Tap chi DIA C H.AT loai .A. so 3(M. I -2 ;(XJ8. ir 5-15
BUOC DAU AP DUNG CAC T H U A T TOAN M8 VA M8S TRONG NGHIEN CUU DU BAO TRUNG HAN DONG DAT
6 DONG NAM A VA VIET NAM
CAO DINH TRIEU', MAI XUAN BACH'. CAO DIKH TRONG"
'yien Vat ly Dia cau. 18 Hoang Qiidc Viet. Cdii Giciy. Ha Not ' Tru&ng Dai iioc Him nghi. Moslnxi
Tom tat: Ket qua buuc^ dau img dimg cac thuat loan MS nhc'wi die bao trung hem dong dat a Doug Nam A va M8S trong nghien ci'ni dir bao trimg han dong dat a Viet Nam cho thdy:
1. Tlmat loan M8 co the sir dung co hieu qua trong nhan dien va dir bao tiling hem dong dat manh (M7.0+) khu viic Dong Nam A: tran dong ddt gay song thchi Ian Sumatra ngay 26/12/2004 da diirrc nhan dang tren ca sa so lieu dong ddt dhi het nam 2003 (bc'm kinh 667 km vd 3000 km): dong ddt gd}' .song than .\r." xa}' ru vao hoi 8 gi(/ 19.25 phut (gia GMTj ngay 17/7/2006 aphia nam dao Jcnxi. hidonesia da dirac bao truuc. sir dung .so lieu den het nam 2005 (ban kinh 281 km): vd dong ddt Nam Dai Loan M7.1 xay ra veto hoi 12 gia 2''-> ''.I phut (gia GMT), ngdv 26/12/2006 cung da dituc bao Intuc.
2. Tlmat toan M8S (M8 ma rang) Id thudt toan phu hcqi dp dung cho nghien dm du bao trung han dong ddt a Viet Nam. Dong ddt Tiidn Giao Ms ^ 6. ". xay ra vdo ngay 24/6/1983 da nhan dien duuc tren casa.so lieu cd duvc den nam I9S0, voi thai gian canh bao Id tir 1981 den 1986.
3. Trong khocmg thai gian tir 2006 den 2010 tren pham vi khu vuv B-TB Lao vd vimg giua Ha Giang vai Trung Quoc co the cd nguy ca.xay ra dong ddt vdi chdn cap km hov 6.5 do Richter (M6.5+).
(narrow), 2-3 km; 4) Chinh xac (exact), 1 km.
I.Mb'DAU
Du bao dgng dat noi toi o day la phai tra lod dugc dong thoi ba cau hoi sau: Dgng dat xay ra o dau? Manh den mire nao'^ Va khi nao xay ra?
Co 4 mire du bao dgng dat theo thoi gian:
1) Dir bao dai han (long-temi) voi don \i thoi gian la 10 nam; 2) Du bao trang han (intermediate - temi) voi don vi thoi gian la 1 nam; 3) Dir bao ngan han (short-tenn) theo thoi gian la 0,01 - 0.1 nam; 4) Du bao tire thi (immediate) theo thoi gian la 0.001 nam.
Co 4 mire du bao dgng dat theo do Ion cua vLing du bao L (km): I) Viing rpng (long-range), d^n 100 km; 2) Viing trang binh (middle-range), 5-10 km; 3) Vung hep
MS la thuat loan di,r bao trang han dgng dat, dugc V.l. Keilis-Borok \a V.G.
Kossoboko\- phat tnen tren co so dau hieu nhan dang nhilng tran dgng dat manh da xay ra trong qua khir de dir bao nguy co phat sinh dgng dat manh trong arong lai [8]. Lan dku tien thuat toan nay dugc img dung \ i o nam 1984 nhim du bao dgng dat M > 8,0 xay ra tren the gidi. Dgng dat Loma Prieta nam 1989 da dugc dij bao thanh cong nho thuat toan nay [1-8].
