Analysis of coordinate time series of DORIS stations on Eurasian plate and the plate motion based on SSA and FFT

This study focuses on analyzing the time series of DORIS beacon stations and plate motion of the Eurasian plate by applying Singular Spectrum Analysis(SSA)and Fast Fourier Transform(FFT).First,the rend terms and periodic signals are accurately separated by SSA,then,the periodic seasonal signals are detected using SSA,and finally,the main components of the time series are reconstructed successfully.The test results show that the nonlinear trends and seasonal signals of DORIS stations are detected successfully.The periods of the seasonal signals detected are year,half-year,and 59 days,etc.The contribution rates and slopes in E,N,and U directions of the trend items of each beacon station after reconstruction are obtained by least-square fitting.The velocities of these stations are compared with those provided by the GEODVEL2010 model,and it is found that they are in good agreement except the DIOB,MANB,and PDMB stations.Based on the DORIS coordinate time series,the velocity field on the Eurasian plate is constructed,and the test shows that the Eurasian plate moves eastward as a whole with an average velocity of 24.19±0.11 mm/y in the horizontal direction,and the average velocity of it is1.74±0.07 mm/y in the vertical direction.

Global plate motion and earthquake activity

The global plate motion rates Ω are not uniform in time and space. The rotation rates were larger than 0. 545°/Ma for Cocos, Philippine Sea, Pacific, Nazca, Australia, India and Arabia plates, but smaller than 0. 315°/Ma. for other plates. Compared to 1997. 0, the Ω values of the three oceanic plates in 2000. 0 increased by,respectively,2.4% ,2. 1% and 41.7%, and the northward movement rates of the the India plate and western part of the Australia plate increased by 3.38 mm/a on the average. The spatial distribution of earthquakes was dependent on earthquake magnitude. Earthquakes of 5.0 ≤ Mw 〈 7.0 were located mainly in plate-margin zones and intra-plate crustal deformation zones joining the southern margin of Eurasia plate. Earthquakes of Mw≥7.0 concentrated basically in the circum-Pacific and South Asia zones, but hardly in midocean-ridge seismic zones. Earthquakes of Mw ≥ 8.0 were located only in the margin zones of the India, Aus- tralia,Pacific and Nazca plates orthogonal to the direction of plate motion. Compared with previous eighteen years, global earthquake activity enhanced obviously after 1994, especially after 2001. The Ω value of a plate was closely related to the activity of strong earthquakes. The largest earthquakes were located in the front-margin zones of plates having the largest Ω values. Energy released by strong earthquakes comes mainly from kinetic energy of the plates. Global seismicity enhancement was caused mainly by the acceleration of the three oceanic plates. Larger enhancement of global earthquake activity lagged behind the movement acceleration of the three oceanic plates by four years.

Global Plate Motions and Their Impact on the Earth's Surface Area Change

Based on their Euler poles,we calculated the relative velocities between every two plates in the typical global plate motion models,respectively,and estimated the area change along these boundaries. In our calculations,plates on both sides accommodated area changes depending on the boundary types: extensional, convergent or transform, so we can estimate area change of each plate and then globally. Our preliminary results show that the area of the southern hemisphere increased while that of the northern hemisphere decreased over the past 1 million years,and global area has increased by 26,000km2 to 36,000km2,which corresponds to the 160m～250m increment on the Earth's radius if all these area increments are attributed to Earth's expansion. Taking the NUVEL-1 model as an example,of the 14 plates in this model,11 are decreasing,but the global area has increased because of the larger increment amount from Africa,North America and Antarctica. Finally,we also discussed factors affecting the global area change such as subduction zone retreating and back-arc spreading.

Implicit expansion rate of the Earth in global plate motions

Based on eight published plate motion models, we separately estimated the net area changes of tectonic plates and the area change of the solid Earth surface over geological time using the Euler vectors of plates with determined boundaries. Then, under the context of a currently expanding Earth, we inferred the change rate of the Earth’s mean radius from the estimated net area changes. The results show that the total increases and decreases in the areas of different plates cannot be compensated. Specifically, the area of the Northern Hemisphere decreases while that of the Southern Hemisphere increases, but the net area of the solid Earth surface slightly increases in th computing period(0.01 Ma). For the latest NNRMORVEL56 plate motion model, the area of the Southern Hemisphere increases by 7802 km2 while the area of the Northern Hemisphere decreases by 7711 km^2. This indicates a net area increase of 91 km2 in the solid Earth surface corresponding to an expansion rate of 0.06 mm/a for the Earths mean radius.This result coincides with the slow rate of expansion derived from geodetic measurements and geophysical modeling.

