Tap cU Cac Khoa hoc ve Trai Dat, 37 (1), 57-62
(VAST)
Vipn Han lam Khoa hpc va Cong nghp Vipt Nam Tap chi Cac Khoa hpc wk Trai Dit Website: http://www.vjs.ac vn/index php/jse
iKk qua do sau tir telua tuy6n Quan Son - Quan Hoa, tinh Thanh Hoa
ve Thanh Scm', Le Huy Minh', Guy Marquis^, NgiQ'ln Ha Thanh', Truong Quai^ Hdo', Nguyin Ba Vinh', Dao VSn Qi^en', Nguyin CMen Thdng'
' Vi^n Vdt lp Dia cdu, Vien Hdn Idm Khoa hpc va Cdng nghi Viet Nam
^Vt4n Vgt ly Dia cdu Strasbourg, CpnghdaPhdp Ngay nh^n bdi: 18-7-2014
Chap nhSn ddng: 10-2-2015
ABSTRACT
The results of deep magnetotelluric sounding on profile Quan Son - Quan Hoa in the province Thanh Hoa In 2013 the 12 stations of deep magnetotelluric sounding (MT) by Geo-mstrument (made m France) on the profile about 25 km of long in the Quan S o n - Quan Hoadislncts of province Thanh Hoa has been carried out The data was processed and 2D modeled by Geotools software. The obtamed 2D resistivity crosS'Section until 30 km of depth represents structural features of earth crust here' High resistivity in the upper part of section until 10 -15 km of depth, indicates the consolidated rocks; low resistivity is distributed in lower part of section may be reflects the rock containing water relating to tectonic - geodynamic conditions, geothennal regime of earth's crust Two low resistivity zones in center of profile with vertical development lightly mdicate the Songma and the Sopcop - Quanson faults respectively, their positions are comcided with the distnbutions of these faults on the geological map.
©2015 Vietnam Academy of Science and Technology
1. Mtf dau
Phuong phip do sau tir telua \k mpt trong nhihig phuong p b ^ dia vat ly co dp s3u khdo sat Idn den hang ch^c km. Tir cdc ehudi so Upu ghi dao dpng cda tnifmg dipn va truong tu thu dupc tgi m6i diem do c6 th^ thu dupc cac du6ng cong dipn trd suat bi^u kien va cdc duimg cong pha phu thupc vao tan s6 phdn anh s\j bien doi tinh chat cua moi trutmg theo chieu sau (Cagnia, 1953; Vozoff, 1972). Phirong phap ndy dS dirpc dp dung c6 hipu qud va cung c^p nhung thong tin mcri ve d$c diem c^u true sdu vd ddi dut gdy kien t^o trong v6 Trdi Dat i3 mpt so noi tr&n Idnh tho Vi^t Nam tir nhung ngm 1990. Th\ic hipn de tM cap Vipn Han lam
*T6c gia lien he. Email* v
Khoa hpc va Cong nghp Vipt Nam "Nghifin cmi can true sau v6 Trdi Dat khu vvc doi diit giiy Song Md bdng phirong phdp thdm do sau tir tellua", laifi.
tuyen do sau tir telua d khu vuc Quan Son - Quan Hoa thupc tinh Thanh Hoa d3 dupc trien khai. Bai bdo ndy trinh bay cac ket qud do, phan dch tai lipu va minh gidi v^ d$c dilm c^u tnic v6 Trdi D^t is khu v\rc nghien cuu.
2. Thiet bi do d^c va ky thu^t do
Thiet bi diuig de thu thdp s6 hpu la tr^m do sdu tir tellua Geo-Instniment cila Vipn Vdt ly Dja cau Paris vipn trp cho Vipn Vdt \^ Dja c^u. Id trgm do sau tir tellua hipn ddi ghi so duy nhat d Vipt Nam hi^n nay. Thiet bj gom: tr^m do trung tdm, ghi lim giii s6 lipu tren may tinh, vd cdc thiet h\ khac' cdc dipn cue, cac dAu do tu, day noi cdc di§n c\ic,...
