Đang tải... (xem toàn văn)
24 Tuyin tap cac cong trinh nghien cu''''u V a t j y ^ ! f £ j ^ KET QUA NGHIEN ClTU BV6C DAU VE DO NGUY HIEIV SONG THAN 6 VUNG BIEN VIET NAM Nguyen Dinh Xuyen Vien Vat ly Dia cau, 18 Hodng OuSc Viet, Cd[.]
24 Tuyin tap cac cong trinh nghien cu'u V a t j y ^ ! f £ j ^ KET QUA NGHIEN ClTU BV6C DAU VE DO NGUY HIEIV SONG THAN VUNG BIEN VIET NAM Nguyen Dinh Xuyen Vien Vat ly Dia cau, 18 Hodng OuSc Viet, Cdu gidy, Hd Noi Mail: ndxuven(cp,smail com Tom t&t: Sau tham hoa song thdn gay bai tran dong ddt Mw9.3 xay a Sumatra 24-12-2004 nguy ca song thdn a vimg ba bien Viet Nam tra moi quan tam lan cua Nha nuac va nhan ddn Trong boi cdnh ay vien Khoa hoc vd Cong nghe Viet Nam da giao cho vien Vat ly dia cau nghien cuu de tai "Danh gia nguy hiem song thdn a vung ba bien Viet Nam va de xudt cdc giai phap phong tranh " Muc tieu cua de tai la - Danh gia, du bao nguy hiem song thdn a viing ba bien Viet Nam - De xudt cdc giai phap cdnh bao va phong tranh song thdn Ket quo buac ddu cua nghien cuu duac trinh bay nghien cuu nhu sau: Song thdn gdy bai cdc tran dong ddt rat manh xay cdc vanh dai dong ddt l&n tren the giai nhu vanh daiThdi Binh duc/ng vd vanh dai Dia Trung hdi - Hymalaya (nai xay dong ddt song thdn Sumatra 2612-2004) khong gdy nguy hiem cho ba bien Viet Nam vi da bi cdc vong cung dao nhu Philippine, Indonesia, Java, Thai Lan, Malaysia che chdn tit phia dong, dong nam, nam, tay vd tdy bac ^ Xac dinh dugc vimg bien Dong cdc viing ngudn song thdn co thi gdy tac dong nguy hiem cho vung ba biin Viet Nam: Cdc doi hut chim tdy Ddi Loan vd Philippine, cdc dai dut gdy thuan vd cham nghich bdc biin Dong, bdc Borneo vd tdy bien Dong Trong so do, nguy hiim han cd Id song thdn gdy bai cdc tran dong ddt manh a dai hut chim Manila vd bai phun trao nui lua vd trugt la ddt dai dut gdy Tdy biin Dong Tinh toan cho thdy dong ddt M8.5 a dai hut chim Manila co thi gdy song thdn cao l-4m a ba bien Trung bg tit Hue den Binh Thuan Kit qua khao sat thuc dia vd cdc tai lieu lich sir cho thdy mot s6 su kien song thdn da xay a ba bien Viet Nam, diin hinh la song thdn cao 23m a ba biin Phan Thiet, Nha Trang gdy bai phun trao nui lua Hon Tro nam 1923 I Phan I: DjA C H A N - DIA DONG LUC 25 Mffdau Sau tham boa song than gay boi tran dong dat Mw 9.3 xay a Sumatra noav 24-12-2004 nguy co s6ng thin vimg ho bien Viet Nam tro moi quan tam lan ciia Nha nuoc va nhan dan Danh gia nguy hiem s6ng than a vimg ba biSn Viet Nam la nhiem vu quan trgng va cap bach Trong boi canh ay vien Khoa hoc va C6ng nghe Viet Nam da giao cho vien Vat ly dia cau nghien cim de tai "Danh gia nguy hilm s6ng than o viing bof bien Viet Nam va de xuat cac giai phap phong tranh" Muc tieu ciia de tai la • Danh gia, dir bao nguy hiem song than o viing bo bien Viet Nam • De xuat cac giai phap canh bao va phong tranh song than De dat dugc muc tieu n6i tren, cac cong tac sau da dugc thuc hien: • Khao sat thuc dia dgc vimg ba bien va nghien ciru cac tai lieu lich sir de thu thap thong tin ve s6ng than da xay viing bo bien Viet Nam • Nghien cim binh kien tao dia dong lire khu vuc Dong Nam a de xac dinh cac viing co kha nang gay song than tac dong den viing bo bien Viet Nam • Danli gia cac dac tnmg ciia cac vimg nguon • Danh gia cao cue dai ciia song than co the xay bo bien Viet nam Mot so ket qua nghien ciru de tai dugc trinh bay bai Mot so khai niem ve song thdn 1 Song thdn vd nguyen nhan phdt sinh Song than - Tsunami (thuat ngir Nhat Ban, co nghia la s6ng hai cang, s6ng vinh) la song trgng lire chu ky dai, dao dong ciia ca cot nuoc bien lan truyen di vai t6c lan, vao bo nhieu dgt Nguyen nhan ciia song than la nhung tran dong dat gay nang hoac dot ngot day bien, nhung vu phun trao nui lira, nhung \ai trugt \b dat o ven bo bien hoac day bien, va mot so tac dong khac nhir thien thach, cac vii no hat nhan duoa bien Tuy nhien, nhimg s6ng than kha thuong xuyen va gay tham hoa tren hanh tinh chii yeu gay boa nhimg tran dong dat Ion, chan tieu nong, voi ca che nguon kieu chom nghich hoac thuan, gay nang hoac day bien tren dien tich rong voi bien Ion Nguoi ta nghiem thay rang chi CO dong dat voi Ion M>6.5 mod gay song than nguy hiem Van toe lan truyen s6ng than phii thuoc vao sau day bien va bieu thi gan dung bai c6ng thu'c Lagrange ^gH d6 g la gia toe trgng truong, H la sau ciia nuoc Van t6c bang 280 m/s_a viing H =4km, lOOm/s a viing H = 1km, 45m/s a viing H =200m Vi chu ky song than dai buac s6ng rit Ion: 200-700km vimg bi§n sau, 50-150km a vimg them luc dia Cho nen kho phat hien dugc hay cam thay song than o ngoai khoi vi a bien ciia song rat nho so voi buac song (0.1 den m so voi hamj chuc, hang tram km) 26 TuyIn tap cac cong trinh nghien ci>u Vat ly Dja c^u 2008 1 Quy mo cua song thdn Dp l&n (magnitude) ciia song thdn Do Ion ciia song than dugc bang cac thang sau: • Thang truyen thong Imamura-Iida: Ion ciia song than xap xi bang m = log2 h d6 h la cao