114 - 121 Dia dong luc Kainozoi mien Bdc Viet Nam 11 - ^^^^
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Mot SO net ve chuyen dong hien dai
phan lanh tho mien Bae Viet Nam theo so Ueu GPS
TrSn Dinh To^ Nguyen Trpng Yem', Vy Quoc Hai', Ducmg Chi Cong , W. Zuchiewicz^ Nguyen Qu6c Cuong', Nguyen ViltNghia^ K. Feigl\ M. Becker^
' Viin Dia chdt, Viin Khog hgc vd Cdng nghe Viet Nam, - Vien Khoa hgc Do dgc vd Bdn do, Bd Tdi nguyin vd Mdi trudng
^ Dgi hgc Khoa hgc vd Cdng nghi AGH, Ba Lan
"* Dgi hgc Visconsln - Mgdison, Hoa Ky
^ Dgi hoc Darmstadt, CHLB Ditc Tom tat
Trong sa dd kiin tgo hiin dgi phdn Idnh thd Miin Bdc Viet Nam, he thdng dirt gdy Sdng Hdng cd mot vi tri dgc biii, dugc coi Id rgnh gidi phig bdc ciia khdi Sunda vdi khdi Nam Trung Hoa. tiep den la dirt gdy Diin Bien Phii, dirt gdy sdng Dd vd dirt gdy San La.
Cdng nghe dinh vi todn cdu GPS da dugc sir dung di do dgc hogt ddng hien dgi dgc cdc ddi dirt gdy ndy trong nhirng ndm vira qua.
Cdc tap sd lieu do nciy ldn ddu tiin dugc xir ly kit hgp bdng phdn mem GAMIT/GLOBK di tinh van Idc chuyin dich tuyet ddi trong Khung ITRF2000 nhdm ddnh gid van tdc chuyen dich ngang ciia cdu triic Ddng Bdc vd cdu true Tdy Bdc ciing nhu chuyin ddng tuong ddi tgi timg dirt gdy.
Kit qud xir ly cho phep dua ra mgt sd ddnh gid budc ddu vi chuyen ddng hiin dgi lanh thd mien Bdc Viet Nam.
1. Dat van de
Phan bae lanh thd Mien Bae Viet Nam trong bai bao nay duoc gidi ban ta' vT tayen 20° bae trd len. Dirt gay Sdng Hdng (DGSH) chia vimg nghien cim ra hai cau tnic kien tao gpi la cau tmc Ddng Bae va cau true Tay Bae. Noi day, ngoai DGSH, diit gay Sdng Chay (DGSC) va diit gay Sdng Ld (DGSLo), ca ba cd ten gpi chung la he thdng dut ^ay song Hong (HT DGSJJ), cdn cd cac dut gay quan trong khac duac coi dang boat dong la dirt gay Dien Bien Phu (DGDBP) - hay cdn goi la dirt gay Lai Chau - Dien Bien, diit gay Sdng Da (DGSD) va dirt gay Son La (DGSLa),
Tai Viet Nam, Vien Dia chat, Vien Khoa hoc va Cdng nghe Viet Nam da su dung cdng nghe dinh vi toan cau GPS d8 do dac chuygn dong hien dai doc HT DGSH (1994-2006), DGDBP (2002-2004), DGSLa va DGSD (2001-2005), Tir sd lieu quan trac nay, nhiing danh gia budc dau ve chuyen ddng tuong doi doc timg dut gay ndi tren da dugc cong bo [2, 8, 9],
Lan dau tien, tat ca cac chudi sd lieu do tren da dugc xu ly ket hgp de nhan dugc trudng van tdc chuyen dgng tayet ddi trong ITRF2000 nham xac dinh van toe chuyen dgng cua cau true Dong B5c va cau tnic Tay Bae, danh gia sir khac biet (neu cd) giiia chuyen dgng hien dai cua hai cau fruc, so sanh ldi giai van toe ITRF2000 nhan dugc tai cac diem do vdi van toe chuyen dgng taong img tinh theo md hinh dgng hgc khdi Sunda va md hinli dgng hoc toan cau, dong thdi tiep tuc danh gia ve chuyen dich taong doi tai timg dut gay quan frac,
Bai bao nay frinh bay nhung ket qua xir ly ndi fren.