A Discussion on Correlations of Plate Motion with Seismic Anisotropy and Stress Field in Plate Boundary Zones

In many parts of the global plates,including subduction zones,mid-ocean ridges and even the interior of the continental plates,seismic anisotropy has a certain correlation with image of absolute plate motion( APM),or is in accord with the predominant direction of the intraplate stress field. In our study,a statistical analysis is done on the correlations of plate motion with seismic anisotropy as well as a stress field within nine plate boundaries which contain major subduction zones in the globe. Results indicate that absolute or relative plate motion( RPM) controls the seismic anisotropy and stress field of the plate boundary,which is especially obvious for the RPM. It can also be inferred that the correlation of RPM is better than that of APM. Because of the complexity of subduction mechanism and diversity of controlling factors at plate boundaries containing subduction zones,the correlation becomes much complex. Sources of anisotropy at various depths show different characteristics,and stress state is controlled by many factors,thus further discussions on the correlations are required.

Subduction tectonics vs.plume tectonics——Discussion on driving forces for plate motion

Plate tectonics describes the horizontal motions of lithospheric plates,the Earths outer shell,and interactions among them across the Earths surface.Since the establishment of the theory of plate tectonics about half a century ago,considerable debates have remained regarding the driving forces for plate motion.The early"Bottom up"view,i.e.,the convecting mantledriven mechanism,states that mantle plumes originating from the core-mantle boundary act at the base of plates,accelerating continental breakup and driving plate motion.Toward the present,however,the"Top down"idea is more widely accepted,according to which the negative buoyancy of oceanic plates is the dominant driving force for plate motion,and the subducting slabs control surface tectonics and mantle convection.In this regard,plate tectonics is also known as subduction tectonics."Top down"tectonics has received wide supports from numerous geological and geophysical observations.On the other hand,recent studies indicate that the acceleration/deceleration of individual plates over the million-year timescale may reflect the effects of mantle plumes.It is also suggested that surface uplift and subsidence within stable cratonic areas are correlated with plumerelated magmatic activities over the hundred-million-year timescale.On the global scale,the cyclical supercontinent assembly and breakup seem to be coupled with superplume activities during the past two billion years.These correlations over various spatial and temporal scales indicate the close relationship and intensive interactions between plate tectonics and plume tectonics throughout the history of the Earth and the considerable influence of plumes on plate motion.Indeed,we can acquire a comprehensive understanding of the driving forces for plate motion and operation mechanism of the Earth's dynamic system only through joint analyses and integrated studies on plate tectonics and plume tectonics.

A VARIATIONAL PRINCIPLE OF PERTURBED MOTION ON VISCOELASTIC THIN PLATES WITH APPLICATIONS

In this paper, in the light of the Boltzmann superpositionprinciple in linear viscoelastic- ity, a mathematical model ofperturbed motion on viscoelastic thin place is established. Thecorre- sponding variational principle is obtained in a convolutionbilinear form. For application the problems of free vibration, forcedvibration and stability of a viscoelastic simply-supportedrectangular thin plate are considered. The results show thatnumerical solutions agree well with analytical solutions.

Studying and Measuring the Plate Motions and Earthquakes Using Pulsar Observations

1 Plate Motions and Earthquakes Modern space technology such as very long baseline interferometry (VLBI), satellite laser ranging (SLR) and global positioning system (GPS) opens a new way to measure and study the earth’s motions with high accuracy. It is one of the frontiers of today’s earth sciences to use these space technologies to learn plate-scale tectonics, kinematics and dynamics. During the 1980s, the NASA Program in Crustal Dynamics succeeded

