著者

長谷川 昭 中島 淳一 内田 直希 梁田 高広 岡田 知己 趙 大鵬 松澤 暢 海野 徳仁

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.121, no.1, pp.128-160, 2012-02-25 (Released:2012-03-05)

参考文献数

120

被引用文献数

6 12

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The mechanisms that generate the three main types of earthquake in subduction zones are discussed addressing their relations to geofluids. Studies on the spatial distribution of earthquakes and seismic velocity structure within the subducted slab provide evidence that strongly supports the dehydration embrittlement hypothesis for the generation of intermediate-depth intraslab earthquakes. Detailed imaging of the seismic velocity structure in and around plate boundary zones suggests that interplate coupling is mainly controlled by local fluid over-pressure. Seismic tomography studies show the existence of inclined sheet-like seismic low-velocity zones in the mantle wedge, not only in Tohoku but also in other areas in Japan, which perhaps correspond to the upwelling flow of the subduction-induced convection system. These upwelling flows reach the Moho directly beneath the volcanic areas, suggesting that those volcanic areas are formed by the upwelling flows. Aqueous fluids derived from the slab are probably transported up through the upwelling flows to the arc crust, where they might weaken the surrounding crustal rocks and finally cause shallow inland earthquakes. All of these observations suggest that geofluids expelled from the subducting slab play an important role in the generation of earthquakes in subduction zones.

著者

中谷 友樹 矢野 桂司

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.117, no.2, pp.506-521, 2008-04-25 (Released:2010-06-02)

参考文献数

37

被引用文献数

3 6

---

To detect spatio-temporal pattern of crime clusters/hotspots, the possibilities of three-dimensional mapping methodologies for crime event data are explored using two approaches: three dimensional kernel-density mapping using a volume rendering technique and visualisation of cylindrical significant clusters that can be detected by space-time scan statistics. Both approaches are intended to visualise spatio-temporal domains with high densities of crime in a three-dimensional space composed of two geographical dimensions and one time dimension. The proposed three-dimensional mapping methodologies are evaluated through application to a dataset of snatch-and-run offences in Kyoto City during the period 2003-2004. The results are summarized as follows: (a) Three-dimensional crime mapping enables effective visualisation of the geographical extents and duration of crime hotspots simultaneously. This method is particularly useful to identify geographical diffusion and movements of crime clusters/hotspots compared to traditional dynamic analyses of crime mapping using cross-sectional maps with arbitrary time intervals.  (b) In practice, the roles of three-dimensional kernel mapping and space-time scan statistics should be complementary. Space-time scan statistics provide clear-cut domains of crime clusters/hotspots that can be used for secondary analyses, such as evaluation of socio-environmental and temporal characteristics focusing on detected domains. However, we should note that the method assumes cylindrical geometrical-constrains of space-time domains. Three-dimensional kernel density mapping provides fuzzy domains with high densities of crime and a useful basis to assess the validity of the assumption of spatial scan statistics and to investigate detailed space-time sequences of crime clusters/hotspots. (c) Empirical analyses of the snatch-and-run offence dataset in Kyoto City revealed constant clusters/hotspots during the study period in central Kyoto and around Kyoto Station as well as transient clusters/hotspots around several railway stations in the suburbs. Temporal differences of transient clusters show geographical movements of hotspots from the north to the south via the west. We also identified that outbreaks of snatch-and-run offences alternated between a pair of cluster areas. These results suggesting so-called displacement phenomena indicate the need to monitor crime events and effects of crime-preventive actions in a widespread space-time context.

