'h4nl: D J A C H A N - D J A DONG Ll/C
BAN DO PHAN VUNG DONG DAT LANH THO VIET NAM TRONG TIEU CHUAN XAY DlTNG VIET NAM
TCXDVN 375-2006: THIET KE CONG TRINH CHIU DONG DAT
Nguyen Dinh Xuyen, Le Tir Son Vien Vat ly Dia cau,
18 Hoang Quoc Viet, Cau gidy, Hd Noi Mail: ndxuven(a),smail. com
Tom tat: Bai bao nay giai thieu ban do phan vung dong dat Idmh tho Viet Nam su dung trong tieu chuan xay dung Viet Nam "TCXDVN 375-2006:
"Thiet ke cong trinh chiu dong dat" lan dau tien duac ban hdnh a nuac ta [12]. Do la ban do gia toe nen (PGA) chu ky lap lai 500 nam cho nen da cung (nen loai A trong bang phan loai nen dat cua tieu chudn khdng chan chdu Au EN-1998). Tren ca sa nhCmg quy ludt bieu hien dong ddt tren lanh tho Viet Nam dugc trinh bay torn tat trong bai nhir moi lien quan giita dong ddt va binh do kien tao dia dong luc hien dai, su phdn bo dong ddt trong khong gian va thai gian, tdn suat lap lai dong ddt, moi lien quan giita cac dac trung dong luc cua chdn tieu dong ddt, quy ludt tat ddn chdn dong theo khoang each, da xac dinh cac vimg phat sinh dong ddt M>5.0 va lap ban do vung nguon lanh tho Viet Nam ty le 1:1.000.000, trong do chi ra nhirng dac trung ca ban cua cac vung nguon la magnitude Mmax ciia dong ddt cue dai CO kha nang xay ra, do sdu chdn tieu cua dong ddt cue dai, tdn sudt dong ddt M>4.5, con goi la toe do xay ra dong ddt. Tren ca sa ban do vung nguon, sic dung chuang trinh CRISISS 99 va phuang trinh tat ddn gia toe nen Campbell 97 da tinh va thdnh lap ban do phdn vimg gia toe nen chu ky lap lai 500 nam, nen da cung, lanh tho Viet nam ty le 1:1.000.000.
• Ma dau
Ban do phan vimg dong dat lanh tho Viet Nam trong tieu chuan thiet ke khang chan /iet Nam TCXDVN 375-2006 la ban d6 phan vimg gia t6c nSn chu ky lap lai 500 nam anh th6 Viet Nam ty le 1:1.000.000. Ban d6 nay la ket qua nghien cim dh tai dgc lap :ap Nha nuoc " Nghien cim du bao dong dat va dao dong nen o Viet Nam" do Vien /at ly Dia cau hoan thanh va da dugc Hoi dong Nha nuoc nghiem thu nam 2005 [5], tugc chinh ly theo yeu c k ciia Hoi d6ng bien soan TCXDVN 375-2006: Gia toe nen
;hu ky lap lai 500 nam tren nen loai A theo bang phan loai n§n dk trong Tieu chuan
10 Tuyin tap cac cong trinh nghien CLFU vgtjy£!g_E^^jjg£l
J khang chin Chau Au EN 1998-1 [2] dugc the hien duoi dang cac duong dang tri 0.04, 0.08, 0.12, 0.16g... (g-gia toe trgng truong, g = 981cm/s^
Ban db nay dirge thanli lap tren co so cac k§t qua nghien cuu quy liiat bieu hi?n dong dat tren lanh th6 Viet Nam: 1' MSi lien quan giua dong dat va binh do kien tao dia dong lire hien dai. 2/ Quy luat phan b6 dong dk trong khong gian va theo thai gian, 3/Qiiy luat lap lai dong d4t, 4/M6i lien quan giira cac dac trimg dong lire (chieu dai, chilu rgng. do Ion (magnitude)) cua chin tieu dong dk, 5/ Quy luat lan truyen chan
dong (cap dong dat, gia toe dao dong nen dat.). ^ Tren co so cac quy luat do xac dinh cac viing phat sinh dong dk manh M ^ 5.0 va
cac dac trung co ban ciia cac viing: 1/Dgng d4t cue dai co kha nang xay ra, 2/Dg sau
chan tieu, 3/ Tan suat lap lai dong dat. . Sir- dung ban do cac viing phat sinh dong d4t (ban do vimg nguon), bang phuang
phap phan tich xac suit, sir dung cac phan mem chuyen dung, da tinh va lap ban do do nguy hi^m dong dit, trong do co ban do phan viing gia toe nen chu ky lap lai 500 nam.
Trong bai nay chimg toi gioi thieu voi doc gia ve ban do tieu chuan noi tren. J 2. Quy luat bieu hien dong dat tren lanh tho Viet Nam
Ket qua nghien cu'u da chi ra nhirng quy luat bieu hien dong dat o Viet Nam, quan trgng doi voi xac dinh cac viing phat sinh dong dat va danh gia do nguy hiem dong dat.
