Hgi nghi Khoa hgc ky niem 35 ndm Vien Khoa hgc vd Cong nghe Viet Nam - Hd Ngi 10 2010
NGHIEN ClTU CAU TRUC SAU CAC DlTT GAY
B A N G PHU^ONG P H A P D O SAU
TlT TELUA
STUDY OF THE DEEP STRUCTURE OF THE ACTIVE FAULTS USING MAGNETOTELLURIC SOUNDINGS
Vo Thanh So-n, Le Huy Minh, Le Tru-ffng Thanh, Nguyen Chien Thang Vien Vat ly dja eiu
A8, 18 Hoing Qude Viet, Ciu Giiy, H i Ndi Email: vtson.igp(§gmail.com
Tom tat:
Bdi bdo giai thieu mot cdch sa bg nguyen ly ciia phuang phdp do sdu tir telua, mot phuomg phdp dja vdt ly nghien ciru cdu vd Trdi ddt dua tren viec do dgc hai thdnh phdn tnrang tir Trdi ddt vd hai thdnh phdn ciia tnrang dien cdm irng vudng gdc vai nhau mot cdch tirang irng. Viec dp dung phuang phdp ndy trong nghien ciru cdu true sdu dai dirt gdy San La, dirt gdy Lai Chdu - Dien Bien vd dirt gdy Sdng Sdi Gdn duac giai thieu. Cdc kit qud dd chi ra rdng trong mat cdt dja dien thu duac tir nghjch ddo 2D sd lieu do sdu tir telua cdc dirt gdy dug'c bieu hien bai viing gidm rd ret cua dien tra sudt so vai mdi tnrang xung quanh, dieu ndy duac gidi thich Id do trong dai dirt gdy ddt dd bj cd ndt nen dien trd' sudt bj gidm di.
Hem nira, trong cdc viing dut gdy hogt dgng nhu dirt gdy Som La vd dut gdy Lai Chdu - Dien Bien, dien trd sudt a dai dirt gdy cd the gidm tcri mot vdi n.m dugc gidi thich la do cd sir ludn chuyen cim chdt long gidi phdng trong qud trinh bien chdt hoac su ndng chdy cue bd a khu vuc dirt gdy. Dien tra sudt a khu vuc dirt gdy Sdng Sdi Gdn cao han nhieu, tir vdi chuc tdi hdng trdm Q.m, dieu ndy cd the dugc cho Id it cd khd ndng cd mat sir bien chdt a khu vuc dirt gdy cung nhu sir ludn chuyen cua chdt long dgc theo dirt gdy, nghTa Id dirt gdy Sdng Sdi Gdn kem hogt dgng. Cdc vi du dd neu minh hga hieu qud vd y nghTa ciia viec sir dung phirang phdp do sdu tir telua de nghien ciru cdu tnic sdu cdc dirt gdy nhdt la cdc dirt gdy
hogt dgng.
Abstract:
The paper present briefiy the magnetotelluric method, an electromagnetic geophysical one used to study the deep stmcture of the Earth 's crust basing on to measure the orthogonal horizontal magnetic and electric fields at the surface. The applications for studying the deep stmcture of the Son La, Lai Chau - Dien Bien and sai Gon River faults have been presented. Its was shown that in the resistivity cross-section obtained by the 2D inversion of the magnetotelluric data, the faults are could be recognised by the rapid decreased resistivity zone in the cnist, which is interpreted by the rupture of the rock in the fault zone. In addition, in the active fault zones such as Son La and Lai Chau - Dien Bien one, the resistivity could
decreased to some n.m, which implicate the circulation of the fluids released by the metamorphism or the partial melting in the fault zone. The resistivity in the Sai Gon River fault zone varies frotn decades to hundreds H.m, which implicates that there is no metamorphism and circulation of the fluids along the faidt, and the Sai Gon river fault is less active than the Son La or Lai Chau - Dien Bien ones. These examples show the effectiveness of the magnetotelluric method for the study of the deep stmcture of the faults.