2. Khai quat hoat dong kien tao hien dai mien Bae Viet Nam
Tren so dd kien tao hien dai MiSn BSc Viet Nam, hoat dgng kign tao thS hien fren cac dirt gay tich cue (hinh 1), HT DGSH n5m d phan tmng tam va dirt gay DGDBP nSm d phia cyc tay dugc coi la hai he thong dirt gay trugt bSng cdng img, hoat dgng kha tich cue frong suot thdi gian Plioxen-De ta', Trong do HT DGSH phuong TB-DN boat dgng tmgt phai [11] va DGDBP cd phuong a kinh tayen tmgt frai tuang img [10, 11], Nam giira hai he thong dirt gay nay la cac he thdng DGSLa va DGSD cd phuong TB-DN, nhung boat dgng frugt phai kem tich cyc ban [11], 0 phia ddng, song song vdi bien gidi Viet-Trung, dut gay Cao BJng-Tien Yen (dut gay Quoc 16 4) cung cd phuang TB-DN nhung l^i cd nhung boat dgng hTjgt trai trong De tir muon, Ditt gay Chi Linh - Dong Trieu - Hdn Gai (dirt gay Qudc 16 18), phuong a vT tayen lai boat dgng chdm trai [10, 11],
Hmh 1. Sa dd he thong dut gay tich cue mien Bae Viet Nam
Xet dudi gdc do dia chin hien dai, HT DGSH va DGDBP cd su khac biet: HT DGSH hiem khi bi anh hudng cua cac tran dgng dSt manh (ldn nhit la M = 5.9, frung binh la 3-4), trong khi dd DGDBP lai sinh ra nhiing fran dgng dit klia manh vdi cap do manh fren 6 [10, 11]. Cac dau hieu boat dgng dirt gay tmgt bang fre dgc HT DGSH va DGDBP bao gdm: bien vi va djch chuyen thung liing sdng nhanh, cac khe sudi:
(10-50 m dgn gan 13 km dgc DGSH; 6-50 m dgn 2-2.5 km dgc DGDBP), thay ddi hinh thai he th6ng thuy
van, thung liing su6i hi chan diu (hien tagng cudp ddng chay), gd tmgt-chin, cac mat tmgt diit gay sip
xgp dudi dang canh ga (en echelon), thgm va ndn phdng vat bdi tich ciing nhu cac doan thung liing sdng
(klie su6i) bj dich tmgt va nhung mat tmgt Idn nam tuygn tinh cao dgn 30-50 m [11]. Doan ddng nam
ciia DGSH va cac phan doan gin phia bae ciia DGDBP cd thanh phan tmgt thuan ldn hon, dugc xac nhan
bdi sy phat trign manh me ciia cac sudn tmgt tam giac, cac them bao mdn bj mat ddng chay be mat do
dugc nang cao va cac thung lung treo. HT DGSH cd phuong TB-DN, thudng di kem vdi cac trung kigu
pull-apart va graben nhd hep, lip day bdi cac tram tich lyc nguygn hat tho fridi Oligoxen va Neogen va cac
ldp boi tich klia mdng De ta [11], 6 day, cudi nut rat pho bien trong cuoi kgt Neogen, rigng cuoi frong cac ldp boi tich De tti lai khong hi nut, Trai lai, DGDBP cd phuong ta a kinh tuyen (B-N) dgn BDB-NTN ciing di kem vdi mgt s6 trung pull-apart, nliung dugc lap day chi bdi cac bdi tich De ta, Cac fram tich De tir nay nam trgn cac bg mat bdc mdn ciia da gdc tadi Paleozoi va Mezozoi va thuong bi cat bdi dut gay.
