31(3), 224-2J5 Tap chl CAC KHOA HOC VE T R A I DAT 9-2009
NHlfiU CO CHU KY N G A N CUA TRUONG DIA TlT vA MOT SO DAC DIEM CUA VECTOR CAM UNG TlT
TREN LANH THO VIET NAM
TRUONG QUANG HAO, VO THANH SON, NGUYgN CHIEN THANG, LE TRUONG THANH, NGUYfiN BA V 1 N H , T R U 0 N G P H U O N G DUNG
I. Md DAU
Phuang phap vector cam irng bidn thien tu (ggi tat la vector ciim irng tu) da duge dd xudt va irng dung til nhirng nam 1960,1970 trong nghien ciru dia dien [7-9,161.Uu diem cila phuang phap nay la dd sau nghien ciru ldn nhd sii dung eae bidn thien trudng tu vdi chu ky tu vai phiit ddn vai gid va dae biet cd hieu qua trong viee xac dinh nhOng dai dj thudng cd dp dan dien cao trong vd Trai Ddt.
Vector cam irng tu khi xay dyng theo phuang phap cila W.D. Parkinson [7, 81 ludn chi vd noi cd dp ddn dien cao dudi ddt. Ndu theo phuang phap ciia H. Wiese [161 vector cd hudng ngugc lai. Cho dil theo phuong phap nao vector cam irng tir cung chi cho ngudi khiio sat bie't noi cd dd ddn didn cao va cdn cho ta each danh gia duge dd ddn dien eua ddt da cdn quan tam.
NhQng noi cd di thudng dp ddn dien cao thudng lien quan ddn ddng dia nhiet, dp ttr hoa cua ddt da, cac qua trinh kidn tao hoac cho cac thdng tin vd dja cha't, dia vat ly khae. Trong phuong phap ciim irng tu cdn sir dung bidn thien cila ba thanh phdn trudng tU H, D va Z. Chiing duge sinh ra phdn chinh la do cac ddng dien so cdp trong tdng dien ly va tir quydn, mdt phdn khae la do cac ddng dien thir cdp duge cam irng trong cac vat ddn dien trong ldng ddt. Cudng dp va dp sau thdm thdu eila ddng cam irng la ham phu thupe vao cudng dp va tdn sd cila trudng so cdp va dp ddn dien noi cd ddng cam dng trong mdi trudng edn khao sat. Nhirng viing tie'p giap giira hai mdi trudng vdi dd ddn dien khae nhau se lam xao trdn ddng cam irng va sinh ra di thudng trong bidn thidn trudng tir. Muc dich cud'i ciing cila. phuang phap vector cam img tu la tim ra ban chdt va hinh thd eila ba't ddng nhdt dd.
Viec ap dung phuang phap cam irng tir d nude ta duge dd cap den trong mPt sd cdng trinh nghien euu [1, 4-6, 10, 131 va ed nhung kdt qua bude ddu.
Trong cdng trinh nay vdi nhirng nghien ciru da c6 va bd sung, chiing tdi ndu mdt sd dae diem vd ap dung phuang phap cam irng tir d nude ta. Trudc tien ndi vd anh hudng cila ddng dien xich dao vao ban ngay ddn bien thien trudng tu tren mpt khu vyc rdng ldn d midn nam Viet Nam ; sau dd trinh bdy cac kdt qua chi hudng eiia vector cam irng tir d mOt .so die'm dien hinh d midn Nam va Bac Viet Nam.
Chiing tdi sir dung sd lieu ghi bidn thien trudng tir tai eae tram dja tit va cac dia diem khae theo bdng 1 dudi day de khao sat va xay dyng vector cam irng bie'n thien tu.
Bdng 1. Vj tri tram va cac diem do bie'n thien tU Dia die'm
do tir Sapa Xuan Giao Phd Rang Phil Thuy Chil a Trdm Hoa Binh Da Nang Da Lat Long An Bac Lieu Rach Gde Hdn Khoai
Toa dd dia cp(N)
22°20' 22 19 22 15 21 00 20 56 20 47 16 14 11 50 10 30 9 16 8 36 8 30
ily X{E) 103°50' 104 07 104 22 105 50 105 41 105 20 108 15 108 25 106 25 105 43 105 02 104 57 Bdng 2 thd'ng ke cac ngay do trudng tir bdng tir kd proton M203 cila IZMIRAN tai cac didm can xich dao tir vao thang 3 nam 1989. Trong thdi gian nay
Ngay
Bdng 2. Thong l<e cac ngay do trudng tUbIng tUI<e proton M203 ciia IZMIRAN
~~9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 Tdng chl sd K
Da Nang Da Lat Thii Dire
Raeh Gde Hdn Khoai
33 26 25 28 65 55 38 38 34
- l - H - - ) - - l - 4 - - l - - t - - t - - | - + -i- -i- -^•
-I-
+
-f
19
-H -t
36 22 29 35 34 20 17 22 36
-I- -I-
-I- -t
-I- -I-
-I- -t-
-I- -I-
+ +
+ +
-t
vao ngay 13 da xdy ra tran bao tir ed bien dp Idn nhdt trong cae bao tu cila chu trinh boat dpng Mat Trdi ldn thir 21.