Do la nhirng quy luat sau:
2. 1. Moi lien qua gii'ta (long ddt vd hinh cto kien tao |
• Dong dat manii M>4,5 (M la do Ion hay magnitude ciia dong dat, trong bai nay M la magnitude theo song mat Ms) chi xa} ra trong cac doi dirt gay sau boat dong, da va dang dong vai tro ranli gioi giira cac mien kien tao \a giira cac don vi kien tao chinh trong cac mien. 6 day ta thay mat dirt doan trong chan tieu dong dat trimg hgp voi mat dirt gay ve vi tri va huong dich chuyen. Nhirng dieu noi tren chimg to rang dong dit manh tren lanh th6 Viet Nam da phat sinli do ket qua dich chuyen theo cac diit gay da t6n tai lau dai va nay van la ranli gioi giira cac khoi co chuyen dong khac nhau ve huong hoac \ic van t6c, tire la nai chuyen dong phan di nlial. Day chinh-la nguyen nhan dan toi hien tugng tap trung dong dat manh trong nhung doi hep trimg voi cac doi pha buy kiSn tao ma tnioc day Nguyen Khac Mao va I. A. Rezanop [6] ggi la tinh dia doi ciia tinh dong dk tren lanh th6 Viet Nam. Chimg toi nghi rang day Idiong phai la dac dilm rieng ciia tinh dong dit tren lanh tho Viet Nam ma la mot quy luat pho bien va nhimg diSu chung toi vira trinh bay chimg minli mot lan nira quan diem cho rang dong dit manh thuong xay ra tren nhimg dirt gay da ton tai lau dai, nay dang boat dong, hiem hon 6 nhirng noi dang hinh thanh diil gay, va khong xay ra o nhimg noi khong c6 nhimg di^u kien nhu vay.
Phiin trao niii lua dien ra o phia Nam cua lanh tho, thuoc vanh dai nui lira dong nam Dong Duong la mot bieu hien ciia van dong kien tao moi va hien dai 6 Viet Nam. Phun trao nui lira cung la nginen nhan phat sinh cua nliung tran dong dat manh cip 7-8 (thang MSK-64).
Phan I: eiACHAN - DjA DONG LUC
2. 2. Bo sail chdn tieu
Do sau chan tieu dong dat thay doi tir doi nay sang doi khac, nliimg it thay d6i trono pham vi timg doi. 0 vimg Song Ma - Son La va Dong Trieu, do sau chan tieu Ion nhit da quan sat thay la 25-30km. O cac vimg Song Hong - Song Chay, Song Ca do sau chin tieu lan nhat khong vu'gt qua 25km, o cac vimg Dong Bac, Song L6, Song Da, Lai Chau - Dien Bien, Truong Son do sau chan tieu kliong vugt qua 20km, con 6 mien Nam Viet Nam do sau chan tieu gioi ban o 15 -17km.
Tir su phan bo chan tieu theo do sau co the xac dinh be day tang sinh chin trong cac dod nhu sau (tang sinh chan chiem phan v6 trai dat tir mat mong ket tinh den gioi ban do sau phan bo chan tieu): Trong doi Dong Bac H=20km-H', H'-be day tang tram tich bing l-3km;
trong doi Dong Trieu, o phan tay bac H^30km-H', H - l k m , a phan dong nam H=20km-H', H-2km; trong dai Song L6, a phan tay bac H=20km-H', H'= 2-3km, o phan dong nam H=15-17km-H', H'=3-7km; trong den Song H6ng -Song Chay H=20-25km-H', H' thay^ddi tir
1km o phan tay bac den 3km 6 phan dong nam (trung Song Hong); trong doi Song Da H=20km-H',H'=l-3km; trong doi Son La - Song Ma - Pu May Tun H=30km-H', H'=0-4km tii' noi 16 mong ket tinh a nep loi Song Ma den phan dong nam ciia doi; trong doi Lai Chau - Dien Bien H=20km-H', H'=0-4km; trong doi Song Ca H=25km-H', H'=r-3km; trong doi Truong Son H= 15-25 km-H', H'=l-31cm; omien nam VietNamH=15-17km-H', H-l-3km.
2. 3. Quan he giua cac dac trung dong luc cua chdn tien vd dac diem cua chdn tieu dong
<!iit manh
Chieu cao chan tieu:
Vi chan tieu dong dat khong phai la mot diem ma chiem mot khoi vat chat voi kich thuoc nhat dinh, dong dat cue dai 6 moi do sau thuoc tang boat dong chi co magnitude ahat dinh phu thuoc vao do sau ay. Tren co so so lieu hien co xac dinh dugc gioi ban magnitude dong dat phu thuoc vao do sau nhu sau:
l g h _ =0,25M -0,30 • (1) Sir phii thuoc nay diing cho khoang do sau tir mong ket tinh den do sau khoang
2H/3+H\ sau do magnitude giam dan theo do sau.
Quy luat ve su phii thuoc ciia magnitude \ ao do sau trinh bay o tren c6 the phat bieu ai nhu sau: Neu chan tieu moi tran dong dat magnitude M co mot chieu cao Iz (M) thi tam 3uc xa nang lugng ciia no khong the nam 6 do sau nho bao nhieu ciing dugc ma ton tai mot 16 sau hmin phia thuoc vao chieu cao chan tieu va be day H' ciia lop nam tren tang boat iong. Cong thirc (1) ehinli la da bi6u thi sir phu thuge nay. Neu coi tam birc xa nang lugng
^iia chan tieu nam o khoang 2Lz/3 ke tir dinli [6] tir (1) ta se co:
lgL,= lgl,5 ( h _ - H ) < lgl.5h„,„ = 0,25M - 0,125 (2) Chieu ddi chdn tieu: Doi voi dong dat manh, duang dang chan dau tien hau nhir lap l_ai
linh dang chin tieu va co the .\ac dinh chieu dai cua chin tieu theo kich thuac dirang dang chan lang cong thirc [6.7,8,9.10]):
22 Tuy§n tap cac cong trinh nghien cCru Vjtjy_g!f g ^ " ^°°8
!