DETERMINATION OF PARAMETERS OF PRESENT GLOBAL PLATE MOTION USING SLR TECHNIQUE

Using thelast 5 years’ (1983—1988) global Satellite Laser Ranging (SLR) data of satellite Lageos, we have determined the present-day change rate of the baseline length among those SLR stations located in the North America, South America, Indaia, Pacific and Eurasia plates. The precision estimated is better than 1 cm/a. The results of this determination agree with those obtained by the geologic tectonic rate model of Minster and Jordan (1978). This indicates that the motion of those regions located faraway from the plate boundary is probably stable in the past million years. In some regions at the plate boundary the result is found disagreed with the M/J model. For example, the determined change rate of the Monumeny Peak-Ouincy baseline across the famous San-Andreas transform fault is 2.9cm/a (M/J:5.3 cm/a). This might be explained with the hypothesis that periodic deformations occurring at the plate boundary and sudden deformations occurring only in the plate boundary zone. We have also found the

Contemporary Crustal Motion and Deformation of South America Plate

This paper presents the contemporary motion and active deformation of South America plate and relative motion of Nazca-South America plate using space geodetic data. The South America plate is moving at average 14.5 mm/a with an azimuth of 15.2° and shrinking in the west-east at 10.9 mm/a. The geodetic deformations of sites with respect to the South America plate are in quite good agreement with the estimated deformations from NNR-NUVEL1A, but the deformation of the western South America regions is very large.

AN EQUATION OF MOTION FOR A THICK VISCOELASTIC PLATE

In this paper an equation of motion is presented for a general thick viscoelastic plate, including the effects of shear deformation, extrusion deformation and rotatory inertia. This equation is the generalization of equations of motion for the corresponding thick elastic plate, and it can be degenerated into several types of equations for various special cases.

Wave Motion in an Ice Covered Ocean Due to Small Oscillations of a Submerged Thin Vertical Plate

在我们学习的这份报纸，一个薄垂直盘子的小摆动生产的表面波浪的产生的问题在深冰沉没了盖住的海洋。二个特别问题这里被认为 viz，波浪产生的问题由于一) 板和 b 滚动) 在一个固定垂直盘子前面的线来源的存在。全体的散发的波浪的振幅为两个问题，从板的距离被草地的合适的应用获得积分定理。这些然后为冰盖子参数的各种各样的值图形地被学习。

RELATIVE MOTION AND DEFORMATION OF PACIFIC PLATE FROM SPACE GEODESY

The circum Pacific tectonic system that contains of convergent, divergent and transform boundaries, is the most active region of volcanoes and earthquakes in the world, and involves many important theoretical questions in geosciences. The relative motion and deformation of Pacific plate is still an active subject of research. In this note, we analyze the deformation of Pacific plate and obtain reliable results of the relative motion rates at the circum Pacific boundaries based on space geodetic data, which reveals the present day motion characteristics of Pacific plate.

Drag Coefficient of a Non-Convex Polygonal Plate during Free Fall

Waterside creatures or aquatic organisms use a fin or web to generate a thrust force. These fins or webs have a non-convex section, referred to as a non-convex shape. We investigate the drag force acting on a non-convex plate during unsteady motion. We perform the experiment in a water tank during free fall. We fabricate the non-convex plate by cutting isosceles triangles from the side of a convex hexagonal plate. The base angle of the triangle is between 0° to 45°. The base angle is 0 indicates the convex hexagonal thin plate. We estimate the drag coefficient with the force balance acting on the model based on the image analysis technique. The results indicate that increasing the base angle by more than 30° increased the drag coefficient. The drag coefficient during unsteady motion changed with the growth of the vortex behind the model. The vortex has small vortices in the shear layer, which is related to the Kelvin-Helmholtz instabilities.

青藏高原及其周缘的各向异性研究

本文利用中国国家台网在青藏地区布设的台站记录到的近5年震级在5.8以上、震中距在东经88°~120°之间的39个远震地震事件进行SKS横波分裂测量,来研究青藏高原及其周缘地区的各向异性及变形特征。在青藏内部地区,SKS横波分裂测量的快轴自西向东逐渐从NE—SW向转为E—W向,再转为NNE向,与GPS速度场方向基本一致,呈顺时针方向变化。造成此地区SKS分裂测量结果的原因可能为缅甸板块向东俯冲时发生向西的后撤运动,使得此区域的岩石圈产生环状变形。川滇地区南部的GPS数据显示了近ES向的地表形变且走滑断层走向为NW—SE向,Pms地壳各向异性快轴方向主要为S—N向或NNE—SSW向,SKS分裂结果揭示了E—W向的上地幔各向异性特征,与Pms快轴方向以大角度相交或垂直,说明云南地区深部软流圈地幔流动场与地壳及地表变形特征不一致,地幔和地壳的变形机制和各向异性来源不同,发生解耦变形。