II. M O T SO TINH CHAT CHUNG CUA BIEN THIEN Tir CO CHU KY NGAN :
HIEU LTNG NGUON
Mdt ehdp nhan co ban trong nghien eiru vector cam irng tu la sy ddng nhdt ciia trudng cam ung so cdp nghTa la thoa man dieu kien ciia sdng phang. Khi a'y thanh phdn thdng dirng Z cila trudng bidn thien tu tren mat ddt chi phan anh su ba't ddng nhdt cila dp ddn dien ben trong ldng ddt. Ndu didu kien .sdng phang khdng bao dam, cdn phan biet giira di thudng ddng dien cam irng trong ddt vdi ddng bdt ddng nhdt trong dien ly gay ra bidn thien tu tren mat ddt. Hieu irng nay ggi la hieu irng ngudn [151. Trdn the gidi cd hai viing chiu tac dpng cila hieu irng ngudn do cac ddng manh tren dien ly, dd Id viing eye quang (Auroral Region) va viing can xich dao tu. Nhung sd lieu ghi ddng thdi trudng tu toan phdn F bang tu kd proton tai cae diem can xich dao tu d Viet Nam tren bang 2 duge sir dung de ehirng minh anh hudng cila ddng dien xich dao ddn bidn thien trudng tu d Viet Nam.
De thdy mure dd anh hudng eua ddng dien xich dao ddi vdi bidn thien tir eila tUng loai chu ky chiing tdi tach bidn thien trudng tir F thanh hai phdn : phdn cd chu ky tu 4 ddn 24 gid va phdn cdn lai cd chu ky nhd ban la phdn duge dimg trong phuang phap cam img tir sau nay (cd the diing hai phuang phap phan tich phd hoac trung binh trugt vdi mdi bude 4 gid de tach hai phdn cua bidn thien tu).
Hinh la cho thdy bidn thien ngay dem va eae bidn thien trudng tir cd chu ky tu vai phiit ddn vai gid eila F vao ban ngay deu ed bidn dp tang ddn khi tidn gdn ddn Xich dao tu (vy dp cp = 80°56'). Tuy nhien cac nhidu vd ban dem va chidu lai cd bien dp vd chu ky kha Idn va kha ddng nhdt trdn lanh thd eua Viet Nam, vi vay ehiing rdt phii hgp cho phuong
phap vector cam irng tu. Cac khao sat edn cho thdy bidn thien cac thanh phdn trudng tu khae nhu H, D, Z vao cac gid ban ngay ddu chiu anh hudng cila ddng dien Xich dao (tire hieu irng ngudn) tren mdt viing rpng ldn d nude ta. Ndi rieng, dd'i vdi bidn thien cd chu ky ngay ddm viing anh hudng ciia ddng dien Xich dao cd thd hinh dung qua hinh lb, duge xay dung bang sd lieu bidn thien trung binb gid cila Sq(H) tren cac tram dia tu Bac Lieu, Da Lat, Ha Npi, Sapa va sd lieu do d Long An trong thing gieng nam 1990 bang may bie'n thien hr MBC ciia Nga.
Hieu irng ngudn edn bidu hien tren cac bang tu d tram Da Lat [10]. Tram nay cd mpt vi tri kha dae biet la nam ve phia bde cua ria bac ddng dien xich dao. O tram nay, vao budi sang khi ddng dien xich dao dang hoat ddng, bidn thien thanh phdn Z(AZ) va thanh phdn H(AH) vdi chu ky tu vai phiit ddn vai gid luOn dao dpng nguge pha nhau, Nguge lai vao chieu mupn va ban dem, khi ddng dien xich dao khdng tdn tai hoac boat ddng yeu, cac dao dpng eua hai thanh phdn tren lai ddng pha nhau {hinh 2). Hien tugng tren chiing tOi cOn nhan thdy d Long An. Trong [101, khi phan tieh nhidu binh vinh ban dem va ban ngay tren lanh thd Viet nam, chiing tdi di ddn kdt luan ve sy cdn thidt phan biet hai loai : nhidu hinh vinh ban dem xudt phat tir dien ly viing eye quang, cd cac quy luat nhu d cae vy dp trung binh, va cac nhidu hinh vinh ban ngay, chiu anh hudng eua ddng dien xich dao.
Tren cac kdt qua nghien ciru vd hieu irng ngudn trong phuang phap cam irng tu trinh bdy kha rd trong [151. Do hieu ung ngudn ma phuang trung binh cila vector cam irng tir ed the quay lech ddn 10° khi sii dung nhidu eila bao tu sinh ra do ddng cd hudng vd phia tay va ddng hudng ve phia ddng trong viing eye quang (lech 10° so vdi trudng hgp sii dung bidn thien tu trong ngay trudng tir yen tTnh).
