Phan III: DjA VAT LY VA CAU TRUC V6 TRAI DAT 2 3 1
NGHIEN c u t ! XAC DINH CAC DAC TRUKG CAu TRUC VA DIA DQNG L i r e
CUA CAC HE DlTT GAY TREN THEM LUC DIA VIET NAM VA BIEN DONG
Biii Cong Que Plen Vdt ly dia cdu
18 Hodng Qudc Viet, Cdu gidy, Hd Npi Mail: bcque(a))in.vnn.vn
Tom tdt: Trin ca sd ngudn sd lieu thuc ti vi cdc trudng di thudng dia vdt ly, dia hinh - dia mgo vd dia chdn kien tgo ciia Bien Ddng vd thim luc dia Viet Nam duac bd sung, lien ket trong cimg ty li thdng nhdt vd sic dung hi phuang phdp nghien cuu duox xdy dung mdi phii hap, cdc dgc diim cdu triic dirt gdy vd ca chi dia dpng luc lien quan da duac xdc dinh vd hi thdng theo cdc kiiu mat cdt cdu triic - dia dpng luc dgc trung. Trin Biin Ddng dd xdc dinh 21 hi diet gdy chu yeu phdn bd theo cdc hudng chii dgo Id Ddng biic - Tdy nam, hudng kinh tuyen, Tdy bdc - Ddng nam vd hudng vT tuyin. Cdc dgc trung cdu triic ciia did gdy nhu dp sdu, gdc nghiing ciia mgt diet gdy, biin dp dich chuyen theo phuang thdng dicng, cdc dgc trung dig ddng luc nhu dp hogt ddng dia chdn vd ca chi kiin tgo tren mgt cdt duac xdc dinh theo sd liiu quan sdt thuc ti. Tdng hap vd ddi sdnh cdc dgc trung cdu triic did gdy vd dia dpng luc liin quan da cho phep phdn chia thdnh mpt sd kiiu mgt cdt cdu tnic - dig ddng luc dgc trung tren Bien Ddng vd trin thim luc dia Viet Nam.
1. Mudau
Cac he dirt gay tren thim lyc dia Viet Nam va tren Bien Dong da dugc de cap trong nhilu cong hinh naliien cim ting hgp tai lieu dieu tra khao sat dia chat va dia vat ly ciia cac tac gia trong va neoai nude nhu Parke, 1971, Frye, 1970, Ho Dac Hoai, Ng6 Thudng San,
1975, Taylor, Hayes 1983, Le Van Cy, 1982, Kulinic 1989 Gatinsky, 1984, Wu Ji Mm 1988, 199o[ Biii C6ng Qui, 1985, 1990. 1996, 1998, 2000, 2005... Trong cac cong trinh noi tren diu thi hien kha ro he dirt gay sau chay gan song song ven bien mien Trung Viet Nam, he dirt gay sdng Hing, song Chay tien sudn tay nam Vinh Bic bg, he dirt gay hudng Dong bac Uen thim luc dia done nam. Tren Biln Dong d ben ngoai them luc dia Viet Nam ciing the hien ro cac he dirt f^ay sSu hudng Dong b i c - Tay nam, hudng kmh tuyen va hudng Tay bac - Dong nam Hoat dgng niii lira lien quan den cac dirt ga>' tren Bien Dong da dugc cac nha dia chan phuong Tay nhu Patte (1923), Lacroix (1933), Saiuin (1967) nghien cim ting hgp tir nhieu
2 3 2 Tuyln tap cac c6ng trlnh nghi§n CCKU Vat ly Dja c i u 2008
chuyen dilu tra khao sat Uong nira diu thi ky 20. Tiep theo do, cac nha nghien cuu cua Viet Nam nhu Nguyen Xuan Han (1991, 1996), D6 Minh Tiep (1995, 1996) da cd nhung cong trinh nghien cuu ting hgp kha chi tilt vehoat dgng nui lira tre va phun trao badan tren vimg them luc dia Viet Nam. Cac nghien cim ve dgng dat tren vimg Bien Dong va them luc dia Viet Nam ciia Nguyen Dinh Xuyen (1989, 1997), Nguyen Kkn Lap (1985, 1990), Pham Van Thuc, Nguyen Van Luong (1980, 1999, 2000), Nguyin Hing Phuong (1998) da dk cap dac diem phan bo va co cau chin tieu cac dgng dat lien quan vdi cac he dirt gay trong v6 trai dat.
Trong cac c6ng trinh nghien cim ve dac diem kien tao, sy hinh thanh va phat trien, tien hoa kien tao ciia Bien Dong cua cac tac gia Viet Nam va nude ngoai nhu Le Duy Bach, 1987, 1990, 1998, Le Van Cy, 1986, Hayes, 1983, 1986, Kulmhic, 1989, Le Nhu Lai, 1995 , 1996, Rangm, 1990, 1995, Taponier et. al, 1982, 1986 Brias et al, 1989, 1990... diu the hien kha ro moi lien he chat che giira dac diem cau true cua cac he dirt gay vdi co che chuyen dgng kien tao va dac diem phan bo img suat trong v6 trai dat.
Nghien curu phat hien cac dac diem cau true cua cac dut gay va cac dac tnmg dia dong luc lien quan vdi dirt gay va danh gia ve moi lien quan giira cac dac diem cau tnic va dia dgng lyc cua dut gay lam co sd cho viec dy bao kha nang hmh thanh, tich hi khoang san ciing nhu nguy CO tao ra nhiing tai bien dia chat nhu dgng dat nui lira, song than, trugt Id dat da... luon la nhiem vu co tam quan trgng, co y nghia khoa hgc va thuc tien Idn. Trong khuon kho cua mgt de tai khoa hgc cong nghe cap nha nude (KC-09-02, 20001-2005) do tac gia bai vilt nay tryc tiep lam chii nhiem [15], tren co sd thu thap, bo sung mdi va xir Iy cac sl lieu, tu lieu dieu tra khao sat hien cd Uen vimg bien Viet Nam va ke can, mgt tap gom 70 ban dl vl dilu kien ty nhien va moi trudng da dugc thanh lap mdi dap ung nhting yeu ciu cao vl ky thuat va tieu chuan chuyen mon. Trong so nhiing ban do noi Uen co cac ban dl dia chit, dia vat ly d ty le 1: 1000000 nhu ban do do sau day bien, ban do di thudng Ugng luc (hieu chinh fai va hieu chmh Bughe) ban do di thudng hi, ban dl dgng dit, ban dl dia chit de tam, ban do de hi...