V. T. Son\a nnk/T^p chi Cac Khoa hpc vl Trdi Dat, T ^ 37 (2015) Cdc dipn cue su dung tiong do sdu tu telua la cdc
dipn cue khong phan cue co the tiep xiic rat nho (mpt vai mV) vd dp troi rdt yen. Dien cue cong nghipp ciia Phap san xuat la rat tdt (thg phdn cue dudi 1 mV), tuy nhien vipc bdo quan phdi rat can than, va co gja thanh rat ddt, de gidm bot chi phi, chung toi dd tu 1dm lay dipn cue theo phucmg phdp Hxajc sii dung d Vien Vat ly dia eau Paris vdi nguyen lipu Id thach cao, thing djch PbCU va CaCl2 thay cho PbCl2/NaCl/HCl. Trong qua trmh do dac va di ehuyen, ede dipn cue dupe ddt trong dat set boa nude de ddm bdo tiep xiic tot vdi ddt, cung nhu it\x(jc ehe day de tranh mua gio khi do dac. Dipn cue phdi dupc Idlm tra can than moi buoi sang tnrdc khi tiln hanh di tdi diem do, cdc cdp dipn circ co the phan cue cd mpt via mV co ibk chap nhdn dupc cho diem do trong mpt ngay. Doi vdi ede vimg c6 dipn trd suat cao, tin hipu dipn telua Idn, cdc dudng telua co the chi keo dai cd l(K)m, vdi moi trudng dipn trd sudt thdp, tin hipu dipn telua nhd, chieu ddi dudng telua phdi tang len 160-180m; khu vuc diem do sdu hi telua phdi tuong doi bang phdng (khu vuc rapng khd sau thu
dai phdi diing thudng la khdng cao nhu nhung ngay trudng tu yen tuih, t>' so tin hipu/nhieu Idn, do do vipc tien hdnh dosdu tir telua tiong nhirng n g ^ ndy la tuong ddi de dang, chat lupng tai lieu thudng tot hon.
Cac diem do sau tu telua phdi trdnh dupc cac nguon nbifiu dipn tir: cac khu vue dan cu, eac dudng day cao the, eac viuig cong nghipp, cac dudng giao thdng, cdc thap phat sdng nhat Id cac thap phat song Vi£n thdng. Chi tien hanh trong dilu kipn thoi tilt kbi trdi khdng mua, khdng co sam chdp (nguon song dipn tii do sam chdp khdng thod man dieu kipn song phdng, khdng cd gid Idn (lam rung day noi) (Cagnia, 1953; Vozoff, 1972;
Quomarudin, 1994).
Tren thuc dia, thiet bi do 2 thanh phan dipn va hai thanh phan tir dupe dat Uieo hai phuong vudng goc vdi nhau, mdt hudng dupe chpn song song vdi phuong eau tnic (gpi la htrdng NS) va mpt hudng dupc chpn vuong gdc vdi phuong eau tnie (gpi la hudng EW). Ddi chu ky lam vipc cila thiet bi (jeo- instniment la tu 10'^ den 10^ gidy. De han ehe thdi hoach Id tot nhat). Sau khi chdn cdc dipn cue can gian do va tilt kipm bp nhd cac nha khoa hpc Phdp kilm tra thi phdn cue va dipn trd suat gjiia cac cap da Iva chpn duoc phuong phdp ghi so hpu hpp ly dipn cue, neu the phan cue giua cdc c^p dipn cue theo 5 ddi chu 1^ sau:
CO khodng dudi 10 mV va dipn trd suat cd mpt vai k£l cd du dilu kipn thu thap so lipu bdo ddm chat lupng.
