the inclination of face cleat was 0°, the elastic modulus of coal body was exclusively dependent on the elastic modulus of coal rock block, the normal stiffness of face cleat and the distance between them. When the distance between butt cleats or the connectivity rate of butt cleat was fixed, the Poisson's ratio of the coal body initially increased and then decreased with increasing of the face cleat inclination.

scholarly journals A Hybrid Artificial Intelligence Model to Predict the Elastic Behavior of Sandstone Rocks

2019 ◽  
Vol 11 (19) ◽  
pp. 5283 ◽  
Author(s):  
Gowida ◽  
Moussa ◽  
Elkatatny ◽  
Ali
Keyword(s):  
Poisson’S Ratio ◽  
Accurate Determination ◽  
Oil And Gas Industry ◽  
Poisson's Ratio ◽  
Elastic Behavior ◽  
Percentage Error ◽  
Ann Model ◽  
Field Development ◽  
Well Completion

Rock mechanical properties play a key role in the optimization process of engineering practices in the oil and gas industry so that better field development decisions can be made. Estimation of these properties is central in well placement, drilling programs, and well completion design. The elastic behavior of rocks can be studied by determining two main parameters: Young’s modulus and Poisson’s ratio. Accurate determination of the Poisson’s ratio helps to estimate the in-situ horizontal stresses and in turn, avoid many critical problems which interrupt drilling operations, such as pipe sticking and wellbore instability issues. Accurate Poisson’s ratio values can be experimentally determined using retrieved core samples under simulated in-situ downhole conditions. However, this technique is time-consuming and economically ineffective, requiring the development of a more effective technique. This study has developed a new generalized model to estimate static Poisson’s ratio values of sandstone rocks using a supervised artificial neural network (ANN). The developed ANN model uses well log data such as bulk density and sonic log as the input parameters to target static Poisson’s ratio values as outputs. Subsequently, the developed ANN model was transformed into a more practical and easier to use white-box mode using an ANN-based empirical equation. Core data (692 data points) and their corresponding petrophysical data were used to train and test the ANN model. The self-adaptive differential evolution (SADE) algorithm was used to fine-tune the parameters of the ANN model to obtain the most accurate results in terms of the highest correlation coefficient (R) and the lowest mean absolute percentage error (MAPE). The results obtained from the optimized ANN model show an excellent agreement with the laboratory measured static Poisson’s ratio, confirming the high accuracy of the developed model. A comparison of the developed ANN-based empirical correlation with the previously developed approaches demonstrates the superiority of the developed correlation in predicting static Poisson’s ratio values with the highest R and the lowest MAPE. The developed correlation performs in a manner far superior to other approaches when validated against unseen field data. The developed ANN-based mathematical model can be used as a robust tool to estimate static Poisson’s ratio without the need to run the ANN model.

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