Dudi day tac gia trinh bay phuong phap nghien cim tong hgp cac tai lieu mdi noi tren vl cac trudng dia vat Iy va cau true dia hinh, dia mao ciia Biln Dong va thim luc dia Viet Nam va nhiiiig ket qua bo sung chinh xac boa va hoan thien co ban vl cac dac dilm ciu hnc va dia dgng luc ciia cac he dirt gay va moi quan he chat che giira nhiing dac dilm ciu true va dja dgng lyc lien quan vdi dut gay trong v6 trai dat.
1.1. Phuang phdp nghiin cuu cdc ddc diim cau true vd dia dpng luc lien quan vai dut gdy 1. I. 1. He phicang phdp nghien cim xdc dinh diet gdy vd cdu true dirt gay
He phuong phap nghien cim xac dinh vi tii va cac dac dilm ciu true ciia dirt gay theo tong hgp tai lieu dia chat, dia vat Iy dugc img dung trong cac cong trinh [10, 12, 13, 15] da tiep hic dugc tac gia bo sung hoan thien theo hudng phii hgp va dap img nhting dilu kien dia chat, dia vat Iy Uen thyc te. Nhung khau chii ylu ciia he phuong phap noi tren gIm:
a Xac dinh vi tri ciia dirt gay theo ting hgp tai lieu dia vat Iy.
• Ban do di thudng trong lyc: dai di thudng bac thang, sy thay dii ciu true trudng, sir doi hudng dudng dang tri, dai di thudng eye bg, di thudng eye dai gradient ngang.
ph^n III: DIA VAT LY VA CAu TRUC V 6 TRAI O A T 2 3 3
• Ban do di thudng tir: dai di thudng cue bo, sy thay doi hudng cau tnic cua trudng, sy thay doi phong cau tnic, ranh gidi cac di thudng kh6i.
• Cac ban d6 ve trudng chan dgng ty nhien (dong dat) va sdng dia chan: dac dilm phan bo chan tam dgng dat, dai di thudng ve tinh dia chan, ranh gidi cac vimg di thudng tinh dia chin, dai di thudng song dia chin.
• Cac mat cat dia chan: sy thay dii dot nggt ciu tnic cua trudng song, sy thay dii dot nggt ciia cac ranh gidi phan xa, khiic xa.
• Ban do dia hinh va dia mao day bien: sy thay doi dot ngot ve do sau, sy bien doi cau tnic dia hinh, ranh gidi giira cac ciu true dia hinh, dia mao.
• Xac dinh dac diem cau tnic ciia cac dirt gay theo cac tai lieu dia chat va dia vat ly.
» Do sau ciia dirt gay xac dinh theo tai lieu trong lyc (cac phuong phap ciia Andreev, Vasilop...)
• Hudng cam va goc nghieng ciia mat dirt gay so vdi phuong thang dimg xac dinh theo tai lieu Ugng lyc (phuang phap ciia Chiapkin, phuong phap giai tich gradient ngang, phuang phap ket hgp tai lieu trgng lyc, tix) xac dinh theo tai lieu dia chan (phuong phap xay dimg mat cat chan tam dgng dat, phuong phap xir ly bang song dia chan...).
• Bien do dich chuyen (ciia 2 khoi) va be rong ciia mat dut gSy xac dinh theo tai lieu trgng lyc va tir bang cac phuong phap tinh phan bo eye tri ciia cac gradient ngang, doi sanh ket hgp dac diem phan bo cac eye dai di thudng tir v^ gradient trgng lyc...
Vi tri va cau triic ciia cac dirt gay sau va khu vyc tren vimg bien c6n dugc xac dinh can cir vao dac diem ciia dia hinh (do sau) day bien, dac biet la nhung dirt gay tre dang trong giai doan boat dgng...
/. I. 2. Xdc dinh cdc dac tnmg dia dpng luc lien quan vdi diet gay
Q Xac dinh co che dia dong lyc dieo mat cat dirt gay. Phuong phap nay lan dau tien dugc xay dyng va trinh bay trong [10], dugc phat trien va van dung Uong cac cong trinh [13, 15].
Phuang phap dugc hinh thanh tren co sd xay dyng va xem xet cac mat cat cau tnic ting hgp dia chit, dia vat ly, D6 la cac mat cat cau tnic dugc xay dyng theo ket qua tham do dia chat va dia vat ly theo mo hinh cau tnic chia lap ngang (do cac ranh gidi co ban va ranh gidi n ^ ngang khac) va chia cat thanh cac khoi theo phuong thang dimg hoac gan thang dimg (do cac dirt gay). Tren mat cat hinh thanh cac khoi tach rdi va chuyen dong hiong tac vdi nhau qua cac dirt gay. Can cir vao dac diem chia cat ra cac khoi bdi cac dirt gay tren mat cat
^t xac dinh cac kilu co chi dia dgng lyc cu the nhu sau:
' Kilu CO chi DDLl: sy syt lim oan vong do lyc trgng luc tac dgng vuong goc vdi mat cit (tir phia tren mat).
• Kilu CO che DDL2: tach gian va sut liin do luc keo dan ve 2 phia dii nghich va trgng lyc tac dgng tir phia tren,
' Kilu CO chi DDL3: chdm nghich va oan vong do nen ep: tac dgng cua luc nen ep '" tir 2 phia dii nghich.
' Kilu CO chi DDL4: chdm nghich va xe dich ngang do cac lyc nen ep va tac dgng khong theo hudng doi nghich.
2 3 4 Tuy§n tap cac cong trinh nghien cu'u Vat ly Dja cau 2008^
• Kilu CO chl DDL5: tach dan va nang len do lyc diy tir phia dudi theo hudrig vuong g6c vdi mat cat.
• Xac dinh co chl dia dgng lyc va img suat kiln tao tren mat cit dirt gay theo kit qua xac dinh CO ciu chin tieu dgng dit [7 ], theo d6 co thi xac dinh cac dang giai phong ling suat theo cac dirt gay dang chdm nghich, dang xe dich thuan hoac tach gian, trugt bang...
Mirc do boat dgng ciia cac dirt gay dugc xac dinh tren co sd danh gia dong thdi cac dac trung ciu tnic va dia dgng lyc ciia chiing theo cac dau hieu nhu tren. Dac biet la cac dut gay bilu hien ro tren nhilu trudng di thudng dia vat ly va img suat kien tao khac nhau, tap trung nhilu chin tieu dgng dit va niii lira, the hien ro tren dau hieu dia hinh, dia mao... la nhiing dirt gay dang trong thdi ky boat dgng manh.