Hinh la, lb va hinh 2 cho chiing ta mOt sd nhan xet:
600
500
400
300
200
100
300
250
200 J
150
100
-100
0 10 20 30 0 10 20
Hinh la. Bidn thien trudng tu toan phdn F (23/3/89) tai cac didm do Da NSng, Da Lat Rach Gde, Hdn Khoai duge tach lam hai phdn : phdn cd chu ky tu 3 ddn 24 gid (a) va phdn ed chu ky nhd (b)
GHI CHO : true tung : thudc ty le don vi nT, true hoanh : gid Ha Ndi: LT
Nhan xet: bidn thien trudng tir F (T) vao cae gid ban ngay chiu anh hudng cila ddng dien Xich dao tren mpt viing rpng ldn d nude ta
Sq(H) (nT) Jan.90 Vietnam
Hinh lb. Phan bd bidn thien ngay dem Sq(H) thang 1 nam 1990 tai Viet Nam.
GHI CHO : thude ty le mdu cd dan vi nT, true hoanh - thdi gian dia phuang, true tung - magnehc, LAT = arctan((tanI)/2). I = dd tu khuynh
- Bie'n thien ngay dem Sq(H) vdi chu ky 24 gid eo bien d() tang ddn khi tidn den xich dao tu va anh hudng cua ddng dien xich dao vugt qua Da Nang vd phia bdc.
- Cae bidn thien co chu ky tir vai phiit ddn vai gid vao ban ngay cd anh hudng kha rd eila ddng dien xich dao.
AD(nT)-20nT
in
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50 40 30 20 10 0 -10 -20 -30
0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 19 20 2122 23 24
190 1 i n
cin
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nT)
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:=^0 1 2 3 4 5 6 7 8 9 10 1112 13 14 15 16 17 18 19 20 2122 23 24 Hinh 2. Trudng bidn thien tii tai Da Lat 16-11-1984 theo gid UT - Cae bie'n thien vd chidu mudn va ban dem vao
ngay cd chi so boat dpng tu K ldn lai rdt phu hgp eho phuang phap vector ciim irng tu vi ehiing cd ba uu die'm : eae bidn thien nay ehinh la loai DPI, DP2 hoac cac nhidu trong bao tu nen chiing cd ngudn d kha xa be mat khao sat dia dien tren mpt khu vyc rpng ldn, do dd bao dam didu kien sdng phang eila trudng sa cdp. Mat khae chu ky cila cae bidn thien nay ttr vai phut ddn vai ba gid va bien dd ciia chung kha ldn se phii hgp cho phuang phap khao sat eila chung ta.
Tdm lai, dd khae phuc hieu irng ngudn td't nhdt la chgn cac bidn thien ed chu ky ngdn vao chieu va td'i dd sii dung cho phuang phap vector cam iing tir trong vting can xich dao.
Hinh la va lb cdn cho chiing ta mpt nhan xet ed y nghia thyc td khi do hr hang khdng hoac do hr tren bidn Viet nam : ehii y dam bao sao eho khoang each giira cac didm dat may ghi bidn thien va khoang thdi
gian la'y sd do cho tung may ghi khi thyc hien cOng tac d viing can xich dao tu phai nhd ban cac khoang each tuong irng khi thuc hien cdng tac d viing xa xich dao tu.
III. QUY TRINH THU THAP VA XLT LY SO LIEU TRONG PHUONG PHAP VECTOR CAM iTNG TLT
1. Ghi bie'n thien trudng tutheo tuydn hoSc dien Chung tdi sii dung sd lieu ghi thudng xuyen d cae tram dia tir Sapa, Phu Thuy, Da Lat, Bac lieu, trong dd hai tram Phu Thuy va Bae Lieu cd may Fluxget ghi bidn thien ba thanh phdn X, Y, Z vdi dan vi 0,lnT, mdi phut mpt sd. Do ddng thdi trudng tu toan phdn F bang hr kd proton vao thang 3 nam 1989 tai ede did'm Hdn Khoai, Rach Gd'c, Long An, Da Lat, Da Nang trong chuong trinh hgp tae giua Vien Dia tir, Dien ly va Truydn sdng (Lien Xd) va vien vat ly dia cdu Ha Npi (bang 2).
Tai cac tram khae cung nhu cac diem do edn lai thidt bi ty ghi trudng tu MBC cua IZMI RAN duge dimg de thu thap sd lieu bie'n thien tu. Tai Bac Lieu va Vung Tau chiing tdi cd dung y xem bidu bidn cila hieu irng bd trong vector earn irng tir. Tai Hoa binh va Chiia Trdm ehiing tdi phat hien viing cd dP ddn dien cao nhd hudng chi cila vector cam iing tu va cd hudng khao sat ehi tidt tidp theo d viing nay trong thdi gian tdi. Nhu vay ehiing tOi ed hai dang sd lieu :
Sd lieu gde
ghi tuang ty bang thidt bi MBC cho cac bang tu va tram INTERMAGNET se cho ra cac bang sd vdi bude ghi 1 phiit cac thanh phdn X(H), Y(D), Z.
2. Cac bSng tu duoe sd hoa
Dd thuc hien cac phep tinh tie'p theo, cac bang tir duge sd hoa bdng bidn phap quet anh va tinh theo chuong trinh viet bdng ngdn ngir MATLAB (hinh 3-5).