Thuat toan M8 mo rpng (M8S) lan dau tien dugc ap dung trong nghien ciai du bao trang han dgng dat tai Italia (Romashkova et al., 1998). Chan cap du bao cua dgng dat
dugc lay a hai miic la MQ = 6,0; MQ = 6,5 va thoi gian dimg de mo phong du bao la tir nam 1972 din 1995 (PFGING - Peresan et al., 1997). So vong tron va ban kinh khao sat doi voi cac muc du bao tuong img la: 14 CI's voi R = 192 km cho Mo = 6,5; va 16 CI's voi R = 138 km cho Mo = 6,0. Su cai tien nay da giam bot gia tri doi hoi tir chuan 20 tran/nam bang mot so nho hon. Tat ca nhiing tham so con lai ciia thuat toan M8 khong thay doi, nhu vay giam bot kha nang tu do cua dir lieu de phii hgp vod kich thuoc [7, 8]. Ket qua la ba trong so bon tran dgng dat manh nam trong vimg khao sat da dugc du bao va canh bao. Hai dgng dat manh uhk ciia Italia la Friuli ngay 6/5/1976, M = 6,5 va Irpinia ngay 23/11/1980, M = 6,7 dugc du bao doi voi mire M6,5+. 0 mire du bao M6,0+, mot tran dgng dat (Bovec, ngay 12/4/1998, M = 6.0) dugc du bao trong khi dgng dat Assisi ngay 26/9/1997, M = 6,4 lai khong du bao dugc. Doi voi mire du bao M5,5+ thi CO 9 trong so 14 dgng dat dugc diJ bao. Trong so cac dgng dat kliong dir bao dugc CO hai tran nam trong lanh tho Croatia (ngay 25/11/1986, M = 5,5 va ngay 27/11/1990, M = 5,6), hai dgng dk sau nam tren lanh th6 Italia (ngay 26/02/1991, M = 5,5 va ngay 5/01/1994, M = 5,8) va mot tran (ngay 19/9/1979, M = 5,8) xay ra each viing canh bao 20 km (Romashkova et al., 1998).
Trong khuon kho bai bao nay, cac tac gia lan dau tien thir nghiem ap dung cac thuat toan M8 va M8S trong nghien cim du bao trung han dgng dat a Dong Nam A va Viet Nam. Day la ket qua ciia nhiem vu hgp tac khoa hgc va cong nghe theo nghi dinh thu giira Viet Nam va Italia giai doan 2004-2006
"Tim kiem giai phap thich hgp trong nghien cim du bao dgng dat o Viet Nam".
II. THUAT TOAN M8
1. Vong tron phan tich du" bao dong dit (CI's) Thuat toan M8 khao sat tinh dia chan trong pham vi dien tich ciia nliQng vong tron CO ban kinh khac nhau. Ban dau nguoi ta sir
dung thuat toan nham du bao dgng dat c6 chan cap M (magnitude) Ion hon hoac bang 8,0 do Richter. Ket qua cho thay voi dgng dit CO M = 8,0 thi ban kinh (R) ciia vimg phan tich la co 6*^. Sau do nguoi ta da nghien cim moi quan he giiia cap do manh (chan cap) dgng dat voi kich thuoc \aing du bao.
Ket qua thu dugc ve moi quan he giira R va M la CO so cho viec khao sat va xac dinh ban kinh ciia vong tron phan tich du bao dgng dat. Giira ban kinh ciia vimg khao sat CI's va chan cap ciia dgng dat du bao Mo co moi quan he nhu sau:
R = R(Mo) = 55,5 (exp(Mo - 5,6) +1) Tir phuong trinh tren ta thay: voi dgng dat Mo = 8,0 CO R = 668 km; Mo = 7,5 (R = 427 km); Mo = 7,0 (R = 281 km); MQ = 6,5 (R = 192 km); MQ = 6,0 (R = 138 km).
2. DIP chin
Anh huong Ion nhat ve hieu qua ciia phuong phap phan tich thong ke tai lieu dgng dat la cac du chan (aftershocks hay con ggi la nhung "dam may" dgng dat nho bao quanh dgng dat Ion theo thoi gian). Cac du chan nay co the bi nham lan voi nhung dgng dat nho hon trir phi chiing dugc khu nhieu hoac loai bo. Trong thuat toan M8 du chan dugc dinh nghia la tat ca nhimg dgng dat nho hon xay ra sau mot dgng dat Ion trong mot khoang thod gian va khoang each la nhung ham ve do Ion cua dgng dat chinh (mainshock).
Khoang thod gian va khoang each vimg du chan (aftershock zone) dugc xac dinh tuong img voi chan cap cua dgng dat chinh tren co so quan he trong Bang 1.
Cac dgng dat xay ra ben trong mot viing du chan dugc loai bo khoi danh muc de tao ra mot danh mtac ciia nhung dgng dat cliinh.
