fjeujum Khi lucmg. Thuy van vd Diing luc hoc Bien_
M O PHONG SO SU LAN TRUYEN SONG THAN DO DONG DAT VAO CAC VUNG VEN Bd VIET NAM
Bu Thi Thu Ha. Dinh Van Manh Vien Co hgc, 264 - Dgi Cin, Ba Dinh, Ha Ndi
Email: [email protected]
Tom tat:
Bdi bdo Irinh bdy mdt so ket qud mo phong so su lan Iruyen .song than do dimg ddl vdo cdc viing ven bo biiin Viet Nam bdng mo hinh Ihiiy dong liec CIIBIO Md hinh CHBIO dugc xdy dung vd phdt Irien tai Phong Co hgc vd Moi trudng Bien. Vien Co hgc, dira Iren ca su he phuong Irinh nuac nong phi luyen 2 chieu, sir dung phuang phdp sai phdn hiru hgn vai ky thudl chong Itiai vd xir ly kho uat cho phep linh todn chi tiet tai cdc khu vuc cdn quan tdm, co xtit dan ste gdy ngcip lut ciia song. Mo hinh so tri vai bu&c lue'ri khd chi liel cho cite viing bien ven ha Nha Trang vd Thira Thien - Hue dd dugc thiel lap vd mo phong sir ngdp lut do song than Iheo mgt sg kich bdn dgng ddt trang khu viec bien Dong co khd ndng gdy song ihiin Itin.
NUMERICAL SIMULATION OF TSUNAMI PROPAGATION IN THE COASTAL AREAS OF VIETNAM Abstract:
This paper presents some results of numerical simulalion of tsunami propagation in Ihe coastal areas of Vietnam by CHBIO hydrodynamics model. CHBIO model was built and developed at the Department of Mechanics and Marine Environment, Institute of Mechanics, based on Iwo- d'tmensional nonlinear shallow waler equations, using Ihe finite difference method wilh nesting grid technology and dry-wet processing
allows detailed calculations in Ihe areas of concern, taking into account the flooding capability of the waves. The model with the detailed grid for Nha Trang coastal areas, and Ihe Thua Thien-Hue has been set up and simulation of tsunami inundation in some scenarios of earthquakes can cause large tsunamis in the East Vietnam Sea.
I.
M 6 DAUSdng thin (ST) khdng xay ra thudmg xuyen, tuy nhien se rat nguy hilm cho eac viing ven bd biin khi chung xuit hien. Khi lan truyin vao viing ven bd bien vdi siic manh tan
llgi ngln Klioa lioe va Cung nghe bien loan quae tan leiu r
phii Idn, ST lam muc nude biin dang cao gay ngap lut, pha buy bd bai, cdng trinh, di: dap, pha buy trane thai cin bing chi do thiiy thach dgng lyc, bicn ddi dia chit, dja mao, de dpa tinh mang va tai san eua cu diin.
Bai toan lan truyen ST do dgng dit tren Biin Ddng da dugc Phong Co hgc va Moi trudng Biin, Vien Co hgc tiln hanh nghien cuu, dac biet ke tit sau tham hga ST An Bo duoni! (Aeeh 26/12/2004) va da din tung budc duge hoan thien the hien qua cac nghien ciru gan day [3,4]. Cac nghien ciru nay da tap trung theo hudng md phdng lan truyen ST theo cac kich ban dgng dit cd the xay ra tren biin Ddng, Da sit dung md hinh thuy dpng luc CHBIO kit ndi vdi md hinh dirt gay bl mat day bien ciia Mansinha va Smylie tinh loan lan truyin ST. Tuy nhien, do sd lieu dia hinh chua dap irng yeu cau cua bai toan, cac ki-i qua tinh loan ehua du chinh xac va chi tiet.
Md phdng sir gay ngap cua sdng thin theo mgt sd kjch ban dgng dat hinh thanh tren biin Ddng bing md hinh CHBIO vdi budc ludi kha chi tiet cho cac vung ven bd Nha Trang va Thira Thien - Hui: se dugc trinh bay d day.
