CHINESE JOURNAL OF GEOPHYSICS Vol.52, No.1, 2009, pp: 23⇠32

NEW MODEL OF ANTARCTIC PLATE MOTIONAND ITS ANALYSIS

JIANG Wei-Ping1, E Dong-Chen2, ZHAN Bi-Wei2, LIU You-Wen1

1 GNSS Research Center, Wuhan University, Wuhan 430079, China

2 Chinese Antarctic Center of Surveying and Mapping, Wuhan University, Wuhan 430079, China

Abstract Since 1995, Antarctic crustal movement campaign has been taking place by Scientific Committee on

Antarctic Research (SCAR) every year. We analyze SCAR campaign data from 1997 to 2004 and some continuous

GPS stations in Antarctica using GAMIT/GLOBK software. Data analysis involves two major procedures. The

first procedure uses the GAMIT software to estimate parameters such as station position and orbital trajectory

on a daily basis for a given 24-hour interval from the union of three data sets: (1) the campaign stations, (2)

the continuously operating GPS stations in Antarctica, and (3) long-running continuous GPS stations around

Antarctica. In the second procedure, we combine the daily solutions with global GPS sub-networks (IGS1, IGS2,

IGS3), which is provided by Scripps Institution of Oceanography (SIO), using the GLOBK software in a “regional

stabilization” approach in order to estimate the positions and velocities. Then the present-day crustal movement

of the Antarctica plate is discussed in the paper. The position of the rotation pole (58.69�N, 128.29�W) and its rate

(0.224(�)/Ma) derived from SCAR GPS data is significantly di↵erent from the NNR-NUVEL-1A estimations or

from some GPS results for the Antarctic tectonic plate. As for the relative angular motion between Antarctic and

Australian, the di↵erences between the results from this paper and some other models are better. All di↵erences

for rotation rate are smaller than 0.01(�)/Ma, and for rotation pole are smaller than 4�. GPS results obtained in

this paper provide a new and more precise model on the Antarctic plate motion.

Key words SCAR, GPS, Velocity field, Antarctica plate, Crustal movement

1 INTRODUCTION

To a very large scale, Antarctica could be divided into two major tectonic domains: the East Antarcticawith stable Precambrian shield, and the West Antarctica with the more complex assemblage of accreted ter-rains. The boundary between the two domains is a major crustal discontinuity marking by the TransantarcticMountains (TAM)-a range crossing the whole continent with a length of 3500 km and its elevation is up to 4500m. West Antarctica includes vast areas of extended, submerged, and continental crust[1,2]. The West AntarcticRift System (WARS) is one of the largest continental rifts in the world. At the same time, it is one of the twomain tectonic regions in Antarctica (the other one is the Cratons area in the eastern Antarctica). Di↵erentfrom the eastern Cratons region, which is relatively stable, the WARS has a very complex tectonic history inthe recent 100 Ma. In addition, the mass change of the Antarctica ice cover is an important reason that causesthe crustal movement of the Antarctic continent[3]. To understand the geological structure of Antarctica, seeA. Morelli et al.[1].

GPS surveying could provide high precise, large-scale and quasi-real-time quantitative data for crustalmovement, which makes it possible to obtain large scale velocity field of the crustal motion in short time. Sofar, GPS technology has already become a powerful tool in monitoring the current crustal motion. Many scho-lars have done researches and analyses on the global crustal motion (including the movement of the Antarcticaplate)[4⇠6] and the regional block motion[7⇠14]. Larson et al.[4], Sella et al.[5], and Bouin et al.[15] have inves-tigated the motion of the Antarctica plate already using GPS measurements. Among them, Bouin et al.[15]

analyze the motion of the Antarctica plate and its relative motion to the neighboring plates by both the IGSand the SCAR data (using two phases of data in 1995 and 1996). They give the rotation pole of the Antarctica

E-mail: wpjiang@whu.edu.cn

24 Chinese J. Geophys. Vol.52, No.1

plate motion at (62.0�N, 146.7�W), with the Euler angular velocity at 0.26(�)/Ma, and compare them to theNNR-NUVEL-1A model, finding that there is big discrepancy between them. However, the result obtained isnot determined under the global frame.