80
60
40
20
Sd lieu npi suy interp
t i
,.--. / / i . i'
-linear
1
200 4O0 600 500 50O 1CO0 1500
eo
60
40
20
200
H: CHUA TRAM 18-19/JUN/1996
/
y
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"''^y^r
200 400 600 800 1000 1200 1400
So sanh SL goo va SL npi suy
Hinh 3. Thanh phdn H Chtia Trdm duge sd boa
(true tung la thudc ty le bien dp, dgn vi nT ; true hoanh mdi phiit mpt sd) 1600
Tuang ty dd'i vdi cae thanh phdn trudng tir d Chiia Trdm, cac thanh phdn trudng tu d Hoa Binh vanai khae ghi bang thie't hi MBS cung duge quet va sd hod sao eho mdi phiit cd mdt .so sau khi da loai trend cila tap hgp sd cd dp dai Idn qua 7-8 gid. Chgn eho mdi dia didm nhidu sy kien nhidu trudng tir vdi nhidu ehu ky trong khoang tu vai chuc phiit ddn vai gid de thuc hien bidn ddi Fourier tap hgp sd lieu da thu.
J. Dpc cac thanh phan trudng tuH, D, Z Dgc thanh phdn trudng tu H, D, Z ttr sd lieu IN- TERMAGNET vdi gia tri nT tram Phu Thuy, tinh cac thanh phdn AZ , AX, AY so vdi gia tri ea sd.
X = H* COS(D), Y = H* SIN (D), AZ = Z - Z o , A H = H - H o , A X = X - X o , A Y = Y - Y o D tinh ra don vi radian.
D(') = D(nT)/Hsin(l') = D(nT)/l 1,3446 D(rad) = D(')*pi/(180*60) Zo, Ho, Xo, Yo la cac hdng so.
Thyc hien cac phdp tinh tren cho tung su kien da chgn trong ca ,sd du lieu cila tram Phu Thuy, va sdp xdp thanh file spe.dat dd tinh phd va td chiic tinh theo chuong trinh Spe-arow.exe.
no
60
60
40
-HI
So lieu
1 ( \
J I
goc
" W|
V""-
-
f
/
J J
100 20O 300 400 500 100
60 60 40
20
So lieu npi suy interp-linear
^-^ . . . - . ' " • ' ' " ' ^ '
1
i
1
J
Afl
1
•
.
y
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1O0
80
60
40
20
500 1000
500 1000 So sanh SL goc va SL npi suy
1500
1
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1
„.,r
/
V
U .A
v\/\
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J
1500
< - Hinh 4.
Thanh phdn D Chiia Trdm duge
sd boa (true tung la
thude ty le bien dp, don vi nT, true hoanh mdi phiit
mdt sd)
Sd lieu goc
Hinh 5. -^
Thdnh phdn Z Chiia Trdm
duge sd hoa (true tung la thudc ty le bien dd, dan
vi nT, true hoanh mdi phiit mdt so)
300
60
50
40
30
Sd lieu npi suy interp
/ 1
1
\
1 J ' I'i
1/
-linear
/
v''
. A V
-
500 1000 1500
60 50 40 30 20
Z: CHUA TRAM 18-19/JUN/1996
y
500 1000 So sanh SL goc va SL npi suy
1500
Phdn ldn cac sy kien nhidu trudng tu trong bao hien bie'n ddi Fourier nhanh dd'i vdi gia trj cac thanh tu hoac nhidu hinh vinh {hinh 6) duge chgn va thyc phdn AZ, AX, AY.
Sa Pa
19 LT
— - — 1 — 1 I 1 1 1 I I I 10 11 1 2 U T 9 10 11 1 2 U T 9 10 11 12 UT
Hinh 6. Cac dudng ghi bidn thien tu tai Sapa, Xuan Giao, Phd Rang, Phu Thuy, ngay 29-12-1989 4. Tinh cac ham chuyen
Cac thanh phdn cila phep bidn ddi Fourier d mdt chu ky nao dd duge chgn dd tinh cac ham chuyen cho thanh phdn thdng dung (Wzx, Wzy) thd hien mdi tuong quan tuydn tinh giiia trudng thdng dimg cua trudng di thudng Za va cac thanh phdn nam ngang cua frudng gay cam irng (Xn,Yn) duge danh gia theo Gough va Ingham [31 va Parkinson [81 nhu sau :
Za = Wzx Xn-H Wzy Yn + 5 (1) d day ta't ca cac dai lugng ddu la phire va phu thupe tdn sd, 5 - phdn khdng tuang quan cila trudng thdng dirng.
Phuang trinh tren thudng duge vie't dudi dang dan gian cho sd lieu bidn thien H, D, Z theo ky hieu truydn thd'ng d mpt tram dja tu :
Z = A H - H B D + 5 (2) Cac hang sd A, B la nhirng sd phirc va phu thudc ca'u triic dp ddn dja dien vd tdn sd, cdn Z, H, D la nhirng gia Ui bie'n ddi Fourier cila bidn thien trudng tir cila thanh phdn thdng dirng Z, phuong bdc H, va phuang ddng D d mdt tdn sd nhdt dinh nao dd. Tidp theo ta cdn xac dinh cac he sd A, B theo phuang phap binh phuang td'i thid'u [61.
