Thuy dien danh thuc dong dat o Song Tranh

Thứ hai, 10 Tháng chín 2012, 05:43 GMT+7

Thuy dien Tien si Tran Tan Van, Vien truong Vien Khoa hoc Dia chat va Khoang san, Bo Tai nguyen Moi truong Ba thang dung tich ho chua khong len, khong xuong dot ngot ma dong dat lai xay ra don dap, lan rong khong chi o Bac Tra My con du tran o Nam Tra My, Hiep Duc, Tien Phuoc... Them tran dong dat sang 7/9 khien mot so nha khoa hoc bat dau nghi den kha nang dut gay gan nha may thuy dien Song Tranh 2 dang hoat dong.

De lam ro hon van de nay, PV da co cuoc trao doi voi TS Tran Tan Van, Vien truong vien Khoa hoc Dia chat va Khoang san, Bo Tai nguyen Moi truong.

Theo ban do thi vi tri ba tran dong dat lon nhat vua xay ra deu khong nam trong quan tu rung chan quanh thuy dien Song Tranh 2. Thay vao do, chung deu nam rat gan voi mot dut gay dia chat mang ten Hung Nhuong-Ta Vi chay theo huong dong-tay nam o man nam dap thuy dien Song Tranh. Mot so nha khoa hoc da bat dau nghi den kha nang dut gay gan Song Tranh 2 “cua quay”, TS co the cho biet y kien cua minh?

Day cung co the la mot kha nang. Tuy nhien, neu la dong dat do dut gay dang hoat dong thi khong phai bay gio moi phat hien ra. Boi neu dut gay hoat dong no se keo dai va thuong xuyen, se xay ra nhieu trong qua khu chu khong phai cho den bay gio. Tat nhien dut gay co the tai hoat dong sau mot thoi gian ngung nghi. Nhung tai hoat dong vao dung thoi diem nay xem ra hoi khien cuong.

Theo logic, neu dut gay hoat dong thi no da duoc ghi nhan truoc do. Khi noi ve dut gay hoat dong thi cac nha khoa hoc thuong tim kiem nhung bieu hien cua no trong mot khoang thoi gian dai, hang chuc, tham chi hang tram ngan nam. Va bieu hien hoat dong cua dut gay khong chi co dong dat ma con la mot vai hay nhieu hien tuong khac cung di kem nhu dich truot, dut gay, nut vo, buc xa cac loai khi co nguon goc tu duoi sau, tham chi phun trao nui lua v.v.

Nhung co y kien khang dinh neu dut gay khong hoat dong thi dong dat da khong xay ra nhu vay, TS co the ly giai?

Cho nay can phan biet ro, dong dat la mot bieu hien cua dut gay hoat dong. Nhung mot dut gay hoat dong khong nhat thiet chi bieu hien qua dong dat ma con co ca nhung hien tuong nhu da neu tren. Nhieu truong hop hoac nhieu kieu loai dut gay hoat dong nhung khong kem theo dong dat.

Vay co the hieu, dong dat tai Song Tranh 2 la do tich nuoc vao long ho hay do dut gay hoat dong, hay do ca hai yeu to tren?

Dong dat do dut gay hoat dong khong goi la dong dat kich thich. Nguoi ta chi goi dong dat kich thich khi no xay ra do tich nuoc ho chua hoac noi chung do con nguoi tac dong lam thay doi truong ung suat bien dang trong vo Trai Dat. Nhung khong phai cu tich nuoc vao long ho la gay ra dong dat kich thich. Binh thuong vo Trai Dat luon o trong trang thai tich luy ung suat, de roi khi dat den mot nguong nhat dinh vuot qua suc ben cua dat da thi se xay ra dut gay, dich dong hoac dong dat, noi cach khac la mot hinh thuc "xa stress", khong cu la o khu vuc ho chua nuoc va vao thoi diem tich nuoc.

Tuy nhien, cac ho chua nuoc, nhat la cac ho thuy dien, thuong duoc xay dung tren cac dong song, ma cac dong song, nhat la song o mien nui, thi thuong nam trung voi cac dut gay. Khi tich nuoc tuc la da chat them mot tai trong lon, lam gia tang ung suat len dat da duoi long ho va cac khu vuc lan can. Neu o do ung suat kien tao da tich luy gan den nguong gioi han thi chinh ung suat gia tang do se kich thich de gay ra "xa stress". Do la ly do nguoi ta goi dong dat kich thich va thuong gan no voi viec tich nuoc ho chua.