Lx = dimax - a dimin (3) trong do: dlmax, dlmin la duong kinh Ion nhat va nho nhat (theo true Ion va true
nho) ciia duong ding chin diu tien, a = /jio-""'''/^',,-!]/ [lo'"-''''-ij voi lo va H la cap do manh o chin tam va tren duong ding chan dau tien, S// va S± la he so tat dan chan
dong theo cac phuong dgc theo va vuong goc voi phuong ciia chan tieu. -i Sir dung ban d6 duong ding chin ciia cac tran dong dat manh va cam thay 6 Viet
Nam da xac dinh chi6u dai chin tieu ciia cac tran dong dat ay va xac lap dugc quan he giira chieu dai chan tieu va do Ion ciia dong dat nhu sau:
lgLx±0,3 =0,5Ms- 1,06 (4) So sanh ket qua xac dinh Lz va Lx ciia dong dat tren lanh tho nuoc ta voi so lieu
quoc te CO the thay kich thuoc ciia dong dat tren lanh tho nuoc ta nam o gioi ban tren, cao hon gia tri trung binh den gan 2 lan.
Dong dat CO kich thuoc Ion hon binh thuong nhu the chi xay ra trong moi truong kern kha nang tich luy img suat, chang han nhu dong dat xay ra tren cac dut gay co san trong dieu kien ma sat nho. tire la moi truona irons viing chan tieu la kem ben vuns..
2. 4. Tdn sudt lap lai dong ddt ] Tan suat lap lai dong dat N*(M>Mo). la so lin suit hien ciia dong dit vai
rnagnitude M>Mo trung binh trong mot nam, dugc bieu dien bing quan he magnitude - tan suat Giitenber-Richter
log N*( M>Mo) ^ a-bM (5) Vi so lieu con it, chua dii de thiet lap quan he tin cay rieng cho timg vimg ngu6n,
do thi lap lai dong dat dugc dung cho cac vimg lanh th6 co chung d\hu kien kiln tao, do la cac viing Dong bac, Song Hong - Song Chay, Tay bic. Song Ca, mi6n Nam Viet Nam va ca vimg uon nep Vict Lao tir Song Hong den dirt gay Hung Nhugncr - Ta Vi-
Ket qua dugc bieu dien bang cac phuong trinh sau voi Mo = 4.5:
• Vimg Dong bac tir dirt gay Song L6 (ria n6n Hoa Nam va doi Katazia):
log N*( M>Mo) = 2,948 - 0,886MS
• Viing Song Hong - Song Chay
log N*( M>Mo) = 3,269 - 0,926 Ms
• Vimg Tay bac
logN*( M>Mo) = 3,261- 0,782 Ms
• Viing Song Ca
log N*( M>Mo) = 3.325 - 0,948\Is
• Toan vimg u6n nip Viet Lao (tir dirt gay song H6ng d6n dirt gay Huno Nbuone -TaVi: ^ • ^
Phan I: DIA C H A N - SIA DONG LUC J3
logN*(M>Mo) = 3,537-0,815Ms
• Mien nam Viet Nam (dia kh6i Indosini):
logN*(M>Mo) =3,52-0,96MS ' 2. 5. Quy liiCit xudt hien dong dat theo thdi gian
Nghien cim quy luat xuat hien dong dat theo thai gian c6 the dua ra k§t luan: su xuat hien dong dat c6 M > 4.5 6 Viet Nam tuan theo luat phan bo Poisson
P(n) = Vn ^! n e N (6) trong do n - so su kien xuat hien trong mot don vi th^i gian
^ - toe do xuat hien ciia sir kien.
voi ^ = 0.6 doi voi viing Tay Bac va '^ = 0.55 d6i voi viing Dong Bac.
Ket luan nay cho phep sir dung cac phuong phap phan tich xac suat de danh gia do nguy hiem dong dat o Viet Nam.
2. 6. Quy luat (at ddn chan dong
• Phuang trinh tat dan cap dong dat
Dong dat magnitue M se gay ra chan dong Ion nhat lomax 6 chan tam
lomax = 1,45 Mmax -3,21ogh + 2,8 (7) trong d6 I dugc danh gia theo thang euong do chan dong MSK-64, h-dg sau chan
tieu, km.
Cuong do chan dong giam dan theo khoang each chan tam A theo quy luat:
Theo phuong cau true
I=1.45M-3.01ogVA2 + h2 +2.6 (8) Theo phuong vuong g6c voi cau triic
1= 1.5M-3.51ogVA2 + h2 +3,0 (9) Trung binh
1= 1.45M-3.21ogVA2 + h2 +2.8 (10)
• Phuang trinh tat dan gia toe dao dong nen dat:
Tren co so ki6m nghiem cac phuang trinh tit din gia toe nen bang s6 lieu^quan sat thuc tl o Viet Nam chimg toi chgn dugc 2 phuong trinh co the coi la phii hgp de tinh gia t6c n6n o Viet Nam. Do la phuong trinh Campbell 97 [1]
14 Tuy4n tap cac cong trinh nghien CLPU Vat ly Dja cau
Ln(AH) = -3.512+0.904MW-l,328Ln V R2 seis+ [0.149 exp(0.647 M\V)] 2 +[1.125-0.112LnRseis - 0.0957MWJF
-[0.440-0.171LnRseis]SSR+[0.405-0.222LnRseis]SHR (11) trong do AH la gia toe giao dong nen cue dai theo phuong nam ngang, tinh theo don vi g (g=981cm/s2), Sseis la khoang each tir ngu6n toi tram ghi, MW la moment magnitude tuong duong voi Ms khi 5.0<M<6.5, F la he so ciia dut gay,F=0 doi voi dirt gay trugt bing, F=l d6i voi dirt gay nghich, S SRva SFIR la cac h? so nen dat:
SSR=SHR=0 d6i voi trim tich hoac dit bo roi, SSR = 1 va SHR = 0 doi voi da nira cirng, SSR=0 va SHR==1 doi voi da goc.