II. CO s d TOAN HOC MO HINH CHBIO
Md hinh thuy dgng lire CHBIO dita tren co sd he phuang trinh nude ndng phi tuyen hai chilu, giai bing phuong phap sai phan hihi ban vdi ky thuat chdng ludi va xu ly khd uot cho phep md phdng chi tiet khu vuc can quan tiim ddng thdi md phdng dugc boat dgng ciia sdng dang gay ngap vung bd [3-5]. Ngoai ra, da dua ra mgt sd ky thuat nhu phep la tron hoac ngi suy lam tang tinh dn djnh ciia md hinh khi tinh toan eho mien dja hinh chi tiet va phirc tap [2,9]. Ro rang, bai loan Ian truyen sdng than xay ra tren quy md dai duang, mo dun cho phep tinh song song tren he tga do cau eung da dugc xay dung.
Kha nang tinh toan va ap dung md hinh CHBIO cho cac qua trinh thiiy dgng luc bien da dugc khang dinh. Hieu chinh va kiem nghiem md hinh trong bai toan lan truyen trieu va nude dang bao da dugc thuc hien [2,9]. Ciing nhu da tien hanh kiem tra mo hinh khi ap dung md phdng lai song than Aeeh cho ket qua kha phii hgp vdi mgt so tac gia khac [3].
HI. MO H I N H SO TRI MO PHONG Sy^ LAN TRUYEN CUA ST VAO CAC VUNG VEN B 6 Vlf T NAM
1. Thiit lap ludi tinh:
De cd dugc sd lieu dja hinh cung cap dau vao cho mo hinh da tiln hanh thu thap so li?u dia hinh tren toan Bien Ddng va so lieu dja hinh chi tiet cho khu vuc nghien ciiu. So lieu dia hinh tren toan Bien Ddng tit cac ban dd ty le 1/1.000.000, 1/500.000 va cac vitng ven bd tir ban dd ty le 1/100.000, 1/50.000, 1/25.000. Ngoai ra, so lieu dja hinh chi tilt eho tinh Thira Thien - Hue cdn dugc thu thap tii ngudn do dac khao sat thuc dia.
a. Ddi vdi viing bd Nha Trang:
Mien tinh dugc thiet lap vdi 4 ludi chong, ludi chi tilt nhit ung vdi viing bd Nha
Zl^jJ^n Khi tugng, Thiiy vdn vd Dgng lire hoc Bien
Trang. So dd ludi ghep xem hinh 3.1 .a). Cac tham sd ludi ghep xem bang 3.1.
Ludi 1 2 - 3 4
Sd cgt 421
120 150 500
So hang 441
120 90 500
Budc ludi (°) 0.056 0.028 0.014 0.0007
Kinh dd gdc ludi 98.78
n
107.18 107.74 109.14
VT do gdc ludi (°) 0.0397 10.1197 11.7997 12.4997
c?
''\
a) Viing ba Nha Trang b) Viing bd Thira Thien- Hue Hinh 3.1. Sa dd ludi tinh
b. Viing bd Thira Thien - Hue
Da thiet lap mien tinh vdi 4 ludi ghep, ludi chi tiet nhat iing vdi vimg bd Thira Thien - Hue. Sa dd eac ludi ghep xem hinh 3.1 .b. Cac tham sd ludi ghep xem bang 3.2
Bang 3.2; Cdc tham so krdi tinh Ludi
1 2 3 4
Sd cot 61 54 48 435
So hang 66 39 39 330
Budc ludi (°) 0.378 0.126 0.042 0.0028
Kinh do goc ludi (°) 99.00 105.426 106.812 106.938
VT do gdc ludi (°) 0.1180 12.970 15.742 16.204 3.2 Lira chon kich ban dong dat co thi gay ST l&n cho viing nghien cii'u
Dua tren ket qua tinh toan lan truyin sdng than tren Biin Dong tir cac viing nguon dgng dit gay sdng than thiy ring vimg ngudn ddi hut chim Manila gay dg cao sdng than dang nguy hiem cho khu vuc bd bien Miln trung [1,3,11]. Vi vay, trong bai toan md phdng su gay ngap cho vimg bien ven bd Nha Trang va Thira Thien - Hui chi chgn ra 3 kjch ban
ngi ngni Khoa hgc va Cong nghe bien toan quoc tan t/tu V
lien quan den vung ngudn ddi hut chim Manila lam dau vao eho md hinh. Cac kich \ dugc lira ehpn t u o n g u n g k y h i e u l a M l , M2, M3 (bang 3.3).