Duong nhien la khi truong ung suat kien tao ban dau chua du lon thi co tich nuoc vao cung kho gay ra dong dat kich thich, va ho chua cang lon thi cang nhieu kha nang xay ra dong dat kich thich lon. Nhung cac thong ke tren the gioi cho thay hau het cac tran dong dat kich thich thuong nho, khong vuot qua 4-5 do Richter, khong vuot qua cuong do mot tran dong dat tu nhien co the xay ra o khu vuc do va khong vuot qua cuong do khang chan cua cong trinh dap neu nhu tinh toan du, thiet ke va thi cong dam bao.

Co the thay khu vuc Song Tranh 2 la khu vuc co day du nhung dieu kien khien dong dat kich thich phat sinh. Vay tai sao nhung nha may thuy dien van duoc xay o day?

Tren the gioi, dong dat kich thich la mot phan cua cuoc song. Khi xay dung mot nha may thuy dien nguoi ta khong de gi chon duoc mot khu vuc ly tuong. Chi co dieu la truoc khi tien hanh, ho phai dieu tra, khao sat day du cac dac diem tu nhien, thi du xem khu vuc do co kha nang xay ra dong dat manh den cap may...de du phong.

Khu vuc Song Tranh 2 khong phai la vung dong dat manh co the xay ra. Ke ca tich nuoc ho chua chac cung khong lam thay doi dang ke nhan thuc do. Vi the, neu co dieu tra, khao sat, nghien cuu day du, thiet ke, thi cong bai ban, chat luong... thi dong dat kich thich o day la cau chuyen binh thuong, giai phong het ung suat no se dan on dinh ma dong dat kich thich, neu co thi thuong cung het nhanh.

Cac du chan keo theo dong dat kich thich duoc thong ke tren the gioi chi o muc 3 - 4 do Richter, cung lam la 5 do Richter. Trong khi cong trinh xay dung duoc thiet ke khang chan o muc 7-8 do Richter. Do do, dong dat kich thich khong anh huong den cong trinh dap neu thi cong tot. Chi co dieu la dong dat kich thich co the tac dong tieu cuc den cac cong trinh va cong dong xung quanh, it nhat la ve mat tam ly, vi ro rang la o do tu truoc den gio nguoi ta chua phai biet den dong dat va cac cong trinh xay dung, dac biet la nha dan, co khi chua tinh den kha nang co dong dat.

TS co the cho biet them ve hoat dong dia chat cua khu vuc nay, neu thuc su co hoat dong dut gay xay ra thi co nhung du bao nguy hiem gi?

Day la khu vuc co dat diem dia chat, kien tao kha dac biet, bieu hien tan kien tao tich cuc, thi du nhu cac hien tuong song thay doi dong chay, xoi lo bo song, bo bien, truot lo... thuoc loai manh nhat ca nuoc. Tuy nhien, nhung bieu hien nhu hoat dong nui lua hay dong dat manh thi chua xay ra. Do do, chac nguoi dan se phai luu y nhieu hon toi sat lo, truot lo o vung nui va xoi lo bo song, bo bien.

TS co loi khuyen gi voi nhung nguoi dan Quang Nam dang rat lo lang? Dong thoi du bao gi ve hoat dong dia chat cua khu vuc nay trong thoi gian toi?

Dut gay hoat dong thi khong biet bao gio no xay ra va xay ra trong bao lau, bao lau lai lap lai. Nhung nhu da noi o tren, khi no xay ra se co nhung bieu hien ma neu de y nghien cuu, va nghien cuu day du, bai ban, thi chung ta co the se du bao duoc truoc de phong ngua.

Toi co the khuyen gi nguoi dan o Quang Nam day? Toi ngoi o day binh yen, va di noi voi ho rang khong nen qua lo lang u? Toi chi nghi la neu cung cap duoc mot it thong tin de hieu biet them, luong truoc ve dut gay hoat dong hay dong dat kich thich, ve quy mo cua hien tuong thi chac la cung tot. Toi cau chuc cho nguoi dan Quang Nam vuot qua duoc giai doan kho khan nay.

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