Cong thirc Campbell cho kit qua tinh gia t6c nin rit gan voi ket qua tinh theo cong thirc dimg cho phin tay Trung Qii6c dugc xay dung tren tap hgp so lieu dao dong nen ciia dong dit vimg Van Nam va mot so so lieu ciia cac dong dat manh 6 Trung Quoc nliir Duong Son, Hai Thanh va mien Tay nuoc My
A(cm/s^)=1291,07e0.5257Ms (R+15)-1.5785 (12) voi do lech chuan a = 0.5203
trong do A la gia toe nen thanh phan nam ngang, ghi tren nen da.
3. Cac vimg phat sinh dong dat manh tren lanh tho Viet Nam 3. 1. Cdc vung dia chdn kien tao vd diii gay sinh chdn
Tren lanh tho Viet Nam c6 the phan ra cac viing dia chan kien tao sau (hinh 1):
Vimg ria nen boat dong Hoa Nam, chiem phan dong bac Viet Nam ke tir dirt gay Song Hong. Viing nay bao gom khoi nang Viet Bac va doi uon nep Katazia 6 phan nam ciia viing . Cac doi ven ria vimg nay. dgc theo dirt gay Song Hong va doi Katazia, la noi boat dong kien tao-hien dai dien ra manh me. Bieu hien dong dat, nhu mot he qua, cung ro rang va manh me; 6 day da xay ra cac tran dong dit cip VII Luc Yen 1953, 1954, Bac Giang 1961 \a nhieu dong dat cap VI-VII. Phin con lai boat dong kiln tao binh 6n hon, kem theo la bieu hien dong dat yeu 6t han; 6 day moi chi xay ra dong dit cip VI.
Vimg uon nep Tay bac Viet Nam, trai rong tir dirt gay Song H6ng din viing dirt gay Lai Chau - Dien Bien o phia tay. Song Ca, Rao Nay 6 phia tay nam. Hoat dong kiln tao hien dai o day dien ra manh me va phan di. Tuong img, boat dong dong dit trong vimg cung bieu hien manh me va phan di. Nhirng tran dong dit manh nhit Viet Nam nhu dong dat cap VIII Yen Dinh, Thanh Hoa. 1635, dong dit cip VIII Dien Bien 1935, dong dat cap VIII Tuan Giao 1983 dIu xay ra trong vimg nay.
Viing uon nep Viet Lao, keo dai tir dirt gay Rao Nay din dirt gay song Tra Bong a Quang Nam. So voi vimg u6n nip Tay Bic Viet Nam, boat dong kiln tao 6 day ylu hon, hoat dong dong dat ciing bieu hien kem ro rang va yeu 6t ban. 6 day ciing chi moi quan sat thay dong dat cap VI.
PhSn I: DjA CHAN - OIA DONG LUC
Dia kbli Indosini, noi tilp vimg u6n nip Viet Lao, keo dai toi dirt gay S6ng Hau.
Gilng nhu viing ria nin Hoa Nam, day la mot vimg nen, boat dong kien tao tuong d6i binh on, trir doi ven ria phia dong ciia viing, noi bj bien cai m?inh trong ky dia chit hien dai. Hoat dong dong dit cung chi bilu hien ro rang va tuong doi manh o dai ven ria nay.
d day da xay ra nhilu dong dit cip VII, nhu dong dat cap VII Phan Thiet nam 1877, 1882, dong dit nui lira Hon Tro, Phu Quy, nam 1923, dong dit cip VII Cheo Reo 1928, dong dit cip VII Song Ciu, Binh Dinh, 1970,1972 va nhieu dong dat O' vimg biln Binh Thuan. Dong dat kem theo hoat dong niii lira o vimg bien, dong nam ciia viing, la mot dac diem ciia viing nay.
Phan dien tich nho con lai - Ca Mau o' phia nam va Muong Te o phia tay bac -thuoc viing uon nep Thai Lan - Ma Lai. Hoat dong kien tao va bieu hien dong dat chi manh me a doi Muong Te.
Cac vimg bi chia cat thanh cac doi nho hon, thuong hep va keo dai theo phuang cau true dia chat, boi mot mang luoi dirt gay sau. Cac dirt gay ay chinh la noi c6 kha nang phat sinh dong dat va dugc ggi la dirt gay sinh chan.
Nhung dirt gay sau chia cat vimg Dong Bac la dirt gay Cao Bang - Tien Yen, dirt gay S6ng Thuong, he dirt gay vong cung Dong Trieu va dirt gay Ha Long - Lingshan huong d6ng bac, chay doc ven bo vinh Ha Long den Lingshan, Quang Tay. Dong dat trong vimg D6ng Bac xay ra tren cac dirt gay nay. Trong khoi nang Viet Bac c6 he dirt gay vong cung Phii Ngir, Son Duong.
Mot loat cac dirt gay sau keo dai theo phuong tay bac - dong nam chia cat vimg Tay Bac la dirt gay Phong Tho, Than Uyen, Muong La - Bac Yen, dirt gay S6ng Da, dirt gay Son La, dirt gay Song Ma, dirt gay Pu May Tun, dirt gay Song Hieu, he dirt gay Song Ca, dirt gay Rio Nay. . . a phia Nam, trong vimg uon nep Viet - Lao cac dirt gay huong a vT tuyen A Luoi, Hue, Da Nang, Tam Ky - Phuoc Son chia cat vimg thanh cac doi nang sut xen ke.