Cae dau thu tir dupc sdn xuat tai Trung tam Dja vat ly tai Garcy (?hsp) cd dd nbgy cd 10"- nT, day noi tu dau thu tir tdi mdy ghi la 50 m, ddm bdo tranh dupc cac nguon nhilu tir nhd d gan vi tri ddt tram ghi
Tin hipu dipn tir gom hai thanh phan dipn Ex, Ey vd hai thdnh phan tir Hx, Hy tir cac ddu do dirpc dua vdo trgm ghi tnmg tain, sau khi dupc khuyech dai, dirpc lpc, hien thi tren man hinh mdy tinh va ghi vdo bd nhd. Trgm do tu telua Geo- Instrument co thi khi^ech dai tdi 3 tripu lan, tuy nhien vdi dirdng telua dai cd 150m dp khuyech dgi cue dai phdi su dpng thudng cd 30.000 lan hogc nhd hon, nghia Id vdi thilt bj nay hodn todn cd thi ghi nhan dupc tin hipu dipn tu chi cd vai phan nghin mV Lmi y rdng dung dd khuyech dgi cdng cao thi nhieu dirpc khi^lch dai cang Idn, sd lipu do cd dp sai sd cdng Itjn. Do dd can phdi dat do dai
- GI: tu 10"^ din 10"' gidy, khodng each lay man Id 0,2 ms,
- G2: tir 10'~ den 1 giay, khodng each 1^ miu Id 2 ms,
- 03: tir 10"^ din 10 giay, khoang cdch 1^ mdu la50ins,
- G5: tCr 1 den 100 giay, khodng each lay mau la 500 ms,
- G7: tii 10 din 1000 gi^, khodng each ld>
mau Id 2500 ins
3. Ket qua do sau tir telua tuy^n Quan Som - Quan Hda
Tren tuyen do sau tu telua Quan Son - Quan Hda vdi chieu dai khodng 25km thuc hipn 12 diem do, dp cao dja hinb cac diem do thay doi trong khodng ttr 110m din 251m (hinh I). Tai timg diem do sau 2 thanh phan trudng dipn va 2 thdnh phan trudng hi dupc bd tri theo hai hudng vudng gdc dudng telua dii ddi vd phai thay doi cho phii hpp vdi nhau: hudng song song vdi phuong c4u triic cd tuy tneo dilu kipn diem do dl dp khuylch dai phuong vi 140° so vdi phuong bdc kinh tuyen va khdng phdi dimg qud Ida Trong nhung ngay nhilu mdt hudng vuong gdc vdi phuang can tnie cd loan tir manh, tin hipu dipn tu manh, dp khuylch phuang vj 50" so vdi phuang bdc kinh tuyen.
Tgp chi Cac Khoa hpc vl Trdi Ddt, 37 (1), 57-62
Hinh 2 la mat cat dipn trd suat bieu kien thdnh phdn EW, hinh 3 ta mdt cdt dipn tid suat bieu kien thanh phan NS cho thdng tin so bp ve phan bo dipn trd sudt phdn anh dac diem eau true dipn tid cua vd Trdi Dat theo chilu sau dudi tuyen do. Can triic dipn trd su^t thap hon phdt triln theo chieu sau phdn bo dudi cdc dilm Ql, Q5, Qll va Q12. Tren cdc tdi Upu dja chat va dja vdt ly khac eac diem Ql, QS
phan bo gan diit gay Song Md, ede diem Qll, Q12- gan diit gf^ Sop Cdp - Quan San. Cau true dipn trd su^t thi hipn ddi dut gdy Sdng Md ed thilt dipn Idn ban hdn so vdi e^u tnic dipn ttd suat trong ddi dut g ^ Sop Cpp - Quan Son. Hinh thai can tnic cua hai mdt cdt ed dang tuong tu cho ph6p nhan dinh tdi Upu do cd chAt lupng tuong doi tot, bdo ddm dilu kipn de tiln hanh phan tich djnh lupng.
K h o a n g e a c h ( k m )
Hinh 2 M$t cit dien tro suit bilu kiln thanh phin EW tuyIn Quan Son - Quan Hoa
V. T. San vd nnk/Ttqi chi Cac Khoa hpc ve Trai Dat, Tj^ 3 7 (2015) Quan Son Quan H6a
n i Oil rts m
QIO L g (/>
K h o a n g each (km)
Hinh 3. Mat cat dien tro suSt bilu kiin Ihanh phSn NS, tuyen Quan Son - Quan H6a 4. Ket qud phdn tich theo md hinh 2D va lu^n
gidi tdi lipu
Mdt cdt dipn trd suat bieu kien tir tdi hpu thuc tl the hipn kha ro tinh phan di ciia mdi trudng theo chilu ngang lien quan den cac dut gay kien tao. Vi vdy phan tich tdi Upu theo md hinh 2D la thich hpp (Jones, 1992; Vozoff, 1972).