Day la co so chinh cho viec loai trir du chan va thanh lap danh miic cac dgng dat chinh phuc vu cho tinh toan du bao dgng dat tren CO so cac thuat toan M8, M8S.
Bang 1 Ban kinh va khoang thai gian loai trip du" chan trong quan he vai dong dit chinh
Chan cap. M
R(M), km T(M), ngay
4.0 40 23
4.5 40 46
5.0 50 91
5.5 50 183
6.0 50 183
6.5 100 365
7.0 100 730
7,5 150 913
8.0 200 1096
3. Lira chon thai gian bit dau va giai han chin cap
Tren co so bai toan nhan dang, cac so lieu dau vao dugc khai trien o dang cac ham so.
Buoc khai trien quan trgng nhat ciia bai toan la phep trung binh hoa theo khong gian va thod gian. Ve khong gian, cac tran dgng dat dugc chgn trong mot ban kinh (CI) da cho truoc phu thuoc vao chan cap ciia dgng dat can du bao. Khoang thoi gian trung binh s nam la khoang thod gian ma trong giod han do ta sir dung cac dgng dat da phat sinh de mo phong du bao. Dieu can luu y den trong viec lira chgn dgng dit phuc vu cong tac phan tich du bao la khoang thod gian c6 so dgng dat dem dugc va gia tri chan cap ciia chimg.
Khoang thoi gian lira chgn cho phan tich dugc xac dinh phu thuoc vao tinh hoan thien cua danh miic dgng dat. Trong nhung nam
1960. do tin cay va tinh day du cua danh muc dgng dat toan cau da dugc cai thien nho viec t6 chirc mot he thong cac tram quan sat dgng dk tren toan the giod. Tir nam 1963, tat ca nhijng dgng dat vod chan cap M = 5,0 hoac Ion hon dugc xac dinli va trong nhieu vimg danh muc dugc hoan thanh tod chan cap M= 4,0. Vi vay, thong thucmg nguoi ta chgn thang 1/1963 la m6c thod gian co daiih muc dgng dk qu6c xk dky dii. Tuy vay. moc thoi gian nay co thg som hoac mugn hon tuy thuoc vao chat lugng ciia nhung danli mt^ic dgng dat dia phuong. No doi hoi khoang thod gian 20 nam ciia dii lieu cho thuat toan de dat nguong (threshold) dir lieu co the xac dinh dugc di thuong dia chan. Trong hau het cac khu virc nghien cim di,r bao. nguoi ta thuong chgn khoang thoi gian la 10 nam cho du bao dgng dk manh. Mot so ham trong thuat toan M8 co the khong phu thuoc \ao khoang thoi gian lira chgn so lieu doi \cn
nhung \iing co so lieu day dii trong khoang thod gian dai. Tai cac xiong nhu vay, chimg ta CO the tha}- doi khoang thod gian (s) dimg cho viec xac dinh so lieu dgng dat phtjc vu viec mo phong du bao.
De chuan bi so lieu phuc \-u tinh toan.
chimg ta can chpn giod han duoi cua chan cap (magnitude cutoff). Gia tri gioi han nay phij tliugc vao do tin cay cua danh muc dong dat, chang han doi \'6d dgng dat toan cau c6 Xhk chgn giod han nay bang 4.0. vi no chua dugc xac dinh chinh xac den M < 4.0.
4. Cac ham dac trung cua thuat toan M8 Thuat toan M8 khong chgn co dinh mot ch4n c4p giod han M nao ca. dimg hon no chgn s6 d8m cua nhung dgng dat theo yeu cau ciia viec tinh toan. Theo \cu cau cua thuat toan. ta chpn nipt trong hai mire phan b6 dgng dk chinh theo thoi gian. so dong dat trang binh theo nam. cua moi \ong tron khao sat (CI):
- Thir nhat la CAT20, thoa man dieu kien gioi han chk\ cap dgng dat. voi gia tri trang binh 20 tran trong mot nam. Vi du. de phan tich mot khoang thod gian 30 nam voi chan cap M gioi han. s6 tran dgng dat can co la:
20 X 30 = 600. Thong thuong, vod dieu kien gioi han nay ta co s6 tran dong dat Ion hon 600. Neu CO it hon 20 tran trang binh trong nipt nam trong \ong tron khao sat, chimg ta phai quyk dinh ti^p tyc hoac ket thuc qua trinh phan tich. Neu s6 tran dong dat trang binh trong nipt nam trong pham vi \ong tron khao sat it hon 16 thi qua trinh phan tich se khong dugc thuc hien.