Dia khoi Indosini bi chia eat bod nhieu dirt gay sau, trong do dang chu y nhat la cac dirt gay S6ng Ba, Ba To - Cirng Son, Tuy Hoa - Cii Chi, song Sai Gon va song Vam Co D6ng. 0 vimg bien co cac dirt gay kinh tuyen 109, Thuan Hal - Minh Hai va nhieu dirt gay a vimg bien Binh Thuan, phan chia cac cau true triing Ciru Long, nang Con Son, trung nam C6n Son...
3. 2. Vung hoat dong nui lira hien dai
Mot trong nhirng bieu hien dgc dao ciia van dong kien tao moi o Viet Nam la cac phun trao ciia nui lua dien ra a phia Nam ciia lanh tho, thuge vanh dai nui lira dong nam Dong Duong. C6 the phan ra hai giai doan chinh. Giai doan Pleistocen som: dung nham phun ra theo cac dirt gay Ion, lap day thung limg va dong bang boc mon tich tu Neogen. Giai doan Holoxen: boat dong ban che hon va thuong phun len tir vi tri sau hon theo dirt gay a kinh tuyen. Trong the ky thir 19 ciing nhu gan day, boat dong niii lira con tiep tiic 6 vimg ven bien thuoc tinh Binh Thuan, Khanh Hoa. Cac vii no niii lira da gay ra nhung tran dong dat niii lua.
Cac tran dong dit cip VII a bo biln Phan Tliilt nam 1877 va 1882 va chuoi dong dat xay ra nam 1928 o ven bien tinh Binh Thuan deu co lien quan voi nhung phun trao bazan theo cac khe nirt hoac cac bong niii lira mod. Hai tran dong dit xay ra nam 1960 va 1963 a vimg dao
J ^ T u y i n tap cac c o n g trinh nghien CLPU Vat ly Dja cauJ008_
Hon Nuoc, theo Saurin, ciing lien quan voi boat dong ciia niii lira ngam a vimg nay. Theo cac ghi chep cii ciing nhu cac dilu tra dong dit cua chung toi thi cac tran kem theo nui lira phun noi tren deu khong manh ban cip VII va thuong gay chin dong trong pham vi nlio hep.
3. 3. Cdc viing phdt sinh dong ddt manh M > 5.0
Cac dut gay sau boat dong ke tren la nod dong dat manh eo the phat sinh. Do la cac vimg phat sinh dong dat hay con ggi la cac \amg nguon. Vi tri cua cac vimg nguon dugc xac dinh tren ban do theo nguyen tac: vimg phat sinh dong dat la dod pha buy lien quan true tiep toi boat dong ciia dirt gay, co chieu rgng trimg binh khoang 10km vod dod trung tam la hinh chieu ciia mat dirt gay, tinh den day ciia tang sinh chan, tren mat dat. Theo cac tai lieu dong dat da quan sat dugc tren lanh tho nuoc ta, be day tang sinh chan trong cac doi dut gay Dong Trieu, Son La, Song Ma, Pu May Tun la H « 35km, trong cac dod dirt gay Song Hong, Song Chay, Song Ca H » 25km, trong cac vimg con lai H ~ 20km. Con theo cac tai lieu kien tao, dia vat ly thi goc cam ciia cac dirt gay thuong la a = 70-800. Tuong ung ta c6 be rgng cua vimg nguon Dong Trieu, Son La, Song Ma, Pu May Tun la W « 12km, ciia vimg Song Hong, Song Chay, Song Ca la W = 10km, ciia cac vimg con lai la W « 8km. Khi dong dat manh xay ra day ciing la vimg cue dong.
Dong dat cue dai trong cac vimg nguon dugc danh gia bang cac phuong phap sau:
- Theo quy mo dirt gay bang cac cong thirc dugc thiet lap theo tai lieu dong dat Viet Nam
M max < 2 log L(km) + 1,77 M max < 4 logH(km) + 0,50
trong do, L - chieu dai doan dirt gay nguyen ven, H - be day ting sinh chin.
Cac cong thuc Uen dugc thiet lap vod cac dieu kien: a) ehilu dai doan dirt gay sinh chin phai Ion hon 3 lan so vod chieu dai chan tieu dong dit cue dai (L ^ 3Lx), b) chilu cao chin tieu dong dat cue dai khong vugt qua be day ting sinh chin (Lz ^H); Lx, Lz xac dinh theo cac cong thu'c (2), (4)
- Bing phuong phap phan bo cue tri Gumbel: sir dung ham phan bo cue tri Gumbel 3, xac dinh gioi han tren ciia phan bo cac gia tri magnitude Ion nhit quan sat dugc trong cac khoang thai gian bang nlia'u trong giai doan quan sat.
- Va bing phuang phap ngoai suy dia chit: Coi tran dong dit manh nhit, da xay ra a phin nao do ciia dirt gay, c6 the xay ra 6 cac phin khac cua dirt gay iy va 6 ca cac dirt gay khac CO cac dac tnmg kien tao tuong duong.
Do sau chan tieu ciia dong dat cue dai la
h = 2H/3+H' trong do H' la be day ting trim tich
Tan suit dong dat trong cac vimg dugc danh gia theo quan he magnitude - tin suit Gutenberg-Richter da trinh bay 6 tren. Cho moi viing ngu6n, tin suit dong dit dugc bilu thi bing 2 dai lugng: he so b ciia do thi lap lai dong dit va tan suit v (con ggi la van tic xuit
Phin I: D!A C H A N - OIA DONG LUC
hien dong dat) ciia dong dat dai dien (nguong) - dong dat quan sat dugc day dii trong giai doan quan sat. Cac vimg nguon trong moi vimg dia chan kien tao dugc gan he s6 b chung cua vimg. Tan suat dong dat v dugc xac dinh theo so lieu thuc te. Nguong la Ms min=4.5.
