A恥恥融龍麗k職膿躍騰灘e鵬s F暇fa翻醗睡恥⑪酋恥e置醜丁眼艦ey

Bulletin of the Geological Survey of Japan，voL41（3），p．99－114，1990 539．128．4551．243．1（560－17） A恥恥融龍麗k職膿躍騰灘e鵬s f暇fa翻醗睡恥⑪酋恥e置醜丁眼艦ey Hirokazu KATo＊，：Kan KAToH：＊＊，Aykut BARKA＊＊＊and Ismail Ku婁gu† KATo，H．，KAToH，K．，BARKA，A．and Ku婁gu伊1．（1990） Alpha track measurements for faults in northem Turkey．B％ll．0601．S％7∂．如醐，vol．41（3），p．99－114． Abs色盟c重：Two kinds of methods of alpha track measurement were carried out for faults inclu（1ing earthquake faults，active faults and non－active geological faults in northern Turkey．One is the“cup method”for detecting the fault trace and the other is the“pipe method”for evaluating the fault activity。， The results by the cup method show that the alpha track measurement is useful to detect not only active faults including earthquake ones but also non－active ones even in the region containing a little radon．They also show the good reproducibility of the alpha track measurement if they are measured in nearly the same temperature condition． The results by the pipe method show that the seasonal change depended on the temperature mainly．But in both of two methods，the underground water supply must be taken into consideration before the evaluation of fault activity． In Mekece region，northwestem Turkey，the seismic gap area of one branch of the North Anatolian Fault Zone，the maximum alpha track density obtained by the both methods is abnormaly high．Furthermore，the result by the pipe method shows the highest value even in winter．These facts indicate that this branch fault of the North Anatolian fault is very active． The authors carried out the geological 夏．亙醜tro西盟e髄o醜 investigation of some faults including earth－ quake faults．and active faults in the North The North Anatolian Fault Zone，about1， Anatolian Fault Zone in northem Turkey， 200 kilometers Iong，is a right lateral employing the alpha track etching method． intracontinental transform bomdary between In recent years，measurements of subsur－ the Eurasian and the Anatolian Plates in face ra（10n concentration have been used to Turkey．This fault zone trends E－W in gen・ detect faults，particularly active faults and to eral with a slight convex to the north in its predict earthquake occurrence （e，9．KING， central part．The seismic activity has been 1980）． intense along this fault zone，a．nd the we11－ Measurements of changes in radon concen－ known earthquake sequence between 1939 tration by the alpha track etching method and1967produced almost continuous surface were carried out in the search for the follow－ breaks，shifting from east to west with age ing faults． along the main part of this fault zone． a） surface breaks resulted from the 1939 Erzincan Earthquake at the northwestem ＊Geology Department margin of the Erzincan Basin，＊＊Environment Geology Department b）surface breaks resulted from the1944 榊（former）General Directorate of Mineral Gerede－Bolu Earthquake to the west of Bolu Research and Exploration（MTA） †General Directorate of Mineral Research and and the active fault segment showing the Exploration（MTA） creep movement at Ismetpa多a，一99一 Bz61」6ガ％（ゾ孟h6 G60Jo9ぢ6αl Sz67z76ッ ρプノ41）ごz％， Vてol．41，〈ろo．3 EURASIAN（BL継＿SEA）PLATE l of Turkey（MTA），Ministry of Energy and 葬…華欝1織！昌 Natural I之esources， Turkey， entitled in “Research on earthquake faults，active faults and earthquake prediction” （1982－1984fiScal ～乱、、、滞K匿 years）and“Research on Quatema．ry crustal 雇ア movement and earthquake prediction”（1985－／ ARABIAN 1987fiscal years）．These projects have been 博R、c慧詫翼ノκ10／ △PLATE conducted within the framework of“the Insti－ tute for Transfer of Industrial Technology PL醒E ・（ITIT）Project”organized by Intemational Fig．1Map showing investigated areas．A black 幽 Research and Dovelopment Cooperation Divi－ arrow indicates slip sense of transform sion，AIST，MITI，Japan． fault and a white arrow indicates that of plate motion．NAFZ：North Anatolian The authors are indebted to Mr．E．Tsu－ Fault Zone，EAF：East Anatolian Fault． kuda of the Geological Survey of Japan for the setting the pipes of alpha track measure－ ments in Turkey．We also wish to thank c）newest surface breaks resulted from the Messrs．1．gHAKMAK and H．Sov of MTA for 1983Horasan－Narman Earthquake to the their help，kindness and warm welcome． east of Erzurum in eastem Turkey， d）act圭ve fault segment at the one branch of 麗：。 Pr直醜c亘瞬e o£ a恥臨匙 tr我ek etch亘ng the NorthAnatolian Fault Zone near Mekece 朧e蝕憾 in northwest Turkey，where an earthquake occurrence is afraid in the near future， Radon measurements are carried out by e）non－active reverse faults in the SinoP detecting alpha particles which are emitted region facing the Black Sea，100kilometers from radioactive decay of radon and its north of the North Anatolian Fault Zone． daughters．As the can。