- Thir hai la CATIO, dugc chgn tir vong tron khao sat giong nhu each sir dung chan cAp gioi han o mire dp thir nhat. nhimg co so tran dong dat trang binh la 10 trong nipt nam.
7
Thuat toan M8 sir dung 7 ham dir lieu dia chan:
- Fl (t) la so lan dgng dat tir mure phan b6 thir nhat CAT20, trong 6 nam truoc thoi diem t du bao;
- F2(t) la so Ian dgng dit [nhu ham Fl(t)]
doi vod muc do phan b6 thir hai cua CATl 0;
- F3(t) = FI(t) - F'l(t), trong do. Fl(t) la so trung binh dgng dat ciia timg 6 nam mot trong khoang thod gian tir khi bSt diu phan tich (to) den (t - 6) nam. SiJ uoc lugng dugc thirc hien tren CAT20;
- F4(t) ciing giong nhu F3(t), nhung dugc uoc lugng tren CATIO.
- F5(t) = II0°'''^V (11)''^ la ty s6 giira tong trgng so chan cap (magnitude weight) va so tran dgng dat do vod mii 2/3: vod Mj Ion hon Mo-0,5,1 la so tran dgng dat trong 6 nam cuoi (truoc moc du bao) thuoc mire phan b6 thir ba (CAT20a): CAT20a = CAT20 - {so tran dgng dat co chan cap Mj Ion hon Mo - 0,5}.
- F6(t) ciing tuong tu nhu F5(t), nhung dugc tinh toan tren mire phan b6 thir tu (fourth population): CAT 10a = CATIO - {s6 tran dgng dat c6 chan cap Mj Ion hon Mo-0,5}.
- F7(t) nham xac dinh so Ian du chan. De tinh toan ham nay chiing ta can xac dinh mire phan bo (so dgng dat trung binh trong mot nam) thir nam, CATMS, gom nhimg dgng dat chinh trong khoang chan cap (Mo - 2,0, Mo - 0,2) trong vong tron khao sat CI da cho. Danh mijc ciia tap hgp nay bao gom so lugng du chan Bj xay ra trong hai tuan dau tien sau moi tran dgng dat chinh. F7(t) dugc lay bang Bj Ion nhat trong CATMS.
Cac ham dugc xac dinh cho timg nira nam mot, tai thoi diem ket thiic t, = to + (i lan nira nam). Ta ky hieu X, la so tran dgng dat trong khoang nira nam cuoi ket thiic tai t,, va S, = S10°''*^^'\ 6 do {Mij} la chSn cAp cua xk ca dgng dat chinh khoang 0,5 nam thir i.
Cong thirc toan hgc ciia cac ham dac trung la:
Fl(t,) = X,.n+X,.,o+... + X, [CAT20]
F2(t,) = X,.n +X,.,o+... + X, [CATIO]
F3(t,) = F,(t,) - ( X, + X2 +...+ XM2) '"••'""' [CAT20 ] F4(t,) = F2(t,) - (X, + X2 +...+ X,,2)'"""'"
[CATIO]
F5(t,) = ( S,_n+ S,_,o +... + S,) /( X,_i 1 + X,.
io+... + X i ) " [CAT20a]
F6(t,) = ( S,.,, + S,,o +... + S,) /( XM , + X,
io+... + X,)^^ [CATlOa]
F7(t|) = max Bj trong nhung nam truoc.
[CATMS]
Nhiing ky hieu trong dau ngoac vuong bieu thi danh muc dugc sir dung de tinh toan gia tri ciia cac ham tuong img.
5. Phieu ung ho
Phieu ung ho ciia cac ham (functions vote) nham dua ra mot canh bao, hoac thod gian xac suat gia tang (TIP - Time of increased probability) cua mot dgng dat voi chan cap bang hoac Ion hon Mo trong vong tron khao sat (CI). Sau ham dau tien bo phieu img ho cho mot TIP thuoc nhom 10%
trong danh muc xep hang. Nhting phieu img ho ciia ham thir bay cho mot TIP thuoc nhom 25% trong danh muc xep hang.