Tai triing Dien Bign Phu, nhieu vien cudi nam frong cac them bdi tich tadi Pleistoxen muon bi cat pho bien bdi cac khe nut song song vdi dudng dut gay chinh [10],
Ci ca HT DGSH va DGDBP dgu xuat hien vdi tin suit kha cao hien tagng tmgt dit vdi cac Idp biin da (nhit la d DGDBP) va cac muong xdi xam thyc. Tmgt, Id ldn nhat frong DGDBP xay ra frong qua khir la do cac fran dgng dat manh [10],
Nghign cim dia mao-kign tao frgn phan doan nim frong lanh thd Viet Nam cua HT DGSH cho thay chuygn dgng tmgt phai frong thdi ki De ta cd t6c do frong khoang 0,43 va 1,1 mm/nam frgn cac doan dirt gay rigng biet cd do dai khoang 8-10 km va 20-25 km taong iing. Toe do ca 5,5-7,8 mm/nam dugc tinh cho toan bg dich chuygn cua DGSH frong su6t thdi ki De tti', Tdc do nang hien dai it nhat la 0,1 mm/nam [11],
Phan tich cac diu hieu dia mao-kign tao va bien do chuygn dich frong De tu cua cac thgm boi tich dgc cac diit gay tmgt frai va tmgt frai-thuan khong chg triing pull-apart frong DGDBP cd the xac dinh toe do tmgt bang toi thigu la 0,6-2 mm/nam frong thdi ki Pleistoxen tmng va Pleistoxen muon, Tdc do nang trong Holoxen ciia ddi nay cd xu hudng tang dan ve phia Bae: tu 0,4-0,6 den khoang I mm/nam. Tdc do nang trung binh tinh cho ca thdi ki De tir ldn hon 0,05 mm/nam [10, II].
Ca hai ddi dirt gay dugc nghign cim fren deu an chira tiem nang phat sinh dgng dat manh, dac biet d phin phia Nam DGDBP va doan Ddng Nam ciia DGSH [10, 11],
3. Do dac chuyen dong hien dai bang GPS doc cac dii't gay chinh
Trgn phan lanli thd nghign cim, HT DGSH, DGDBP, DGSLa va DGSD da dugc quan frac bang cdng nghe GPS, So do cac ludi thigt lap dgc HT DGSH (ludi GPS Thac Ba va ludi GPS Tam Dao - Ba Vi), DGDBP (ludi GPS Lai Chau - Dien Bien) va DGSLa va DGSD (ludi GPS Son La) cimg cac chu ky do da dugc gidi thieu chi tigt frong cac cong bd [2, 8, 9] ciia nhdm tac gia, Sy phan bd cac digm do va cac dut gay quan trac dugc gidi thieu trgn hinli 3,
Ta phan biet hai loai diem do: (1) cac digm bo fri gan dut gay de do dac hoat dgng ciia dirt gay nay va (2) cac digm nam xa dirt gay dg dac trung cho chuyen dgng cua ndi khdi cau tnic,
Hai diem: CAM tai Cam Pha va diem XUY (tai Phu Luang) nam klia xa DGSH nen dugc chgn dai dien cho chuyen dgng cua cau tnic Ddng Bae,
Digm NAM (Van Chan) va digm HOA! (Da Bae) nam tuong ddi xa ca DGSH d phia dong va DGDBP, DGSD d phia tay nam, dugc nhan dai dien cho chuyen dgng cua cau tnic Tay Bic.
Dgc DGDBP cd cac digm sau: DON (Mudng Lay) va LEM (Mudng Cha), NGA (Sin Ho), HAM (Mudng Cha) va TAU (Huyen Dien Bign),
Dgc cac ddi DGSLa va DGSD cd cac digm: NAH (Mai Son), va NAD (Yen Chau), NOI (Cd Ndi), LOT (Hat Ldt), QTA2 (thanli phd Son La), TPU (Mudng La) va MON (Bic Yen),
Trgn HT DGSH, d canh phia tay cd cac digm LAP (Yen Lap), SON (Thanh Son), BAV (Ba Vi), d canh doi dien gdm cac digm NTH (Thanh Ba), HUN (Dgn Himg), nam tren canh giiia DGSC va DGSLo la cac digm SOC (Sdc Son), TAM (Nui Tam Dao), DOI (Ygn Son) va frgn canh ddng bic DGSLo cd digm OAN (Na Duong),
Tat ca nhiing digm do nay dudi day dugc goi la cac digm dia phuong.