Tiiu ban: Cdc khoa hgc vi trdi ddt ISBN: 978-604-913-01^6-8
I. Mffdau
Phuong phip do siu tir telua li phuong phip dia vit ly nghien ciiu eiu tnic dien trd cua vd Trii dit dya tren viee do dae hai thinh trudng tir ty nhien vi hai thanh phin trudng dien cam img theo cie hudng vudng gdc vdi nhau tren bl mat Trii dit. Ca sd ly thuyet eiia phuong phip da duge Cagnia dua ra tir nim 1953 [2]. Phuong phip niy da dugc img dyng rdng rai khip the gidi trong nghien cim ciu tnic vd Trii dit vdi nhilu muc dich khie nhau:
nghien cim ciu true cie be trim tich [10], cie \aing boat ddng [1,4,5,7,13,19], eic viing dja nhiet [11]... 0 Viet Nam phuong phip niy eiing di duge sir dyng trong nghien cim ciu tnic ddi dirt gay Sdng Hdng [12,15,17,18], nghien cuu cie ddi dut gay Son La [8], ddi dirt gay Lai Chiu [9], td hgp vdi phuong phip dia dien nghien cim tim kiem nude ngim [3,15]... Trong bii bio niy ehung tdi gidi thieu mdt sd ket qui ip dung phuong phip niy trong viec nghien cim cie dut gay dia chit cd do boat ddng khie nhau: dirt giy Son La, dut giy Lai Chiu - Dien Bien va dirt giy Sdng Sii Gdn qua dd minh hga bieu qui eiia phuong phip nay trong viec nghien cuu eiu tnic cie diit giy dja chit.
2. Cff Sff cua phu-ffng phap
Khi nhirng thing giing cua tmdng tir Trii dit tir khdng gian di tdi be mat Trii dit d dai tan sd nhit djnh cd the coi nhu li sdng dien tir phing, mdt phin nang lugng cua nd thim nhip vio Trii dit theo phuang thing dimg xudng dudi. Do dit di Ii din dien, phin trudng tir bien ddi theo thdi gian thim nhip xudng dudi da lim xuit hien eic ddng dien cim ung dugc ggi li cic ddng dien dit eiing bien ddi theo thdi gian, phy thudc vio dien trd suit eiia dit da.
Ggi eic thinh phin trudng cie thinh phin tmdng tir theo hai hudng x vi y la Hx vi Hy, vi eic thinh phin tmdng dien tuong ung li Ex va Ey. Vdi gii thiet sdng phing vi bd qua ddng dich, xem mdi tmdng li nira khdng gian ddng nhit ding hudng, tir cie phuong trinh Maxwell Cagnia thu dugc mdi lien he:
p = 0,2T\zf (1)
trong dd p li dien trd suit mdi tmdng tinh bing Q.m, T la chu ky tinh bing giiy, Z li trd khing duge xie djnh bdi:
^ E.
= 4^e" (2)
vdi m=x,y, n=y,x, E tinh bing mV/km, H tinh bing nT, co li tin sd, p li do tir thim duge liy li ddng tir thim trong chin khdng (p=po=47i.lO'^H/m). Trong trudng hgp mdi trudng bit ddng nhit dien trd suit tinh dugc d tren dugc ggi li dien trd suit bilu kiln pa. Do siu thim nhip ciia sdng dien tir vio mdi tmdng phy thudc vao Pa va chu ky T:
p = ~^\0pj (3)
ZTT
trong dd p tinh bing km, pa tinh bing Q.m va T li ehu ky tinh bing giiy. Doi vdi hiu hit cac loai dit di dien trd suit thay ddi tir mdt vii din hing chuc ngin Q.m, vdi chu ky do dac thdng thudng cua phuong phip do siu tir telua tir 10"^ din 10^ giay, do sau thim thiu thay ddi tir vai m den vii chuc km, dieu dd cimg im chi ring do siu nghien cuu cua phuong phip tir telua c6 the dat tdi vii chyc km. Hien nay trong mdt sd edng trinh nghien cim ngudi ta sir dyng ehu ky dii tdi 10 giiy, do siu nghien cuu dat tdi xip xi 100km, nghTa la tdi do siu ciia ldp manti tren.