6. Canh bao v§ thai gian xac suit gia tang Thod gian xac suat gia tang dugc dua ra cho CI khi 5 trong so 6 ham dau tien va ham thir bay da bo phieu img ho trong 3 nam truoc do, va khi dieu kien nay xuat hien trong 2 lan danh gia nira nam lien tiep. Moi mot TIP dugc dua ra cho thod han 5 nam (tinh tir thod diem dua ra canh bao). Khi du:
lieu mod dugc them vao danh miic thi nguyen nhan va giod han cac ham bo phieu CO the thay doi. nhu vay mot TIP co the ket thuc som hon hoac keo dai hon 5 nam.
/ . u h u x m g trinh M8
Phan bieu dien cuoi ciing cua thuat toan M8 la chuong trinh M8 vod mot tap hgp nhung gia tri nhat dinh ciia cac thong so. Gia tri ciia thong so cung cap cho chuong trinh la
gia tri ngam dinh (default \'alues). Tu\ \'ay.
chuong trinh M8 ciing cho phep nguod sir dung ap dung nhting phuong an khac nhau cua danh miic dgng dat tren co so quan diem cu the chung nhat cua dac trung hoat dgng.
Bang 2 Bang cac thong s6 SLF dung trong Chu^yng trinh M8
Hang so H ,
m M' Ma
i) Tb Te T.
dt s, u. e
X
^ex
P
Y H,G
Ten giao tiep Mo
M MM
Ma To Tb Te T' dt s, u, e
Tau Tex beta d H.G
Mota
Gioi iian ciian cap diing de xac djnh (dir bao) dgng dat manh Gi6i ban duoi ciia chan cap dong dat dung de tinh toan Gioi han tren ciia chan cap dong dat diing de tinh toan Giai han ciia chan cap de xac dinh dtr chan
Thai diem bat dau qua trinh phan tich Thai diem bat dau xac dinh dir bao Thai diem ket thiic xac djnh du bao
Thai diem xay ra dong dat dac trung trong viing khao sat Khoang thai gian giiJa hai lan xac dinh gia tri
Khoang thai gian cua moi lan xac dinh Khoang thai gian keo dai cua mot TIP
Khoang thai gian keo dai cua cac phieu tinh toan Hang s6 cua irpng so ham mii trong s(t)
Luy thira cua mau so tronu s(t) Phieu gioi iian
III. BU'aC OAU 1>NG DUNG THU" NGHIEM CAC THUAT TOAN MS, M8S TRONG NGHIEN CUU DIJ BAO DONG D A T KHU VLTC DONG NAM A VA B A C VlfeT NAM
1. ThLF nghiem ap dung thuat toan MB trong du- bao dong d i t khu VLFC Dong Nam A
Chuong trinh M8 da dugc sir dung de dir bao dgng dSt khu XTIC Dong Nam A. gioi han tir 85" d^n 140° do kinli D va tir -15" dkn 25" do vT B. Danh muc dgng dk sir dimg la tir nam 1900 d k \\k thang 7/2005 (theo tai lieu ciia ISC va ciia NEIC). Day la khu \ycc CO hoat dgng dgng dk tich cue \ a chan cap Ion. dat tieu chuin cho \iec su dung thuat toan M8 trong du bao trung han dgng dat.
Mire du bao la M8,0+ \'a M7,0+; khu \irc dir bao CO ban kinli R = 668 km (tirong img \oi Mo = 8,0), R = 281 km (tuong img \ 6d Mo = 7.0); luoi chia loa do bang 5 x 5 ; thod gian
dung trong du bao la tir 1985 den 2005; han du bao la 5 nam ke tir 2006.
1) Diu tien la viec img dung thir nghiem chuong trinh M8 trong nhan dang dgng dat ngay "26/12/2004 vod M9.0 xay ra tai Sumatra. K^t qua cho thay dpng dat nay da dugc nhan dang tren co so so lieu dpng dat d^n nam 2003 \ a thuat toan M8 voi ban kinh 667 km va 3000 km (Hinh 1).
2) Sir diiiig thuat toan M8 nham du bao trung han dpng dk tai 2 dod Sumatra va Java. K^l qua du bao dugc bieu dien trong Hinh 2. S6 lieu dpng dk dugc su dung den nam 2005. Theo ket qua nay tlii tir nam 2006 di^n 2010, dpng dk co nguy co xay ra Ion nliSt tai trang tani dod Ja\'a. dong bac va tay doi Sumatra (Hinh 2).