So lieu do tren cac ludi nhin chung cd khac biet it nhieu, xet dudi gdc do s6 lugng chu ky' do -^ a thdi lugng do tai moi digm trong tirng chu ky. Ludi GPS San La dugc do 4 chu ky (2001, 2002, 2004 va 2005) vdi ba ca do 10-12 gid tai moi digm, Cac digm ludi Lai Chau-Dien Bien dugc do 3-4 chu ky, moi chu ky do 3-4 ngay dem. Cac digm ludi GPS Thac Ba dugc do 4-8 ca 16 gid vao 1994 va 2000, Ludi GPS Tam Dao - Ba Vi dugc do 5 chu ky, 1994 va 1996 vdi hai ca do 5 gid trgn mdi digm (trir digm HUN do 6 ca), 1998 do hai ca 10 gid tren diem, (rieng HUN do 8 ca), nam 2000 do hai ca 23 gid trgn diem va chu ky 2006 do 4 ca 23 gid tren digm (HUN do 12 ca), Digm HOA chi do ba chu ky' (1998, 2000 va 2007), Nliin chung, so lieu do du dieu kien dg xu ly bing phin mgm GAMIT/GLOBK [3] ,
4. Xu- ly so lieu do GPS bing gamit/globk
Tap hgp so lieu do tai cac diem dia phuang (dudi day ggi la s6 lieu do dia phuang) da dugc dua vao xir ly bang phan mgm GAMIT/GLOBK phign ban 10,34 [3], theo quy frinh chuan ba budc.
Da chgn mgt sd diem ciia ludi IGS (IGS la ten viet tat cua Intemational Global Navigation Satellite Systems Service - Td chuc cac he thong dinh vi ve tinh; ludi IGS la ludi toan cau cac fram dinh vi ve tinh thudng trite do IGS quan ly): TSKB (Tsukuba), WUHN (Vu Han), TAIW (Dai Bic), TNML (Dai Loan), SHAO (Thirgng Hai), KUNM (Cdn Minh), LHAS (Tay Tang), KIT3 (Kitab), IISC (Bangalor), PIMO (Quezon), NTUS (Singapore), YARl(Yarragadee) va TIDB (Tidbinbilla), nam bao quanh Viet Nam dg tao khung quy chigu ITRF2000; s6 lieu do tai nhimg diem IGS nay dugc xir Iy kgt hgp vdi so lieu do dia phuong,
Cac san pham chinh xac ciia IGS: tga do chinh xac ve tinh, tga do va van tdc chinh xac frong ITRF2000 ciia cac digm IGS da dugc su dung.
Truac bet GAMIT xir ly s6 lieu ttrng ca do frong timg chu ky trgn timg ludi. Phan mgm cung cap cac dir lieu de danh gia chat lugng kgt qua xir ly timg ca do. Kgt qua cho thay, ldi giai cua tat ca cac ca do deu dat chat lugng theo tieu chuan cua phan mgm, cho phep su dung de xir ly kgt hgp.