With the continuous perfection of the data processing method, the increasing number of the GPS stationsin the Antarctic continent and the longer time span, it is already possible for us to further investigate the present-day crustal movement of Antarctica and establish new motion model with higher accuracy for it, which heldimportant scientific meanings. Under this background, we have integrated the current precise data processingmethods, determined a new motion model of the Antarctica plate using data of 8 years, and made comparisonsand analyses between the new model and those previous ones.

2 GPS DATA PROCESSING

2.1 Geodetic Data Description

The SCAR Epoch Crustal Movement Campaigns (formerly SCAR Epoch GPS Campaigns) have been car-ried out since 1995 under the umbrella of the Scientific Committee on Antarctic Research, Geoscience StandingScientific Group (GSSG), the former Working Group on Geodesy and Geographic Information. They are partof the program named Geodetic Infrastructure in Antarctica (GIANT). The main goals of the SCAR EpochCrustal Movement Campaigns are to establish and maintain a high-precision geodetic reference frame, togetherwith investigations on the movements of the interior parts of Antarctica and its motion with respect to theneighboring plates. Recently, the SCAR GPS Campaigns has become an important component in the frame ofthe SCAR Group of Specialists on Antarctic Neotectonics (ANTEC). Some international institutions have doneresearches by using the SCAR GPS Campaign data, and have gained some scientific achievements[15].

The SCAR GPS campaign has been carried out every year since 1995. It covers an observation period ofthree weeks each year, starting from 00:00 UTC, January 20th, and closing at 24:00 UTC, February 10th. TheInstitute fur Planetare Geodasie, Technische Universitat Dresden holds the responsibility for maintaining theDatabase of the SCAR Epoch Crustal Movement Campaigns. So far, the Great Wall and the ZhongShan GPSstations in China have been participated in 12 (1995⇠2006) and 9 (1997⇠2006) campaigns respectively.

Data analysis in this paper starts from 1997. In 1998, GPS stations involved in the campaign reachedthe most, while the number of stations reduced gradually after that. GPS data used in the paper is shown inTable 1.

2.2 GPS Data Processing

We have analyzed all campaigns and continuous GPS data collected in Antarctica and its peripheral regionsfrom 1997 to 2004, using the GAMIT/GLOBK software[16⇠18]. This approach determines the station positionand velocity vectors in a single, self-consistent reference frame[19⇠21], which is di↵erent to some degree withprevious data processing methods used in the investigations of the motion of Antarctica (see Bouin et al.[15]).In this way, we could not only weaken the influence of the net-form change along with time, but also obtainmore precise GPS results by unifying data process.

Data analysis process involves two major procedures, as described by previous researchers[19⇠21]. First isto use the GAMIT software to estimate parameters such as station position and orbital trajectory on a dailybasis for a given 24-hour time span from the union of three data sets: (1) SCAR Epoch Crustal MovementCampaign stations, (2) continuously operation GPS stations in Antarctica, and (3) long-running continuousIGS stations in Antarctica and its peripheral region. In the second procedure, we combine the daily solutionswith three global IGS sub-networks (IGS1, IGS2, IGS3), using the GLOBK software in a regional stabilizationapproach, so as to obtain the time series and the velocity field.

Strategies of daily solution are listed as follows:(1) Daily solution is calculated using ionosphere-free combination (LC), double-di↵erence, and phase so-

lution.

Jiang W P et al.: New Model of Antarctic Plate Motion and Its Analysis 25

Table 1 List of SCAR GPS stations

ID Station name Station owner 1997 1998 1999 2000 2001 2002 2003 2004

ART1 Base Artigas Uruguay * * *

ARCT Arctowski Poland * * *

BELG Belgrano ASH Argentina *

DAL1 Dallmann Argentina/Germany * *

DALL Dallmann II Argentina/Germany * *

ESP1 Esperanza Argentina *

FAL1 Falkland Island U.K *

FERR Ferraz Brazil * * * *

FOR1 Forster Germany * * *

FOR2 Forster II Germany *

FOS1 Fossil Blu↵ U.K *

GRW1 Great Wall China * * * * * * * *

HAR1 Hartebeesthoek South Africa *

MAIT Maitri India *

MON1 Montevideo Argentina * * * *

MAR1 Marambio Argentina *

OHG1 O’Higgins Chile/Germany * *

PAL1 Palmer U.S.A *

PRA1 Arturo Prat Chile *

PUN1 Punta Arenas Chile *

REYJ Rey Jorge Chile *

ROT1 Rothera U.K *

SMR1 San Martin Argentina *

TNB1 Terra Nova Bay Italy *

VER1 Vernadsky Ukraine *

WASA Wasa Sweden * *

ZHON Zhongshang China * * * * * * *

(2) Eleven global permanent tracking stations (SANT, HRAO, YAR1, OHI2, VESL, SYOG, MAW1, DAV1,CAS1, MAC1, and MCM4) are constrained as reference stations.