2. Dac diem phan bo va cau triic cua cac 6\rt gay tren Bien Dong
Dac diem phan bo va cau hnic ciia cac he dirt gay tren Bien Dong va them lyc dia Viet Nam da dugc nghien cim xac dinh va the hien trong cac cong trinh [9, 12, 15] vdi viec hoan thien he phuong phap nghien cim mdi tren co sd tong hgp va sir dyng nguon so lieu dugc bo sung md rgng dang ke, co do dong nhat cao, trong cong trinh nay cac dac diem phan bo va ciu tnic ciia dirt gay dugc xac dinh day dii, hoan chinh co do tin cay kha dong deu. Tren ban do cau tao dirt gay dugc bo sung, md rgng vdi cac dirt gay dugc phan thanh 3 loai: dut gay bac 1 CO do cam sau tren 30km, keo dai hang tram km la ranh gidi giua cac mang v6 tuong img vdi cac cau tao bac 1 nhu cac viing trung tnmg tam, cac khoi tieu lyc dia, cac vimg sudn lyc dia, them luc dia. Dirt gay bac II co do cam sau 20 - 30km Uai dai tir hang chuc tdi hang Uam km, la ranh gidi phan chia va tao thanh cac cau tnic bac 2 trong v6 trai dat nhu cac ddi nang, ha, cac \amg trung, cac be tram tich de tam... Dirt gay bac III nho hon ve do cam sau, CO do dai ban che, chia cat cac cau tao bac 2 thanh cac khoi khac nhau...
Tren Bien Dong da xac dinh 21 he dirt gay chu yeu c6 the nh6m thanh cac nhom dirt gay theo cac hudng chii dao la: Dong bac - Tay nam, Tay bac - Dong nam, hudng
kinh tuyen va hudng vT tuyen. ,J:
2. 1. Nhom ddi gdy co hudng Dong bdc - Tdy nam . =. j Nhom dirt gay hudng Dong bac - Ta\' nam co vi tri thong soai va nli bat tren binh dl cau tnic dirt gay cua Bien Dong. Cac d'it gay hudng nay co do dai hang tram deri hang nghm cay sl, phan bo hau bet d cac \Ting phia Bac, Dong nam va tnmg tam Biln Dong. Tren phin phia bic Biln Dong cac dirt gay hudng Dong bac co do sau hi 30km din 50km va Idn hon, xuyen cit v6 trai dat, chay tien them va sudn luc dia phia Dong nam Tnmg QuIc va chum lai d suan phia nam dao Hai Nam, cac dut gay nay deu cam nghieng ve phia tnmg tam Biln Dong vdi goc nghieng khong Idn. Tren phan phia Tay bac va dong nam true tach dan Biln Dong cac dirt gay hudng Dong bac - Tay nam co do dai Idn, chay gan song song, chia cit cac viing quin dao Hoang Sa va Trudng Sa \'a \nng mang sau Bomeo - Palawan thanh nhilu dai cau tnic vdi cac khoi \o nang ha xen ke va co do dich chuyen Idn theo chilu sau. Do sau ciia cac dirt gay Uen 30kni, xuyen cat v6 trai dat toi lop manti va cam nghieng theo cac hudng ti^
ngugc nhau. He dirt ga\' tren vimg Bomeo - Palawan cam nghieng vl hudng Dong nam vdi
pnan III: PjA VAT LY VA CAU TRUC V6 TRAI OAT 2 3 5
goc nghieng gan 30o so vdi phuong thing dimg. Cac dirt gay Uen sudn Tay bic quin dao Xnidng Sa cam nghieng ve phia Tay Bic vdi goc nghieng nho hon. Cac dirt gay tren phin tiung tam Bien Dong chay song song true tach dan hudng Dong bic - Tay nam, chia cit va Idiong che cac sudn phia Tay bac va Dong nam ciia triing Uung tam Biln Dong, chum lai d vung Tay nam Bien Dong (khu \arc Tu chinh Uen thim luc dia dong nam Viet Nam). Cac dirt gay d vimg trung tam Bien Dong theo hudng dong bic - Tay nam diu co do dai Uen 1000km, cam sau vao phan tren Idp manti, c6 do cam nghieng kh6ng Idn ve phia true ciia vimg thing.
Ngoai 3 viing chii yeu n6i tren, cac dirt gay hudng D6ng bac - Tay nam c6n phan bl tren phan Tay bac ciia Vinh Bic bg va tren thim luc dia dong nam Viet Nam . Tai cac vimg noi tren cac dirt gay c6 do dai tir 100km din 300km, co do sau tren 30km phan chia v6 trai dat thanh cac dai cau true nang, ha hoac la ranh gidi ciia cac bl trim tich de tam tren them luc dia d6ng nam Viet Nam.
2. 2. Nhom dut gdy hudng Tdy bdc - Dong nam
Cac dirt gay hudng Tay bac - Dong nam phan bo chii yeu tren phan phia Tay Biln Dong a cac vimg Vinh Bac bg, Vinh Thai Lan va them luc dia Dong nam Viet Nam. Day la nhiing viing cac dirt gay hudng Tay bac - D6ng nam the hien ro va n6i bat tren cac trudng di thudng trong lyc, tir, tren cac mat cat dia chan tham d6 va ca so lieu dia hinh, dia mao. 0 cac \amg trung tam Bien Dong va phan phia nam, Tay nam Bien Dong cac dirt gay hudng Tay bac - Dong nam chi the hien ro tren trudng di thudng tir va trpng lyc va da s6 dirt gay loai nay la nhiing dirt gay chuyen dang, theo do dien ra co che tach dan hinh thanh Bien Dong.
\ Cac dirt gay hudng Tay bac - D6ng nam Uen Vinh Bac bg co do dai hang Uam km, vdi do c3m sau Uen 30km, chay gan song song vdi dudng true va kh6ng che cac sudn Tay nam, Dong bic ciia be tram tich song Hong, trong so cac dirt gay n6i tren c6 cac dirt gay song Hong, song Chay, song L6... phat trien tiep tuc tir Uen phan dat lien thuoc vimg thing Ha Noi. Cac dirt gay nay,cam nghieng ve phia true ciia viing trung, co bien do sut lim Idn, hinh thanh bl trim tich de tam c6 be day tram tich eye dai tdi 15km. Tren vimg Vinh Thai Lan cac diit gay hudng Tay bic - Dong Nam chay song song Uuc va khong che vimg hnng sut lim dang rifto Ma Lai - Thi Chu vdi be day tram tich de tam eye dai xap xi 10 km. Cac dirt gay noi tren ciing co do dai Idn va cam sau Uen 30km vdi do nghieng nho so vdi phuang thang diing va bien do sut lim ciia cac khoi qua dirt gay la kha Idn (1km - 5km).