2000 : bias-free 2000 : bias-fixed
0 1 ooaoocBOoaooffiooffiooaoosooo
Baseline length (km)
0 100(200l300aOO(500(SOO(700(3000 Baseline length (km)
Hinh 2. Phan bd sai s6 tmng phuong trgng so cac thanh phan tga do cua hai loai ldi giai ta sd lieu do 2000
Tigp theo, GLOBK da tich hgp kgt qua tinh tung ca do frong timg chu ky' dg tinh tga do tmng binh img vdi thdi gian do cua chu ky' va lap cac phuong trinh chuan, Phan mgm tim hai loai ldi giai la ldi giai co dinh (bias-fixed) va ldi giai tu do (bias-free). Dp chinh xac qua frinh tich hgp nay - thg hien qua sai so tmng phuang trpng s6 (WRMS) ba thanh phan tga do: do vT (North), do kinli (East) va do cao (Vertical) ciia timg loai ldi giai - dugc minh hga bang vi du kgt qua xu ly sd lieu do chu ky' 2000 trgn hinh 2,
Cu6i cimg, GLOBK da kgt hgp kgt qua xir ly ciia tat ca cac chu ky do frgn cac ludi dg tinh van tdc chuygn dgng cua cac digm.
Van t6c chuygn dong tayet ddi ciia cac digm dia phuong da dugc tinh quy chieu theo van toe trong khung ITRF2000 do IGS cdng bo ciia cac digm IGS da lya chgn d frgn,
Vdi ldi giai da nhan dugc, tri hieu chinh vao thanh phin van toe cua cac diem IGS dugc lya chgn phan Idn be hon 1 mm/nam (trir KIT3 dudi 2 mm/nam) va sai s6 tmng phuang van tdc thanh phan cua cac digm IGS nay dgu dudi 1 mm/nam. Van tdc chuygn dgng tai digm CAM nhan dugc taong ta' nhu kgt qua trong [6]. Nhiing bing chimg nay cho thiy, khung quy chigu da dugc xac dinh tdt, phii hgp cao (± 1 mm/nam) vdi khung 1TRF2000 cua IGS, Van tdc chuygn dgng tai cac digm dgc HT DGSH dugc xac dinh chinh xac hon ca, vdi sai so trung phuang thanh phan ca 1 mm/nam, van tdc tai cac digm ludi GPS Lai Chau- Dien Bien. va ludi GPS Son La dugc xac dinh kem chinh xac hon, vdi sai sd taong ung khoang 2 mm/nam.
Dieu nay phii hgp vdi thdi lugng va chat lugng s6 lieu thu dugc tai cac diem tren timg ludi. Vdi sai sd thanli phan van toe da dat dugc va nhat la so sanh vdi van toe chuyen dgng cua digm do, cd the khang djnh rang van tdc chuygn dong tayet ddi cua cac diem dia phuong da dugc xac dinh chinli xac va tin cay, Kgt qua tinli van tdc chuygn dgng tayet ddi tai cac digm dia phuang trong kliu vyc nghign cuu dugc gidi thieu trgn hinli 3,
Hmh 3. Tmdng van tdc chuygn dgng tayet ddi frong ITRF2000 tai cac digm d mien Bic
Nhu da biet. ta cac dir lieu dia chat, dia vat ly va dia chan, da xay dung nen md hinh dong hgc toan ciu Nuvel 1 va sau do dugc hoan thien ngn Nuvel-1A [1], Theo md hinh nay lanh thd Viet Nam thugc mang Au - A. Sau nay, vao nam 2000, trgn co sd ket qua do GPS cua Dg an GEODYSSEA, Michel G va nnk [4] da dg xuat md hinh dong hpc (dudi day gpi quy ude la md hinh Michel) khdi Sunda, Khoi nay dugc coi la chuyen dgng rigng biet so vdi mang Au - A va cd mgt phin ranh gidi phia bic la DGSH, Nam 2007 Simons W, va nnk,[6] cdng bd nhirng kgt qua mdi vg chuygn dgng cua khoi Sunda, Nhd su dyng nhigu s6 lieu do hon, sy phan bd ciia cac digm chi tigt hon, nen cd the danh gia md hinh cua Simons W va nnk
(dudi day ggi quy ude la md hinh Simons) vg chuygn dgng ciia khdi Sunda la chinh xac hon va chi tigt hon so vdi mo hinh Michel, Cung cin lim y them ring, vao thdi gian nay, chi cd so lieu do ba chu ky
^ 9 9 4 , 1996 va 1998) tai hai diem tren lanh thd Viet Nam tham gia vao tinh toan frong hai cdng frinh trgn, la CAM (Cini Pha) - dugc xem la nim trgn khdi Nam Tmng Hoa va NONN (Da Nang) - dugc coi la nam tren khdi Sunda,
DS tien khai quat vg chuyen dgng ciia khu vyc nghign cu'u cung nhu de lien he vdi ba md hinh ndi frgn, da tinh van tdc chuyen dgng tayet ddi tai cac digm dia phuang theo md hfrih Simons, md hinh Michel ciing nhu theo md hinh dgng hgc toan cau Nuvel -1 A,
5. Thao luan cac ket quii tinh toan
Tmdc het, nliin khai quat cd the de dang nhan thay tinh ddng nhat cao ve chuygn dgng (ca cudng do lin hudng) tai cac vi fri do dac. Tuy nhign, di vao chi tiet, cd the phat hien thay mgt sd khac biet.