(3) Precise satellite orbits and Earth rotation parameters from IGS are used and tightly constrainedaccording to the related accuracy.

(4) GPS satellite orbit parameters were estimated together with all station coordinates.(5) The sample rate is 30 seconds, and the cut-o↵ angle is set at 15 degree.(6) Tropospheric delay correction is applied using Saastamoinen model.(7) Antenna phase center corrections for satellites and receivers using the model from IGS.(8) Ocean tide loading correction is applied using the model provided by GAMIT.(9) Model corrections for satellite clock o↵sets (the clock parameters are taken from Broadcast Ephemeris);

Model corrections for receiver clock o↵sets (the clock o↵sets are computed from pseudorange observations).We use the GLOBK software to generate time series and estimate velocity field. Strategies are as follows:(1) For a global analysis, three global sub-networks analyzed by Scripps Orbit and Permanent Array

Center (SOPAC), namely IGS1, IGS2 and IGS3, are used to combine with the SCAR Epoch Crustal MovementCampaign stations. The total number of global stations reaches nearly 200.

(2) Daily solutions with loose constraints are transformed to International Terrestrial Reference Frame(ITRF)-2000 by estimating a seven-parameter similarity transformation, using up to 24 global sites whosepositions are defined in ITRF-2000 (See Fig. 1).

26 Chinese J. Geophys. Vol.52, No.1

Fig. 1 Distribution of IGS fiducial stations in adjustment

(3) For the continuously observing stations, the position estimates are correlated from one day to thenext. Since they are not independent, we place lower bound on their uncertainties by adding white noise to thehorizontal (including the south-north component and the east-west component) as well as vertical componentsrespectively (2 mm, 2 mm, 5 mm).

2.3 Results Analysis

2.3.1 Time seriesBy using the GLOBK software, we can get time series for the selected stations from 1997 to 2004, which

could be applied to analyze the velocity of stations and their periodical changes. In this paper, we give thetime series for campaign station GRW1 located in Antarctic Peninsula, and the continuous station ZhongShan,which is located in East Antarctic (Fig. 2). Notably, for the ZhongShan station, we process the data within a

Fig. 2 The time series of Great Wall and ZhongShan GPS stations

Jiang W P et al.: New Model of Antarctic Plate Motion and Its Analysis 27

time span of 2 or 3 days at regular intervals, apart from the combined calculation of the SCAR campaignmeasurements. Fig. 2 shows a steady northeast moving trend of the Antarctic Peninsula in horizontal direction,while in vertical direction, the motion is unstable. During the data processing, we can not be sure whether theantenna height at this station in 1998 was right, so in the meantime, the geodetic height is just for reference.The times series of ZhongShan site, which is close to IGS station DAV1, looks strange and interesting. It showsa southwest moving trend of the station in horizontal direction, with certain periodical fluctuation in the westand the east component respectively. The movement of ZhongShan site in vertical direction has an obviousperiodicity. To explain this kind of periodic motion, there are two major reasons. One is that it belongs to thecyclical changes of the site itself[22], while the other reason is that, it is caused by the di↵erent circumstances ofsnow cover on the antenna[15]. However, according to its anomaly motion in horizontal direction, it is di�cultto explain the movement. We will study it in the future.2.3.2 Velocity Field

We estimate velocities for stations in Antarctic after global adjustment. For the coordinates of the stations(20�S⇠90�S) and their velocities, see Table 2, and for the velocity field, see Fig. 3 and Fig. 4.

Fig. 3 Horizontal motions of SCAR stations and

some IGS stations in Antarctic and its adjacency

Fig. 4 Horizontal motions of SCAR GPS stations

in King George Island of west Antarctica

From Table 2 and Figs. 3⇠4, we can see that, in general, the Antarctica plate is moving towards thesouth-America plate, while departing from the Australian plate gradually. With respective to the Australianplate, the velocities of GPS sites on the Antarctica plate are 7⇠8 cm/a mostly. Some research show that theAustralian plate was departing from the Antarctica plate at the speed of 7⇠8 cm/a 50 Ma ago[23], which is alsogot approval in this paper.