Trong trudng hgp mdi trudng ed dien trd suit bit ding hudng vin de trd nen phiie tap hon. Gii sir mdi trudng li 2D, ngudi ta dinh nghTa hai kilu dien trd suit khie nhau: dien trd
Hgi nghi Khoa hgc ky niem 35 ndm Vien Khoa hgc vd Cong nghe Viet Nam - Hd Ngi 10 2010
suit theo hudng song song vdi phuong eiu tnic la PTE vi dien trd suit theo phuong vudng gdc vdi phuong eiu tnic PTM,
p,,,=0,2T\Z,,\\p,j,,=0,2T\Z,J (4)
ZTE va ZTM duge xie dinh tir cac do dae trudng dien vi trudng tir theo cic hudng song song vi vudng gdc vdi phuong ciu true mdt cich tuong iing. Khi cic do dae duge tien hinh theo hudng X (thudng li hudng Bic-Nam) vi hudng y (thudng la hudng Ddng-Tiy) khdng theo eac hudng ciia cau tnic, mdi lien he giiia cie trudng dien vi tmdng tir do dac cd dang:
Z 7
"^xx ^x
z,, z.
^ x
H. (5)
trong dd Zxx, Zxy, Zyx, Zyy li cic thinh phin cua tenxor trd khing. Trong trudng hgp niy ngudi ta ed the ip dung mdt phep quay tga do de tim ra cic hudng chinh cua ciu true, eac thinh phin dudng cheo eiia tenxor trd khing img vdi cic hudng ehinh bing zero, vi ed the tinh toin eic thanh phin dien trd suit theo eic hudng chinh. Cic dudng cong do siu tir telua theo eic hudng ciu tnic li co sd cho viec minh giii tiep theo de tim kiem md hinh eiu true dien trd eiia vd Trii dit phii hgp vdi cie dudng cong dien trd suit do dae. Trong trudng hgp ciu tnic 3D phiie tap, viec ip dyng phuong phip do siu tir telua khi ban che.
Mye dich eiia viee minh giii sd lieu do sau tir telua li xiy dyng md hinh eiu tnic dja dien ciia vd Trii dat phii hgp tdt nhit vdi cie ket qui do dac. Trong trudng hgp mdi trudng ddng nhat, hoac phin ldp ngang ddng nhit, ngudi ta cd the diing phuong phip nghjch dio 1D xiy dyng md hinh eiu true dja dien vd Trii dit theo phuong thing diing hgp tdt nhit vdi cic dudng cong do siu tir telua tai mdi diem do, mat cit dia dien tren toan tuyen do dugc xiy dyng tir td hgp ket qui phin tieh d mdi diem tren tuyen Nbir vay cie bit ddng nhit eiia mdi trudng theo phuong ngang (neu ed) thi phep nghjch dio ID khdng the phat bien duge. Khi mdi trudng ed ciu tnic phiic tap ban nhu mdi tmdng 2D thi ngudi ta phii ip dung phuong phip nghieh dio 2D. Mdt trong nhirng phuong phip nghieh dio 2D thudng duge sir dyng la phuong phip giim du nhanh (Rapid Relaxation Inverse-RRI) ciia Smith va Booker [14] cho phep xiy dung md hinh dja dien giii thich mdt cich ddng thdi tit ci cic dudng cong do siu tir telua tren tuyen. Md hinh ed the duge xiy dyng tir ddng thdi ei hai loai dudng cong dien trd suit PTE va pxM hoac tir timg thinh phin mi ehu yeu li sir dyng eic dudng cong pjM- Do cd the lam hgp tit ci cie dudng cong dien trd suit tai cic diem do tren tuyen nen mat cit dien trd suit thu dugc cho thdng tin tin cay ve cac bit ddng nhit theo phuong ngang tren tuyen do, chinh vi the phuong phip do sau tir telua li phuong phip khi hieu qua trong eac nghien cuu ciu true vd Trai dit trong cie viing cd thay ddi rd ret ve tinli chit dja dien nhu cic ddi dirt gay, cic viing dja nhiet... Dudi diy chiing tdi gidi thieu mdt sd ket qui nghien eiin ehi tiet ciu tnic eic ddi dut gay hoat ddng sir dung phuong phip do sau tir telua da tien binh trong nhiing nim gin diy minh hga hieu qui eiia phuong phip.