cue dai ciia run-up tinh bang met (lida et al,1967) • Hatori (1979) mo rgng thang cho viing xa bing each xem xet hieu img khoang each R va dirng duong h - R toa log - log roi lay mire chuan la m=3 h=0.5m khoang each R= 1000km Gia tri m tang len mot don vi nang lugng tang lan (hay bien tang V5 lan) Dieu co the bieu thi nhu sau: m = 3+log[(/2/0.5)(RyiOOO)'^^] / log Vs h bang m, R bang km Dieu chi rang cao song than suy giam theo y^ khoang each theo R' • Thang Ion song than (tsunami magnitude) Mt Thang dugc dinh nghia bai Abe (1979): cho song than truyen qua Thai Binh Duong (Abe 1979): Mt = IogH + C + 9.1 Cho song thin khu vuc (lOOkm < 3500km) (Abe 1981): Mt = logH + logA + 5.8 H la bien Ion nhat, bang m, o tram thuy tri6u, C la he s6 phu thuoc khoang each, A la khoang each, km Thang chuan vod moment magnimde Mw Phuong trinh tren cho thay, bien s6ng than H giam theol/ R khac vod gia thilt Imamura - lida sir dung thang m, va c6 the chi c6 gia tri doi voi cac khoang each khu virc Cir&ng dp song thdn Soloviev (1970) chi rang, thang ??z ciia Imamura-Iida gidng thang cuong dong dit hon la thang lan (magnitude) Ong cung phan biet cao cue dai h ciia song thin voi cao trung binh h,b sau d6 dinh nghia cuong i song thin nhu sau: \= \og2{^h,,) So sanh cong thirc voi cong thirc Imamura - lida ta thiy, cao trung binh cua song thin bang ^ ^ lan cao cue dai Cuong cue dai i o bo gin ngu6n nhit dugc ',,j dimg de dinh lugng nguon song than Bang duoi day phan hang cuong s6ng than theo cao va mire tac doner cua s6ng than Ph^n I: DjA C H A N - DjA DONG LLfC i htb Mo ta song than ''max 11.3 Tham boa Pha buy hoan toan hoac m6t phan cac c6ng trinh xay dimg den mot khoang each tir bof Ngap lut bo den sau Ion Tau Ion bi hu hai doi chiit Cay coi bi bat g6c hoac gay vi song Thuong vong nhieu 5.7 Rat Ion Ngap lut bo den sau nhat dinh Ben cang va cac cong trinh nang khac gan bo bi hu hai Cac c6ng trinh nhe bj pha buy Vai noi cay tr6ng bi cuon sach, bo bien bi phu diy rac ban nhu cac vat noi, ca hoac dong vat bien khac Ngoai trir tau lan, tau thuyen bi day len dat lien hoac cuon bien X6i 16 lan cira s6ng Cac cong trinh cang bi hu hai Nguoi bi nhan chim Song kem theo tieng on Ion 2.8 Lon Ngap lut bo' den sau nhat dinh Dat mirgn bi rira troi Tuong chan va de bi hu hai Cac c6ng trinh nlie gan ba bi hu hai Cac cong trinh cimg gan bo bi hu hai nhe Thuyen buom Ion va cac tau nho bi hat len bo hoac cu6n bien Bo bien bi phii rac voi cac vat n6i 1.4 Kha Ion Nhan biet rgng rai Ngap lut bo' thoai Thuyen bu6m nhe bi cuon len ho Hu hai nhe cac cong trinh nhe gan ba a cira song dong chay bi dao nguge den mot khoang each nhat dinh 0.5 0.7 Nho Nhan biet boi nhirng nguoi s6ng doc bo bien, gia dinh voi bien ca Tren cac bo bien rat bang phang noi chung co the nhan biet song -1 0.25 0.35 Rat nho S6ng yeu den mire chi nhan biet dugc a cac tram thuy trieu Bien vd cao cua song thdn Bien dugc tir khong (zero) (mire can bang) den dinh (peak) hoac duong hay am Do cao song dugc tir day (trough) den dinh Do do cao s6ng than dugc tir day den dinh a tram thuy triSu, bien song than dugc tir mire can bang thai di6m Dp cao ngap lut (inundation height) vd dp cao dat t&i (run-up height) Neu khong eo tram ghi thuy trieu thi cao s6ng than bang khao sat thuc dia E)o cao song than tren dat lien tir mire nuoc bien thai diem toi ciia song than gQua cao ngap lut {inundation height) Khoang each nam ngang tir bo bien (6 thai diem toi ciia song thin) ggi la khoang each ngap lut {inundation distance) Do cao ngap lut a khoang each ngap lut Ion nhat ggi la cao dat toi {run-up height) 28 Tuy§n tap cac cong trinh nghien ci>u Vat ly Dja caujOOj Nhung ghi nhan ve song than 6* vung bo" bien Viet Nam L Kit qud dieu tra, khao sdt song thdn & viing b& bien Viet Nam Viec khao sat da dugc ti6n hanh tai 33 di8m phan b6 tuong d6i deu tir Mong Cai d§n Ca Mau Phuong phap khao sat chinh la di6u tra nhan dan tai cac diem dan cu vimg ven bien Tat ca cac hien tugng s6ng bien nhu song bao, nuoc dang, thuy trieu, song chua ro nguon goc deu dugc chii y, nhirng s6ng chua ro nguyen nhan dugc dac biet xem xet Ket qua khao sat dugc tong hgp duoi day: ^ 1 Song thdn nguon goc tugng / trugt la ddt ngdm ngoai khai Ngoai song bao, thuy trieu, nuac dang, da phat hien mot so hien tugng song than chua ro nguon goc S6ng cao den 2m, tran vao bo nhieu dgt, nhung tac dong pham vi khong rgng lam D6 la s6ng than, c6 the gay boi hien tugng tugng hoac trugt dat duoi day bien o viing bien xa - B& bien Trd Co nam 1978: S6ng than da thuc sir xuat hien vimg bo bien Tra Co, Mong Ciii, mot dep troi S6ng cao den 2m da tran vao bo nhieu dgt, lam niit tuong nha bep sat ba, cac hang cay phi lao ven bo Sir kien dien khong gian hep, co tinh dia phuong, khong lien quan voi sir co dong dat nao Phan tich so bg dan den ket luan, day la hien tugng s6ng than nguon goc tugng hoac trugt dat, CO the xuat phat tir tam tran 16c xoay hoac