Ndu phdn thyc va phdn ao cila A va B duge ky hieu la Ar, Ai va Br, Bi thi bien dd cua cac vector thyc Gr va ao Gi va gde OR va 0, duge tinh theo :
|G^| = (A2+B2)i/2, 0,=tan-^{B,/A,) (3)
\G,\ = {Aj+Bjy'2, 6* = tan-1(5//A/) (4) S. Chay chuong trinh Spe-arow.exe
Chay ehuong trinh Spe-arow.exe se cho kdt qua dting chay tie'p chuong trinh arwhao.exe dd cho ra ke't qua cud'i ciing vdi cac gia tri cac thanh phdn cila vector thyc Ar, Br va cac thanh phdn ciia vector ao Ai, Bi trudng bidn thien tir irng vdi tung ehu ky bidn thien da chgn, kem theo eae sai sd danh gia cae dai lugng da tinh duge. Tu cac gia tri Ar, BR, A|, Bl irng vdi tirng chu ky, ta cd the tinh tie'p cac dai lugng dae trung cHa chiing. Trudc tien chiing tdi ve cac vector cam irng dien tu theo hinh 7 tren he toa dd vudng gde, Ar (hoac Ai) hudng ve phia nam, Br (hoac Bi) hudng vd phia dOng theo each cila Parkinson [7, 81 va sau dd danh gia dp ddn dien dgc theo cdng thirc thyc nghiem eila Rokitian.snki [91.
Didu thii vi nha't trong phuang phap nay la eae vector thyc xay dyng theo phuang phap cila Parkin-son [7, 81 ludn chi vd nai cd dd ddn dien eao (nhung ndu theo phuang phap eila Wie.se [16|
thi vector chi hudng nguge lai !). Vi vay ndu hai vector duge xay dung cno hai vi tri d each nhau vai ba chuc kilomet ma ed hudng chi vdo nhau thi
cd the dinh vi duge vat thd cd dp dan didn cao gay ra sy lech hudng cila hai vector dd (trudng hgp vector cam irng Hod Binh va Chiia Trdm, hoac cae vector cam irng tu hai bdn dirt gdy sdng Hdng [61.
Mpt didu dae biet nOa la hudng cila vector cdn phu thudc vao ehu ky bidn thien tu nen ta edn cd thd bie't thdng tin vd vat thd ed dp ddn dien eao nam d khoang dd sau ndo.
Bdng 3. Do dan dien doc G mot so noi tren dut gay song Hong
N / A < 0 B > 0
W A > 0 B > 0
s
A < 0 B < 0
^ y oy
A > 0B < 0
E
Hinh 7. Cach ve vector cam img ttr theo Parkinson
6. Suphu thupe vao tan sdcua Gg va G, trong mdi trudng hai chieu
Khi nghien euu su phu thupe vao tdn sd cua cac vector cam irng cho trudng hgp cdu triic hai chidu Chen va Fung [21 da ehirng minh : tdn tai mpt ehu ky dae trung Te, tai dd dp Idn cila eae vector cam irng thuc dat gia tri Idn nhdt. Khi qua chu ky dd, vector ao ed sy ddi hudng 180°. Hon nua ndu bidt chu ky dae trung Tc cd the danh gia dp ddn dien dgc G (G = aQ, Siemen.m), a - dd ddn cd don vi Siemn/m, Q - tidt dien mat cat ngang, Q
= h*L, tinh ra m^ eila vat thd cd di thudng dp ddn dien. COng thiie thyc nghiem do Rokytyansky [91 dua ra ;
G = 5 X 10" X (T,)'-^ (9) d day Tc tinh bang giay, G tinh bang Siemen.m (do'i vdi edu true hai chidu, h va L la be ddy va bd rPng cila bang di thudng ed ddng dien chay qua)
Mdt vai danh gid dd ddn dien dgc G eila dirt gdy sdng Hdng.
Trong bdng 3, dd ddn dien dgc G a Sapa va Xuan Giao cd ciing ed va ldn nhdt, edn d Ha Ndi dd ddn dien dgc nhd nha't. Trudc day, trong cdng trinh [11, vdi sd lieu bidn thien ttr d Sapa va Yen Bai bude ddu chiing tdi da danh gia dp ddn dien dgc g viing nay ca lO' simen.m, rtre ciing ed vdi nhiing danh gia dd ddn dien dgc d bang 3.
Tram SaPa Xuan Giao Phd Rang Yen Bai HaNpi
Tc (phiit) 47 48 40 40 28
G (Siemen.m) 6,9 X 10*
7,0 X 10*
5,7 X lO"
5,7 X lO"
3,7 X 10*
IV. MOT SO KET QUA VECTOR CAM UNG TLT TREN PHAN PHIA NAM LANH THO Mpt sd .sd lieu dung dd ve vector cam irng tu phdn phia nam (Long An, Da Lat, Bac Lieu,Viing Tau) ghi trong hdng 4.