Van t6c xay ra dong dat v la so tran dong dat magnitude bang va lan hon 4.5 xay ra trung binh trong 1 nam trong vimg nguon
V= N*(Ms >4.5) = NS(Ms >4.5)/t
Bang 1 - Cac vung phat sinh dong dat M > 5.0 tren lanh th6 Viet Nam
TT
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
Ten vung
Sen La
Song Ma - Fumaytun Phong Tho
Than Uyen
Mwang La - BSc Yen Song Da
Lai Chau - Dien Bien Mu'ang Te
Mu'O'ng Nhe Ha iLfu Song Ma Song Hieu
NghTa Lo - Thanh Son Bac Mu'O'ng Nhe Song Ca - Khe B6 Rao Nay
Khe Giira - VTnh Linh Tra Bong
Dong Trigu - Dong Bi Song H6ng - Song Chay Cao BJng - Tien Yen Dong Bac trung Ha Npi Cam Pha
Song Lo
Thai Nguyen - B i c Can Qu6c Lo 13A
Van Son - Ha Giang Dal<r6ng - Hue Da N i n g
Tam Ky - Phu'ccc Son Song P6 Co
Song Ba
Ba T o - Cung Son Kinh Tuygn 109.5 (doan 1) Kinh TuySn 109.5 (doan 2) Tuy Hoa - Cu Chi
Thuan Hai - Minh Hai Song Sai Gon Song Vam Co Dong Song Hau
Ba T o - Kon Tum Kon Ha Nu'ng - Song Re Nha Trang - Tanh Linh Ham Tan - Loc Ninh LOG Ninh - Thu DSu MQI Cifu Long - Con Son
Mmax
6.8 6.8 5.5 5 5.5 5.5 6.2 5.5 5.5 5.5 5.5 5 5.5 6.1 6.1 5.5 5.5 5.9 6.1 5.5
5.5 5.5 5 5.0 5.0 5.0 5.5 • 5.5 5-5 5.5 5.5 5.5 6.1 6.1 5.5 5.5 5.5 5.5 5.5 5.0 5.0 5.0 5.0 5.0 5.5
Mmin
4.5 4.5 4 5 4.5 4.5 4.5 4.5 4,5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4 5 4.5 4.5
•4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4,5 4 5
b
0.84 0.84 0.84 0.84 0.84 0.84 0.86 0.86 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0,84 0,89
0,89 0,89 0,89 0,84 0.89 0,89 0,89 1,00 1,00 1,00 1.00 1.00 1,00 1,00 1,00 1,00 1,00 1,00 1,00 1,00 1.00 1,00 1,00 1,00 1,00 1,00 1,00
h
22 22 12 12 12 12 12 12 12 12 12 10 12
17 12 12 12 22 17 12 12 12 12 10 10 10 12 12 12 12 12 12 17 17 12 12 12 12 12 10 10 10 10 10 12
V
0,11 0,11 0.01 0.01 0.04 0.04 0.07 0.03 0.03 0,01 0,01 0,02 0,03 0,11 0,02 0,01 0,06 0,06 0,22 0-03 0.04 0.02 0.03 0.02 0.02 0.01 0.02 0,02 0,02 0,02 0,02 0 12 0,02
^ , 1 0,02 0,06 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.01 0.07
trong do N2 (Ms>4.5) la ting s6 dong dit Ms >4.5 quan sat thiy trong thoi gi^m t nam trong vimg nguln. Dong dit Ms >4.5 c6 thi moi chi xay ra o phin nay, phan kia cua \amg
1_8 Tuy4n tap cac cong trinh nghien CLPU Vat ly Pja cku_20QB_
nguon nay, vimg nguln kia, ma chua bilu hien hit kha nang sinh chan. Vi the, thien ve an toan dia chan, chimg toi khong liy gia tri v tnmg binh, ma gan cho vimg nguon gia tri
V = vAs S/AS
Trong do vAs la van toe dong dat quan dugc trong phan dien tich AS ciia viing nguon, eon S la dien tich cua toan vimg nguin iy. Bilu thirc nay ciing dugc sir dung de gan van toe xay ra dong dat cho cac vimg nguon khac trong cimg mien kien tao nbmig o d6 chua quan sat thay dong dat.
Ket qua la da xac dinh dugc cac vimg nguon sau voi cac thong so dia chan co ban cua chimg la (bang 1, hinh 3):
• Cac vimg Son La, Song Ma - Pu May Tun: dong dat cue dai M max = 6,8, chan dong cue dai o chan tam lOmax = 8-9 (theo thang MSK- 64), do sau chan tieu h = 23km.
Dong dat co M = 6,7- 6,8 da xay ra 6 Yen Dinh, Thanh Hoa nam 1635, o Pu May Tun each Dien Bien 30km ve phia dong nam nam 1935, o Tuan Giao thang 6 nam 1983.
• Cac viing Song Hong - Song Chay, Song Ca: M max < 6,1 , h = 17km, lOmax = 8 (thang MSK- 64). Thuc te trong cac vimg nay moi chi xay ra cac tran dong dat M = 5,4: Ha Ngi nam 1285, Nghe An 1821, Luc Yen 1954.