trugt dat duoi day bien vimg bien xa - Ba bien Dien Chdu: Theo loi ke ciia nhOng nguoi cao tuoi, vao cu6i thi ky 19 hoac dau the ky 20, hien tugng s6ng than ciing da xay o Dien Chau (Nghe An), mot dep troi Song cao nhu s6ng bao xay o day nam 1984, tuc song biln Ion cao ngang thanli tre ven bien, tran sau vao dat lien hon 1km, lam ngap nha din 1,5m, cuon troi rat nhieu nha cii'a Co le day cung la song than nguon goc tugng hoac trugt la dat viing biln xa nhu o' Tra Co nam 1978 2 Song thdn nguon goc dong ddt niii lira - Song than 1923 & viing bien Phan Thiet, Khdnh Hod: i, >| Theo ghi chep ciia TS Armand Krempt (trg ly cua bac sT Alexandre Yersin), nam 1923 song thin da pha hong chuong ngira ciia bac sT Alexandre Yersin Nha Traiig Vi tri chu6ng ngira each bo bien 5-6m Su co lien quan voi phun trao nui lira va dong dit dao Hon Tro, quan dao Phii Quy Con o Phan Thilt dan s6ng bai biln phai so tan khong tra lai nira Vimg biln nam Trung bg va Nam bg la viing hoat dong nui lira hien dai Nam 1923 phun trao niii lira dien a dao Hon Tro quan dao Phu Quy da gay dong dit nui phIn liDjACHAN-DjADONG LUC 29 lira 6.1 Richter Nam 1960, 1963 hoat dong niii lira lai dien nhung ylu ban Viec phun trao nui- lira Hon Tro gay song than cho thay boat dong nui lira ciing la mot nguin song than dang chii y vimg Bien D6ng - Song thdn 1991 & ba biin Tuy Hod, Phil Khdnh: Mot hien tugng dang chu y nira da xay Tuy Hoa, Nha Trang 4/5-1991, tmac niii lira Pinatubo, Philippines, phun trao Nuoc bien riit xa, nhieu tau nho 16 tren bai cat, mgi nguoi sg hai chay vao bo, kh6ng hieu la hien tugng gi xay Mot luc sau nuac lai tra lai nhung dimg xa nen khong ro cao ban hay bang muc nuoc ban dau Ong Do Minh Tiep, mot nguod doan can bg dia chat khao sat, dao h6 lay mau o bo biln, va nhimg nguod chimg kien hien tugng, danh gia: nuac da rut 2m so vod muc binh thuong Nhilu nguoi dan cung chimg kien hien tugng va deu to sg hai Sang 5/5 toan bo viing Khanh Hoa bi bao phii mot lop tro bui day vai mm den vai cm Do la tro bui tir niii lira Pinatubo 2 Cdc ghi chep lich sir vi song thdn & viing b& bien Viet Nam Theo tai lieu lich sir chi c6 su kien s6ng than a ba bien Viet Nam dugc ghi lai: 1877 Binh Thuan, 10.56*^, 108.05°E Dong dit lin Lin diu nuoc s6ng dang len, nha ngoi rung dong manh, hai lan sau hoi nhe 1882 Binh thuan ba bien dong dat, song cuon len cao, co nhieu tieng n6 to gan mot Nguyen Khac Mao, cac nghien ciru dong dat Viet Nam (Nguyen Khac Mao, 1973, 1975), cho rang hai tran dong dat deu co lien quan voi nhirng phun trao bazan theo cac khe nirt hoac theo cac hong niii lira moi Do la mot nhirng bieu hien noi bat ciia boat dong kien tao moi ky de tir va van dang tilp tuc Phun trao nui lira Hon Tro 1923, Hon Nuoc 1960,1963 la minh chimg Mot so thong tin ve co song thdn Trong khu6n kho de an hgp tac khoa hoc Viet nam - Lien bang Nga, doan can bo khoa hoc ciia Vien Vat ly trai dit (lien bang Nga) va vien Vat ly dia cau (vien KHCN VN) GS Rogogin, TSKH Ngo Thi Lu PGS Cao Dinh Trilu, va cac cong sirda tien^ hanh hai cu6c khao sat vao thang 11-12 nam 2005 va thang - nam 2006, nham tim kiem nhirng vet 16 dia chat co dau hieu bieu hien ciia s6ng than va lay mau ve phan tich tuoi tuyet doi nham xac dinh tu6i hinh nhirng tram tich co ngu6n g6c bien dugc song Ion hat len bo' va phii tren lop dat th6 nhuang Da phat hien diem, la: Cira Lo, Song ciu, Nha Trang, Phan Rang, Phan Thiet va Vung Tau Thang nam 2007 da to chuc chuyen thuc dia thir dgc ba bien tir Cira Lo tai Mong Cai va da phat hien them diem nira tai Ciia Lo Ket luan ciia phan tich dia chit cho thiy lop phii them dugc tao hoan canh xao trgn dii doi ciia nuoc Dieu kien bieu hien ro rang dc^c trung song Ion Vi vay co the dua mot gia thiet rang cac dilm khao sat la vet tich de lai cua hoat dong song than tac dong den ba bien Viet Nam qua khir 30 TuyIn tap cac cong trinh nghien CLPU Vat ly Dia c a u j O O j Tu6i tuyet doi ciia mlu vat dia chit dugc xac dinh bing phuong phap carbon ^hong xa (thuc hien tai Vien Khao c6 hgc vao nam 2006) Kit qua phan tich tuoi tuyet doi cua cac miu dia chit tai cac lop phii thim da cho thay la co it nhat la dgt phii them tren dien rgng, vao cac nam each day 380 nam, 610 nam va 960 nam, chu ky trung binh la 320 nam Do cao t6i da ciia ting chira diu tich s6n2 co thi len toi 18m Voi dac trung co thi gia thilt vl su t6n tai c6 s6ng thin da gay tac dong manh me vao bo bien Viet Nam Nhung dl khing dinh cac th6ng tin noi tren la c6 song thin va danh gia dugc cao cua chimg thi can phai lam ro hai van de: 1/ Chimg minh cac diem 16 mo ta o tren la dau tich ciia song than, a viing bo bien Viet Nam, s6ng bao co the dat cao 8-10m, tran sau vao dit liln, mang theo cac vat lieu biln, cung co the de lai cac dau tich cua s6ng Ion 2/ Do cao ciia dia tang mang dau tich ciia song vao thai diem s6ng toi Nguy cff song than 6" viing ba bien Viet Nam Song thin la song trgng krc gay bo'i cac