Nhu trgn da ndi tdi, chuyen dgng tuyet ddi tai hai digm CAM va XUY cd thg nhan lam dai dien cho ciu true Dong Bic, Trong truong hgp nay, cau tnic Dong Bae hien dang chuyen dgng ve phia ddng vdi van toe (33 ± 1) mm/nam va vg phia nam vdi van tdc (12 ± 1) mm/nam.
Va neu chip nhan van tdc chuyen dgng tai digm NAM va digm HOA dai dien cho cau tnic Tay Bae, thi khoi nay ciing dang chuygn dgng vg phia ddng vdi van tdc (33 ± I) mm/nam va vg phia nam vdi van toe (11 ± 1) mm/nam.
Gang nhieu digm dugc nhan lam dai dien cho mgt cau tnic cang tdt, song hai diem ciing la du. Tuy nhign trong dieu kien cu the ciia khu vuc nghien cim, sy phan bd cua nhung diem da chgn cdn tuong ddi gin cac dut gay (chua dat tieu chuan la trgn 100 km theo [7], nen tinh dai dien chuyen dong ciia cau tnic Dong Bic va ciu tnic Tay Bae d day mdi chi cd y nghia gan diing va can tigp tyc dugc quan tam,
Chuyen dgng tai cac diem dpc HT DGSH rat ttrang ddng nhau va dat ca (32 ± 1) mm/nam ve phia ddng va (11 ± 1) mm/nam vg phia nam, nghia la cudng dp dgu nhd hon 1-2 mm/nam so vdi cau tnic Dong Bic va ciu tnic Tay Bae. Sy giam cudng do nay phii hgp vdi ly thuygt md hfrih khdi kien tao [5] cho rang chuygn dgng tai mgt digm la hieu giua chuyen dgng quay cua khdi mang diem dd va chuyen dich do tich luy bign dang dan hdi tai dirt gay, Kgt qua nay dugc so sanh vdi hudng chuyen dgng phai vdi tdc do 0,43 va 1 1 mm/nam trgn cac doan dirt gay rieng biet ciia HT DGSH frong De tit mudn theo cac sd lieu phan tich dia mao kign tao [11],
Doc DGDBP, van tdc chuyen dgng nhan dugc cd tinh phan di rd hon ca ve cudng do lan hudng. Trgn canli phia tay, frong khi chuygn dgng tai DON va LEM klia frrong ddng va cd van tdc (34 ± 2) mm/nam vg phia dong va (10 ± 2) mm/nam vg phia Nam thi tren canh doi dien, van toe chuygn dgng tai diem NGA dat cue dai ve phia Ddng la (38 ± 2) mm/nam va (9 ± 2) mm/nam ve phia Nam, frong khi tai HAM va TAU van tdc tucmg img dat (32 ± 2) mm/nam va (10 ± 2) mm/nam. Kgt qua tinh chuygn dgng tuong ddi gitia hai canh ciia diit gay nay [8] da chi ra rang, hien tai dut gay dang dich chuygn bang frai vdi van tdc ude dat 1-3 mm/nam, cd thg xem la phii hgp vdi tdc do chuygn dgng 0,6-2 mm/nam frong thdi ki Pleistoxen truno va Pleistoxen mudn xac dinh bang phuong phap phan tich dia mao kien tao [11].
