Analysis of Tectonic Plate Velocity Variations in the Sunda Strait Based on GPS Time-series Data

Indonesia is an earthquake-prone country located in the junction of four tectonic plates, namely the Indo-Australian, Eurasian, Philippine, and Pacific. The convergent boundary between tectonic plates is also called a subduction zone that can produce great earthquakes in the future. One of the subduction zones in Indonesia is the Sunda Strait subduction zone which predicted can release a M7.8 earthquake. Previous research stated that there is a change in tectonic plate velocity after an earthquake ruptured. It is likely that this could happen in the Sunda Strait area which has experienced several large earthquakes. In this study, we conducted research to find out the information on the tectonic plate velocity changes in the Sunda Strait. We used Global Positioning System (GPS) time-series data provided by Indonesia Geospatial Information Agency (BIG). The time series data is used to calculate the earthquake displacement, the changes in GPS velocity of before and after earthquake, and the changes in velocity of each time interval. Our results show that the horizontal displacement due to the earthquake at all GPS stations ranged from 3.34 mm to 7.36 mm in the north-south direction and -27.45 mm to 0.18 mm in the east-west direction. Furthermore, the result of the changes in GPS velocity before and after an earthquake ranged from 2.25 mm/year to 12.60 mm/year and 1.80 mm/year to 13.35 mm/year. The pattern of change in velocity is likely due to post-seismic deformation from the 2012 Indian Ocean earthquake, the 2016 Sumatra earthquake, and also other tectonic factors.

Numerical investigation of turbulent offset jet flow over a moving flat plate using low-Reynolds number turbulence model

The present study reports the numerical simulation of turbulent plane offset jet flow over a moving plate. The effect of plate velocity on various flow characteristics are discussed in detail including the special case of a stationary plate. For turbulence closure, low-Reynolds number (LRN) model proposed by Yang and Shih (YS) is applied because it is computationally robust and reported to perform well in many complex flow situations. The computations have been carried out with a Reynolds number of 15000 for various offset ratios (OR=3, 7 and 11) for plate to jet velocity ratios in the range 0-2. Finite volume method with a staggered grid arrangement has been used to solve the transport equations. The application of LRN model along with integration to wall approach enables to capture one closed loop of Moffatt vortex near the left corner of the wall for the stationary plate case. The spreading of jet has been found to reduce with increase in the plate velocity. The jet half-width lies very close to the wall for the plate to jet velocity 1.5 and 2. For two extreme limits of plate velocity i.e. Uplate = 0 and 2, the nearly self-similar profiles are observed at different axial locations in the wall jet region. Also, the flow is observed to exhibit nearly self-similar behavior when velocity profiles are plotted for various offset ratios at a given axial location in the wall jet region for Uplate = 0 and 2.

NI-AL POWDER MIXTURE INITIATION DURING SHOCK-WAVE LOADING AND HEAT TREATMENT

This paper studies shock wave loading and heat treatment of a Ni-Al powder mixture in a metal matrix. We had found that a monophasic product NiAl was synthesized at the flyer plate velocity of 1500 m/s, immediately, or at 550 m/s during heat treatment (up to 750 °C) and for 3 hours heat treatment. Initiation temperature of powder mixture was about 600 °C. The results got are perspective for the development and production of composite materials with an intermetallic layer.

Thermo-mechanical numerical modelling of the South American subduction zone: a multi-parametric investigation

The South American subduction zone remains a topic of debate with long-lasting questions involving the origin of non-collisional orogeny and the effect of very large trench-parallel extent, slab sinking to great mantle depths, and aseismic ridge subduction. A key to help solve those issues is through studying the subduction zone dynamics with buoyancy-driven numerical modelling that uses constrained independent variables in order to best approximate the dynamics of the real subduction system. We conduct a parametric investigation on the effect of upper mantle rheology (Newtonian or non-Newtonian), subduction interface yield stress and slab thermal weakening. As a means of constraining those model variables we attempt to find best-fits by comparing our model outcomes with the present-day upper- and lower-mantle slab geometry observed on tomography models and obtained from earthquake hypocentre locations, as well as with estimates of Cenozoic velocities obtained from kinematic reconstruction. Key ingredients that need to be reproduced are slab flattening close to the surface, strong oscillation of the Farallon-Nazca subducting plate velocity and progressive decrease in trench retreat rate after a long period of time. We include these ingredients to define a model fitting score that contains a total of 9 criteria. Our best fitting model involves significant slab thermal weakening in order to attain the fast Farallon-Nazca subducting plate velocity and to better reproduce the subduction partitioning in the past 48 Myr, due to strong reduction of the shear stresses resisting downdip slab sinking and of the slab bending resistance. We further find that a non-Newtonian upper mantle rheology promotes slab folding and realistic associated oscillation of the subducting plate velocity. Our parametric study also indicates that the subduction interface must be weak in agreement with earlier laboratory subduction models, but not too weak, with a yield stress of ~ 14–21 MPa, otherwise the fit becomes poor. Our models moreover suggest that slab folding at the 660 km discontinuity can be a cause of the Farallon-Nazca subducting plate velocity oscillation. Whether and how this slab folding process induces periodic/episodic variations in deformation of the Andes remains an open question that requires further research.