Bdng 4. So lieu dung de ve vector cam iimg
Gr 1. Vung 0,85203 0,634196 0,535261 0,542971
Ar ' Tau
0,8519 0,6324 0,5313 0,5395 2. Bac Lieu 0,383402 0,385408 0,386948 0,404228 0,37943 0,38092
3. Long 0,6321 0,6635 1,1178 0,3393 0,9408 0,3294 0,3797
0,3668 0,3669 0,3605 0,3990 0,3569 0,3594 An -0,5389 -0,5635 -1,0319 -0,2063 0,9407 0,3274 0,3382 4. Da Lat 0,621770 0,286386 0,248319 0,209246 0,171772 0,450983 0,257687 0,192705 0,223613
0,1567 0,1501 0,1225 0,1373 0,0938 0,1580 0,1774 0,1897 0,1627
Br
0,0149 -0,0477 0,0650 0,0613 0,1116 0,1180 0,1406 0,0648 0,1288 0,1237 -0,3304 -0,3503 -0,4298 -0,2694 -0,0141 -0,0366 -0,1725 -0,6017 -0,2439 -0,2160 -0,1579 -0,1439 -0,4224 -0,1869 -0,0339 -01534
Chuky (phut)
204 102 93 68 1024 186 204 170 157 146 2048 204 102 68 51 50 41 1024 512 341,3 256 204,8
170,7 146,3 128,0 113,8
Vung Tdu va Bac Lidu ndm sat bd bidn nam Viet Nam. Kdt qua khao sat cho thdy hieu irng bd bidu hien kha rd trong cac vector cam irng tu d hai dia diem nay : hudng eila eae vector xay dyng theo Parkinson (81 chi vd nai cd ddng didn cam iing trong nude bidn vd cae ldp trdm tich ma dp ddn dien trong thyc td ludn Idn ban rd ret dd ddn didn
Vector thyc - Long An
90 2
Vector thuc - Bac Lieu
90 0-5
eae Idp ddt da gdn bd. Mat khdc theo Cao Dinh Trieu [14], Le Tii San va nnk [121, phia nam Vung Tau va Bac Lidu tdn tai diit gdy Thuan Hai - Minh Hai nam trong vimg cd kha nang phat sinh ddng da't M.smax = 5,1-5,5. Dd ed thd la nguyen nhan lam cho hdu bdt cac vector cam irng tu hudng vd phia nam {hinh 8).
Vector thUc - Da Lat
90 1
Vector thyc - Vung Tau
90 2 120^^7^~^0
21 Ov /djr \ J30 2MX .'^'f' ^.. 330
24[>-4;„^-^0 2Al>y^^^0 Hinh 8. Phan bd eae vector thyc tai Long An, Da lat, Bac Lidu va Vung Tau
Tai Long An cae vector cam iing tu cd su phu thupe vao chu ky. Vdi ehu ky dai cac vector cd hudng tay bdc, chi vd dirt gdy Viing Tau - Tdng Le Sap (II-2), viing phat sinh dpng ddt Msmax = 5,1- 5,5 [14[.Cdn vector vdi chu ky ngdn ban lai hudng ve ddng nam hoac chinh nam.
Tai Da Lat, c6 nhidu yeu td la nguyen nhan lam cho cac vector chi rdt tap trung vd phia ddng nam quanh 340° (hinh 8). Dd ed thd la cac dirt gdy chay qua phia ddng nam Da Lat, nam trong cac viing phat sinh dpng ddt cdp 6,7 [12, 17].
V. M O T S O V E C T O R CAM LTNG TREN PHAN MIEN BAC (PHU THUY, HOA BINH, CHUA TRAM)
Sd lieu dimg dd ve vector cam iing eho phdn phia Bdc ghi trong bdng 5.
Dua theo hai hudng eheo nhau eila cac vector cam irng tu d hai did'm Hod Binh vd Chtia Trdm cd the du doan tdn tai mdt khu vyc cd d6 ddn dien cao nam phia tay nam niii Ba Vi {hinh 9). Tuy nhien eung cd the vector cam irng ttr tai Chua Trdm chi vd diit gdy d phia tay Chtia Trdm.
Bdng 5. So lieu dung de ve vector cam iimg cho Phu Thuy, Chua TrSm va Hoa Binh
Gr
ill
XR (AR)
(2)
YR (BR) _i3L_
0,2044 0,1659
1. Phii Thuy 0,1864 0,1456
0,0839 0,0795
ChuKy (phut)
(4) 204,8 102,4
Gi i 5 I 0,3908 0,6372
XI (AI) _16}_
0,1397 0,2083
YI (BI)
JZI.