13. Nhom ddi gdy hudng kinh tuyen
Cac dirt gay c6 hudng kmh m>en tren Bien D6ng phan bo d cac vimg them luc dia phia Tay va phia Dong ciia Biln Dong, Uen vimg quan dao Trudng Sa, Uong Vinh Thai Lan va Jren thim luc dja phia D6ng Nam Viet Nam. Cac he dut gay hudng kmh tuyen Uen thim luc
% miln Truno Viet Nam va them luc dia phia Tay dao Ludong la nhung he dirt gay noi bat v6i chilu dai tdi hang nghin km, cam nghieng ve cac hudng ben dudi luc dia Cong tum va
^ Lud6n" xuven cit v6 frai dat va cam sau vao Idp manti Uen vdi do sau Uen 100km.
Dai cac dirt aav hudng kinh myen chay song song va c6 cau tao toa tia Uen mat cat vdi
^\ mat dirt gay chmh theo kieu ddi hiit chkn ciia v6 dai duong va la noi phat sinh cac dgng
2 3 6 T u y l n tap cac c o n g t r i n h nghien CLPU Vat ly Dja ciiu 20oj
dit, niii lira co cudng do kha manh. Diln hmh ladai diit gay ven bd phia tay dao Ludong c6^
CO ten la ddi hiit chim Manila, vdi hang tiarn chin tam dgng dat tap trung d day va cudng.dj eye dai c6 thi dat 8 do Richter hoac Idn hon. He dirt gay hudng kmh hiyin d phia Tay Bign Ddng con co ten la he dirt gay kinh hiyln 109oE ciing la he dirt gay co quy mo phat tri^
rgng, co do cim sau Idn va trimg vdi dai chan tam dgng dat va nui lira tre tren them luc dia miln Trung Viet Nam. Tren vimg quin dao Trudng Sa co 3 dut gay hudng kinh hiyen chaj song song vdi nhau, co do dai hang tram km. Ba dirt gay nay gan trimg vdi cac dudng kiiJi tuyen 114oE, 115oE va 116oE. Tren cac dirt gay nay ciing da ghi nhan mgt sd chan tan dong dat manh vdi cudng do xap xi 4-5 do Richter.
2. 4. Nhom ddi gdy hudng vi tuyen
Tren binh do cau tnic dirt gay Bien Dong cac diit gay hudng vT tuyen co bieu hien md nhat va yeu nhat. Cac dirt gay hudng vT tuyen co do dai ban che, phan bo rai rac ol phan phia Bac Bien Dong, vimg trung tam va phan phia Nam va Dong nam viing quai dao Trudng Sa. Cac dirt gay hudng vT tuyen cd quy mo phat trien va do cam sau ban chl chi CO vai tro lam phan di binh do cau true v6, khong co anh hudng quyet dinh va chi phoi dac diem cau tnic va kien tao ciia Bien Dong noi chung.
3. Dac diem dja dong lyc cua cac he dut gay tren Bien Dong 3. 1. Co che kien tao liin quan vai dirt gdy
Cac he dirt gay hudng kinh tuyen tren cac viing ria phia Dong, Dong bac va Don^
nam ciia Bien D6ng la nhiing he dirt gay sau lien quan vdi co chl kiln tao chdm nghiep ciia cac mang vd trai dat va hinh thanh cac ddi hiit chim Rikiu - Dai Loan, Manil^
Palawan.
Cac he dirt gay hudng kinh tuyen tren ria phia tay Biln Dong ciing lien quan vdi c(|
che kien tao nen ep - chdm nghich theo hudng vT tuyln va trugt bing ngang theo huan^
kinh tuyen. Dang mat cat cau triic v6 d day ciing tuong tu nhu tren ria phia dong nhung quy mo phat trien va muc do hoat dgng ciia dirt gay ylu hem. He dirt gay chay song song tren them luc dia mien Trung Viet Nam theo hudng kinh tuyln giira 109°E va 110°E, tren mat cat chimg c6 cau tao toa tia, tat ca chum vao mat dirt gay chii dao (^
phan tren lat cat) va mat dirt gay chii dao thi cim sau va nghieng vl phia dudi luc dia Cong tum tren lanh tho nam Trung bg Viet Nam va Dong bic Campuchia.
Dgc theo cac he dirt gay sau hudng Dong bic - Tay nam tren Biln Ddng la cac CD che kien tao lien quan vdi cac qua trinh tach dan, sut liin hinh thanh Biln Dong. Tre«
mat cat cau tnic v6 cac dirt gay nay deu cam nghieng vl phia true Biln Dong va tao r0 nhirng xe dich, trugt bac co bien do Idn tren m.at cit. 6 cac vimg tren thim luc dia donj nam Trung Quoc, tren them luc dia Viet Nam (Vinh Bic bg, Vinh Thai Lan) va trei vimg quan dao Trudng Sa ta thay dgc theo cac he dut gay hudng Tay bic - Dong naU va Dong bac - Tay nam deu phat trien kha pho biln cac co chl kiln tao tach dan sut lul cue bg tao nen cac bon trung co dang dia hao hoac rifto. Lien quan vdi co chl kiln ta<
Ph^n III: DjA V A T LY VA CAU TRUC VQ TRAI DAT 2 3 7
nay la hang loat be tram tich de tam c6 kich thudc va be day tram tich khac nhau tren cac viing them luc dia Trung Qu6c, Viet Nam va tren cac vimg quan dao Trudng Sa, Hoang Sa ciia Viet Nam.
3. 2. Dac diim dia dpng luc hien dai
Dac diem dia dgng lyc hien dai lien quan vdi dirt gay tren Bien Dong the hien kha ro trong cac hoat dgng dgng dit va nui lira,
Dac diem phan bl chin tam dgng dit [6 , 15, 18, 19, 21]:
Noi bat tren binh d6 cau tnic dirt gay vdi dac diem phan bo chan tam dgng dat Bien Dong la ddi chan tam dong dat lien quan vdi diit gay Manila d phia tay dao Ludong.
Day la ddi c6 do boat dgng dia chan cao nhat tren Bien Dong . Dong dat trong ddi nay xay ra d do sau tir 10km den 200km va theo hudng tang dan tir phia Bien di ve phia ben dudi dao Lud6ng. Dgng dat trong ddi nay c6 cudng do eye dai tdi 7dg Richter.