tran dong dat Ion ngoai khoi lam nang/ha dot nggt day biln tren dien rgng voi bien Ion S6ng than ciing gay boi phun trao nui lira va trugt Id ngam ngoai khoi va a bo bien Ket qua nghien cim da chi rang chi co dong dat M > 6.5 moi co the gay song than nguy hiem Vi vay de danh gia nguy co song than vimg ba bien Viet Nam can phai nghien cim boi canh kien tao dia dong lire, lam ro dieu kien phat sinh song than va xac dinh cac vimg nguon song than CO the anh huong den bo bien Viet Nam Binh cdu trite - kiin tao kainozoi khu vuc Dong Nam A Tren co so' t6ng hgp cac tai lieu ciia cac ban (CCOP Working Group for Compilation of the Geotectonic Map Geotectonic Map of East and Southeast Asia, Le Nhu Lai, Phiing Van Phach, Biii C6ng Que, Nguyen The Tiep, Trin Van Tri, Pham Nang Vu, Phan Trung Diln, Ngo Van Dinh 2006; Phiing Van Phach; Biii Cong Qui; Nguyen The Idep, Le Nhu Lai; Tran Van Tri, Nguyen Trgng Tin, Phan Trung Diln, Ngo Van Dinh, Phi Truong Thanh, 2006; Pubellier Manuel, Rangin Claude, Le Pichon Xavier 2005), cac van lieu cong bo tren cac tap tri, bao cao hoi thao va ngoai nuoc, tai lieu tren mang Internet, chimg toi da xay dung Ban Kiln tao Dong Nam A (hinh 1) Tren ban d6 da the hien dugc cac kien true co ban ciia khu vuc nhu he qua ciia cac chiiyin dong Kainozoi nhu sau: • • Loat cac sieu doi hut chim: nhu doi hiit chim mang biln Sumatra keo dai din 000km, tir phia ria TB ciia D6ng Nam A tai phia dong dao Timor; doi hiit chim mang biln Philippin keo dai tren 3000km Ngoai phai kl din cac doi hut Loat cac biln ria, hinh tach gian sau ciing (Tamaki K and Honza E 1991) (nhu biln Selebes tir khoang 57-42 trieu nam; Bien Dong Viet Nam tir 32-15,5 trieu nam; biln Su Lu tir 19-17 trieu nam; bien Molucca tir 40-35 trieu nam; biln Banda tir 20-15 trieu nam (tai lieu (HoUoway, N.H 1982) cho ring Nam Banda co tu6i hinh v6 dai duong 6-3 trieu nam); bien Makassar tir 23-17 trieu nam; Biln Andaman tir 11 trieu nam den nay) Phan I: DjA C H A N - DjA DONG LUC 31 Cac dirt gay tmgt bing Ion nhu: dut gay phuong a kinh tuyen Sagaing trugt phai giai doan hien vod van tic Uimg binh 20 mnVnam; dirt gay phuang TB-DN Song H6ng - Ailao Shan trugt phai giai doan hien tai, nhien vod van tic tuono d6i nho; dirt gay phuong TB-DN Sumatra (tren ddo Sumatra) trugt phai vod van tic tir 15 mm/nam phia DN, tang len 25mm/nam a phia TTB; dirt gay phuang a kinh tuyIn Philippin (tren cac dao Philippin) trugt trai, voi van toe doan giira dat tod 35 mm/nam Sir ton tai kieu cap doi cac doi but chim va cac doi dut gay trugt bang: cap hut chim va trugng bang cimg ten Sumatra; cap hut chim - trugt bang ciing ten Philippin, cap hilt chim Timor (doan phia d6ng ciia doi hiit chim Sumatra) va trugt bang Sorong Hinh BANf)6KIENT.^O m.\ IXINGLt (' KHV VT.1CDONGN.4M A ThUjihlap.'iii PbansCeutruc iau Oia dpusl^n Vl^n Ou chac f a dia fa(l;f bi/n-VUn KHCSVN Tae jfia: PhUngVOit PiiAch, Bu: Cdng Qui N^yia [Aiih Xa-jtn, Nguyifi Ngpc Thuy, CBO DLah Triru Dinh Yin Toan Pligm S&ng VH tld l^ol J2-2006 20'H lOtJ lori'E iM's 11U-E iia'E 6,5 voi ca che nguon kieu chom nghich hoac thuan, thuong xay o cac doi hiit chim, cac dai dirt gay chom nghich hoac thuan, 2/ cac doi boat dong nui lira, 3/ cac doi trugt 16 ven bo va duoi day bien Tir cac tai lieu da co ve kien tao dia dong lire khu vuc Dong Nam a trinh bay tren va ket qua nghien cuu boat dong nui lira, kha nang trugt 16 vimg them luc dia Viet Nam theo'cac tai lieu dia chan tham dau chimg toi vach cac vimg nguon song than tiem an vimg Bien Dong nhu sau: Cdc dai hiit chim - Nam Dai Loan - Tay Philippines (Manila, Sulu, Selebes, Makasart, biln Banda bic, bien Banda nam) 2 Cdc dai diet gdy phdt sinh dong ddt song thdn (dong ddt gdy song thdn) - Cac dirt gay trugt bang - thuan bac bien Dong - Cac dirt gay trugt bang - thuan tay bien Dong, - Dut gay chom nghich bac Borneo - Dut gay choon nghich Java 3 Cdc vimg hoat dong nui hia hien dai Vimg boat dong nui lira Holocen them luc dia Trung bg Cdc dai trugt la ddt Cac doi trugt lo dat lien quan voi boat dong ciia doi dut gay Tay biln Done Dong dat song than da quan sat thay khu vuc Dong Nam A dugc chi tren hinh Ph§n I: DjA C H A N - DIA DONG LUC 33 Hinh BAN DO D(:)NG DAT GAY SONCi THAN 100'E KHIT ^T/C DONG NAM A 120'E, 115'E 105°E 130 •£ 20 "N 20-N H'N 15'N 10°N 10'S - irj.5=E 95 •£ 125 °E i20"e 110"E 150'E C n r ( L\I-LEGENDS 06ir,ijtchri ^^ Cur i jv bOc II' Fo'jif 01 odec i A Our ciOf rrnjon r.winw:J loyr ':Cxir:^rii^r r L3r^ ot iV.-;r^ r-trr / ,eini ^ ' ^ O.iii di r r ' u c n a Ml P.:i't-ori o;jrencLfie.'ra-ik.' B Our J -jy r^gr*c^ Thruit loUr C C'O'J-Iiv rtuor b o n g S r n k c i p ' ^ O cr,3"n rO,n LiOriO d5r idno r t j n '.' V6 d-a ducng CAC Kl HIEU VIET TAT LM> »'• lu> !ôi*l UXOM ' i M > 111' K b ' t I W " ! l i l i K t l B ^ l n J K1 I » , - > j i l>> n i M l l SU K I - t i J U L K b * I t ! U.ll flMI li >i I I S Kii I' ,: >C ku ,.