著者

沢村 武雄

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.60, no.4, pp.190-194, 1951-12-30 (Released:2009-11-12)

参考文献数

10

被引用文献数

3 1

著者

吉田 明夫

出版者

Tokyo Geographical Society

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.103, no.3, pp.201-206, 1994-06-25

被引用文献数

1 1

---

Correlation between earthquakes in Kanto region and intermediate-depth earthquakes in Hida region, central Japan is re-investigated. We found that a significant correlation exists between earthquakes with depth of 70 km and deeper in western Kanto and intermediate-depth earthquakes in Hida region, but such a correlation is not seen for earthquakes in eastern Kanto. This result shows that earthquakes occurring in the Pacific slab are well correlated each other, but earthquakes which occur in relation to the subduction of the Philippine Sea plate are not correlated with intermediate-depth earthquakes in the Pacific plate. Intermediate-depth earthquakes in Hida region have a tendency to precede earthquakes in western Kanto. This feature may be related to the dynamics of the plate motion which oceanic plate is pulled by the subducted slab.

著者

古川 雅英

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.102, no.7, pp.Plate6-Plate6, 1993-12-25 (Released:2009-11-12)

著者

廣野 哲朗 小村 健太朗 藤本 光一郎 伊藤 久男 ジェームズ モリ ジロウ 佐藤 比呂志

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.122, no.2, pp.323-342, 2013-04-25 (Released:2013-05-31)

参考文献数

111

被引用文献数

2 2

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Several fault-drilling projects have been conducted with the common aim of seeking direct access to zones of active faulting and understanding the fundamental processes governing earthquakes and fault behavior, as well as the factors that control their natural variability. Here, we review recent scientific drilling projects related to the Nojima Fault which slipped during the 1995 Hyogo-ken Nanbu Earthquake, the Chelungpu Fault which slipped during the 1999 Taiwan Chi-Chi earthquake, the San Andreas Fault Observatory at Depth, and the Nankai Trough Seismogenic Zone Experiment. We also briefly introduce the ongoing drilling research by the Geophysical Observatory at the North Anatolian Fault Zone, the Deep Fault Drilling Project at the Alpine Fault, and the Japan Trench Fast Drilling Project. One of the main findings of fault-drilling research is a better understanding of the physico-chemical processes of the primary slip zone during an earthquake, which is closely related to the mechanism of dynamic fault weakening. In the case of the Chelungpu fault, integrated research with borehole experiments, core sample analyses, and numerical simulations were performed, and the results indicate that thermal pressurization occurred during the 1999 earthquake, explaining the peculiar seismic behavior during the earthquake. These fault-drilling projects related to active faults certainly improve our knowledge and understanding of earthquakes. In addition, we discuss new technical problems related to handling core samples, identifying the latest slip zone, and overprinting by ancient earthquake events.

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.18, no.4, pp.284-284, 1906

著者

藤井 理行

出版者

Tokyo Geographical Society

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.114, no.3, pp.445-459, 2005-12-25

被引用文献数

4

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This paper describes past climate and environmental changes during the past 101 to 105 year time scale obtained by recent studies on ice cores from Arctic and Antarctica. Shallow ice cores from Greenland and Svalbard show clear North Atlantic Oscillation (NAO) signals and explosive volcanic activities in the Northern Hemisphere and the equatorial regions. A deep ice core drilled to 2503 m at Dome Fuji, Antarctica covers the past 320 ka, which includes 3 glacial-interglacial cycles with Milankovitch cycles of about 20, 40, and 100 ka. Major chemical compositions and microparticle flux show high concentrations in glacials and low concentrations in interglain high-middle latitudes during glacial-interglacial cycles. The Dome Fuji deep ice core contains 25 visible tephra layers. An analysis of the chemical compositions shows the possible source volcanoes in and around the Antarctica.