Viing chan tam dgng dat d dong bac Bien D6ng co hang chuc chan tam dgng dat trong do c6 dong dat vdi cudng do cue dai M = 6,75, nhirng dong dat nay nam tren he dirt gay hudng D6ng bac - Tay nam va kinh tuyen tren ria dong bac ciia Bien Dong.
• Dai chan tam dong dat tiep theo nam tren he dirt gay hudng kinh tuyen tir Dai Loan den dao Lud6ng. Trong dai nay co nhimg dgng dat manh vdi M = 6-7 va do sau chan tieu dat tren 100km [21 ]
• Dai chan tam dong dat Palawan co it dong dat hon s6 vdi cac dai da neu. Cac dgng dit d day lien quan vdi he dirt gay sau Palawan. Nhung trong thdi ky khoang vai nghin nam gan day dirt gay Palawan thuoc dang ddi Beniof thu dgng va boat dgng yeu [25, 26],
• Tren viing ria phia Tay Bien Dong, doc theo dai dirt gay hudng kinh tuyen tren thim luc dia mien Trung Viet Nam la dai chan tam dong dat vdi magnitude tir 4 den 5,5 do Richter. Ddi dirt gay nay c6 kha nang phat sinh nhung dgng dat gay chan dgng cue dai tdi cap 8 tren vimg ven bien Nam Trung bo Viet Nam [19].
• Ci vl phia ven bien ciia he dirt gay noi tren la cac chan tam dgng dat c6 cudng do nho ban phan bl d cac khu vyc Nha Trang, Tuy Hoa vdi M < 4 va do sau chan tieu nim trong v6 trai dat, cac dong dat nay phat sinh tir cac dut gay toa tia tir he dirt gay chinh hudng kinh tuyen neu tren.
• 6 khu vyc ngoai khoi Viing Tau, Ca Mau da ghi nhan nhieu dong dit vdi M tir 3 din 5 do Richter va do sau chan tieu tir 20 km den 30km. Cac dong dit nay ciing lien quan vdi boat dgng ciia he dirt gay sau hudng kinh tuyen tren them luc dia mien Trung Viet Nam.
• Trong Vinh Bic bg quan sat dugc mot so dong dat vdi M < 4. Hau het cac dgng dat phat sinh trong cac dirt gay Song Hong, Song Chay, Song Ma, Son La, Song Ca keo dai tir trong dat lien ra phia Bien Dong, Do sau chan tieu ciia cac dgng dat nay nho hon 20km.
2 3 8 Tuy4n tap cac cong trinh nghien ci>u Vat ly Dja c l u 2008
• Dang chii y la dai chin tam dong dat phia Dong nam dao Hai Nam nam dgc thee diit gay sau hudng Dong bac - Tay nam. Trong dai chan tam nay co it nhat 3 va dgng dat manh vdi M = 6-7 va do sau chan tieu xap xi 30km.
• Dai chan tam dgng dat phia Tay dao Loi Chau (Trung Quoc) gom nhiing dgng di\
yeu va c6 chan tieu nong, phan bo tap trung tren cac dut gay hudng Ddng bac - Tay nam va hudng vT tuyen.
Tren viing quan dao Trudng Sa co 2 nhom chan tam dgng dat chu yeu. Nhom chan tam d phia bac quan dao tap trung chii yeu tren 2 diit gay sau hudng kinh tuyen va dirt gay kinh tuyen 114°E va 115°E. Cudng do ciia cac dgng dit nay dat 6 - 6,5 do Richter vaco do sau chin tieu Idn [13, 18].
Nhom chan tam dgng dat tren phan Tay nam quan dao Trudng Sa lien quan vdi cac diit gay hudng Dong bac - Tay nam theo hudng true tach gian Bien Ddng.
Tren quan dao Trudng Sa (Viet Nam) cac dgng dit ghi dugc cd M < 5,6 va do sau chan tieu 30kin phan bo tren cac dirt gay hudng Dong bac - Tay nam cit qua viing quan dao.
Dac diem hoat dgng cua nui lira [2, 3,6. 19]:
Theo ket cjua dieu tra khao sat thyc tl thi tren Biln Ddng da cd nhilu niii lira hoat dgng. Dac diem phan bo cac niii lira tren Biln Dong lien quan vdi binh do ciu tnic dirt gay ciia v6 trai dat tren viing bien Viet Nam. C6 thi ghi nhan nhimg khu vuc boat dgng niii lira chinh nhu sau:
• Khu vyc ngoai khoi Trung bg tir Dong Hdi din Da Ning lien quan vdi he dirt gay Song Hong, Song Chay tren sudn Tay nam Vinh Bic bg.
• Dai^ nui lira ngoai khoi nam Trung bg lien quan vdi he dut gay sau hudng kinh tuyen (dirt gay Tay Bien Dong).
• Dai nui lira ngoai khoi Phan Thilt, keo qua Con Dao lien quan vdi he dut gay khu vyc hudng Dong bac - Tay nam. Trong dai nay c6 niii lira Hon Tro da dugc ghi nhan boat dgng nhieu lan trong nam 1923.
• Dai nui lira tren khu vyc Tu chinh va Tay nam quin dao Trudng Sa the hien rat ro tren cac mat cat dia chan, lien quan vdi cac diit gay hudng kinh tuyln va hudng Ddng bac - Tay nam.
• Dai nui lira tren them lyc dia Tay nam tir Rach Gia din Ca Mau lien quan vdi dirt gay ven bd Rach Gia - Ca Mau co hudng kinh tuyln [19].
4. Cac kieu mat cit cau true - dja dong luc chii yeu tren Bien Dong va them luc dia Viet Nam c i u true dirt gay va co che dia dgng lyc lien quan vdi dut gay la nhung ylu tl co ban ludn khong che va tac dgng qua lai, anh hudng tryc tilp trong suit q u i trinh phat triln kien tao ciia v6 trai dat tao nen binh dl ciu true hien tai. Kit qua dilu tra khao sat va nghien cim tong hgp ve dia chit va dia vat ly tren Biln Ddng va thim luc dia Viet Nam trong hon 50 nam vira qua da cho phep xac dinh dugc nhiing ylu t l co ban vl ciu tnic v6 trai dat va dia dong lyc ciia hau bet cac don vi kiln tao chu ylu, tren co sd do co the lya chgn xay dimg nhimg kieu mat cat ciu true va dia dgng lyc dac truno
Phin III: DjA VAT LY VA CAU TRUC V6 TRAI D A T " 2 3 9
4. 1. Mpt so kieu mat cdt cdu true - dia dpng luc ddc trung tren Biin Dong + Mat cat qua ddi hiit chim Manila.