Chiing tdi su dung mem Geotools cho phep thuc hipn nghjch ddo 2D bang phuong phdp gidm du nhanh (Rapid Relaxation Inverse - RRI) (Geotools Corporation, 1997; Smith et al., 1991) doi vdi so Upu timg thdnh phan NS hay EW, hoac dong thdi ed hai thdnh phan NS \a EW. Kit qud phdn rich bdng phuong phap nghtcb ddo 2D vdi so lipu do tren tuyen do sau tii teUua Quan Son - Quan Hda dupc lua chpn la md hinh phan bd dipn trd suat tdi dp sdu 30km dupc trinh b ^ d hinh 4.
Gia trj dipn trd suat eiia vd Trai Dat d ddy thay doi tir vai i l m (ben dudi dilm Q12 va Q3) tdi hdng ngdn £l.m is phan tren vd tdi dp sau lO-lSkm, d dp sdu dudi kbodng 20km dipn trd suat tuong ddi thap chl cd vai chuc Cim (3 phan be mgt dp sdu nhd hon khodng 1 km dipn trd suat nhd han phan ben dudi phdn anh tinh chat \d phong hda. Bieu hipn eiia dirt gdy Sop Cpp - Quan Son vd diit gay Song
Ma tuang ling cdc ddi dipn trd suat thap hon h ^ so vdi hai ben ria. Diit gdy Sop Cpp - Quan Son ndm d vj til gan diem Q12, dut gay Sdng Md ndm d vj tri gan dilm Ql (ve phia dilm Q5) phii hpp vdi vj tri phdn bo cdc diit gdy ndy tren bdn do dja chat. Theo kit qud do tir telua cdc dirt gdy ndy ed hudng cdm gan nhu thdng diing vd phdt triln den dp sau hon 30km. Gia tri dipn trd suat trong ddi diit gdy th^p hon bin so vdi hai b€n ria Id do nude cd khodng chat is trong vd cd the tham nhdp vao khe rdng ciia da bj pha huy, ddi dut gdy sau cung thudng Id dudng din ddng nhi^t tu dudi sdu Un (Ingham, 2005; Le Huy Minh va nnk, 2011; Pham et al., 1995, Doan Vdn Tuyen, Dinh Vdn Todn, 2011; DodnVdnTuyenvd nnk, 2001).
Kilu can true vd cd ldp dipn trd suit ben dudi nhd ban ldp vd giiia dupc gpi Id cau tnic vd PhaneroMi (Jones, 1992; Touret et al., 1994). t6n tai phd bien, quan sat dupc d nhieu vimg tren the gidi. d kieu cau tnie vd ndy vipc xdc dinh ranh gidi Moho tii tai lipu tir telua se kho khdn vi su chenh tpch dipn lid suat giua Manti va Idp vd b€n dudi kem ro rpt, thdng tin ve mdt Moho chl cd the thu dupc mpt each tin c ^ tii phan tich so U^u dja chan thdm dd sau.
60
Tap cM Cac Khoa hoc ve Trai Dat, 37 (1), 57-62
g l 2 y x Q5 •' QIO
• ^
fSi."
I
^
Khoang cAch (km I
764 501 329 215 141 92,6 60,7 39.8 26 1 17.1 11.2 7.36 4.B2 3.16
Hinh 4. Mit cM dia dien tuyen Quan Son - Quan Hoa, kit qua nghich dao 2D 5. Ket luan
Da thvc hipn 12 diem do sdu tii telua trea tuyen Quan Son - Quan Hda la mpt npi dung cua de tai
•'Nghien ciiu can tnic sdu vd Trai Dat khu vuc ddi dut gdy Sdng Ma bdng phuong phdp thdm dd sdu tu teUua".