著者

河本 大地

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.117, no.3, pp.xiii-xiv, 2008-06-25 (Released:2010-05-14)

著者

宇井 忠英

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.110, no.2, pp.285-288, 2001-04-25 (Released:2009-11-12)

参考文献数

5

被引用文献数

3

著者

石橋 克彦

出版者

Tokyo Geographical Society

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.108, no.4, pp.399-423, 1999-08-25

被引用文献数

4 18

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A large volume of historical documents in Japan show that great subduction earthquakes have repeatedly occurred along the Suruga-Nankai trough off southwest Japan since A.D. 684 with an interval of 100-200 years. They occurred as pairs of <I>M</I>8 events, one in the eastern half (Tokai earthquake) and another in the western half (Nankai earthquake), as was the case for the 1854 Ansei earthquakes, while sometimes occurring as single giant events like the 1707 Ho'ei earthquake. Although the space-time pattern of their recurrence is the best-known in the world, we should study more past events in order to understand the tectonophysical bases of their recurrence. In this respect I review the present understanding of historic Tokai and Nankai earthquakes and discuss related problems from the viewpoint of historical seismology. In this paper, the first of the three in all, I review the events until the early half of the 14th century. The keys to identifying older events are strong ground motion and damage in Kyoto, Nara, and Osaka, those in wider area of southwest Japan, tsunamis along the Pacific coasts of southwest Japan, typical coseismic vertical crustal movements of the Kochi plain, the Muroto and Oma'ezaki points, and the Ise and Suruga Bay coasts, temporal inactivity of specific hot springs, and aftershock activities recorded in Kyoto. The 684 Hakuho earthquake was definitely a Nankai event, and possibly included a Tokai event simultaneously (possibly Ho'ei type). The 887 Nin'na earthquake was also a definite Nankai event and was probably a Tokai event as well (Ho'ei type). The 1096 Eicho earthquake was clearly a Tokai event, but the following 1099 Kowa earthquake has some discrepancies that prevent it from being regarded as a <I>M</I>8 Nankai event. It is not clear yet whether great earthquakes occurred or not in the ca. 200 year intervals of 684-887 and 887-1096. It seems probable that great Tokai and Nankai earthquakes took place in the mid-13th century, but a more detailed investigation of historical seismology is required to discover the missing event.

著者

日置 幸介

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.103, no.5, pp.522-527, 1994-10-25 (Released:2009-11-12)

参考文献数

17

被引用文献数

1 1

---

Following an episode in Northeast Iceland known as the “Krafla Rifting Episode” 1975-1981, a transient accerelation of the spreading rate between the North American and Eurasian plates was observed by geodetic surveys 1987-1990 using Global Positioning System (GPS). This post-rifting crustal deformation can be interpreted as the response of the shallow elastic layer to the rifting episode (dyke intrusions) delayed by mechanical coupling with an underlying viscous layer. We also found a smaller amount of radial displacements possibly caused by the inflation of the magma chamber beneath the Krafla Caldera.

著者

小出 良幸

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.2, pp.317-317, 2002-04-25 (Released:2009-11-12)

被引用文献数

1

著者

Radvanec Martin

出版者

Tokyo Geographical Society

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.118, no.4, pp.686-699, 2009-08-25

参考文献数

30

被引用文献数

2

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この研究は,1945年8月6日,午前8時15分,広島の原子爆弾爆発による熱線の強力な影響を,2片の被爆瓦片を用いて研究したもので,この瓦片は元安川に架かる元安橋下流約100mの西岸で1977~1982年にかけて発掘されたものである。爆発から1.318秒後,爆心地で破壊された建物から衝撃波によって吹き飛ばされた大変熱くて融解した多数の破片は,元安川西岸に堆積した。この瓦片はおそらく,破壊された清病院の石塀,西向寺および(もしくは)西蓮寺からのもので,川の水で急激に冷却されたものと思われる。<br> 瓦片は安山岩質の火山砕屑岩からなり,その表面は3.18mmの深さまで融解していた。そのガラス質の層は,安山岩から玄武岩質安山岩の組成をもつ。これらはクリストバル石および/もしくはリンケイ石,ピジョン輝石(X_Fe = Fe/(Fe + Mg)= 0.37-0.44),角閃石(X_Fe = 0.33-0.42),曹灰長石(Ab_48.2-40.6An_51.8-55.5Or_0-3.9)およびK-長石(Ab_8.2Or_91.8)が融解生成したものである。融解が3.18mmの深さにまでおよんでいることと,上記鉱物質のそれぞれ異なる融点および溶融深度から,爆発後の爆心地の物体表面の温度6287℃が算出された。この表面温度は,深さ2.68~3.18mmの区間における残存鉱物と,溶融深度の関係から導き出した。回帰直線<i>T</i> = -1715.1<i>d</i> + 6287(<i>d</i>は深さ)(<i>R²</i> = 0.989)を外挿して求めたものである。安山岩瓦表層部の温度勾配は1mmあたり1715℃で,深さが2.86mmから3.18mmの間では,融解ガラス質と本来の鉱物質は等量である。3.64mm以下では,火山砕屑安山岩の構造および鉱物組成は,本来の組成を有している。