Day la kieu mat cat dien hinh dang ddi Beniof vdi mgt mat dirt gay cam sau va nghieng ve phia dudi dao Lud6ng (philipin) vdi do cim sau 150km - 200km, goc nghieng tir 30° den 60° so vdi phuang thing dimg. Cac chan tieu dgng dat phan bl day da.c tren viing mat dirt gay, trong do co mot s6 chan tieu d do sau xap xi 200km. V6 trai dat d 2 canh ciia dirt gay Manila c6 be day trung binh 20km bi xe dich manh theo phuong thang dimg vdi bien do 5-7km. Co che dia dgng lyc tren mat cat la dien hinh ciia cac mat cat dang chdm nghich do nen ep tir 2 phia, hau qua ciia su md rgng Bien Dong tir viing trung tam va bi va cham vdi mang v6 bien Philipin dang chuyen dgng theo hudng ngugc lai. Ket qua la mang v6 ciia Bien D6ng bi hiit chim xu6ng phia dudi mang Philipin tao thanh mang sau Manila c6n mang v6 bien Philipin troi len phia tren hinh thanh dao Lud6ng nhu hien tai [ 15, 21 ].
+ Mat cat qua ddi hiit chim Palawan - Borneo.
Ve cau tnic dang mat cat Palawan - Bomeo tuong ty vdi mat cat qua ddi hiit chim Manila. Mat dirt gay hudng D6ng bac - Tay nam cam chun xuong phia dudi mang Palawan hinh thanh mang sau Bomeo d canh phia Tay bac va mang Palawan - Bac Kalimantan tr6i len d canh phia Dong nam. Ve dac diem dia dong lyc thi co sy khac biet vdi bieu hien dgng dat, niii Midi boat dgng yeu dac tnmg cho kieu beniof thu dgng [25, 26].
+ Mat cat vimg trung tam Bien D6ng
B I day v6 ke ca Idp nude la 10-12km, trong do be day Idp nude la 5km, Idp tram tich la 1km, phan v6 cirng (Idp badan) co be day khong qua 5km. Khong ton tai Idp granit, r5 rang v6 trai dat thuoc kieu v6 dai duong. Cac dirt gay c6 do sau 20-30km chia cit Idp v6 cimg va cam sau vao Idp manti thugng vdi goc nghieng nh6 va gan theo phuang thing dirng. Co che dia dong lyc d day la lyc nang day tir phia dudi (Idp manti) va lyc tach dan ngang ve hai phia ciia true tach dan Bien Dong. Vat chat long, nong chay tir phia dudi trii len lap day khe nirt (khoang tach dan) hinh thanh v6 mdi co be day nho va thanh phin ding nhit (Idp badan) [22, 24, 28].
4- Mat cit cac viing quan dao Trudng Sa va Hoang Sa.
' V6 trai dit co bl day t6ng the tir 20 den 25km, phia tren ciing la Idp nude co be day trung binh 2-3km. Phin v6 cimg gom 3 Idp. Ldp tram tich c6 be day nho va bien doi tir 1 den 5-6km bi uln nip va phan di, chia cat m.anh, Idp granit co be day tnmg binh 5-6km bi chia cit thanh cac khii va xe dich manh theo phuong thang dung tao thanh cac triing dang dia hao lip diy trim tich c6 kich thudc nh6. Ldp badan d phan dudi c6 be day tnmg bmh 10-12km.
Cac dirt gay tren mat cat co do cam sau 20-30km, cam nghieng theo cac hudng khac nhau va g6c nghieng nho, khong qua 15-20o theo phuong thing dung.
'W' Kilu v6 tren mat cat thuge kieu v6 a luc dia. Co che dia dgng lire tren mat cat la dano nen ep va tach dan sut liin phan di tao thanh cac khoi nang sut tuong d6i img vdi cac atol va cac khii nang syt cac triing tram tich dang dia hao xen ke va phan bo thanh timg dai tren cac viing quan dao [13, 25, 32, 36].
^
2 4 0 Tuy6n tap cac cong trinh nghien ciju Vat ly Dia c l u 2008
4. 2. Mpt so kieu mat cdt cdu triic dia dpng lire ddc trung tren them luc dia Viet Nam .\
+ Mat cit Vinh Bic bg:
V6 trai dit co be day biln dii 26-3 0km theo hudng giam dan tir 2 ben ria ve phia trung tam ciia Vinh. Tren mat cit ton tai 3 ldp co ban: tram tich, granit va badan. Be day cua cac ldp bien doi manh theo chilu ngang. Ldp tram tich co chieu day nho (l-2km) d 2 phia ria va tang len rat nhanh ve phia tnmg tam, dat eye dai 10-15 km dgc theo true cua bon triing Song Hong.
Ldp granit co be day trung binh 12-13km d cac vimg ria nhung d vimg tnmg tam gia tri nay chi cdn lai 3-4km. Be day ldp badan ciing bien doi theo quy luat tren. Doi nghich vdi xu the vong xuong ciia mat mong Uam tich la sy nang len cua mat mo ho dgc theo true ciia bdn triing song Hong vdi gia tri do sau la 25-26km, Uong khi gia tri do sau mat moho d 2 mien ria tang len tren 30km. Cac dirt gay trong mat cat gom ca 3 loai, dut gay bac 1, bac 2 va bac 3, phan bo day dac tren mat cat vdi do cam sau eye dai tren 30km goc nghieng ciia mat diit gay trong khoang 15-30o so vdi phuong thang dimg va nghieng tir 2 hudng doi nghich ve phia true cua bdn triing. Bien do dich chuyen thang dimg cua cac dirt gay tir 2-3km d ven ria den 7-8km d phan tnmg tam. Sir sut bac qua cac dirt gay tir 2 ben ria vao trung tam la rat Idn tao nen mpt be tram tich kainozoi co be day eye dai dat 15-16km. Dang cau tnic cua mat cat bilu hien kieu v6 luc dia vdi co che dia dgng lyc kha dac Uung la tach gian, sut liin tao rifto dac biet tich eye trong kainozoi [23, 30, 31].