-., B ' li Cac viing neuon song than tiem an da neu va cac dac trims ciia chimg dugc tap hop bang Mmax- dong diit cue dai co klia nang xay ra, B- nghieng cua ao thi lap lai dong dit logN* = a- BM \- tain suit cua dong dit nguong Mng = 5.5, goi la toe xay dong dat, N*(Mma\)- tan suet cua dong dat cue dai Mmax TuySn tap cac cong trinh nghien cu'u Vat ly Pja cau 2008 34 Bang Dac trung ciia cac viing ngudn song t h i n t i l m an vung Bi§n Dong TT Ten vung nguon Dac tru-ng kien tao Bac Philippine+ +tay Dai Loan - doan - doan - doan +Ryukyu (nam Dai Loan) doi hilt chim Mang sau Malina - doan -doan dai hut chim Bien Sulu - doan doi hilt chim - doan Bien Selebes - doan 1(bac Sel Sea) - doan (nam Sel Sea) doi hilt chim dai,km 264 7,3 246 7,2 180 7,0 1153 292 V N* (Mng=5.5) (Mmax) 0,86 0,86 2,22 0,004 8,5 2,97 0,007 0,88 0,95 0,004 0,86 0,42 0,008 B Mmax 8,2 7,3 368 7,5 642 7,8 346 7,4 0,42 0,008 648 7,8 0,75 0,008 0,33 0,017 0,86 0,57 0,016 0,80 0,12 0,0030 7,2 0,80 0,06 0,0015 7,0 0,80 0,90 0.06 0,0015 0,0103 0,0016 0,86 Bien Banda bac doi hut chim 632 7,8 0,86 Bien Banda nam doi hilt chim 304 7,2 0,86 Makasart - doan doi hilt chim 167 7,0 7,4 326 - doan diet gay nghich Bac Borneo * 10 11 0,86 - doan 158 - doan 533 Bien Jawa Borneo) - doan 0,86 (nam diet gay nghich - doan Bac Bien Dong -bon trOng Chau Giang -nam Hal Nam-nam Dong sha du't gay tru-gt bSngthuan l a y Bien Dong du't gay tru'gt bangthugn - doan 1: nam Hai Nam-Tuy Hoa - doan 2: ti> Tuy Hoa vS phia nam 6,9 7,7 592 7,8 200 7,1 1087 548 6,1 811 6,1 •J Phin I; DjA C H A N - DjA DONG LUC 35 3 Dp cao song than lan nhdt co khd nang a viing ba biin Viet Nam Theo chimg toi, s6 cac viing nguon neu bang thi doi hut chim Manila CO the gay song than nguy hi6m nhit cho viing ba bi^n Viet Nam, boi vi o day co thg phat sinh nhung tran dong dit song thin manh nhit va khoang each tir nguon din bo ben Viet Nam la ngan nhat, it vat can tren duong truy6n Cac viing ngu6n gin nhit nhu cac dirt gay a vimg th§m luc dia Viet Nam kh6ng gay dong dit lan hon M6.5 va co ca che trugt bang-thuan, kem kha nang gay song thin Nhu vay, dong dit manh nhit co kha nang a dai hiit chim Manila co th6 gay s6ng thin Ion nhit a ba biln Viet Nam Dong dat manh nhat co kha nang a co Ion M8.5 Bh danh gia song thin Ion nhit CO the xuat hien a bor biin Viet Nam chiing t6i tinh mot kich ban song thin cho truong hgp Kjch ban tinh toan Ngu6n: Magnitude Diem g6c mat dirt gay: Manila Trench (dai hiit chim Tay Philippines) Mw = 8.5 119.4 E, 14.8N Cac thong so nguon kjch ban tinh toan Magnitude Strike Dip Rake Do sau Mw (do) (do) (do) h(km) 277 15 8.5 Chieu dai Chieu rpng L(km) W(km) Dich tru-pl 313 18 90 Au(m) 68 5.28 Viec tinh toan dugc thuc hien bang chuang trinh may tinh cac nha khoa hoc ciia Dai hgc t6ng hgp Tokyo va Mexico xay dung, Chuang trinh dugc trinh bay tai Hoi thao dao tao ve mo hinh so lan truyen song thdn va bien cho cdc nuac dang phdt trien, Philippine, 8-2005 Ket qua tinh toan dugc trinh bay tren hinh 4, 5, va bang Bang 06 cao song thSn a mot s6 dja diem doc ba biln Viet Nam triycyng ho-p dong d i t MS.5 xay a dai hut chim Manila Dja danh Do cao (m) Dia danh Do cao (m) 3.74 Ca Mau Quang Ngai Bac Lieu Quang Nam 1.82 Soc Trang 0.06 Da Nang Tra Vinh 0.22 Hue 1.5 0.69 Ben Tre 0.39 Quang Tr| Tien Giang 0.21 Quang Binh 1.03 0.61 TP HCM(Can Gio) 0.29 HaTTnh Vung Tau 0.37 Nghe An 0.43 Thanh Hoa 0.57 Ninh Binh - Nam Dinh 0.6 Khanh Hoa 3.15 Ninh Thuan 1.56 Phil Yen 2.97 Binh Dinh 2.95 \ ! Thai Binh 0.58 Hai Phong - Quang Ninh 44 Tuygn tap cac cong trinh nghien ciru Vat ly Dja cSu 2008 36 Hinh Ban d6 song t h i n a vCing bi§n Dong truo-ng hap dong dat Mw8,5 xay a dai hut chim Manila The map of MAXIMUM COMPUTED TSUNAMI HEIGTH ofVielnam 24 45 22 |^'-*%| 20 35 18 16 2.5 14 I 1.5 Hinh Ban song than a viing bien Bac Viet nam tru'ang hap dong dat Mw8,5 a da[ hut chim iVlanila The IMUtl&ATION Map of tlie Noilh ;,< Vieliiam 1.4 1.2 0.8 •jos 37 Phin I: DjA C H A N - DjA DONG LUC Hinh Ban d6 song t h i n a ba bi§n Nam Viet Nam truang hap dong d i t iVlw=8.5 a dai hut chim Manila The INUNDATION Map o f l h a Soulli ofVielnam 1 1 ip- I ) -"yny- ' ""m^m ' \i ) - • • ' • " * ( : • •^v .: ' Ir >-^ J11 • • ^ ^ ^ I -^^^ ^.m -'^H?