著者

森 和紀

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.1, pp.52-61, 2007-02-25 (Released:2009-11-12)

参考文献数

27

被引用文献数

2 2

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Changes in the components of hydroclimatological characteristics including precipitation, evapotranspiration, and runoff over the last 100 years were investigated in the Kiso, Nagara, Ibi, and Kumozu River Basins as a case study. Annual precipitation in the study basin has tended to decrease since the first half of the 1970s. On the other hand, the smooth trend curve indicates that annual evapotranspiration has increased over the long term, especially since the 1980s. Smoothed secular changes in the difference between annual values of precipitation and potential evapotranspiration are analogous to those of annual precipitation. The average annual runoff ratio for each year has also shown a tendency to decrease during the last few decades. It is pointed out that the notable characteristics of current frequency-magnitude distributions in anrange in each year. Under conditions of extreme meteorological events that increased air temperature in the summer of 1994, river water quality showed a remarkable change compared to its average value in a normal year. The most striking feature due to high temperature was a very low value for the concentration of dissolved oxygen, especially in July and August. The facts identified in the present study provide a meaningful perspective of the possible consequences of global warming for hydrological processes, and are also useful basic data for evaluating the effects of future climate change on the aquatic environment.

著者

須田 耕樹 上野 健一

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.123, no.1, pp.35-47, 2014-02-25 (Released:2014-03-07)

参考文献数

24

被引用文献数

1 6

---

The distribution of weather divides in Japanese winters was identified using 30-year data of the Automated Meteorological Data Acquisition System (AMeDAS) operated by the Japan Meteorological Agency. Two kinds of weather divide were defined, one is a cloudy weather divide (CWD) determined by the high-frequency grids of large gradients in the sunshine duration distribution, and the other is a precipitation area border (PAB) where the edge of daily precipitation areas frequently appeared. The CWD appeared continuously in eastern Japan along the Pacific backbone ranges, but it was discontinuous in the central mountain ranges and western Japan. The CWD also appeared in Pacific coastal areas, such as east of Kamikouchi, south of the Kii Peninsula, and southeast of Shikoku Sanchi. The PAB overlapped with the CWD distribution in eastern Japan, and it was enhanced throughout the Sekigahara-Tamba Kochi and Chugoku Sanchi areas, but the CWD in pacific coastal areas was not associated with the PAB. Most of the weather divides were caused by the winter monsoon pressure pattern, and some PABs in northwestern Tohoku and Hokkaido areas occurred with passing pacific coastal extratropical cyclones. The distribution of the weather divides in cold-winter years was dependent on the dominance of Satoyuki/Yamayuki weather patterns, and weather divides became unclear in warm winters.