+ Mat cat trong Vinh Thai Lan:
Be day v6 trai dat bien doi tir 30km dgc ddi ria giam din 24-25km dgc ddi trung tam ciia cac bon trung do sy nang len kha manh ciia mat moho. Ldp trim tich c6 bl day tang dan tir 2 ben ria. vao phia true ciia bon triing tao nen cac bl tram tich kainozoi nhu Patani, Ma Lai - Tho chu. Cac idp granit va badan diu co xu thi giam be day tir 2 phia ria vao trung tam ciia Vinh. Cac dirt gay trong Vinh cd hudng chu dao Tay bic - Dong nam va c6 do cam sau tdi 30km cam nghieng ve phia tryc cua cac bin triing Kainozoi.
Bien do dich chuyen thang dimg ciia cac diit gay kha Idn va tang din tir l-2km d ben ria den 5-6kmi d vimg trung tam, Co che dia dgng lyc chii dao dugc thi hien tren mat cit la tach dan sut lim kem theo nhung pha nen ep va xe dich cue bg [27, 29].
+ Mat cat cau true - dia dgng lyc thim lyc dia Dong nam Viet Nam.
Tren mat cit thi hien 2 be tram tich Kainozoi Idn la Cim Long va Nam Con Son, phan each nhau qua dai nang Con Son. Be day trimi tich cue dai trong cac bl tuang ung la 7-8km va 10-12km. Cac ldp granit va badan c6 be day tuong duong va biln dii trong khoang 8-15km, ciing vdi ldp tram tich, cac ldp nay bi uln nip va chia cit qua cac dirt gay tao nen binh do cau tnic phirc tap, da dang. Cac dirt gay co do sau tir 10km din 30km cam nghieng ve phia tnic ciia cac bin trung Kainozoi. Bien do dich chuyin thing dimg ciia cac dirt gay khong Idn, trung binh tir 2-3km. Q sudn phia dong cua mat cit cac dirt gay cam nghieng ve phia true ciia cac bl trim tich. Cac dirt gay d phin phia tay cua mat cat cam nghieng theo chieu ngugc lai. Tuy nhien cac dirt gay diu chii ylu co ciu tnic thuan hinh thanh trong giai doan tach dan sut lun tao nen cac bl trim tich Kainozoi.
Pha kiln tao tach dan Bien Dong hinh thanh ddi dirt gay sau kinh do 109°E d phia dong ciia vimg va lyc nen ep ve phia Tay da tac dgng tryc tilp lam biln dii binh dd ciu tnic ciia vimg them luc dia dong nam, ghi diu in kha dam tren mat cit cua vimg [29, 34].
Phin III: DIA VAT LY VA CAU TRUC V6 TRAI D A T 2 4 1
+ Mat cat cau tnic - dia dgng lyc tren thim luc dia mien Trung.
Dac diem noi bat tren mat cit la sy sut liin manh d phan tren lat cat d phia biln va tren sudn luc dia, noi c6 dgc die dia hinh rit Idn va tuong img vdi no la sy nang len"
manh ciia mat Moho tir phia dit liln ra hudng biln. Cung theo hudng nay be day v6 trai dit giam nhanh tir 30-35km trong dit liln xuIng c6n 17km d each bd khong xa. Ldp granit ciing giam be day rat nhanh theo hudng tren va biln mit han d ben ngoai sudn luc dia. Ldp badan co be day on dinh, biln dii nhe tir 15 din 17km, He dirt gay hudng kinh myln co do cam sau tir 30km doi vdi cac dirt gay toa tia, cdn mat dut gay chinh cam sau tdi 100km va cam nghieng ve phia dudi dia khii Congtum Uen dit hen. Cac dut gay chay dgc ven bd va mot so dirt gay tren dat lien deu cam sau tdi mat dirt gay chinh noi tren tao thanh he thong dut gay toa tia Uen mat cat. Bien do dich chuyen tao nen sy sut lim theo dirt gay ciia cac khoi v6 Uen mat cat la kha Idn, dat eye dai 4-5km. Dgc theo he dirt gay sau hudng kinh tuyen va tren dai ven bd ghi nhan klia nhieu dgng dit (va ca niii lua) c6 cudng do eye dai M
< 4,5. Co che dia dgng lyc tren mat cat la nen ep do sy tach dan md rgng Bien Dong tao nen cau tnic chdm nghich qua dirt gay. Ket qua la mang v6 Bien Dong trugt chim cam xuong ben dudi dia kh6i Cong tum va dgc theo he dirt gay chdm nghich nay da timg xay ra dgng dat niii lira va ca boat dgng phun trao badan (trong ky de tu). Hoat dgng tan kien tao d day van cdn tiep dien trong hien tai [19, 26, 27].
5. Ket luan
1. Ket qua dieu tra khao sat ve dia chat va dia vat ly Uen Bien Dong va them luc dia Viet Nam Uong hon 50 nam qua da tao nen co sd so lieu thyc te phong phu cho phep nghien cim xac dinh dac diem cau tnic va dia dgng lyc ciia cac he dirt gay d cac ty- le tnmg binh tren toan Bien D6ng va chi tiet tren nhieu viing, Uong do co them luc dia va dai ven bd ciia Viet Nam.
2. He phuong phap nghien cim xac dinh cac dac tnmg cau tnic va dia dgng lyc ciia cac dirt gay tren Bien Dong va them luc dia Viet Nam dugc xay dyng tren co sd phan tich va ting hgp cac nguon so lieu thyc te ve cac trudng dia vat ly cho kha nang phat hien tin cay va chinh xac cac dac trung cau tnic va dia dong lyc lien quan vdi dut gay, dong thdi danh gia dugc mgt each cu the moi quan he phuc tap va da dang giira cac dac trung do trong qua hinh tiln boa va phat trien kien tao ciia vimg.
3. Tren Biln D6ng tin tai nhieu he dirt gay c6 dac diem cau tnic, quy m6 phat trien va mirc do boat dgng kiln tao rat khac nhau. Theo so lieu thyc te cho den nay da phat hien, xac dinh dugc 21 he dirt gay chii yeu vdi cac dirt gay tir bac 1 den bac 3. Mang ludi dirt gay
• tren Biln Dong phat hien theo 4 hudng chu dao la Dong bac - Tay nam, hudng kinh hjyin, Tay bic - Dong nam va hudng vT hiyen, Uong do cac hudng Dong bac - Tay nam -A va hudnc kinh myln la noi bat va thong soai, chi phoi co ban binh do cau tnic va cac ,. boat dgng kiln tao dia dgng lyc Uen toan Bien Dong.