Table 2 also shows that, velocities of the GPS stations in the west Antarctica are faster than those in theeast Antarctica, and the Antarctica Peninsular is an active region, which could reflect the geological structureof the Antarctica and its crustal movements. The east Antarctica has a stable Precambrian shield[3], whileresults of aeromagnetic surveys in the west Antarctica show the presence of large volumes of volcanic rockand associated subvolcanic intrusions, of the order of a million km3[24]. In the last million years, volcanism hasrenewed on at least four of the islands (Deception, Livingston, Greenwich, and King George), which is coincidentwith rifting and volcanism in the adjacent Bransfield basin[25]. Therefore, the west Antarctica (including theAntarctica peninsula) is much more active than the east.

28 Chinese J. Geophys. Vol.52, No.1

Table 2 The coordinates and velocities of SCAR GPS and IGS stations

Site Long. Lat. Sess SPAN Vew

Mew

Vns

Mns

U Mu

(�W) (�S) day (mm/a) (mm/a) (mm/a)

VESL 2.842 71.674 137 1999.0⇠2004.8 0.46 0.24 8.68 0.22 0.16 0.47

GOUG 9.881 40.349 61 1999.0⇠2004.1 20.60 0.76 17.39 0.47 –10.65 1.47

WASA 13.414 73.043 27 1997.1⇠2000.1 –3.37 0.48 11.02 0.44 –2.12 1.22

MON1 56.260 34.888 66 1997.1⇠2001.1 –0.44 0.64 10.58 0.39 4.17 0.99

OHIG 57.900 63.321 242 1997.1⇠2002.1 14.13 0.26 9.41 0.24 7.45 0.47

LPGS 57.932 34.907 130 1997.1⇠2004.8 –2.25 0.46 10.82 0.29 0.52 0.83

FERR 58.393 62.086 80 1999.1⇠2003.1 14.17 0.26 17.74 0.24 5.34 0.50

ARCT 58.469 62.161 51 1999.1⇠2001.1 10.71 0.30 12.75 0.31 –18.50 0.79

ART1 58.903 62.185 113 1997.1⇠2004.1 8.77 0.25 15.91 0.23 –16.44 0.40

GRW1 58.962 62.216 161 1997.1⇠2004.1 8.84 0.25 16.25 0.23 –4.39 0.40

CORD 64.470 31.528 82 2000.1⇠2004.1 –0.27 0.53 9.87 0.32 –2.64 0.92

UNSA 65.408 24.727 74 2000.4⇠2004.8 3.44 1.02 10.33 0.56 –6.95 2.36

RIOG 67.751 53.785 117 1999.4⇠2004.8 2.45 0.46 9.75 0.35 1.92 0.69

SANT 70.669 33.150 367 1997.1⇠2004.8 19.15 0.30 15.79 0.21 –0.37 0.49

EISL 109.383 27.148 142 1997.1⇠2003.8 66.13 0.63 –6.28 0.36 –2.81 1.06

CHAT 176.566 43.956 180 1997.1⇠2004.8 –40.86 0.23 31.94 0.15 2.31 0.41

AUCK 185.166 36.603 184 1997.1⇠2004.8 3.81 0.31 39.16 0.20 1.24 0.40

MCM4 193.331 77.838 503 1997.1⇠2004.8 9.05 0.13 –11.41 0.12 3.01 0.31

NOUM 193.590 22.270 146 1998.1⇠2004.8 20.84 0.39 45.35 0.21 1.40 0.57

MAC1 201.064 54.500 342 1997.1⇠2004.8 –11.93 0.18 31.31 0.14 0.94 0.35

TIDB 211.020 35.399 99 1997.1⇠2004.8 18.01 0.27 54.60 0.17 1.66 0.51

TID2 211.020 35.399 140 1998.1⇠2004.8 19.41 0.28 54.84 0.17 4.73 0.47

HOB2 212.561 42.805 172 1997.1⇠2004.8 14.79 0.28 55.81 0.18 2.76 0.40

ALIC 226.114 23.670 132 1998.1⇠2003.4 33.18 0.34 58.03 0.20 4.48 0.63

CEDU 226.190 31.867 140 1999.0⇠2004.8 30.15 0.28 58.29 0.17 2.64 0.42