• Vimg Dong Trilu: M max < 6,0, h = 25- 30km, lOmax = 7 ( MSK- 64). Cac vimg khac la: Cao Bang - Tien Yen, Song Lo, Muong La - Bic Yen, Song Da, Lai Chau - Dien Bien, Muong Te, Muong Nhe, Rao Nay, A Luod, Hul, Tam Ky - Phuoc Son, Hung Nhugng - Ta Vi, Ba To - Cimg Son, Song Ba, ven biln Binh Thuan, Song Hau:
M max < 5,5, h = 10-15km, lOmax = 7 (MSK- 64). Tin suit lap lai dong dit thip.
Cac thong so b,v ghi trong bang 1
4. Ban do phan vung gia toe nen chu ky lap lai 500 nam lanh th6 Viet Nam
Do nguy hiem dong dat [3], trong do co cac gia tri gia tic nIn chu ky lap lai khac nhau, dugc danh gia tren co so ban do \amg nguon bang phuang phap phan tich xac suit Cornell [2], sir dung phuong trinh tit dan chan dong phii hgp. Nhu da trinh bay o tren, hai cong thirc thich hgp hon ca la cong thirc Campbell 97 va cong thuc Xiang Jianguang va GaoDoncr [13]
cho vimg Van Nam, nhung cong thirc Xiang GaoTong cho sai si Ion hon. Trong tinh toan nay chimg toi da sir dung cong thirc Campbell 97. Viec tinh toan dugc thuc hien nho phin mim chuyen dimg CRJSISS99 [4]. Ket qua da thanh lap dugc cac ban dl gia tic nIn chu ky lap lai 500, 1000, 2500, 5000, 10.000 ty le 1:1.000.000 cho nIn da cimg (nIn loai A trong bang phan loai nen dat theo tieu chuan khang chan chau Au EN- 1998, (bang 2)), cho lanh th6 Viet Nam. Ban db gia toe nen chu ky lap lai 500 nam ty le 1:1.000.000. nl'n loai A, lanh thi Viet Nam, voi cac gia tri gia toe nen (PGA) dugc the hien bing cac duong ding ud 0.04, 0.08 . 0,12 , 0.16, 0.20... g. (hinh 2) dugc dua vao tieu chuin xay dung Viet Nam T C X D V N ' 3 7 5 -
2006: Thiet ke cong trinh chiu dong dat
Tir gia tic dinh nguoi sir dung co the chuyen doi sang cip dong dit theo cac than"
ra tront MSK-64, MM, bang each sir dimg quan he giua cap dong dit va gia tic nIn dua
Phan I; DjA C H A N - DIA DONG LLCC
19 cac thang nay (bang 3). Ket qua quan sat gia toe nen tren the gioi cho thay gia tie nIn a cac diem quan sat khac nhau trong mot viing c6 cimg cap dong dat c6 the chenh lech nhau rit nhieu, co khi den 10 lan. Thang MSK chi ra khoang phan bo 90% so lieu va gan gia toe dinh trung binh can ap dimg cho timg cap, con thang MM gan cho timg cap gioi ban tren ciia khoang phan bo gia toe dinh.
Bang 2. Phan loai n§n d i t trong TCXDVN 375 2006 - Thilt k l cong trinh chju dong dit, lly theo Tieu chuIn khang c h i n chau Au EN-1998
Loai nen
A B
C D E
SI 82
Mo ta mat cat thach hoc
Da hoac cac thanh tao dja chat giong nhu' da, gom nhi§u nh§t la 5m vat ch4t bo roi tren mat
Cac lap cat, cupi soi rat chat, hoac set rat curig, day it nhat hang chuc met, dac trirng boi si/ tang dan theo dp sau cua tinh chat cq ly
Cac t^ng day cat, cupi, sol chat va trung binh , hoac set CLfng b§ day tu' vai chgc den hang tram met
Cac t§ng d i t bo roi d i n trung binh (co hay khong co cac lop d§t x6p), hogc dat chu yeu la x6p den chac Mat c i t gom lop b6i tich tren mat voi gia tri Vs ciia logi C hoac D va be day thay doi tu 5 den 20m, ben duoi la vat lieu CLfng hon voi Vs>800m/s
Cac tang gom hoac chua mot lop day it nhat 10m set mem /bun voi dp deo cao (Pl>40) va chua nuoc cao Cac tang dat co kha nang hoa long, set nhay cam, hoac cac d i t khac khong co trong loai A-E hay 81
Cac thong so Vs,30
(m/s)
> 8 0 0 360 - 800
1 8 0 - 3 6 0
< 180
<100
Nsp,
>
50 15 -50
<15
Cu(kPa)
>250
70 -250
<70
10-20
Bang 3. Bang chuy§n d6i tip dinh gia toe nen sang d p dong dat
Thang MSK-64 Cap dong dat
V VI VII VIII IX X
Khoang gia toe dinh
(a)g
Gia toe dinh trung binh (a)g
0,015-0,03 '
> 0,03-0,06 : 0.05
> 0 , 0 6 - 0 , 1 2 i 0.10
> 0,12-0,24 i 0.20
>0,24-0,48
> 0,48
0.40 0.8
Thang MM Cap dong
dit
V VI VII VIII
Dinh gia toe nen (a)g 0,03-0,04 0,06-0,07 0,10-0,15 0,25-0,30 IX 1 0,50-0,55
x >0,60 5. ket luan
Ban d6 phan viing gia toe nen chu ky 500 nam trinh bay ttong bai nay da dugc xay dung tren co sa nhung ket qua nghien cim day dii nhit ve dong dat tren lanh tho Vi^t Nam, bing phuong phap phan tich xac suat va chirong trinh tinh do nguy hiem dong dat dit hien dai dang dugc diing rgng rai tren thi gioi hien nay. No dugc dua vao Tieu chuin xay dimg Viet Nam 'TCXDVN 375-2006: Thilt k6 cong trinli chiu dong dat"
20 Tuydn tap cac cong trinh nghien cu-u Vat ly Dja cau^OOj^
»"
moi dugc ban hanh phuc vu cong tac quy hoach va xay dung khang chan 6 nuoc ta. Sir dung ban d6 nay va Tieu chuin TCXDVN 375-2006, nguoi lam cong tac quy hoach va xay dung tim dugc cac giai phap bo tri hgp ly cong trinh va cac giai phap khang chan hgp ly bao dam an toan cong trinh va tiet kiem von dau tu. Gia toe nen tren ban do dugc tinh cho nen da cimg, khi xay dung cong trinh can phai hieu chinh gia toe nen theo dieu kien nen dat o dia diem xay dung theo cac huong dan trong tieu chuan.