Time (Years)
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Hinh 1. Are/" qua du bao dong ddt Sumatra ngay 26/12/2004 ciia nhom nghien cuu SAND thuoc Trung torn Vat ly Ly thuyet Trieste: diing thuat toan MS vod danh miic dong ddt giai doan 1985 - 2003; dung ban kinh R = 667 km cho chuan M8.0+; dung R = 3000 km cho chuan M9,0. Kit qua cho thdy tai vong tron nghien cihi 34 co tog do tdm 3°B - 97°D co bieu hien thai diem gia tang xac suat vdo nam 2004. Dong ddt Sumatra (26/12/2004) co chieu dai vimg nguon ca 1000 -1300 km, Mw = 9,0.
Theo ket qua nay thi tran dgng dat gay song than M7,7 xay ra vao hoi 08 gio 19,25 phut (gio GMT) ngay 17/7/2006 tai vimg nam dao Java, Indonesia da dugc bao truoc.
Thong so ciia dgng dat M7,7 ngay 17/7/2006 nhu sau: - tga do: 9,334" N;
107,263° D (theo nguon USGS); - chan cap:
7,7 do Richter; - do sau chan tieu: 10 km;
gay song than lam tren 100 nguod thiet mang Of Indonesia. -
3) Dod dgng dat Manila dugc cac nha dia chan Viet Nam coi la dod co nguy co xuat hien Ion nhat dgng dat gay song than anh huong tod bo bien va hai dao Viet Nam. Vi vay, viec du bao dgng dat c6 M7,0+ (R = 281 km) trong pham vi dod nay la can thiet va CO y nghia. Ciing tuong tu quy trinh nghien cim du bao dgng dat tren lanh tho Viet Nam, doi voi dod Manila chimg toi ciing tien hanh hai buoc. Co mot dieu duy nhat
khac biet la dimg M8 thay vi M8S nhu da sir diing cho Viet Nam.
- Buoc 1: sir dimg tai lieu co truoc 1996 nham du bao cac dgng dat da xay ra trong thoi ky tir 1996 dSn 2000 co M7,0+. Danh muc dgng dat chinh dugc lay tir 1975 den het nam 1995. Buoc thod gian tinh (dt) bang 0,5 nam. Ket qua cho thay 5 trong so 6 dgng dat da xay ra trong pham vi dod Manila va ke can da dugc nhan dang chinh xac theo thuat toan M8 (Hinh 3).
- Buoc 2: sir dimg tai lieu dgng dat den nam 2005 nham du bao khu virc c6 nguy co xay ra dgng dat voi M7,0+ trong thod ky 2006 den 2010. Danh muc dgng dat chinh dugc lay tir nam 1980 den 2005. Buoc thoi gian tinh (dt) bang 0,5 nam. Ket qua da chi ra dugc khu vuc co nguy co xay ra dgng dat M7,0+ trong thod gian tir nam 2006 den
10
2010 bao trimi phan dien tich b k doi Manila va nam Dai Loan (Hinh 4).
Dieu dang noi o day la tran dgng dit nam Dai Loan M7.2 xay ra vao hdi 19 gio 26.21 phiit (gio Ha Noi) ngay 26/12/2006 lai rcri chinli \ ao khu \ ire du bao na>'.
Tliong so ciia dgng dat M7.1 nga>' 26/12/2006 nhu sau (ngu6n USGS): - thoi diem xay ra dgng dk: 12 gio 26. 21 phut (gio GMT); - toa do: 21.819" B; 120.543" D;
- chan cap: 7.1 do Richter: - do sau chdn tieu: 10 km
Hinli 2. Nhung vimg ke 6 la vimg dtroc trong thai ky> 2006-2010 theo ki}l 2. DIP bao trung han dong dIt cho miln B I C Viet Nam
Hoat dgng dgng dat tren lanh tho Viet Nam va ke can co cac bieu hien chung nhat la:
- Chan cap cue dai khong vugt qua 7,0 do Richter;
- Phan bo dgng dat khong dong deu theo dien, tap trang chu yeu tai cac kliu vuc Tay Bac Bg. Bac Lao va phan laiili tho Trang Quoc giap vod Lao Cai - Lai Chau;
canh beta co nguy ca xay ra dong ddt qua tinh cua Chiamg trinh M8.
- Mat dp trang binh dgng dat hang nam khong Ion. nho hon 10 tran trong mot nam, chii yeu nam trong khoang 3-6 tran.