著者

宮地 政司

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.59, no.3, pp.61-63, 1950-06-30 (Released:2009-11-12)

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最近測地学方面で行われた無線報時の利用による二, 三の研究成果を紹介し, 我國の無線報時の現況とその利用法の概要を述べ, それ藤広い分野を有つ地学のどこかで役立つ事を願5ものである。測定や観測を静的なものと動的なものに大別する事が出来る。歴史の示す様にそれは静から動へと発展している。近代の科学の発展はこの動的測定に負5ものが非常に多い様である。こゝでいう動的とは「時」の利用によるもので, それが無線報時の手段で簡單に自由にそして必要な精密さで利用出来る様になつたのは極めて最近でこゝ二三十年来の事である。先づ二, 三の最近の研究成果を述べてみよう。

著者

鈴木 康弘 堤 浩之 渡辺 満久 植木 岳雪 奥村 晃史 後藤 秀昭 STREL'TSOV Mihail I. KOZHURIN Andrei I. BULGAKOV Rustam TERENTIEF Nikolai IVASHCHENKO Alexei I.

出版者

Tokyo Geographical Society

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.109, no.2, pp.311-317, 2000-04-25

被引用文献数

1 4

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We have prepared a preliminary active fault map of Sakhalin, Russia, based on an interpretation of aerial photographs and satellite images. Major active structures include 110-km-long active faults along the western margin of the Yuzhno-Sakhalinsk Lowland in southern Sakhalin and 120-km-long active faults along the western margin of the Poronaysk Lowland in central Sakhalin. These active faults are parallel to but are located as far as 10 km east of the Tym-Poronaysk fault. Geomorphic surfaces on the upthrown side of the fault are tilting westward, therefore, the faults are considered to be west-dipping low-angle reverse faults. The vertical component of slip rates of these faults are >0.3 mm/yr in southern Sakhalin and 1.0-1.5 mm/yr in central Sakhalin. The net-slip rates could be much greater because the faults are low-angle reverse faults. If these faults rupture along their entire length during individual earthquakes, the earthquakes could be as great as M7.6-7.7. In northern Sakhalin, we have identified a series of right-lateral strike-slip faults, including the 1995 Neftegorsk earthquake fault. The slip rates for these faults are estimated at 4 mm/yr. The right-lateral shear in northern Sakhalin and east-west compression in central and southern Sakhalin may reflect relative plate motion in far-east Asian region.

著者

竹内 章

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.100, no.4, pp.540-551, 1991-08-25 (Released:2010-11-18)

参考文献数

62

被引用文献数

7 6

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Central Japan has been tectonically situated at a triple juncture among Izu-Bonin, Northeast Japan, and Southwest Japan Arcs. Neotectonics of central Japan is geohistorically reexamined with the special reference to the results of ODP Leg126 transect of Izu-Bonin Arc. Three major points are claimed as follows:(1) The tectonic belt along eastern margin of Japan Sea (EMJS) is characterized by severe compressional deformation including thrusts and folds have developed within the Miocene rifted trough, Uetsu sedimentary basin, by a tectonic reversal which occurred at the end of Miocene around 6 Ma. Since then, the belt have behaved as a newly formed plate boundary between Eurasia and North America Plates.(2) During the period of 2.8-1.4 Ma, a bimodal volcanism occurred at the both flanks of the southern Hida Mountain Range. Area of such explosive acidic volcanism was bounded by a rift-like depression zone called “Omine Rift” was formed along the north-central segment of Itoigawa-Shizuoka Tectonic Line. This means that backarc rifting of Izu-Bonin arc forced the above colliding boundary between Northeast Japan and Southwest Japan to expand.(3) As for plate tectonic frame-work in central Japan, two possibilities are pointed out based on contemporal changes throughout central Japan.a) An eastward motion of Southwest Japan (EUR) has started at about 6 Ma, which immediately caused the jump of plate boundary from central Hakkaido to the EMJS following the tectonic reversal in the inner Northeast Japan arc.b) Philippine Sea plate has changed the direction of its movement from North-northeast to West-southwest around 3.5 Ma, which activated the backarc rifting of Izu-Bonin arc.

著者

加藤 茂

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.99, no.2, pp.Plate1-Plate3, 1990-04-25 (Released:2009-11-12)