Kit qud phdn tich tdi Upu tir telua theo md hinh 2D Id mat cdt phdn bo dipn trd suat theo chieu sdu din 30 km dudi tuyIn do cd gia tri tu vdi Q.m tdi hang ngan fl.m Phan tren vd tdi dp sdu 10-I5km, dipn trd suat rat cao phdn anh dd rdn chde, d dd sdu dudi khoang 20km dipn trd suat tucmg doi thap chi cd vdl chyc 0.m ed thi phan anh trang thai deo, chira nude ciia da hdn quan den dieu kipn kiln tao- dja dpng luc. ehi dp dja nhipt ciia vd Trai D^t Hai
ddi dipn trd suat rat thap phat trien theo chieu sau d giira tuyen do Id bilu hipn ro net ciia dut gdy Sop Cpp - Quan San va dirt gay Sdng Md phii hpp vdi vi tri cua cac dut gay nay tren bdn d6 dia ch^t.
Phuong phap tir telua vdi cdc thilt bj hipn cd a Vipn Vdt ly Dia cau da thuc hipn cd hipu qud trong nghien cuu can tnic sau vd Trai Ddt vd xac djnh eac }'eu to can tnic ciia ddi dut gdy kiln tao cho gidi quyet nhipm vp ciia de tai d khu vuc nghien cuu vd cd the ap dung cho cdc \Ting khac tren lanh thd Vipt Nam.
Bdi bdo Id mdt phan ket qud thuc hipn ciia de tdi cdp Vipn Han lam Khoa hpc va Cdng nghp Vipt Namnias6VAST05.06/12-13.
V. T. Son va nnk/Tap chi Cdc Khoa hpc vl Trdi Ddt, T ^ 37 (2015)
Cagnia L., 19S3: Basic dteory t^ magnetotelluric mettiod of geopfaysical pro^iecting, GeofAystcs, 18,605-635.
Geotools Cofporatiini, 1997: ( k o t o o l s M T U s e r ' s guide.
Ingham M., 200S: High resolution electrical i m a g n ^ of faults zones, Phys. Eaifli Planed Inter, 150,93-105.
Jones A., 1992: Electrical craiduciivity of the contmental lower crust Contiiiental t o w n Crust, edited by D. M. Fountain, R.
J. Annihis and R. W. Kay.
Le Huy Mmh. Dinh Van Toan, V6 Thanh Son, Nguyin Chien Thing, Ngu>ln Ba Duin, Nguyin Ha Thanh, Le T n i o i ^ Thanh, Gu> Marquis, 2011 Ket qua xir ly bua>c diu sd U8u do sau tu tellua tuy€n Hoa Binh - Thai Nguyen va tuyen Thanh Hoa - Ha Tay Tap chi cac Khoa h^c ve Trai Dii, 33(1). 18-28
Pham V. N., Boyer D., Nguyen Van Giang el Nguyen ThJ Kim Thoa, 1995 Propnetes electriques et stnicture profonde de la zone de faille du Fleuve R o v ^ au Nord Vietnam d'apres les resuhats de sondage magneto-tellunque, C R.
Acad. Sci Paris. 320, serie Da, 181-187
Quomamdin M., 1994: Proprietes dectriques et sHuctures de la o o u t e en France, (Pms^anaoes ECOTS, G P F ) d'apres les resultals de sondage magneto^ellurique. These, Umversite Paris 7-
Smttfa J T & Boekex J. R., 1991: The r ^ d relaxaticm inverse for two and three dimensiraial magoetoteUuric data, J.
Ge<vhys. Res., 96, N O . B3,3905-3922
Touret J. I . R. et Marquis G , 1994 Ruides piofondes et conductivite eleclrique de la crtnite continentale inferieure, C R. A c a i SCL Paris, 318, Serie II, 1469-1482.
E>oan Van I \ i y ^ Dinh V o i Toan, 2011 Dac dilm c i u true 3o d i n dien va moi quan he voi dj diirinig (fia nhiet o dm diit gay Song Hong. T ^ chi Cac Khoa hoc v i Trai Dit, 33(2X 10-17
Doan Van Tuyen, Ehnh Van Toan va Nguyin T r ^ i g Yem, 2001: Bac <£em c i u true ^ a d&ig luc doi dut gay Song Hong tren cu sd tai Ueu tii tehia. T ^ chi Tha d i i t , A267, 21-28
Vozoff K-, 1972. The magnetotellunc mefliod m the exploration of sedimentary' basm Geophysics. 37, No I, 98-14L