Bang 3.3. Tham so cdc kich bdn dgng dat gdy song than lua chgn mo phdng [ 1,1 T
Kjch ban
Do ldn ddng
dit Kinh
dp ngudn
(°) VTdg ngudn
o
Chieu dai dut
(km) Chieu rdng dut g l y (km)
Dp sau chan tieu (km)
Gdc cam (nghieng)
(°) Goc trugt (°)
Hudmg diit g l y (djch chuyen)
(°) Khoa
djch chnyS
13.7]
Ml 119.1 17.5 483 89 23.2 15 90 177
M2 8.6 I19.I 16.5 361 76 19.7 90 177
mi
M3 8.0 I I 9 . I 15.5 47 90 177 5.:
3. K i t qua tinh toan:
a. Vung bd Nha Trang (NT)
Hinh 3.2 Phdn bd dp cao song cue dai vitng ba NT theo kich bdn Ml
Hinh 3.3. Phdn bo ngdp viing ba NT theo kjch bdn Ml
Hinh 3.4. Phdn bo do cao song cue dai
viing ba NT theo kich bdn MI Hinh 3.5. Phdn bo ngfip vung baNT theo kich ban MI
H^i^anJChi tugng, Thuy vdn vd Bdng luc hgc Bien
V C
Hinh 3.6. Phdn bo do cao song cue dgi Hinh 3.7. Phdn bo ngdp vung ba NT theo viing bo NT theo kich bdn Ml kich bdn MI
b. Vimg ven bo biin Thiia Thien - Hui (TTH)
Hinh 3.8 Phdn bo do cao song cue dai Hinh 3.9 Phdn bo ngdp viing TTH theo viing TTH theo kich bdn Ml kich ban Ml
T
^ V
'{^^'
Hinh 3.10 Phdn bo dg cao song cue diii Hinh 3.11 Phdn bo ngdp vitng TTH theo vitng TTH theo kich bdn M2 kich bdn M2
Hin nghi Khoa hoc vd Cong nghe hiin loan qudc lan thii
Hinh 3.12 Phdn bo do cao song cue diii Hinh 3.13 Phdn bo ngdp viing TTH theo vdng TTH theo kich bdn M3 kich bdn M3
3. Mot s& nhan xet kit qua tinh toan a. Ddi vol vung bd Nha Trang
Do cao ST cd thi dat tai 14 din I5m tai khu vuc bd ddn sdng, khu v^rc trong vjnh do cao sdng nhd ban do cd su che chin cua bd ddn sdng phia ngoai, dong thdi do hinh dang ciia vinh cd cua khong hucJng ve hudng ddn sdng.
Khi lan truyin vao trong vinh, dg eao sdng giam din, sau dd lai tang len khi tien sat bd tai mgt s6 khu virc nhd cd dia hinh ddc.
b. Ddi vdi vung bd Thira Thien - Hue
Tai viing bo Thira Thien - Hui, do cao ST khoang 3 din 4m, tai mgt sd khu vue nhd cd dia hinh ddc do cao ST cd the dat tdi 5m.
Khi lan truyin vao hong dam pha, do cira dam hep, do cao sdng suy giam nhanh, mirc do lan sau gay ngap khdng dang ke.
Vdi ciing mgt kjch ban dgng dit, viing bd Nha Trang c6 do cao ST ldn hom so vdi vung bd Thira Thien - Hui. Dilu nay cd thi dugc giai thich la do vimg bd Nha Trang do dia hinh vung thim ngln va doc, nang Iugng ST bi suy giam khong dang ke, cdn ddi vdi vung bd Thira Thien Hui cd viing them ven bd trai rgng va it doc nang lugng ST da bi suy giam.
Loi cam on
Tac gia xin cam cm su tai hg kinh phi cua De tai cap Vien Khoa hgc va Cdng nghe Viet Nam "Phat trien va hoan thien md hinh dvr bao sdng bao, nuac dang va thiiy trieu cho vung bien Viet Nam"
TAI LIEU THAM KHAO
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Tieujxin Khi lugng, Thiiy vdn va Dong luc hoc Bien
2. Dd Ngoc Quynh. Cong nghe du bdo nude ddng do bdo. Bao cao tdng ket de tai.
KT03.06 (2001).
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Bulletin of the Seismological Society of America, Vol.75, No.4, 1135-1154, 1985.
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