Do dac trung hoat dpng dgng dat \'eu vod chan cap khong cao nen chimg toi ap dung duiat toan M8S (M8 mo rgng) cho chuan M6,5+ voi ban kinli R = 192 km. buoc thod gian (dt) la 0,5 nam. Danh inuc dpng dat dugc sir dung la danh muc day du co dugc tir cac nguon khac nhau (Viet Nam, ISC, NCAA, NEIC) tir nam 1900 d k nam 2005.
Qua trinh phan tich dugc tien hanh theo 2 buoc sau:
Hinh 3. Ket qua dir bao dong ddt a dai Manila trong khoang thai gian tit: 1996 den 2000. Cac diem cham den Id vi tri chdn tdm dong ddt co M >7,0 da xay ru trong khoang thai gian nay vd da du bao dirac (5 trong so 6 tran). Cham mau trang la vi tri chdn tdm tran dong ddt da xay ra nhung khong du bao duac (1 trong so 6 tran).
Hinh 4. Ket qua dp dung MS trong die bao dpng ddt a dai Manila giai doan 2006-2010.
Dien tich ke o Id khu vitv co nguy caxay ra dpng ddt co M > 7.0.
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Hinli 5. Ket qua dp dimg thuat loan M8S nhan dien dpng ddt Tiidn Giao ngay 24 6' 1983.
Ms ^6.7 do Richter 1) Chay M8S nham nhan dien dgng dat
da xay ra trong qua kliu, dgng dat Tuan Giao Ms = 6,7 xay ra vao ngay 24/6/1983. Cac thong so dugc lira chgn gom: phii kin khu vuc nghien cim (Bac Viet Nam va lan can, 18-24° B; 101-108° D) bSng nlifnig vong tron ban kinh R = 192 km, tuong img vod M6,5+, nhimg vong tron nay co tam phan bo theo luoi l"xl", mo phong tir 1975 d&i 1980 voi tAn so dgng dat tamg binh la 3-6 tran/nam trong moi \ong tron du bao, khoang thoi gian mo phong la tir nam 1981 va keo dai trong 5 nam.
Ket qua cho tha\' dgng dat Tuan Giao da dugc du bao theo so lieu den nam 1980 va tren co so chay chuong trinh M8S (Hinh 5).
2) Chay chuong trinh M8S nham du bao dgng dat co nguy co xay ra trong 5 nam sau nam 2005. Cac thong so dugc lira chgn gom:
phu kin kliu vuc nghien cim (Bac Viet Nam va lan can, 18-24° B; 101-108° D) bang nliung vong tron ban kinh R = 192 km, tuong img voi M6,5+, nhung vong tron nay CO tam phan bo theo luoi T x T , mo phong tir 1995 din 2005 vod tan so dgng dat trang binh la 3-6 tran/'nam trong moi vong tron du bao, klioang thod gian mo phong la tir nam 2006 ^•a keo dai trong 5 nam.
Kk qua tinh toan cho thay trong pham vi nghien cim co 2 khu virc c6 ngu>' co xuat hien dgng dk M6,5+ trong khoang thoi gian tir 2006 d k 2010.
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Hinh 6. Nhiirtg dien tich ke 6 Id vimg canh hc'io dpng dot du doan co the xdy ra Irtmg khoang thai gian 2006-2010 tren ca .sa sir dimg Chuang trtnh MSS.
IV. K^T LUAN
Tlieo so lieu thong ke cua nhom nghien cim SAND thuoc Tmng tam Vat ly Ly tliuyet Trieste tlii ti-en 80% tran dgng dat manh xay ra tren the gioi co M > 8,0 deu co the dir bao tiiroc khi sir diing Chuong trinh M8. Ket qua buoc dau img dimg thuat toan M8 iiliani dir bao dgng dat Dong Nam A va M8S trong nghien cim du bao trang han dgng dat o Viet Nam cho thay:
1) Thuat toan M8 c6 the sir dung c6 hieu qua trong nlian dien va du bao tmng han dgng dat manli (M7.0+) khu virc Dong Nam A: trail dgng dat gay song than Ion Sumatra ngay 26/12/2004 da dugc nhan dang tren co so so lieu dgng dat den het nam 2003 (ban kinh 667 km va 3000 km); dgng dat gay song than M7,7 xay ra vao hoi 8 gio 19,25
phiit (gio GMT) ngay 17/7/2006 tai khu vuc nam dao Java, Indonesia da dugc bao truoc, sir dung so lieu den het nam 2005 (ban kinh 281 km); va dgng dat Nam Dai Loan M7,l xay ra vao hoi 12 gio 26,21 phiit (gio GMT), ngay 26/12/2006 cung da dugc bao tmoc.