KARR 242.903 20.981 148 1998.1⇠2004.8 38.68 0.33 56.86 0.18 2.52 0.54

PERT 244.115 31.802 160 1997.1⇠2004.8 39.19 0.25 57.05 0.16 –4.34 0.38

YAR1 244.653 29.047 251 1997.1⇠2002.1 39.11 0.44 55.97 0.25 –1.03 0.68

CAS1 249.480 66.283 351 1997.1⇠2004.8 2.13 0.15 –10.26 0.12 4.86 0.29

DAV1 282.027 68.577 384 1997.1⇠2004.8 –1.27 0.16 –5.51 0.14 2.65 0.31

ZHON 283.630 69.371 146 1997.1⇠2004.8 –5.02 0.17 –7.11 0.15 –1.65 0.36

KERG 289.744 49.351 361 1997.1⇠2004.8 5.83 0.21 –3.22 0.15 3.45 0.35

MAW1 297.129 67.605 270 1998.1⇠2004.8 –2.04 0.19 –2.03 0.18 4.33 0.41

SYOG 320.416 69.007 192 1999.4⇠2004.8 –2.66 0.23 2.20 0.21 5.00 0.52

RBAY 327.922 28.796 33 2001.1⇠2003.4 18.45 1.05 16.35 0.61 –0.23 2.41

HARK 332.292 25.887 183 1998.1⇠2000.4 23.87 0.59 18.24 0.44 5.85 1.54

HRAO 332.313 25.890 444 1998.1⇠2004.8 17.68 0.25 17.29 0.17 –0.86 0.44

SUTH 339.190 32.380 147 1999.0⇠2004.8 15.65 0.36 18.27 0.23 1.42 0.65

FOR2 348.163 70.774 26 2001.1⇠2004.0 –1.75 0.33 6.02 0.35 0.60 1.15

FOR1 348.175 70.778 52 1998.1⇠2004.1 –1.91 0.27 6.23 0.26 1.69 0.58

Note: Vew

denotes the east-west component of velocity, while Mew

denotes the MSE (mean square error) of the east-west

component; Vns

denotes the north-south component of velocity, while Mns

denotes the MSE of the north-south component; U

denotes the vertical component of velocity, while Mu

denotes the MSE of the vertical component.

Jiang W P et al.: New Model of Antarctic Plate Motion and Its Analysis 29

Table 3 gives the velocity field of GPS sites in the Antarctica plate calculated by the model developed inthis paper (SCAR), REVEL 2000[5], Larson 1997[4] and ENS 97[15]. From the second to the eighth column,it represents the east-west component of the velocity field and its precision, the north-south component andits precision respectively, using di↵erent models. From Table 3, we can see that the number of stations in theAntarctica plate calculated by Sella et al.[5] in 2002 is 9, with 8 of them are the same as used in this paper,while Larson[4] calculates 2 stations and ENS 97 calculates 6. According to Table 2 and Table 3, we find thatalthough the results show consistency with previous researches in the trend[4,5,15,26], major di↵erences existboth in quantity and direction aspects. Except for the 5 mm discrepancy at the OHIG site, majority di↵erenceof the velocity field between SCAR and REVEL 2000 is 1⇠2 mm/a. And there is significant deviation betweenSCAR and ENS 97, at 5⇠6 mm/a mostly. If only considering the precision, the accuracy in the north-south andeast-west components of the GPS velocity field calculated by SCAR model are mostly 0.2⇠0.5 mm/a, which issuperior to the other three models, thus providing reliable data to develop the motion model of the Antarcticaplate.