Bai bao nay dugc hoan thanh voi sir ho trg kinh phi ciia de tai nghien ciru co ban ma so 7.113.06. Tap the tac gia xin chan thanh cam on.
ABSTRACT
SEISMIC ZONING MAP OF THE TERRITORY OF VIETNAM IN THE VIETNAMESE BUILDING STANDARD TCXDVN 375-2006: EARTHQUAKE
RESISTANCE DESIGN OF CONSTRUCTIONS
Nguyen Dinh Xuyen, Le Tu Son
This paper presents the seismic zoning map of the territory of Vietnam in first time approved Vietnamese Building Standard TCXDVN 375-2006: Earthquake Resistance Design of constructions. This is the Peak Ground Acceleration (PGA) with return period of 500 years on ground type A in accordance with the ground classificaion table in Europ Earhquake Resistance Standard EN-1998. On the basis of the earthqukake manifestation laws briefly presented in this paper such as relation between earthquakes and recent tectonic setting, spatial-tim_e earthquke distribution, earthquake return frequency, relation between the focal dynamic characteristics, shakingg attenuation laws etc., the seismic source zones M>5.0 in Vietnam have been delineated and source zone map in scale 1:1.000.000 of Vietnam has been compiled. On the basis of this map using the computer program CSISSISS 99 and Campbell 97 attenuation law the PGA map of 500 years return period on ground type A have been calculated and compiled in scale 1:1 .ODO.OOO.
6. Tai lieu tham khao
1. Campbell W. Kenneth, 1997. "Empirical near-source attenuation relations for horizontal and vertical components of peak ground acceleration, peak ground velocity, and Pseudo-absolute acceleration response specta", Seism Res Lett 68(1), pp. 154-179.
2. Cornell C. Allin (1968). "Engineering seismic risk analysis". Bull. Seism Soc Am., 58(5), pp. 1583-1606.
3. Leon Reiter, 1990. Earthquake Hazard Analysis"
Phin I: DjA CHAN - DjA D Q N G LUC 21
4. Columbia University Press, New York, 1990.
5. Mario Ordaz, A. Aguilar, J. Arboleda, Phan mem CRISISS99. Univer. of Mexico (UNAM). 1999.
6. Nguyen Dinh Xuyen (chii bien), Le tir Son, Nguyen Nggc Thuy, Cao
7. Dinh Trieu,Tran Van Thang, va nnk, 2004. "Nghien cuu du bao dong dat va dao dong nen a Viet Nam", Bao cao tong ket de tai dgc lap cap Nha nuoc, Vien Vat ly Dia ciu, Vien KHCN VN, Bg KHCN VN.
8. Nguyen Khic Mao va I. A, Rezanop [1968]. "Dong dit mi^n Bic Viet Nam".
Nha khi tugng. Ha Ngi, 1968.
9. Shebalin N. V. 1969, "Truong chan dong va chan tieu dong dat manh", Luan an TS, Vien vat ly trai dat, Vien HLKH Lien X6, Matxccrva (Nga).
10. Shebalin N, V. 1971, "Ve Magnitude gioi ban va cap do manh gioi ban ciia dong dit". Tin tire Vien HLKH Lien X6, Vat ly trai dit No 6. 1971 (Nga).
11. Shebalin N. V. 1974. "Chin tieu dong dit manh tren lanh th6 Lien X6", NXB Khoa hgc Mat 1974 (Nga).
12. Shebalin N. V. 1975, "Ve viec danh gia cuong do chan dong, thang cap dong dat va cac phuang phap do cuofng do chan dong", NXB Khoa hgc Matxcova, 1975.
13. Shebalin N. V. 1983, "V^ van de danh gia do nguy hiem dong dat trong cac viing dong dat boat dong yeu", Tuyen tap "Nghien cuu tinh dong dat trong cac viing ' dong dat boat dong yeu" NXB Khoa hgc, Matxcova, 1983 (Nga).
14. TCXDVN 375-2006: "Thi6t kg cong trinh chiu dong dit", Bg Xay dung, Ha Ngi I 2006.
15. Xiang Jianguang and Gao Dong (1994), "The strong ground motion records ' obtained in Langcang - Gengma earthquake in 1988, China, and their pplication", ' Rept. at International Workshop on Seissmotectonics and Seismic Hazard in
Southeast Asia, Hanoi. 1994.
22 T u y i n tap cac cong trinh nghien cu-u Vat ly P!a_cau_2O01
Hinh 1:
BAN DO DIA CHAN - KIEN TAO VIET NAM VA KE CAN
110^ US'
i l n I: 0!A C H A N - OjA O O N G LUC 23
Hinh 2:
B.4\ DO PHAN VUNG G U T 6 C N'f N LANH THO VIET NAM Chu ky lap lai 500 nam, nen A