3. Cau true sau diit gay So-n La theo so lieu do sau tii- telua
Dut giy Son La la mdt trong nhirng dirt gay boat ddng manh nhat d Viet Nam. Tren ddi nay da xiy ra trin ddng dit M6,8 do Richter vao ngay 24 thing 6 nim 1983 tai viing ddi mii Phuong Pi, huyen Tuin Giio. De tim hieu die tnmg dja dien cua ddi diit giy, ehung tdi di tiln hanh 2 tuyen do siu tir telua cit ngang qua dirt giy d khu vyc xa Pu Nhung (Tuin Giio) va khu vyc Chieng Ve (Mdc Chiu). Tren tuyin Pii Nhung chgn duge 7 dilm do tren do dai tuyin li 4,9 km; tren tuyen Chiing Ve ed 8 dilm do tren do dii tuyin li 6,2 km. Tai moi dilm do chirng tdi tien hinh do bai thinh phan tmdng dien va hai thinh phin tmdng tir theo eic hudng ciia ciu tnic dia chit (B140°), vi theo hudng vu^' JTQC vdi hudng ciu tnic dia chit
Tieu han: Cdc khoa hgc ve trdi ddt ISBN: 978-604-913-016J_
(B50°). Md thinh phan
hinh ciu tnic dja dien cua ddi dirt gay tren 2 tuyin thu duge tir nghjch dao 2D dien trd suit vudng gdc vdi phuong cau tnic dugc trinh biy tren hinh 1.
PCX fm P»i*«>
30M mo
K k o ^ cich (m)
a) b)
Hinh I. Mat cdt dien tra sudt dirt gdy San La theo ket qud phdn tich 2D tdi lieu tir telua a) tuyen Pu Nhung vd b) tuyen Chieng Ve
Mat cit dien trd suit tuyin Pii Nhung cho thiy ring phan tren cua mat cit cd dien trd suit khi eao, hang tram din hing ngan Q.m irng vdi ldp vd ben tren va Idp vd giira, ldp vo ben dudi d do siu 10-30km ed dien trd suit thip hon cd 10 Q.m hoac nhd hon. Ddi dut gay Son La theo diu hieu dia chit d giiia cic diem POl va P02. Tren mat cit dien trd suit dudi diem P02 ed dien trd suit thap hon han so vdi cac diem xung quanh, diy li diu hieu cua dirt gay Son La, vi d vi tri dirt gay dit da bi phi buy, nude ed chiia khoang vit d trong vd cd the tham nhap vao ddi diit gay lim cho dien trd suit cua ddi dirt gay nhd hon so vdi dien trd suit eua dit di xung quanh. Nhd hinh thii thay ddi cua dien trd suit trong mat cit cho phep chiing ta vach ra dirt gay Son La d tuyen Pu Nhung nhu tren hinh 1. Khoang vai km tren be mat dirt gay cd xu the nghieng ve phia diu tuyen tire la hudng ve phia ddng bac, dudi sau hon dirt gay cam gin nhu thing diing vi dat den do sau hon 30km. Ngay d vi tri dirt gay dudng ding tri dien trd suit 10 Q.m d do siu 8 km, phin diu tuyen do siu niy tang nhanh chdng tdi 20km, phan cudi tuyen d do siu tuong ddi dn djnh khoing 12km. Su thay ddi nhanh chdng cua do siu be mat ldp dien trd suit thip d phan diu tuyen ed the lien quan tdi khi ning dirt gay Son La la ranh gidi giiia phire nep ldi Sdng Ma vi rifto Sdng Di. Ket qua phin tich trgng lyc cho 1 biyen cat ngang qua dirt gay San La gin khu vuc Tuin Giio [16] cho thiy phin tay nam dirt gay mat do ldp vd ben tren va ldp vd giira (2,7 g/cm^) ldn hon d phin ddng bic (2,5 g/cm^), phan CO mat do vit chat ldn hon cd the ed dien trd suit cao bon do do rong cua da cd thi nhd ban, ket qua do sau tir telua phii hgp vdi kit qui do dac trgng lyc.