Table 3 Horizontal velocities of SCAR, REVEL 2000[5], Larson(1997)[4] and ENS 97[15]

for determining the plate motion of Antarctica (unit: mm/a)

Site VSCAR�E

VSCAR�N

VREVEL�E

VREVEL�N

VENS97�E

VENS97�N

VLarson�E

VLarson�N

ACRT 10.7±0.3 12.8±0.3

ART1 8.8±0.3 16.0±0.3

CAS1 2.1±0.2 –10.3±0.1 3.7±0.6 –11.6±0.7 8±6 –13±5

DAV1 –1.3±0.2 –5.5±0.2 –2.1±0.7 –6.6±0.7 2±6 –10±4

DUM1 15±2 –13±2

FERR 14.2±0.3 17.7±0.2

FOR1 –1.9±0.3 6.2±0.3

FOR2 –1.8±0.3 6.0±0.3

GRW1 8.8±0.3 16.2±0.4

KERG 5.8±0.2 –3.2±0.2 5.2±0.8 –5.3±0.7 8±1 –10±1

MAW1 –2.0±0.2 –2.0±0.2 –3.5±0.7 –3.6±0.7

MCM4 9.0±0.1 –11.4±0.1 10.6±0.7 –12.2±0.6 14±8 –11±5

MCM3 8.7±1.5 –10.5±1.4

OHIG 14.1±0.3 9.4±0.2 10.1±0.9 14.7±0.8 13±5 5±20 15.3±1.9 11.8±1.7

PALM 11.7±1.5 14.1±1.9

SYOG –2.7±0.2 2.2±0.2 –4.4±1.2 0.3±1.0

VESL 0.5±0.2 8.7±0.2 –4.7±1.4 8.2±1.8

WASA –3.4±0.5 11.0±0.5

ZHON –5.0±0.2 –7.1±0.2

3 PLATE MOTION ANALYSIS

Using the site velocities of 16 stations in the Antarctic plate under ITRF2000 and the velocities of these16 stations with respect to the Australian plate, we calculate the rotating motion of the Antarctica plate in thecases of no-net-rotation (NNR) and relative to the Australian plate, respectively. Comparisons have been madebetween di↵erent models (Table 4 and Table 5). For easy to compare, Table 5 shows the rotation velocity ofAustralian plate with respect to Antarctica plate using di↵erent models. Both in Table 4 and Table 5, SCARrepresents the results obtained in this study, and ENS 97 represents the achievements done by Bouin et al.[15].

From Table 4 we can see large discrepancies exist between NUVEL-1A and the other four models, whichtake GPS measurements as their observables. The reason is that, in the NUVEL-1A model, there are systematicerrors in the estimates of the opening rate between Antarctica plate and the other three plates, namely South-

30 Chinese J. Geophys. Vol.52, No.1

Table 4 Comparison of rotation velocities for the Antarctica plate

Angular velocity ((�)/Ma) Latitude (�N) Longitude (�W) �max

(�) �min

(�) ⇣(�) �!((�)/Ma)

SCAR 0.224 58.69 128.29 0.4 0.3 –74.8 0.01

REVEL 2000 0.226 58.48 134.00 1.6 1.0 32 0.01

Larson et al. (1997) 0.24 60.5 125.7 6.6 3.6 1 0.03

NNR-NUVEL-1A 0.24 63.0 115.9 – – – –

ENS 97 0.264 62.0 146.7 – – – –

Note: �max

, �min

denote the length of the semi-major axis and the semi-minor axis of the error ellipse, respectively. ⇣ denotes

the clockwise length azimuth angle from the north. �! denotes the precision of the angular velocity.

Table 5 Comparison of relative angular motions for the Australian/Antarctic plates

Angular velocity ((�)/Ma) Latitude (�N) Longitude (�E) �max

(�) �min

(�) ⇣(�) �!((�)/Ma)

SCAR 0.648 12.16 41.68 0.2 0.1 –86.6 0.001

REVEL 2000 0.653 14.71 39.70 1.6 0.8 33 0.004

Larson et al.(1997) 0.65 9.8 43.2 4.4 2.6 20 0.01

NNR-NUVEL-1A 0.65 13.2 38.2 1.3 1.0 –63 0.01

ENS 97 0.66 10.9 41.6 – – – –

Note: �max

, �min

denote the length of the semi-major axis and the semi-minor axis of the error ellipse, respectively. ⇣ denotes

the clockwise length azimuth angle from the north. �! denotes the precision of the angular velocity.

America plate, Africa plate and Nazca plate. It was this kind of misfit that has increased the inaccuracy of theplate motion of Antarctica[27]. As a result, the large di↵erences between NUVEL-1A and the other models arewithin expectation.