^ ^-^' 103 *» ^^^ai^&^ *'' H^ ^BB^ii^ 1.2 w^^^*^l^^^3 jt^fe'","* "^-^^r^ i^3-*'^^ o ^ ^ ' • : : ; mmm Is j^i t"" !M •_•• -;;,) y/^j^ K^*L>»^^ i^i7!S^^»S^»r ^^^^1 HBHSMBH 108 107 108 Longitude 109 no 112 Nhu vay, song than Ion nhat tir cac ngu6n xa se dat toi cap -2 (do cao -4m) a vimg bo bien Viet Nam tir Hue den Ninli Thuan, \aing ba bien tir Quang Tri tra va tir Binh Thuan tra vao song than nho ban cap 1, cao duod m Nhting viing co the phai chiu tac dong Ion hon bod song than phat sinli cac vimg nguon gan Vimg nguon gan dang luu y la dirt gay kinh tuyen 109-110°E Day la mot dirt gay Ion, kieu trugt bang thuan Dong dat kien tao phat sinh doi khong co kha nang gay song than nguy hiem ca che dich trugt kh6ng thuan Igi va magnitude nh6 Song than co the phat sinh 6f day boat dong nui lira va targt la theo dirt gay dong dat hay trugt 16 Tuy nhien, nhting gi da xay va du doan cho thay song than cac ngu6n gan gay ciing chi dat cap 1-2 Chu ky lap lai ciia dong dat cue dai M8.5 doi hut chim Manila danJi gia theo so li?u dong dat la khoang 250 nam Tuy nhien gia tri thieu tin cay vi so lieu dgng dat dimg de tinh toan c6 ca nhijng tran xay a lan can vimg ngu6n Hon niia, khong phai tr^ dong dat nao ciing gay song than dii c6 ca che ngu6n kieu chom nghich hoac thuan Neu, tlieo s6 lieu GPS, coi chuyen dgng tuong d6i kieu trugt chom nghich giira mang v6 dai duong a bien D6ng va kh6i v6 luc dia Philippin co van t6c lOmm/nam thi thai gian tich luy dich targt cho dgng dat cue dai M8.5 a doi hiit chim Manila se la khoang 500 nam 4.Cac giai phap phong tranh Vai nhirng danh gia ve nguy ca song than nhu da trinh bay, viec ap dung cac giai phap phong tranh song than Viet Nam la can thi6t Mot la vi c4n phai c6 quy hoach va cac giai phap phong ch6ng hgp ly d6i vai cac c6ng trinh a cac viing co nguy ca song 38 Tuyin tap cac cong trinh nghien cOu Vat ly Pja chu 2008 than de giam nhe hau qua co the xay Hai la d6 tranh tam ly hoang loan vi nhirng thong tin v6 can cir, dam bao 6n dinh xa hoi Vai nhirng ket qua nghien cuu ban dau, chung toi kien nghi cac giai phap sau: Thiet lap he thong cdnh bao song thdn phu hop He thong ay sir dung cac thong tin hien a nuac, khu vuc va tren the giai ve dgng dat va song than de dua cac canh bao som ve song than a vimg ba bien va hai dao nuac ta Sa d6 he th6ng bao tin dgng dit va canh bao song than a Viet Nam dugc trinh bay tren hinh Hinh Sa d6 he th6ng bao tin dong dat va canh bao song t h i n Viet Nam Vien KH&CN Viet Nam Mang liroi tram dia chan Vetinh Cac tram dia chan Viet Nam (cac tram qua ve tinh Cac tram l Vien KH&CN Viet Nam + Bo TNMT Kich ban song than ' »-: —^ Trung tam (uv ban) canh bao song than i Be TNMT Mang ludi tram ghi song than Cac tram song than V.N i Trung tam thu va XLT ly so Heu quan sat song than Thong bao M>4,0 -TV -Radio -Chinh phii va cac CO quan huru trach -Cac thap bao dong -TV Canh bao sam • -Radio -Chinh phu va cac ca quan hiru trach -Cac CO quan sir dung - Cac tram song than khu vuc He thong g6m mot Trung tam canh bao va cac mang lu6i quan sat dgng d^t va song than ciia Viet Nam, khu vuc va the gici Tmng tam co nhiem \-u thu nhan tire tl'ioi cac kit qu^quan sat cua cac mang luoi tram quan sat nuac, thong tin tir cac Tmng tam canh bao khu vuc va quoc te, xir ly tong hgp s6 lieu, dua cac quyk dinh canh bao va thong bao nhanh cho cong d6ng va cac ca quan hiru trach Quy hoach vd dp dung cdc giai phap phong chSng song thdn hffp ly cho cdc cong trinh cdc viing nguy hiem song thdn * N6i chung khong nen bo tri cac klui dan cu, cac e6ng trinh cong cong tren nhimg dien tich nguy hiem song than cap 1-2 Doi vai nhung cong trinh xay dung nhirng vimg d6, can ap dung cac giai phap cong trinh de giam tac dgng ciia s6ng th4n^ nhu tuong ch5n, rime cay, cac giai phap ket cau, vat lieu, b6 tri mat bang Phan I: D J A C H A N -DjA DONG LUC Bk lam viec truac hit phai nghien cim danh gia chi tiet nguy hiem song than a nhimg vimg c6 nguy co song than ma nghien cim chua thuc hien dugc, Cac ban d6 ngap lut phai dugc lap a ty le Ion, rat chi tiet, chang ban ty le 1:10.000 O nhirng viing nguy hiim cao phdi chudn hi nffi dia diem lanh nan song thdn vd cdm biin hif&ng ddn 4 Pho bien kien thirc ve song thdn cho nhan ddn, dac hiet Id cir ddn cdc vung ngu hiim song thdn Ket luan Song than gay boi cac tran dgng dat rat manh xay cac vanh dai dong dat lan tren the giai nhu vanh daiThai Binh duong va vanh dai Dia Trung hai Hymalaya (noi xay dgng dat song than Sumatra 26-12-2004) kh6ng gay nguy hiem cho bof bien Viet Nam vi da bi cac vong cung dao nhu Philippine, Indonesia, Java, Thai Lan, Malaysia che chan tir phia d6ng, d6ng nam, nam, tay va tay bac Trong pham vi bien D6ng co hai nguon song than dang chu y Thir nhat la doi hiit chim a phia tay Philippine Dgng dat cue dai doi co the dat toi 8,5 Richter Trong truong hgp ay s6ng than cao l-4m se tran toi ba bien Viet Nam tir Hue toi Ninh Thuan gia sau dgng dat Chu ky lap lai dgng dat cue dai doi la khoang 250-500 nam Ngu6n thir hai la doi dirt gay chay theo kinh tuyen 109-110 gan ba bien Viet Nam Trong doi c6 kha nang phat sinh dong dat, phun trao niii lira va targt la dat Nhung dgng dat cue dai a day nh6 hon 6.5 Richter (theo quan sat thuc te va danh gia ciia chimg toi, dgng dat cue dai a day c6 Ion 6,1±0,3 Richter), ca cau dich chuyen chii yeu la.trugt bang, cho nen it kha nang gay s6ng than Ion Con boat dong nui lira/trugt la dat ngoai them luc dia, nhu phun trao nui lira kem theo dgng dat manh toi 6,1 Richter a Hon Tro, Phu Quy, co the gay chan dgng cap VII va song than voi cao den 2m a vimg ba bien gan nhat Vai nhung danh gia ve nguy ca song than rihu da trinh