Tren mat cat dien trd suit tuyen Mdc Chau, dudi dilm Cv2 va Cv5 dien trd suit nho hon ban so vdi cae diem xung quanh, tren bin dd dia chit day la vi tri ed diu hieu eua dirt gay Son La. Dang tiec la tuyen do khdng the keo dii d phin diu tuyen vi dieu kien dja hinh va khu vuc bien gidi Viet - Lio. Su thay ddi cua dien trd suit d dudi diem Cv2 vi Cv5 la rit rd r?t d do sau tir khoing I km den khoing 23km, hinh inh cua dirt gay Son La tren tuyin nay la rit rd rang. Dirt gay Son La tren tuyen Mdc Chiu nghieng ve phia ddng bic vdi gdc cim gin nhu thing dimg. Tren hinh 1 dudng ding dien trd suit dudi diem Cv5 thay doi rd ret din do
Hgi nghj Khoa hgc ky mem 35 ndm Vien Khoa hgc vd Cong nghe Viet Nam - Hd Ngi 10 2010
siu khoang 24km, do viy ehiing tdi cho ring dirt gay Son La d vj tri niy cd do xuyen siu nhd hon d vj tri tuyin Pii Nhung, cd le vi viy boat ddng dja chin ciia doan dirt giy Son La d khu vyc Mdc Chiu kem hon d khu vyc Tuin Giio. Be mat ldp dien trd suit thap dudi 10 Q.m nam d do siu khoing 10km. Dudi vi tri dirt gay hi do siu 1km dien trd suit ciing chi cd 10 Q.m.
Chiing ta biet ring ddng dit phii xiy ra trong vung bien dang din hdi ciia vit chit cua vd Trai Dat. Theo sd lieu quan sit duge tai Vien Vit ly dja eiu, chan tieu ddng dat tren cic dirt gay d ddi dirt gay Son La ehi tip tmng d khoing do siu 1-25 km, nhu viy ed the ndi do sau cd 25 km li ranh gidi cua ting sinh chin tren diit gay nay. Theo Touret vi Marquis [18]
neu ldp vd ben dudi d do siu 25-30km ed dien trd suit nhd hon 30 Q.m thi ldp vd dudi niy phai d trang thii chiy deo vi d nhiet do khoing 400°C. Nhu viy ket qui do sau tir telua vi phan bd chin tieu ddng dat cho phep khing djnh ring d do siu 25-30km dudi ddi dut gay Son La khdng xuit hien ddng dat do vat chit d trang thii chiy deo. Nguyen nhan tdn tai chay deo niy cd the li hien tugng ndng chay eye bd do mat Moho ed the ning len vi ldp vd ben dudi chju sy tic ddng cua ddng ddi luu nhiet tir manti, hoac do nhiet va nude giii phdng trong qui trinh bien chat d khu vyc dirt gay, day la nhiing hien tugng tieu bieu trong cic ddi dirt gay boat ddng. Chiing ta se xem mat cat dien trd suit tren mdt dut gay boat ddng khie li dirt giy Lai Chiu-Dien Bien.
4. Cau true sau dut gay Lai Chau-Dien Bien theo so lieu do sau tir telua
Gidng nhu dirt gay Son La, dirt gay Lai Chiu - Dien Bien li dirt giy hoat ddng manh nhat d khu vyc Tiy Bac. Tren ddi diit gay da xuit hien nhieu trin ddng dat: ddng dit Dien Bien nam 1935, M=6,75; ddng dit Na Pheo, ngiy 16/6/1980, M=4,6; ddng dit Lai chiu ngiy 1/1/2001, M=4,2; dgng dit Dien Bien ngiy 19/2/2001, M=5,3. Ciing vdi boat ddng ddng dit cdn nhieu di thudng dja hda d cic khu vyc Lai Chiu, Na Pheo, Pe Ludng, Him Lam; nhieu ngudn nude ndng d Hua Pe, Pe Ludng.. 0 khu vyc ldng chio Dien Bien da tien hinh 2 tuyen do sau tir telua, trong dd cd I tuyen dii 4,6 km cit ngang qua toin bd khu vuc ldng chio gdm 7 diem do. Tai mdi diem do tien hinh do 2 thinh phin dien vi 2 thanh phan tir theo hudng ciu tnic bic-nam (NS) vi theo hudng vudng gdc vdi ciu tnic ddng-tiy (EW). Md hinh ciu tnic dja dien cua ddi dirt gay tren tuyen thu dugc tir nghjch dio 2D thinh phin dien trd suit EW dugc trinh biy tren hinh 2.