Chuygn dgng tayet doi tai cac digm nam frgn ba khdi ciu tttic ma ranh gidi la DGSLa va DGSD cd thg xem la tacmg ht nhau, vdi van tdc chuygn dgng ve phia Ddng dat (34 ± 2) mm/nam va vg phia nam (10 ± 2) mm/nam. Va nliu vay cd thg coi la tuong dong vdi van tdc chuygn dgng ciia ciu tnic Tay Bic.
Ndi each khac, boat dgng hien dai tai hai DGSLa va DGSD, ngu cd, la yeu va nim frgn frong mign sai so (2 mm/nam). Dieu nay cung kha phii hgp vdi kgt qua xu ly rieng le tmdc day [9].
Cd thg nhan thiy, van toe chuygn dgng tayet ddi tai cac digm frgn viing Tay Bic, ttfr diem NGA la tuan" ddng vdi van toe dugc xem la dac titmg cho chuyen dgng cua viing nay, vdi do lech khoang
1 mm/nam.
D6i sanh ket qua tinh van toe tayet ddi frong ITRF2000 ta so lieu do GPS nay vdi ket qua tinh theo cac md hinh dgng hgc da cho nhifrig ket qua thii vi.
So vdi kgt qua tinh van tdc chuygn dgng theo md hinh Simons da nhan dugc sy phii hgp rat cao: dp lech dudi mirc 1 mm/nam doi vdi cac digm nhan lam dac tmng cho cau tnic Dong Bae va cau tnic Tay Bic; tai cac digm dgc DGSLa va DGSD dp lech be nhit, dat dudi 1 mm/nam; tiep dgn, tai cac diem dgc HT DGSH do lech ude dat 2 mm/nam va tai cac digm dgc DGDBP do lech ldn hon ca, uoc d^t 2-4 mm/nam. Xet vg van tdc thanh phin, kgt qua tinh theo md huih Sfrnons ldn hon 1-2 mm/nam vg phia Ddng va nhd ban 1 mm/nam ve phia nam.
So vdi ket qua tinh theo md hinh Michel cac do lech taong ung ye van tdc deu ldn hon 2 lan va xet theo thanh phin van tdc, do lech chu yeu la thanh phin chuygn dgng ve phia dong.
Trong khi dd so vdi van tdc chuygn dgng tinh theo md hinh Nuvel - 1_A, van toe chuyen dgng tayet ddi frong 1TRF2000 nhan dugc dgu Idn hon khoang 10 mm/nam va chu yeu la thanh phin chuyen dgng ve phia ddng.
Ket luan " '
Tu nhirng phan tich tren, cd thg nit ra may nhan dinh sau:
1) c i u tnic Ddng Bic va ciu tnic Tay Bic hien dang chuygn dgng vg phia ddng vdi van toe (33 ± 1) mm/nam va vg phia Nam vdi van tdc taong img (12 ± 1) mm/nam va (11 ± 1) mm/nam. Sy phan di chuygn dgng, ngu cd, giua hai cau tnic la rat be frong khoang 1 mm/nam, ma ket qua xu ly nay chua cho phep cung cap bang chimg rd rang.