bay, viec ap dung cac giai phap phong tranh song than a Viet Nam la can thiet Mot la vi can phai co quy hoach va cac giai phap phong ch6ng hgp ly doi vai cac cong trinh a cac viing co nguy ca song than de giam nhe hau qua co the xay Hai la de tranh tam ly hoang loan vi nhimg thong tin v6 can cu, dam bao 6n dinh xa hoi D6i vai Viet Nam, giai doan hien nay, vai nhung ket qua nghien cim ban dau, chung t6i kien nghi cac giai phap sau: Thiet lap he thong cdnh bdo song thdn phii hgp He th6ng ay sir dung cac th6ng tin hien a nuac, khu vuc va tren the giai ve dgng dat va song than de dua cac th6ng bao dgng dat va canli bao song than a viing ba bi6n va hai dao nuac ta So d6 he thong bao tin dong dat va canh bao song than Viet Nam dugc trinh bay tren hinh Quy hoach vd dp dung cdc giai phap phong chong song than hgp ly cho cdc cong trinh cdc viing nguy hiem song thdn 40 TuyIn tap cac cong trinh nghien cij-u Vat ly Dja c i u 2008 O nhimg viing nguy hiem cao phdi chudn bi nai dia diem lanh nan song thdn vd cdm bien huang ddn PhS biin kiin thirc vi song thdn cho nhdn ddn, dac biet Id cu ddn cdc viing nguy hiem song thdn Tai lieu tham khao 10 11 12 13 Abe k., 1979 Size of great earthquakes of 1873-1974 infered from tsunami data J Geophys Res 84 1561-1568 Abe k., 1981 Physical size of tsunamigenic earthquakes of the Northwestern Pacific Phys Earth Planet, 27, 194-205 Bautista P Leonila Ma Historical Tsunami of the Philippine (1589 to 1999) PHIVOLCS Oct.4, 2001 Bautista P Leonila Ma., Kazuo Oike Estimation of the Magnitudes and Epicenters of Philippine Historical Earthqukes Tectonophysics 317 (2000) 137-169 Bill Cong Que, Phimg Van Phach Ve nhimg yeu to cau truc-kien tao chinh tren vimg bien Viet Nam va ke can Tap chi Khoa hgc va Cong nghe bien 4(T.l), Ha Ngi 2001 CCOP Working Group for Compilation of the Geotectonic Map Geotectonic Map of East and Southeast Asia Published by Geological Survey of Japan March 2000 Hall R., 2002 Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacfic: computer-based reconstructions, model and animation Journal of Asian Earth Sciences 20 (2002) pp 543-531 Hall, R., 1996 Reconstructing Cenozoic SE Asia In; Hall, R., Blundell, D.J (Eds.), Tectonic Evolution of Southeast Asia Geol Soc London, Spec Publ., vol 106, pp 203-224 Hamilton, W., 1979 Tectonics of the Indonesian region U S Geol Surv., Prof Paper 1078, 345 pp Holloway, N H., 1982 North Palawan block, Philippines-its relationship to Asian mainland and role in evolution of South China Sea AAPG Bull 66, 1355-1383 Leloiip, P H Arnaud, N., Lacassin R., Kienast, J R., Harrison, T M., Phan Trong Trinh, Replumaz, A., Tapponnier, P., 2001 New constraints on the structure, thermoehronology and timing of the Ailao Shan-Red River shear zone, SE Asia J Geophys Res Leloup, P H., Lasassin, R., Tapponnier, P., Sebarer, U., Dalai, Z., Xiaohan, L., Liangshang, Z., Shaocheng, J., Trinli, P T., 1995 The Ailao Shan-Red River shear zone (Yunnan, China), Tertiary transform boundary of hidochina Tectonophysics 251, 3-84 Le Nhu Lai Phiing Van Phach, Biii Cong Que, Nguyen Thi Tiep, Tran Van Tri, Pham Nang Vu, Phan Trung Dien, Ngo Van Dinh Ban cdu true kiln tao vimg biln Viet Nam va kl can, ty le 1: 2000 000 D I tai KHCN-06 va KC-09-24 Vien Dia chat va Dia vat ly Bien, Ha Ngi 2006 14 Vletcalfe I 1997 The Paleo-tethys and Paleozoic-Mezozoie tectonic evolution of Phan I: DjA C H A N - DjA DONG LUC 41 Southeast Asia Proceeding of the international conference on Stratigraphy and tectonics evolution of Southeast Asia and South Pacific Pp260-272 15 Morley, C K., 2002 A tectonic model for the Tertiary evolution of strike-slip fauhs and rift basins in SE Asia Tectonophysics 347, 189-215 16 Nguyen Khic Mao, 1973 Nhan xet vl phan viing dgng dat men nam Viet Nam Tap chi Tin tire boat dgng khoa hgc, 1973 Bo Giao due va dao tao 17 Nguyen Khac Mao, 1975 Dgng dk miln Nam Viet Nam Tap san "Sinh vat Dia hgc" tap XIII, No4 Ha Ngi 1975 18 Phimg Van Phach, Nguyen Dinh Xuyen, Nguyen Ngoc Thuy, Biii C6ng Que, Cao Dinh Trilu, Dinh Van Toan, Pham Nang Vu Ban d6 kien tao khu vuc d6ng nam A, ty le 1: 000 000 Vien Dja cbdt va dja vat ly biln Ha Ngi 12-2006 19 Phiing Van Phach; Biii C6ng Qui; Nguyen Thi Tiep, Le Nhu Lai; Tran Van Tri, Nguyen Trgng Tin, Phan Trung Diln, Ng6 Van Dinh, Phi Truong Thanh Ban d6 cac bl trim tich de tam biln d6ng va phu can, ty le 1: 2000 000 D I tai KC-09-02 va KC-09-24 Vien Dia chit va Dia vat ly Biln, Ha Ngi 2006 20 PHIVOLCS.2002 Earthquake, Earthquake Hazards and Philippine Seismieity 21 Pubellier Manuel, Jason Ali, Christopher Monnier 2003 Cenozoic Plate Interaction of Australia and Philippine SeaPlates: hit-and-run tectonics Tectonophysics 363 (2003) p 181-199 22 Pubellier Manuel, Rangin Claude, Le Pichon Xavier 2005 Deep Offshor Tectonics of Southeast Asia A Synthesis of Deep Marine Data in Southeast Asia DOTSEA Working Group Mem.Soc.Geol.France, n.s., n*^ 