4. Thim lyc dia Viet Nam co dac diem cau triic dirt gay phuc tap vdi cac he dirt gay sau i va khu vuc phat trien theo cac hudng, dan cheo va giao cat nJiau tao nen cau triic klioi tang phirc tap va da dang. Dgc theo ven bien Viet Nam co cac he dirt gay noi tiep hi Vinh Bic bg din tan Ha Tien t^o nen vimg ranh gidi phan chia va co vai tr6 khong che
2 4 2 Tuy§n tap cac c6ng trinh nghidn cu-u Vat ly Dja c l u 2008
manh 2 miln ciu tnic khac nhau la miln ciu tnic tren dat liln va vimg them luc dia tren Bien Dong.
5. He dirt gay ven biln miln Tnmg Viet Nam la he dirt gay sau cd ciu tnic phirc tap, phat tiiln theo hudng kinh myln vdi quy mo Idn vl bl rgng, do cam sau. He dirt gay nay tao nen chl do dia dgng lyc manh me va tich eye, anh hudng manh va lan rgng doi vdi toan bg vimg thim lyc dia ciing nhu tren dit liln Trung bg va Nam trung bg Viet Nam.
6. Moi quan he tuong tac giira ciu tnic dirt gay va dia dgng lyc tren Bien Ddng va them luc dia Viet Nam dugc thi hien ro va diy dii Uen cac mat cat cau hTic - dia dgng lyc dac hung cit qua cac he dirt gay chii yeu d cac vimg mang sau Manila, vimg Palawan - Bomeo dgc ven biln va thim luc dia Philipin, vimg tach dan trung tam Bien Dorig, cac vimg quan dao Trudng Sa va Hoang Sa, cac vimg them luc dia mien Tnmg va them luc dia dong nam Viet Nam, cac vimg tnmg tam Vinh Bac bd va Vinh Thai Lan.
Cdng trinh dugc hoan thanh vdi sy ho trg ciia chirong trinh nghien ciiru co ban.
6. Tai lieu tham khao
1. Le Duy Bach, Ngo Gia Thang, 1990. Phan vimg kien tao them luc dia Viet Nam va cac mien ke can. Tap chl Cac khoa hgc ve Trai dat, so 12 (3), Ha Ngi.
2. Phan Tnmg Dien, 1992. Cac m6 hinh tich tu tram tich Kainozoi va cac kieu ria tren them lyc dia Viet Nam. Tap chi Diu khi. NI - 1992 - Ha Ngi.
3. Nguyen Xuan Han va n.n.k, 1991. Hoat dgng niii lira tre khu vyc Bien Ddng Viet Nam.
Dia chat tai nguyen. Vien Dia chat. Ha Ngi.
4. Nguyen Hiep va n.n.k, 1994. Dac diem dia chat va tiem nang diu khi quin dao Trudng Sa. Tnmg tam TTTL Dau khi. Ha Ngi.
5. Ho Dac Hoai, Ngo Thudng San 1975. Cau tnic dia chit va tiiln vgng diu khi thim luc dia Viet Nam, Tnmg tam TTTL Dau khi, Ha Ngi.
6. Nguyen Khn Lap, 1984. Mgt so dac trung ve biln dang dia chin- kiln tao v6 trai dit vimg Dong Nam A. Dia chat. N 165, Ha Ngi.
7. Nguyen Van Luong, 1999. Dac diem bien dang v6 ti-ai dit ti-ong cac he dirt gay sau boat dgng d ven bien Viet Nam. Cac cong ti-mh nghien cim dia chit - dia vat Iy biln. Ha Ngi.
8. Biii Cong Que, Nguyen Hiep, 1991. Dac dilm cac tiirdng dia vat ly thim luc dia Viet Nam va vimg ke can. Bao cao tong kit dl tai 48B-03-02. Chuong tiinh nghien cim biln.
HaNgi.
9. Bill Cong Que, 1995. Mgt so kieu mat cit ciu tine v6 ti-ai dit thim luc dia Viet Nam va Bien Dong. Tap chi Dia chat, 228. Loai A.
10. Biii Cong Que, Nguyen Giao, 1996. Dia chit, dia dgng lyc va tilm nang khoang san vimg bien Viet Nam. Bao cao ting kit dk tai KT- 03 -02, chuong tiinh nghien cim biln, HaNgi.
11. Biii Cong Que, 1999. Co sd khoa hgc cho viec xac dinh ranh gidi ngoai thim luc dia Viet Nam. Bao cao tong ket de tai KHCN-06-04. Chuong tiinh nghien cim Biln, Ha Ngi.
Phin III DjA VAT LY VA CAu TRUC V6 TRAI D A T 2 4 3
12. Bui Cong Que, 2000. B6 sung, hoan thien de xuit ban cac ban d l dia chit dia vat ly vimg bien Viet Nam va kl can. Bao cao ting kit dk tai KHCN-06-12. Chuang trinh nghien cim bien. HaNgi.
13. Bill Cong Que va n.n.k, 2001. Dac dilm cac trudng dia vat Iy, ciu tine v6 Uai dit va tilm nang khoang san vimg quin dao Trudng Sa. Tap chi khoa hoc cong nghe biln N1/2001 - HaNgi.
14. Biii Cong Que, Nguyen Nhu Trung va n.n.k 2001. Di thudng Ugng lyc ve tinh va cac yeu to ciu tiiic kiln tao khu vyc Biln D6ng. Tap chi KHCN biln, N3, 2001. Ha Ngi.
15. Bill Cong Que, 2005. Xay dyng tap ban do nhung dac trung co ban ve dieu kien ty nhien va moi tiardng vimg biln Viet Nam va kl can. Bao cao ting kit dk tai KC-09-02.
Chuong tiinh nghien cim biln KC-09-Ha Noi.
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ABSTRACT
STUDY AND DETERMINATION OF STRUCTURAL AND GEODYNAMIC CHARCTERISTICS OF THE FAULTS SYSTEMS IN THE CONTINENTAL
SHELF AND EAST VIETNAM SEA.
On the base of the updated source of practic data of the geophysical fields. Seabed topography, geomorphology and seismotectonics, using the new methods of data analysis and interpretation, the structural and geodynamic characteristics of the faults are determined and systematized on the typical structural and geodynamic sections. In the East Vietnam Sea have been determined 21 main fauh systems disfributed on 4 major directions as NE - SW, longtitude, NW- SE and latitude. Structural characteristics as a depth, an inclination of fault surface, a displacement amplitude and geodynamic characteristics as seismic activity, tectonic mechanism m the sections are detennined on the practic data. Analysis and comparision of the structural and geodynamic characteristics of the faults have allowed to determine some typical structural and geodynamic sections in the East Vietnam Sea and its continental shelf.