Mat cat dien trd suit d hinh 2 cho thiy rang phan tren ciia mat cat cd dien trd suit khi cao, tir hing tram Q.m d viing diu tuyen den hing ngan Q.m d phin cudi tuyen irng vdi ldp vd ben tren va Idp vd giira. Tdn tai vimg dien trd suit thap dudi 10 Q.m dudi diem D24 va D21 thap hon ban so vdi cic diem xung quanh. Vi tri dudng ding trj 10 Q.m dudi diem D24 d do sau khoing 9 km vi dudi diem D21 khoing 10km, vung gidi ban d ben trong dudng dang tri 10 Q.m gin nhu thing dimg d phia dudi giira diem D21 vi D26, phin phia dudi cac diem D24 va D2 nghieng thoai hon lam cho vimg dien trd suit thap dudi 10 Q.m md rdng d phia dudi sau. Vimg dien trd suit thap nay iing vdi viing dut gay LC-DB vi d vi tri dirt giy dat di bj phi hiiy, nude ed chira cie khoing chit trong vd cd the tham nhip vio ddi dirt giy lam cho dien trd suit eua ddi dirt gay nhd hon so vdi dien trd suit eua da viy quanh nhu da thay d mit cit dien trd suit cua dirt gay Son La. Hinh thii phit trien cua ddi dien trd suit thip dudi 10 Q.m nhu d hinh 2 cho ehiing ta thiy dirt gay LC-DB li dirt giy xuyen vd, vdi hudng cam gin nhu thing dirng. 0 dudi diem D27 ciing tdn tai vung cd dien trd suit thip dudi 10 Q.m d do sau 8-16 km, ed khi nang viing nay lien quan tdi mdt dirt giy nhd ban li dirt gay Dien Bien - Pie Nua d ria phia Tiy eua ldng chio Dien Bien, tuy nhien do viec do dae chua cit qua hoin toan khu vuc dirt gay niy nen chiing ta khdng thu dugc hinh inh diy du cua nd.
Tieu ban: Cdc khoa hgc ve trdi ddt ISBN: 978-604-913-OK;J.
NoongLuA^
D26 D21 D24 D23
NoongBoo D22 D25 Lc(P)
W 1,0 U 2,0 2^ 3,0 3^ 4,0 Khoing cich (km)
//i/j/2 2. Mat cdt dien trd sudt dirt gdy Lai Chau-Dien Bien theo ket qud do sdu tir telua
Chiing ta se xem xet mdt mat cit dien trd suit tren mdt dirt gay khie li diit gay Sdng Sii Gdn.
5. Cau true sau dut gay Song Sai Gon theo so lieu do sau tir telua
Mot tuyen do siu tir telua dugc tien hinh tir khu vyc Cu Chi sang Ben Cit cit ngang qua dirt gay Sdng Sai Gdn vdi do dii tuyen li 15,2 km. Viec do dac dugc thyc hien theo hai hudng song song vdi phuong ciu tnic (N150°) v i vudng gdc vdi phuong eiu tnic (N50°). Mat cit dia dien cua tuyen nghien cim thu dugc nhd nghjch dio 2D thanh phin dien trd suit vudng gdc vdi phuong eiu tnic duge trinh biy d hinh 3.
Tren mat cat dien trd suit d hinh 3 ehiing ta eiing quan sit thay mdt ranh gidi thay ddi dien trd suit rit rd ret dudi diem 005, 012 v i 013, ranh gidi nay duge cho li bieu hien eua dirt gay Sdng Sai Gdn, dgc theo dirt giy dien trd suit thip hon xung quanh; dirt gay Sdng Sii Gdn cd hudng cam gin nhu thing dimg v i eiing la dirt gay sau xuyen vd. So sinh vdi cac mat cat dien trd suit d hinh 1 v i hinh 2, thi dien trd suit d hinh 3 ed dien trd suit cao hon nhieu. Ldp dien trd suit thip ed vii chyc den khoing trim Q.m d tren mat cd do day chi khoang vii trim m. Phin ldn mat cit ed dien trd suit tir vii tram den hing chyc ngin Q.m, dgc theo dirt gay vimg ed dien trd suit ed 50 Q.m nam tu do siu 25 km din ban 30km. Nhu viy khdng gilng nhu d mat cit dien trd suit tren cac dirt gay Lai Chiu - Dien Bien hay dirt gay Son La d do sau ldp vd giira va Idp vd ben dudi 10-30km hoac ban khdng tdn tai ldp dien trd suit thip cd mot vii den 30 Q.m, nhu viy ldp vd ben dudi d khu vuc dirt gay Sdng Sii Gdn khdng thi d trang thii chiy deo, dgc theo dut gay hi do sau khoing 1km den 25 km dien trd suit cd hang trim den mdt ngan Q.m, nhu vay ciing khd ed the cd nude khoing thim nhip v i o diit gay, nghTa la do boat dgng ciia dirt giy Sdng Sai Gdn phii kem hon nhieu cac dirt gay Lai Chiu - Dien Bien va dirt giy Son La. Thyc t l tren diit gay Sdng Sai Gdn d khu vuc Viet Nam hoin toan chua ghi nhan dugc ddng dit.