2) Thuat toan M8 mo rgng (MSS) co the phii hgp voi viec nghien cim du bao trung han dgng dat 6 Viet Nam. Dgng dat Turn Giao Ms = 6,7, ngay 24/6/1983 da nhan dien dugc tren co so so lieu co dugc den nam 1980, voi thoi gian canh bao la tir 1981 d k 1986.
3) Trong khoang thod gian tir 2006 den 2010 tren pham vi khu vuc B-TB Lao va viing nam giira Ha Giang voi Tmng Quoc co the CO nguy co xay ra dgng dat voi chan cap
> 6.5 do Richter (M6.5+).
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earthquakes (Mo 7.5) diagnosed by Algonthm M8 in Japan and adjacent temtones. J.
Geophys. Res.. 95./B8 : 12413-12422.
5. Keilis-Borok V.I., Soloviev .A.A.
(Editor), 2003. Nonlinear dynamics of the lithosphere and earthquake prediction.
Springer. Heidelberg.
6. Kossobokov V.G., Healy J.H., Keilis- Borok V.I., Lee W.H.K., 1997. Algonthm for earthquake statistics and prediction.
lASPEl Software Library, 6. Seismol. Soc.
Am.. El Ceirito, CA.
1. Kossobokov V.G., Healy J.H., Dewey J.W., 1997. Testing an earthquake prediction algonthm. Pure Appl. Geophvs..
149:219-232.
8. Kossobokov V.G., Romashkova L.L., Panza G.F., Perecan A., 2002.
Stabilizing intermediate-temi medium-range earthquake prediction. J. Seism. Earthquake Eng, 4/2-3 : 11-19.
VAN LIEU
1. Gabrielov A.M., Dmitrieva O.E., Keilis-Borok V.I., Kossobokov V.G., Kouznetsov I.V., Levshina T.A., Mirzoev K.M., Molchan G.M., Negmatulaev S.Kh., Pisarenko V.F., Prozoroff A.G., Renehart W., Ronvain LM., Shebalin P.N., Shnirman M.G., Schreider S.Yu., 1986. Algonthms of long-term earthquakes' prediction. CERESIS, Lima (Peru), pp.61.
2. Keilis-Borok V.L, Kossobokov V.G., 1988. Premonitory activation of seismic flow: Algorithm M8, Workshop on Global Geoph. Inf. with Applications to Res. in Earthquake Prediction and Reduction of Seismic Risk, ICTP, Trieste, pp. 17.
3. Keilis-Borok V.I., Kossobokov V.G., 1990. Premonitory activation of seismic flow: Algorithm M8. Phys. Earth and Planet. Mem.. 61 : 73-83.
4. Keilis-Borok V.I., Kossobokov V.G., 1990. Times of increased probability of strong
SUMMARY
Primary results of earthquake prediction in Southeast Asia and North Viet Nam on the basis of Algorithms M8 and MSS
Cao Dinh Trieu. Mai Xudn Bach. Cao Dinh Trong In this paper the authors present the pnmary results of earthquake prediction in Southeast Asia and North Viet Nam based on M8 and M8S algoritlims. The following conclusions can be made:
1) The algorithm M8 can be effectively used for earthquake prediction with the M7.0+ in Southeast Asia: the great Sumatra earthquake M9.0 (26/12/2004) was predicted on the basis of the earthquake catalogue to the end of 2003 (R = 667 km and R = 3000 km); the Java earthquake M7.7 (17/7/2006) was predicted on the basis of earthquake events to the end of 2005 (R = 281 km); and the South Taiwan M7,l (26/12/2006) was also predicted on the basis of events to the end of 2005.
2) The extended algonthm M8S can be effectively used for earthquake prediction in Viet Nam: the T u k Giao earthquake M6.7 (24/6/1983) was predicted on the basis of earthquake events to the end of 1980, with the duration of TlP's from 1981 to 1986.
3) Dunng the time from 2006 to 2010, the danger of earthquake M6.5+ can occur in the areas of Northwest Lao and North Ha Giang Province.'
Ngay nhan bdi: 9/1/2007
Ngtrai hien tap: Nguyen Dinh Xuyen
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