Considering the GPS results, as for the angular velocity and the latitude of the Euler pole, results obtainedin this paper are close to that of REVEL 2000, while the longitude has a major di↵erence between these twomodels. There are two reasons to explain this phenomenon. Firstly, the number of observation stations andthe time span of data applied are di↵erent, for example, there are 2 stations used in the Larson model, witha time span of more than 2 years, while ENS 97 involves 6 stations with a time span from 1995 to 1998, andREVEL 2000 processes data from 1993 to 2000 using 7 stations. In this paper, however, we collect data of 16stations spanned from 1997 to 2004. Secondly, di↵erent models adopt di↵erent methods. Although ENS 97 usesGAMIT software to do the calculation, the result is not determined under the global frame; Both Larson et al.and REVEL 2000 adopt GIPSY to process data but with di↵erent observation models[28]; Here, we select theGAMIT software to do the calculation work and the analysis is done under the global frame by using more than200 IGS stations, so our method and data model adopted are more developed and perfect than previous ones.Thus the plate motion model determined by SCAR could be more reliable than the other models, whether fromits data processing method and the distribution of stations, or the precision of velocity field aspect.

In the NUVEL-1A model, motion of the Antarctica plate is restrained mainly by the relative movementto the Australian plate. Accurately speaking, the Australian-Antarctica plate boundary data provides bettergeometric covering than other plate boundaries when deciding the Euler pole of the relative motion betweenplates[15]. Therefore, it is very significant to investigate the movement of the Antarctica plate by analyzing andcomparing the relative motion between the Australian plate and the Antarctica plate determined by di↵erentsets of data or methods.

Table 5 shows closeness between these five models on the whole in the motion of the Antarctica plate withrespect to the Australian plate. The angular velocity has a discrepancy of about 0.01(�)/Ma, while the longitudeand latitude of the Euler pole have discrepancies within 4�. Di↵erences between the five models are better thanthe results shown in Table 4. There are two reasons to explain the closeness to NUVEL-1A: the motion modelof the Antarctica plate is mainly constrained by the rotation motion relative to the Australian plate in the

Jiang W P et al.: New Model of Antarctic Plate Motion and Its Analysis 31

NUVEL-1A model, and at the same time, as for the solution mode determined by the GPS measurements,relative motion could eliminate some systematic errors.

In short, comparing with the NUVEL-1A model, or those previous GPS models, our research provides amore accurate motion model for the Antarctica plate because of the more rigorous method and larger sets ofdata used in the model.

4 CONCLUSION

By analyzing the SCAR campaign data from 1997 to 2004, data of some continuous GPS stations inAntarctica, together with the global GPS sub-networks provided by SOPAC, namely IGS1, IGS2, and IGS3,using GAMIT/GLOBK software, we have determined the time series of the SCAR campaign stations, andresolved their site positions and velocities. Based on the time series, we have discussed the movement of theGreat Wall and ZhongShan GPS stations. Then we have discussed the network deformations according tothe tectonic structures, calculated and analyzed the angular velocity and position of the rotation pole of theAntarctica plate and the values relative to the Australian plate. Some comparisons have been made betweenNUVEL-1A and REVEL 2000. GPS result shows the Euler pole of the Antarctica plate at (58.69�N, 128.29�W)and its angular velocity at (0.224(�)/Ma), which is significantly di↵erent from the NNR-NUVEL-1A predictionsand some previous GPS results. With respect to the Australian plate, there is a discrepancy of about 0.01(�)/Main the angular velocity between our research and other known models, while for the position of the rotationpole, the di↵erence is within 4�. Comparing with the NUVEL-1A model, or those previous GPS models, ourresearch provides a more accurate motion model for the Antarctica plate because of the more rigorous methodand larger sets of data used in the process, thus could provide a new motion model with higher accuracy todescribe the movement of the Antarctica plate. In a word, GPS surveying well describes the present-day crustalmovement of the Antarctica plate. There is no doubt that further GPS observations and investigations will playa vital role in resolving the dynamic mechanism problem of its current crustal movement.

ACKNOWLEDGMENTS

The research was supported by State 863 projects (2007AA12Z312), “The 10th Five-Year” Key Projects inGeomatics by the State Bureau of Surveying and Mapping (1469990324236-04-06), and the New Century Out-standing Support Program for the Talents by the Ministry of Education. We thank everyone who participated incollecting the vast amounts of GPS data used in this study. We thank MIT for providing the GAMIT/BLOBKsoftware. Pictures have been produced with the GMT package[29].

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