How thermochemical piles initiate plumes at their edges

<p>Deep-rooted mantle plumes are thought to originate from the margins of the Large Low Shear Velocity Provinces (LLSVPs) at the base of the mantle. Visible in seismic tomography, the LLSVPs are often numerically modeled as dense and viscous thermochemical piles. Although the piles force lateral mantle flow upwards at their edges, it is not clear if, and how, plumes are predominantly initiated at the pile margins. In this study, we develop numerical models that show a series of plumes periodically rising from the margin of an approximately 300 km thick dense thermochemical pile, with each plume temporarily increasing the pile’s local thickness to almost 370 km due to upward viscous drag from the rising plume. When the plume is pushed towards the pile center by the lateral mantle flow, the viscous drag on the dense material at the pile margin decreases and the pile starts to collapse back towards the core-mantle boundary (CMB). This causes the dense pile material to extend laterally along the CMB (about 150 km), locally thickening the lower thermal boundary layer on the CMB next to the pile, which initiates a new plume. The resulting plume cycle is reflected in both the thickness and lateral motion of the local pile margin within a few degrees of the pile edge, while the overall thickness of the pile is not affected. The frequency of plume generation is mainly controlled by the rate at which slab material is transported to the CMB, and thus depends on the plate velocity and the sinking rate of slabs in the lower mantle. Within Earth, this mechanism of episodic plume initiation may explain the suggested link between the positions of hotspots and Large Igneous Provinces (LIPs) and the LLSVP margins. Moreover, a collapse of the southeastern corner of the African LLSVP, and subsequent triggering of plumes around the spreading pile material, may explain the observed clustering of LIPs in that area between 95 and 155 Ma.</p>

Modelling of Artificial Neural Network to control the cooling rate of a Laboratory Scale Run-Out Table

Run Out Tables (ROTs) have been used for long time in order to achieve different microstructure of steel in the industries. The microstructure of steel controlled by the cooling rate which in turn depends on various factors like the plate velocity, nozzle bank distance, coolant flow rate, and many others. Achieving new steel grade thus demand a proper combination setting of all such parameters. The observed data like upper nozzle distance, lower nozzle distance and mass flow rate of coolant from the laboratory scale ROTs are used to find out the cooling rate which is important parameter for achieving desired properties in steel. An Artificial Neural Network has been used here to creating an empirical relation between the observed data and thermodynamics parameter which will determine the cooling rate and validate it.

Influence of moving plate velocity on conjugate heat transfer due to the impingement of an inclined slot jet

In this paper, a dimensionless numerical study of the flow-field and heat transfer characteristics of an incompressible turbulent slot jet impinging obliquely over a moving surface of finite thickness is presented. Simulations were performed using [Formula: see text] eddy viscosity turbulence model. The temperature field was solved simultaneously in the solid and the fluid domain. For a fixed impingement distance and a fixed Reynolds number, the impingement angle ([Formula: see text]) and plate velocity ([Formula: see text]) were varied in the range of 30–75∘ and 0–0.3, respectively. In the results, the length of the potential core depends on the jet inclination, which increases with increase in jet angle. The jet angle and plate velocity have more influence on the uphill side compared to the downhill side. The location of stagnation displaces toward the uphill side as the inclination angle decreases, and the drifting of stagnation point is noted with the variation in plate velocity. The average skin-friction coefficient increases with increase in [Formula: see text] and [Formula: see text], and the influence of [Formula: see text] on the skin-friction coefficient is reduced as [Formula: see text] increases. The maximum Nusselt number ([Formula: see text]) increases with increase in [Formula: see text], and the drifting of [Formula: see text] is observed with increase in plate velocity. It is found that the average Nusselt number increases quickly with increase in plate velocity for lower angles of impingement. The distribution of local heat flux follows the same trend as the local Nusselt number.

Mixed convection jet impingement cooling of a moving plate

The mixed convection heat transfer details of a jet impinging targeted a moving heated plate are studied numerically under steady laminar flow conditions. The governing parameters for the present problem are: Reynolds number (Re), Grashof number (Gr), the velocity of the heated plate (U), jet width and distance from the heated plate. The results are presented to show the fluid and heat flow structure at different conditions with fixed width of the jet and fixed distance from the heated plate and different other parameters. It is observed that the bouyancy effects are more obvious at low values of Reynolds number and plate velocity and the forced convection is dominating at high values of Re and U. At low values of the plate velocity (U/V < 0.5 with Re = 200 and Gr = 1×104) it is observed that the heat transfer is reduced due to the opposing effects of the jet flow and the flow induced by the plate on one side of the plate. However the increase of the plate velocity more than (U/V > 0.5 with Re = 200 and Gr = 1×104) the heat transfer is increased due to the combined effect of the jet flow and the stronger flow induced by the movement of the heated plate.