鈴鹿東縁断層帯における地下水観測井の新設−北勢観測井−
		Late Cenozoic ore deposits and their sulfur isotopic ratios of the northeastern Hokkaido, Japan
		Recent surface faulting of the North Anatolian fault along the 1943 Ladik earthquake ruptures
		八尾地域の前期中新世地磁気層序の精密化

鈴鹿東縁断層帯における地下水観測井の新設−北勢観測井−

佐藤 努(地震地質部)・高橋 誠(地震地質部)・佃　栄吉(地震地質部)・上村　尚(日鉄鉱コンサルタント��)・菅原豊松(日鉄鉱コンサルタント��)

2000

第51巻 第1号，1-16頁

8図，5表

Keywords: groundwater, Hokusei, Fumotomura fault, Suzuka-toen fault zone, Earthquake prediction

[ 要　旨 ]
北勢観測井は，地質調査所が1997年から1998年にかけて設置した活断層モニタリング施設の一つである．地震予知研究を視野に入れた活断層モニタリングを目的とし，鈴鹿東縁断層帯に属する麓村断層を貫くように掘削されている．麓村断層の下部には向斜構造が発達しており，北勢観測井の構造は，断層および向斜軸付近の地層を帯水層とする2種類の地下水の観測を同時に行うため，2重管構造となっている．井戸の深さはそれぞれ内管が500m，外管が290mで，前者のスクリーン深さ（429-439m）は向斜軸付近に，後者の2番目のスクリーン（184-205m）は麓村断層付近に設置されている． 　北勢観測井における麓村断層の深度は，コア試料の観察などから170m〜190m付近と推定される．断層付近の帯水層の地下水は，その上下3つの帯水層から得られた他の地下水と比べてSiやFeを多く含むことが判明した．しかし揚水試験から得られた透水量係数は，どの帯水層もほぼ同じ値を示し，およそ10-6 m2/sであった．

Late Cenozoic ore deposits and their sulfur isotopic ratios of the northeastern Hokkaido, Japan

Shunso ISHIHARA(Geological Survey of Japan), Masahiro YAHATA(Geological Survey of Hokkaido), Yukitoshi URASHIMA and Yasushi WATANABE(Geological Survey of Japan)

2000

vol. 51 (1) P. 17-28

4 figs., 3 tables

Keywords: Late Cenozoic, Kitami province, volcanogenic, base metal deposit, gold-silver deposit, mercury deposit, δ³⁴S value, ilmenite series, magnetite series

Abstract: Sulfur isotopic ratio (δ³⁴S) was determined on sulfide minerals and ores from base metal deposits (23 samples), gold-silver deposits (29 samples) and mercury deposits (9 samples), and a large number of negative δ³⁴S values were discovered. Together with the previously reported data, the base metal deposits have two groups of δ³⁴S values: -12.9 to -9.8 and -2.7 to +6.2 permil. The first group is considered genetically related to ilmenite-series granitoids, which have -6.3 permil on an average δ³⁴S value of the rock sulfur. The second group is essentially formed with magnetite-series volcanic and subvolcanic activities (Motokura-Jotoku), but locally contaminated with sedimentary sulfur from the wall rocks (Kitami). Gold-silver deposits have a wide range of -9.0 to +9.0 permilδ³⁴S. The values are especially low (-9.0 〜-0.7‰) in those of the Omu-Sanru graben and the northernmost part of the Monbetsu-Kamishihoro graben, where important ore deposits of Konomai, Hokuryu, Numano-ue and Sanru are distributed. These negative δ³⁴S values may indicate the existence of reduced-series volcanic rocks in these regions. A regional N-S variation in the δ³⁴S values of the gold-silver deposits seen in the northeastern Hokkaido is considered to reflect essentially the regional difference in the ilmenite/magnetite-series volcanic activities. Mercury deposits have the most negative values (-14.2 to +0.4 ‰) among the three commodity groups, and could also be related to ilmenite-series volcanism.

Recent surface faulting of the North Anatolian fault along the 1943 Ladik earthquake ruptures

Toshikazu YOSHIOKA(Earthquake Research Department, GSJ), Koji OKUMURA(Hiroshima University), Ismail KUSCU(General Directorate of Mineral Research and Exploration of Turkey) and Omer EMRE(General Directorate of Mineral Research and Exploration of Turkey)

2000

vol. 51 (1) P. 29-35

6 figs., 1 table

Keywords: North Anatolian fault, Turkey, active fault, paleoseismology, trench, Ladik earthquake

Abstract: We excavated the North Anatolian fault on the surface rupture of the 1943 Ladik earthquake in order to specify the recent faulting history of the segment. A trench was opened across the fault on an alluvial fan surface northwest of Havza. The sediments exposed on the trench walls consist of massive pebbly silt and gravel bearing pottery fragments of the Roman period. A few fault strands cut through these sediments. One strand of the faults cuts the sediments up to just below the ground surface. This strand was presumed to be formed during the last event of 1943. We recognized at least three faulting events including the 1943 event. The radiocarbon ages of charcoal pieces and animal bones indicate that the penultimate event was likely to have occurred after the 11th century and before the 14th century. The estimated interval of 600 to 900 year recurrence time is much longer than the estimates from trench studies on the North Anatolian fault in Gerede and Erzincan are 280 km west and 380 km east of this site, respectively.

八尾地域の前期中新世地磁気層序の精密化

伊藤康人(大阪府立大学)・渡辺真人(資源エネルギー地質部)

2000

第51巻 第1号，37-45頁

7図，2表

Keywords: Yatsuo, Toyama, Japan, magnetostratigraphy, Miocene, Neogene

[ 要　旨 ]
　富山県八尾地域に分布する下部中新統について地磁気層序の精密化を行った．岩稲層・医王山層・黒瀬谷層の試料について段階交流消磁と段階熱消磁を行った結果，岩稲層の初生磁化は正帯磁であることがわかった．一方，医王山層と黒瀬谷層から得た試料の安定磁化方位は逆帯磁である．傾動補正を施した黒瀬谷層の残留磁化方位は，従来の研究と同様，有意な偏角偏位を示さない．八尾地域の化石層序学的研究と年代データを考慮すると，岩稲層・医王山層下部と医王山層上部・黒瀬谷層は，それぞれ標準地磁気層序のChron C5CnとC5Brに対比される．