176, 32p, plates+CD 23 Rangin, C, Le Pichon X., Mazotti S., Pubellier, M., Chamot-Rooke N., Aurelio M., Walpersdof A and Quebral R 1999 Plate Convergence measured by GPS across the Sundaland/Philippine Sea Plate deformed boundary: the Philippine and Eastern Indonesia Geophysics J Inst (1999), 139, 296-316 24 Rangin, C & Pubellier, M 1999 "Distribution of Deformation Across the Sundaland/Philippine Sea Plate Boundary from GPS Resuhs and Tomographic Studies", International Conference on Tectonics PALAWAN 99, Stratigraphy and Petroleum and Mineral System of Palawan, Borneo and Surrounding Area.Puerto Princess City, Palawan ^Island, Philippine 29Nov-3 Dec 1999 25 Rangin, C, Jolivet, L., Pubellier, M 1990 A simple model for the tectonic evolution of southeast Asia and Indonesia region for the past 43 Ma Bulletin de la Socie'te' Ge'ologique de France 8, 889-905 26 Rangin, C, Silver E.A., 1991 Neogene tectonic evolution of the Celebes- Sulu basins: new insights from Leg 124 drilling Proceedings ODP, Scientific Results 124, 51- 63 27 Sibuet Jean-Claude, Hsu Shu-Kun, Le Pichon Xavier, Jean-Pierre Le Formal, Donald „ Reed, Greg Moore and Char-Shine Liu East Asia plate tectonics since 15 Ma: ' constraints from the Taiwan region Tectonophysics, 344, (2002) 103-134 24 Soloviev S I., 1970 Recurrence of tsunamis in the Pacific In "Tsimamis in the Pacific Ocean", (W.M Adam, Ed., pp 149-164, East- West Center Press, Honolulu i 42 T u y I n tap cac cong trinh nghien CLPU Vat ly Dja cSu 2008 28 Tamaki K and Honza E 1991 Global Tectonics and Formation of Marginal Basins: Role of the Western Pacific Episodes Vol.14, No.3 Sept 1991 29 Tapponnier, P., Peltzer, G Armijo, R., 1986 On the mechanism of collision between India and Asia In: Coward, M P., Ries, A C (Eds.), CoUision Tectonics Geol Soc London, Spec Publ vol.19, pp 115-157 30 Taylor, B., Hayes, D.E., 1980 The tectonic evolution of South China Basin In: Hayes, D E (Ed.) The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands Geophys Monogr., AGU, Washington, D C, vol 23, pp 89-104 31 Taylor, B., Hayes, D E., 1983 Origin and history of the South China Sea Basin In: Hayes, D E (Ed.), The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands Geophys Monogr., AGU, Washington, D C, vol 27, pp 23-56 ABSTRACT PRELIMIN ARY RESULTS OF STUDY ON TSUNAMI HAZARD IN COASTAL ZONE OF VIETNAM After the tsunami catastrophe caused by the Sumatra Mw9.3 earthquake on Dec 26 2004, tsimami hazard in coastal zone of Vietnam has became great concem of Vietnamese Government and people In such context, the Institute of Geophysics has been assigned by Vietnamese A.cademy of Science and Technology (VAST) to carry out the project 'Assessment of tsunami hazard in coastal zone of Vietnam and recommendation of prevention solutions" The objective of this project is • • To evaluate, forecast the tsimami hazard in coastal zone of Vietnam To recommend tlie tsunami earh warning and tsimami prevention measures The preliminary results of this study are as follows: Tsimami caused by the large earthquakes in the seismic belts of -• Pacific and Mediteranean-Hymalaya not remarcably affect the coast of Vietnam, as the latter was protected from the East, South East, the South, the West and North West by an arch of number islands like Philippine Indonesia, Jawa, Thailand, Malaysia In results of study of tectonics-recent geodynamics, seismic and volcanic acti\ities of South East Asia were indentified in South Chia sea the source zones where may arise the tsunami affecting the coastal zone of Vietnam; those are: the subduction zones in west Taiwan and Phylippines (Manila, Sulu, Selebest, Makasart, North anf South Barida seas), the thrust faults of North Bomeo and Java, the normal fauls in north and west South China sea, the zones of volcanic eruptions and landslide in shelf of Central Vietnam Among them the most dangerous for Vietnam are the tsunami caused by the largest earthqualves in Manila subduction zone They can cause tsunami of l-4m height in some places in coastal zone of Central Vietnam ^ In results of study of historical notes and field investigation some records of tsunami 23m height in costal zone were obtained, one of them is the tsunami accompanized the Hon Tro volcanic eruption in 1923 ... trieu nam; Bien Dong Viet Nam tir 32-15,5 trieu nam; biln Su Lu tir 19-17 trieu nam; bien Molucca tir 40-35 trieu nam; biln Banda tir 20-15 trieu nam (tai lieu (HoUoway, N.H 1982) cho ring Nam. .. -bon trOng Chau Giang -nam Hal Nam- nam Dong sha du''t gay tru-gt bSngthuan l a y Bien Dong du''t gay tru''gt bangthugn - doan 1: nam Hai Nam- Tuy Hoa - doan 2: ti> Tuy Hoa vS phia nam 6,9 7,7 592 7,8... 189-215 16 Nguyen Khic Mao, 1973 Nhan xet vl phan viing dgng dat men nam Viet Nam Tap chi Tin tire boat dgng khoa hgc, 1973 Bo Giao due va dao tao 17 Nguyen Khac Mao, 1975 Dgng dk miln Nam Viet Nam