ier fluid including those These surveyed areas are indicated by alpha particles flows up through faults and squares in Figure1． associated fractures in the basement rocks Most results of alpha track measurements and covered sediments，the radon concentra－ in Turkey have been already published frag－ tion is expected to attain a maximum value mentarily（KATo，1984，1986；KAToαα1．， on the fault trace． Radon concentration 1985，1989），however enough consideration changes in response to the vertical flow of was not made．The authors outline some subsurface fluid occurred in association with faults described previously as metioned above earthquake faulting and is expected to in northem Turkey，compile those prelimi－ increase markedly just before an earthquake． nary results of alpha track measurements by The authors tried two methods of alpha the cup method，and important remarks track measurements as shown in Figure2． obtained by the pipe method and discuss Both methods use small strips of cellulose better way for earthquake prediction． nitrate film which is sensitive to alpha radia－ This study is a part of the joint research tion，and explained as follows，here temporar・ projects operated by the Geological Sur▽ey of ily called the cup method and pipe method． Japan（GSJ），Agency of Industrial Science Cup method：This is an easy and useful and Technology（AIST），Ministry of Intema－ way to detect the fault trace．Small plastic tional Trade and Industry（MITI），Japan，and cups to which inside bottom film strip is Mineral Research and Exploration Institute attached with adhesive tape，are placed 一100一ノ1々）hごz渉名αo左 ηz6㏄銘γε盟z6η孟sノわ7カ％」云s わz7zo7孟h67％ Tz6名たツ（κごz∫0 6オごzl．） Pl麗睡丁開OD CUP繭妊丁開OD particles generated by radon isotopes．The rub，ber5曾◎pper alpha tracks are counted under the micro－ scope and calculated by T．D．＝N／（S×T） where T．D．is alpha track density，N is the number of tracks，S（cm2）is area of the film and T is the exposure time（day）．Obtained track density represents the average concen－ tration of radon isotopes at the measuring point．麗．：瞭z甑a囎：Regi樋亘盟一l Geo恥gic島璽我脳丑 se飽朧o且09亘e翻 set回崩囎gs The Erzincan Basin is one of the Neogene－ Quatemary intramomtain basins along the North Anatolian Fault Zone．The Erzincan Basin measures about50km in length and10 皆6c謂 km in width．The basin is situated at1，150m－ Fig．2 Schematic illustration of two kinds 1，130mhighabovesealeveL of alpha track measurement（pipe Miocene marine sedimentary rocks mcon－ method and cup method）。 formably overlies the basement rocks of pre－ Neogene age． upside－down in shallow holes at a depth of Volcanoes of、Pliocene－Pleistocene age with about a few tens centimeters．They are well preser▽ed conical shapes are arranged spaced at intervals of about a few meters on sporadically on the subsidiary faults which a line which is normal to probable fault trace， mn nearly parallel to the North Anatolian and then are covered with soil and rock frag－ Fault Zone．These volcanoes are composed of ments whose thicknesses are about10centi－ a wide variety of rocks facies such as meters，and are retrieved about one week or rhyolite，dacite and andesite． more later． The basin is filled with Holocene gravels in Pipe method：At one site radon concentra－ which minor faults develop associated with tion is to be measured repeatedly in such a the active movement of the North Anatolian long term as half year to about a year by this Fault Zone．The Erzincan Earthquake whose method because retriving and changing films magnitude was7．90n a Richter scale occur－ is much easier than the cup method．Plastic red on26December，1939aromd theErzincan pipes with a diameter of about6centimeters Basin in eastem Turkey，although its precise and a length of about50centimeters are epicentral situation may not be reliable．This placed on and arom（1a fault line。The film earthquake produced a350km long fault strip is suspended from the rubber cap put on break between Erzincan and Amasya．The the top of the pipe and is replaced to new one maximum horizontal displacement of right for each measurement。 Iateral sense is about350cm and the maxi－ Retrieved films are processed in 20％ mum vertical displacement of south side up is NaOH solution for100minutes at60。C to about200cm（KETIN，1948）． produce visible track－1ike images of alpha The Erzincan Basin is situated along or 一101一 Bz61」θ’1％（～プ孟h6 （セoJo9／641S％7z／6ッ（ゾノ4ψθn，レリ乙4ヱ，．八石o．3 2⑯⑪m・臨1曜眉5 負恥観唱騰冨 3。3：：：：言。39：匿。馨23● 百・㊧鞠趣聡 5⑪ ｝恕臨1回r 、ヴ＝ F 注昼竈騒層⑪ 唱3 5m 』胸k鵬 3⑭。45’醐．輪鞭欝縫・・鷺レ㌧嬉レレ、誓、レ唱5⑪ 工D．／’ 3雪も⑭，匿騰撫鋸、賜睡r ロ髄⑪ 鵡’、！，， ’趨ノドぎ嬢”・ンーマ＝臼魯幅！ 5 奮 2 5 囁 7 IF 皿皿圏幽幽團冒圃占鼠層魑 5鵬躯琶 Fig。3 Simplified geologic map of the Erzincan region with results of the alpha track measure－ ments（modified from KATo，1984）．1：Pre－Neogene basement rocks，2：Pliocene sedi－ mentary rocks，3：Pliocene－to Pleistocene sedimentary rocks，4：Quatemary vo王canic rocks，5：Fan deposits including terrace deposits，6：Salt

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