-0,365 -0,6022
ChuKy (phut)
(8) 204,8 102,4
Bdng 5 (tie'p theo) (1)
0,1339 0,3156 0,2957 0,3379 0,3912 0,3285 0,2459 0,2212 0,27425 0,296618 0,381352 0,534534 0,723137 0,760859 0,624142 0,0742 0,0748 0,0932 0,1520 0,4085 0,5647 0,5412 0,2558 0,2211 0,6081
(2) 0,1232 0,1834 0,1971 0,1755 0,1707 0,1748 0,1487 0,1583 2. Chua Tram
-0,1068 -0,0449 0,0283 0,0530 -0,1346 -0,3679 -0,1153 J. Hoa Binh
-0,0227 -0,0145 -0,0528 -0,1298 -0,3969 -0,5358 -0,4809 -0,2521 -0,2117 -0,6081
(3) 0,0525 0,2568 0,2204 0,2887 0,352
0,2781 0,1958 0,1545 0,2526 0,2932 0,3803 0,5319 0,7105 0,6660 0,6134 -0,0706 -0,0734 -0,0768 -0,0791 -0,0967 -0,1782 -0,2482 -0,0433 0,0637 0,0029
(4) 68,3 51,2 41,0 34,1 29,3 25,6 22,8 20,5 68,3 51,2 41,0 34,1 29,3 25,6 20,5 204,8 102,4 68,3 51,2 41,0 34,1 29,3 25,6 22,8 20,5
(5) 0,7636 0,8606 0,1631 0,1803 0,1181 0,1343 0,2051 0,1498 0,661289 1,077050 0,667835 0,856543 0,921789 0,430784 0,378285 0,2238 0,2409 0,2788 0,2988 0,1909 0,1374 0,4529 0,4115 0,2009 0,1061
(6) 0,3175 0,1348 0,0598 0,0588 0,0708 0,1035 0,1453 0,1159 -0,4690 -0,9370 -0,2167 -0,4443 -0,6244 -0,2288 -0,0387 0,2187 0,2354 0,2701 0,279
0,1393 0,109
0,3397 0,2686 -0,0548 -0,1034
(7) -0,6945 -0,85
0,1517 0,1704 0,0945 0,0856 0,1447 0,0949 0,4662 0,5311 0,6317 0,7323 0,6781 0,3650 0,3763 0,0476 0,0510 0,0692 0,1069 0,1306 0,0836 0,2996 0,3118 0,1933 0,0239
(8) 68,3 51,2 41,0 34,1 29,3 25,6 22,8 20,5 68,3 51,2 41,0 34,1 29,3 25,6 20,5 204,8 102,4 68,3 51,2 41,0 34,1 29,3 25,6 22,8 20,5
Hinh 9. -^
Sa dd kidn tao vd eae vector earn
iing bie'n thien tir tai
Hod Binh, Chiia Trdm vd Phil
Thuy
Hudng cila vector cam irng hi d Phii Thuy chi vd phia sdng Hdng.
KET LUAN
• Trudng bidn thien tu d phia nam chiu anh hudng eiia ddng dien xich dao, cdn nghien eim anh hudng eiia ngudn nay trong bai toan cam irng tu trong khu vyc phia nam. Trudc tien cdn chpn eae nhidu trudng tir vao chidu td'i va ban ddm.
• Cac nhidu nhd trong bao tir cung la eae bidn thien ttr rdt phii hgp cho phuang phap cam irng tu vi chiing cd nhieu chu ky khae nhau va bidn dp Idn so vdi cac nhidu trong trudng hgp ngay khdng cd bao tir.
• Cac ke't qua neu len mpt sd dae did'm eila phuang phap cam irng ttr va mpt vai Ung dung trong khao sat dia chdt - dia vat ly : eae vector cam iing tu chl hudng vd vimg ed dut gdy sau trong ldng ddt va viing ed boat dpng dPng ddt manh.
• Phuang phap danh gia dd ddn didn dgc theo chu ky eye dai Tc nhu da trinh bdy d tren cho chiing ta mdt dae trung mdi ve tinh ehdt vat ly cila dirt gdy sau hoac viing cd ddng ddt manh.
• Cae ke't qua khao sat cdn cho ehiing ta mpt biie tranh tdng quan vd anh hudng eila ddng didn xich dao ddn trudng bidn thien tu d midn nam nude ta, se Id tai lieu tham khao cho cdng tae khao sat dia vat ly ed lien quan ddn sii dung bidn thien trudng dia tu tren bidn va ddt lien.
TAI LIEU DAN
[1] lu.D.ABRAMOVA, lu.R SIZOV, TRUONG QUANG HAO. 1992 : The preliminary results of magnetovariahonal investigation on territory of Vietnam. Researchers on the main and anomalous fields of the Earth. Edited by N.M. ROTANOVA.
30-35. Moscow. IZMIRAN.
[21 RRCHEN and RC.W. FUNG,1985 : Signifi- cance of the sign changing of the imaginary arrow in geomagnetic induehon inveshgadon. Geophys.
J.R. Astr. Soc. ,V. 80, 257-263.
]3] D.J.GOUGH and M.R.INGHAM,1983 : Inter- pretadon methods for magnetometer arrays. Reviews of geophysics and space physics. Vol. 21,4,805-827.
[4] TRUONG QUANG HAO, B.R, ARORA 1994 : Preliminary results of studies of conducdvity anomaly
at the faults of Red river. Proceedings. International Workshop on Seismotectonie and seismic hazard in South East Asia. p.231. Hanoi, Vietnam.