Hgi nghi Khoa hgc ky' niem 35 ndm Vien Khoa hgc vd Cong nghe Viet Nam - Hd Ngi 10 2010
004 012013 009003007
001 S ° " 9 S - ° ° " 002 I 014003 I 015
Ben Cat
10000 O
•O' 0)
c
20000
30000
SW Khoang each (m)
2000 4000 6000 8000 10000
N 6 3 E Hinh 3. Mat cdt dien tra sudt dirt gdy Sdng Sdi Gdn
theo ket qud do sdu tir telua 6. Ket luan
Tir cic ket qui da neu cd the nit ra mdt sd ket luan sau:
- Phuong phip do sau tir telua vdi viee do dae eic tmdng tir vi tmdng dien ty nhien trong dai chu ky 10"^ den 10^ giay la mdt phuong phap rat hiru hieu cho phep xie dinh hinh inh dja dien cau tnic siu cua cic dirt giy dia chat. Tren eic mat cit dja dien vj tri dirt gay dugc xie dinh bang ddi dien trd suit giim do nggt so vdi mdi tmdng xung quanh.
- Mat cit dien trd suit thu duge bing phuong phip do siu tir telua d cic ddi dut gay hoat dgng cho thay dgc theo dirt gay dien trd suit thip cd mdt vai Q.m duge giii thich bing su luin chuyen cua nude khoing trong ddi dirt gay, Ii dau hieu quan trgng trong viec dinh gii miic do hoat ddng ciia dirt gay; dien trd suit dgc theo ddi dirt gay eing nhd, dirt gay ed the cd do hoat ddng eing manh.
- d do sau d ldp vd dudi 25-30 km trong khu vuc dut gay ma dien trd suit nhd dudi khoang 30 Q.m, thi ddng dat khd cd the xiy ra dudi do sau nay, do trang thai vat chit d day cd the d trang thai chay deo, it cd khi ning tich luy img suit. Nguyen nhan cua su chay deo cd the lien quan tdi eac qua trinh bien chat giii phdng nhiet vi nude d lin can dut gay hoac su nang len cue bd ciia Manti gin khu vyc dut gay.
Tiiu han: Cdc khoa hgc vi trdi ddt ISBN: 9 7 8 - 6 0 4 - 9 1 3 - 0 1 6 ^
TAI LIEU THAM KHAO
1. P. A. Bedrosian, M. J. Unsworth, G. D. Egbert, C. H. Thurber, ""Geophysical images of the creeping segment of the San Andreas fault: implications for the role of cmstal fluids in the earth process", Teetonophysics, 2004, 385, 137-158.
2. L. Cagnia, ""Basic theory of magnetotelluric method of geophysical prospecting", Geophysics, 1953, 18, 605-635.
3. Nguyen Vin Giing, Ding Thanh Hii, Ly Minh Ding, ""Nghien ciru ddnh gid tiem ndng mrac ngdm tgi Dd San, Hdi Phdng", Tap ehi Cac Khoa hgc ve Trai Dit, 1994,
16(4), 147-151.
4. M. Ichiki, M. Mishina, T. Goto, N. Oshiman, N. Sumitomo, and H. Utada,
""Magnetotelluric investigations for the seismically active erea in Northern Miyagi Prefecture, Northeastern Japan", Earth Planets Space, 1999, 51, 351-361.
5. M. Ichiki, N. Sumitomo, T. Kagiyama ""Resistivity stnictuer of high-angle subduction zone in the Southern Kyushu district. Southwestern Japan", Earth Planets Space, 2000,
52, 539-548.