2) Vdi CO sd sd lieu do hien cd va vdi each tinh toan da gidi thieu fren, ket qua nhan dugc ve van tdc chuygn dgng ciia cac cau tnic Ddng Bae va Tay Bae kha phii hgp vdi kgt qua tinh toan theo md hinh dgng hgc khdi Sunda do Simons W, nnk, dg xuat [6],
3) Cd dau hieu rd rang vg xu thg chuyen dich phai cua DGSH, DGSC va DGSLo vdi van tdc chuyen dich taong ddi nhigu kha nang nam frong khoang I - 2 mm/nam,
4) Chuyen dgng hien dai ciia cau htic Tay Bae nhin chung klia dong nhat, trir khu vuc chung quanh diem NGA tai Sin Hd, Cd bieu hien chuyen dich frai kha ro cua DGDBP vdi van tdc ude dat 3 mm/nam tai NGA. Trong klii dd DGSLa va DGSD, hien tai ngu cd boat dgng thi rat yeu vdi van tdc nam trong mign sai so (dudi 2 mm/nam),
5) Nhung kgt qua trac dia nay kha phii hgp vdi cac kgt qua nghien ciiru dia mao kien tao dgc cac ddi dut gay boat dgng tich cyc trong De ta muon.
Tai lieu dan
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Insignificant horizontal sfrain across the Red River fault near Thac Ba, Vietnam from GPS measurements 1994-2000.
['3]TA. Herring R. W. King S.C. McClusky, 2006. fritroduction to GAMIT/GLOBK, Release 10.3.
Departement of Earth, Atmospheric, and Planetary Sciences, Massachssetts Institute of Technology. 5 December 2006,
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[5]J.M. Nocqiiet, E. Calais, Z, Altamini, P. Silldd, and C Boucher, 2001, Intraplate defomiation in westem Europe deduced from an analysis of the International Terrestrial Reference Frame 1997 (1TRF97) velocity field. Journal of Geophvsical Research, Vol, 106, B6, 11,239-11,257, JUNE
10,2001,
[6] W.J.F. Simons, A. Socquet, C. Vigny, B.A.C Ambrosius, S. Haji Abu, Chaiwat Promthong, C Subaiyg, D.A. Scisito, S. Mgtheussen, P. Morgan, and W. Spakman, 2007, A decade of GPS in Southeast Asia:
Resolving Sundaland motion and boundaries. Joumal of Geophysical Research, Vol. 112, B06420, doi:10.1029/2005JB003868, 2007,
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Spakman, 2006: Microblock rotations and fault coupling in SE Asia triple junction (Sulawesi, Indonesia) from GPS and earthquake slip vector data, Joumal of Geophysical Research, Vol. I l l , B08409, doi:10,1029/2005JB003963, 2006,
[8] Tran Dinh To. Vy Quoc Hai, 2005: Xac dinh chuygn ddng hien dai ddi dirt gay Lai Chau - Dien Bien tif sd lieu do GPS (2002-2004). Tap chi Cac Khoa hpc vg Trai dit, T.27 (1), 6-13, 2005,
[9] Tran Dinh To. 2006: "Processing results of GPS measurement data from the Son La and Song Da fault zones ", Joumal of Geology ISSN 1859-0659, series B, No. 27 / 2006, tr. 115-122, Ha Noi,
[10] W. Zuchiewicz, Nguyen Quoc cuong, A. bluszcz, M. Michlik, 2003. Quatemary sediments in Dien Bien Phu fault zone, NW Vietnam: a record of young tectonic processes in the light of OSL-SAR dating results. Geomorphology, 60 (2004) 269-302,
[II] W. Zuchiewicz, Nguyen Quoc Cuong, 2009, Palaeoseismicity and palaeoearthquakes of Northem Vietnam based on geomorphic analysis of active faults. Case stadies of the Red River and Dien Bien Phu fault zones. Proceeding of Workshop on Earthquakes in Vietaam : Seismic Risk and Mitigation, Hanoi, March 12-13,2009. IMC, HaNoi: 27-30.
Abstract
Outline of recent movements of northern Vietnam from GPS data
On the recent tectonic sketch of the northem Vietnain, the Red River fault system has a special position, beiiig the boundary between Sunda and South China blocks. A less important are Dien Bien Phu, Da River and Son La fault systems,
GPS technology has been used to measure recent tectonic activity along these fault zones during the last years.
It's the first time all the measurement data have been analysed by GAMIT/GLOBK to get the ITRF2000 solutions for point absolute motion rates of the stady areas.
Analyzing results conducted to the first interpretation of recent motions in the territory of northem Vietaam,