[5] TRUONG QUANG H A O . 1 9 9 7 : Nghien eiru bidn thien cua trudng dja tu d Viet Nam. Thanh tyu nghien ciru Vdt ly dia cdu 1987-1997. Trung tam Khoa hgc Tu nhien va Cdng nghe Qudc gia. Vien vat Ly Dia Cdu. Ha Npi.
[6] TRUONG QUANG HAO, VO THANH SON.
2004 : Dae didm vector cam irng ttr hai ben dirt gdy sPng Hdng. Tap chi Cae Khoa hgc vd Trai Ddt, T.
26, 2,136-145.
[7] W.D, PARKINSON, 1959 : Direction of rapid geomagnede fluctuations. Geophys. J. Roy. Astr.
Soc. V. 2, 7-74.
[8] W.D. PARKINSON. 1983 : Intr. oduetion to Geomagnetism, Scottish Academic Press, Edin- burgh and London
[91 I.I. ROKYTYANSKY, 1982 : GeoeleeUomagnetic invesdgadon of the earth's crust and mantle. Springer - Verlaag. pp. 1295. New York.
[10] N.M. ROTANOVA, TRUONG QUANG HAO, 1992 : The bays of geomagnetic disturbances on territory of Vietnam. The research on the problems of the main and anomalous fields of the Earth. 72- 79, Moscow. IZMIRAN.
[11] U. SCHMUCKER, 1970 : Anomalies of geo- magnetic variations in the southwestern United states.
Bull. Scripps Inst. Oceanogr., 13,1-165.
[ 12] LE Tir SON, NGUYEN D I N H XUYEN, N G U Y I N QUOC DUNG, 1997 : Cac kdt qua nghien ciru dia ehdn cdng trinh. Thanh tyu nghien ciiu Vat Ly Dia edu 1987-1997. 92-7 J7. Nxb KHvKT. Ha Npi.
|13] VO THANH SON, 1997 : Ap dung phuang phap cam irng tu nghien ciru ba't ddng nhdt trong vd Trai Ddt, tuydn Hod Binh - Bdc Giang. Tap chi Cae Khoa hgc vd Trai Ddt, T. 19, 4, 301-305.
]14] CAO DINH TRIEU, 1995 : Md hinh mat dd vd Trai Ddt lanh thd Viet Nam. Tap chi Tin hoe va Didu khien hgc, T. 11, 3, 56-64.
[151 ARI. VIUANEN, 1996 : Source Effect on Geomagnetic Induction Vectors in the Fennoscandian Auroral Region. J. Geomag. GeoelecU. 48,1001-1009.
[16] H. WIESE, 1965 : Geomagneti.sche Tiefentel- lurik .Abb. 36, 146 pp. , Dtsch. Akad. Wiss. Berlin, Gomagn. Inst. Potstdam.
[17] NGUYIN DINH XUYEN, NGUYEN NGOC THtJY, 1997 : Tinh dpng ddt va dd nguy hiem ddng ddt tren lanh thd Viet Nam, 34-91. Nha xudt ban Khoa hgc va Ky thuat. Ha Npi.
S U M M A R Y
The short period geomagnetic variations and features of Induction vectors in territory of Vietnam The concept of induction method was original introduced by Parkinson (1959) and independently by Wiese (1965), and is now used largely on the whole world. Its advantage is that the study depths is great by using the magnetic variations of period from minutes to hours. Moreover this method is very effective in the determination of the canals having high electric conductivity in the Earth.
Geomagnetic induction vectors were calculated at the Vietnam magnetometer stations using the variations of bay-like fluctuations and magnetic disterbances having period about ten minutes to several hours.
The source effect on geomagnetic variations can be clearly seen at recording sites near the Equatorial electrojet. As a practical rule, we use data of eveming and night time for calculating induction vectors.
In the South of Vietnam, at Vung Tau and Bac Lieu stations the induction vectors show clealy the coastal effect, but at Long An one, they show a clealy
frequency dependence. In longer periods, the induction vectors at Long An tend to point toward to Ham Tan fault, but in the short period of variations the vectors tend to E-S direction.
In the regions of Hoa Binh and Chua Tram the induction arrows show the evidence of higher conduc- tivity structure in W-S direction of mountain Ba Vi.
In observing the variation of bay-like fluctuations having period about ten minutes to some hours in the territory of Vietnam the distinct difference in the variations of components Z at Phu Thuy (Hanoi) and at Sa Pa is that they are always in the opposite phases. On many bay-like magnetic disturbances registered simultaneously at Sa Pa, Xuan Giao, Pho Rang, Phu Thuy (Hanoi) on October of 1989 the above is discovered. The phase opposition in the variation of components Z occurred even at Xuan Giao and Pho Rang which are not far from each other on the two sides of the Red River while the variation of components H and D are almost similar.
By following the direction of magnetic induction vectors, the regions of high electrical conductivity at the faults of Red River can be detected.
The longitudinal conductivity G (product of con- ductivity and cross sectional area) of the anomalous body by using the empirical relation given by Roki- tyansky (1982) at some stations are estimated.
Ngdy nhdn bdi : 15-01-2009
Vien Vat ly Dia Cdu, Vien Dia Ly