面向多规格蒸发器传热管检修的新型机器人机构设计及其运动规划

面向核电站蒸汽发生器的管板爬行式检修机器人存在适应性差、检修效率低等问题。为实现蒸汽发生器多规格传热管的检修任务,设计了一款新型机构的四足爬行检修机器人,并对相关的步态规划展开了研究。首先,根据需要适应多规格管板的要求,提出机器人的构型以及整体方案设计,确定了爬行机器人的主要运动方式,并给出了工具工作空间;之后,根据不同类型管板开展了机器人步态规划相关研究,规划了三角形、正方形两种排布管板上的直线运动步态与转向运动步态;最后,利用V-REP与Python联合仿真进行机器人运动仿真实验,结果表明,爬行机器人能够完成多规格管板下的直线运动与转向运动,证明了机构的合理性与运动的可行性。

Active Motion of Tectonic Blocks in East Asia: Evidence from GPS Measurement

The relative Euler vectors of the Pacific, Philippine, Amurian, Okhotsk, N.Honshu and South China plates or blocks are deduced from earthquake slip vectors, transform faultazimuths and spreading rates, which are consistent with new results derived from the InternationalTerrestrial Reference Frame ITRF2000 velocity field, the velocity field of GPS stations in China andthe GPS measurement data of the GEONET network in Japan. Based on the two groups of Euler vectors,analysis and comparative study of the relative motions and deformations of the tectonic blocks inEast Asia reveal the present-day motion characteristics of the blocks.

心电图平板运动试验与动态心电图在冠心病诊断中的效能对比分析

目的比较心电图平板运动试验与动态心电图在冠状动脉粥样硬化性心脏病(coronary atherosclerotic heart disease,CAD)诊断中的效能。方法选取2022年1月—2024年1月长治市人民医院心电诊断科收治的158例疑似CAD患者,均实施心电图平板运动试验、动态心电图检查。以冠状动脉造影结果为金标准,分析二者对冠心病的检出结果、诊断效能及CAD病变检出情况。结果冠状动脉造影结果显示,158例疑似CAD患者中阳性102例、阴性56例,其中动态心电图检测处阳性90例、阴性44例,心电图平板运动试验组阳性98例,阴性50例。心电图平板运动试验的灵敏度、特异度、准确度分别为96.10%、89.30%、93.70%,均高于动态心电图诊断的88.20%、78.60%、84.80%,差异有统计学意义(χ^(2)=4.347、4.391、9.828,P均<0.05)。结论心电图平板运动试验诊断CAD的灵敏度、特异度、准确度高于动态心电图。

A rotating elastic plate/block model for Eurasia

On the assumption that a plate is elastically deformable and may rotate as a whole, we found that Eurasian area may be divided into an Eurasian plate and three blocks of the Xiyu, the North China and the Southeast Asia according to tectonic frame of the East and Southeast Asia and the ITRF2008 velocity field in Eurasian area. F tests show that the accuracy of this elastic-plate/block model is significantly higher than the corresponding rigid-plate models; the area covered is notably larger also.

运动梯形板的自由振动

以往对运动二维结构动力学的研究局限于矩形板,且运动效应仅关注单一方向,故研究了梯形板固有振动的运动效应,分别考察了两个方向上的运动速度对固有振动的影响。从Minldin板理论出发,将预应力统一到系统势能,应用虚功原理建立了双向运动梯形板的控制方程,其中运动效应体现为科氏力项和离心力项。为应对控制方程在梯形边界情况下的求解挑战,采用8节点等参坐标变换技术将求解域映射为矩形,进而利用微分求积法将控制方程离散为代数方程组。数值结果以四边固支的边界条件为例,与ANSNYS结果对比证实了该方法的准确性。研究发现:运动效应对梯形板振动有削弱作用,且与速度方向密切相关;预应力与振动频率正相关,且与模态相关。