6. M. Ingham, ""High resolution electrical imaging of faults zones", Phys. Earth Planet.
Inter., 2005, 150,93-705.
7. C. Lemonnier, G. Marquis, F. Perrier, J. P. Avouac, G. Chitraka, B. Kafle, S. Sapkota, U. Guatam, D. Tiwari & M. Bano, ""Electrical structure of the Himalaya of Central Nepal: high conductivity around the mid-cmstal ramp along the MHT\ Geophys.
Res. Lett., 1999, 26, No21, 3261-3264.
8. Le Huy Minh, Vd Thanh Son, Nguyen Chien Thing, Nguyen Trgng Vii, Nguyen Dinh Xuyen, G. Marquis, Trin Vin Thing, ""Mat cdt cdu true dja dien dai dirt gdy San La theo ket qud do sdu tir telua". Tap ehi Cae Khoa hoe ve Trai Dit, 2008, 30(4), 491- 502.
9. Le Huy Minh, Pham Vin Nggc, D. Boyer, Nguyen Nggc Thuy, Le Tmdng Thanh, Ngd Vin Quin, G. Marquis, ""Nghien ciru chi tiit dirt gdy Lai Chdu - Dien Bien bdng phuomg phdp do sdu tir telua". Tap ehi dia chit, 2009, A311(3-4), 11-21.
10. A. L. Padiha, I. Vitorello and P. A. Brito, ""Magnetotelluric soundings across the Taubate basin. Southeast BraziF, Earth Planets Space, 54, 2002, 617-627.
11. [M. A. Perez-Flores & A. Sehultz, ""Application of 2-D inversion with genetic algorithms to magnetotelluric data from geothermal areas", Earth Planets Space, 2002, 54, 607-616.
12. Pham V. N., D. Boyer, Nguyen Van Giang et Nguyen Thi Kim Thoa, ""Proprietes electriques et structure profonde de la zone de faille du Fleiive Rouge au Nord
Vietnam d'apres les resultats de sondage magneto-tellurique", C. R. Acad. Sci. Paris, 1995, 320, serie Ila, 181-187.
13. Pham V. N., D. Boyer, P. Therme, X. C. Yuan, L. Li & G. Y. Jin, "Partiel melting zones in the emst in Southern Tibet from magnetotelluric reuhs", Nature, 1986 319, No6051,5;6'-i/^.
14. J. T. Smith & J. R. Booker, ""The rapid relaxation inverse for two and three dimensional magnetotelluric data", J. Geophys. Res., 1991, 96, NO. B3, 3905-3922.
Hgi nghj Khoa hgc ky' niem 35 ndm Vien Khoa hgc vd Cong nghe Viet Nam - Hd Ngi 10 2010
15. Nguyen Thi Kim Thoa, Nguyen Van Giing, Pham Van Nggc, D. Boyer, ""Khdo sdt nuac ngdm bdng to hcxp cdc phirang phdp tir telua vd do sdu dien", Tap chi Khoa hgc Cdng nghe, 1994, XXXII 2, 51-61.
16. Cao Dinh Trilu, ""Sir dung phirang phdp vi trgng lire nghien cim dai phd hiiy cua dirt gdy San La tgi viing chdn tdm ddng ddt Tudn Gido", Tap chi Dia chit, 2005, A286,
29-38.
17. Doin Vin Tuyen, Dinh Van Toin, Nguyen Trgng Yem, Pham Vin Nggc, D. Boyer,
""Ddc diem cdu tnic sdu dai dirt gdy Sdng Hdng tren khu vuc Tdy Bdc vimg triing Hd Ngi theo ket qud phdn tich tdi lieu tir telua". Tap chi Cic Khoa bge ve Trii Dit, 1999, 21(1), 3/-i5.
18. Doan vin Tuyen, Dinh Vin Toin va Nguyen Trgng Yem, ""Ddc diem cdu true dja dgng lire dai dirt gdy Sdng Hdng tren ca sa tdi lieu tir telua". Tap ehi Dia chit, 2001, A267, 21-28.
19. M. Unsworth and P. Bedrosian, ""On the geoelectric structure of major strike-slip faults and shear zones", Earth Planets Space, 2004, 56, 1177-1184.
20. K. Vozoff, "The magnetotelluric method in the exploration of sedimentary basin", Geophysics, 1972, 37, No 1, 98-141.