著者

岡村 行信

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2010, no.33, pp.15-25, 2010

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Geologic structure around the source area of the 2007 Chuetsu-oki earthquake and the Sado Basin was examined based on seismic profiles. The earthquake occurred in the fold belt of the Niigata basin, one of the largest Miocene rift basins in Japan. High-resolution multi-channel seismic profiles in and around the source area showed that there are active folds and inactive folds. One of the NE-SW trending active folds has been related to the SE dipping source fault of the 2007 earthquake, which continues from the shelf to the basin. The fold is parallel to the strike of the source fault of the 2007 earthquake, but is located about 5 km northwest of the source area. Other folds above and around the source area of the 2007 Chuetsu-oki earthquake are inactive. The active anticline accompanies 5 m vertical offset on the erosional surface during the last glacial age and the surface sediments covering the Sado Basin. The active anticline does not continue to the north of 37°38′N. The slope of the SE side of the Sado Basin is underlain by nearly horizontal sediments and the slope has been developed by progradation of shelf slope during glacial ages. These observations on seismic profiles indicated that the active fault and anticline related to the 2007 Chuetsu-oki earthquake does not extend to the northeast along the southeastern slope of the Sado Basin except in the southern most part.

著者

岡村 行信

出版者

Japanese Society for Active Fault Studies

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2008, no.28, pp.31-39, 2008

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Method and result of offshore active fault survey were reviewed. Acoustic and seismic waves are widely used for offshore topographic and geologic surveys. Higher frequency acoustic waves have high-resolution but attenuate rapidly in water or sediments, thus they are mainly used for seafloor topographic survey or shallow high-resolution seismic profiling survey. Multi-narrow beam sounding provided evolutionary detailed seafloor topographic maps that clearly show fault traces. Lower frequency seismic waves are widely used for survey of deep sea and deep subsurface geology, but their resolution is generally too low to evaluate the activity of faults in late Pleistocene or Holocene time. Multi-channel seismic profiling survey and digital signal processing technology tremendously improved quality of seismic profiles. Offshore active fault maps around Japan were published in 1980's and 1990's based mainly on analyses of single channel seismic profiles. The events of active fault have been identified only in shallow bay areas using high-resolution seismic profiles and sediment cores. In contrast, it is generally difficult to determine events in open sea areas, because of low quality of seismic profiles. Multi-channel seismic profiling system using a high-frequency sound source made it possible to obtain high quality seismic profiles in the open shallow sea area and showed an active fault in the source area of the 2007 Noto-Hanto earthquake. In the deep sea, low-frequency seismic profiling system generally show clear geologic structure including active faults, but it is difficult to determine their activity in the late Pleistocene and Holocene period. Analyses of turbidites and dive surveys using submersibles have been conducted to determine the ancient events of fault activity in the deep-sea area. There is no enough data of offshore active faults, especially in very shallow marine area along coast.

著者

鈴木 毅彦 小荒井 衛

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.1989, no.6, pp.23-29, 1989-01-14 (Released:2012-11-13)

参考文献数

6

著者

松山 紀香 岡田 篤正

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.1991, no.9, pp.69-92, 1991-10-31 (Released:2012-11-13)

参考文献数

15

著者

金折 裕司 川上 紳一 矢入 憲二

出版者

Japanese Society for Active Fault Studies

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.1991, no.9, pp.26-40, 1991

著者

高田 圭太 中田 高 野原 壯 原口 強 池田 安隆 伊藤 潔 今泉 俊文 大槻 憲四郎 鷺谷 威 堤 浩之

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2003, no.23, pp.77-91, 2003-06-30 (Released:2012-11-13)

参考文献数

28

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Large inland earthquakes bigger than Mj 7.2 during the historical past on Japanese islands have mostly been generated from active faults (Matsuda,1998). The 2000 Tottoriken-seibu earthquake of Mj 7.3 (Mw 6.6), however, occurred in the area where distinctive active faults were not mapped before the earthquake, and the surface ruptures associated with the earthquake were small and sparse. Active faults are hardly recognized even by detailed interpretation of aerial photographs after the earthquake but sharp lineaments. In Chugoku district in southwest Japan is characterized by less densely-distributed active faults with lower activities than other areas in Japan, and the 1943 Tottori earthquake of M 7 occurred by reactivation of the Shikano fault with rather obscure fault traces.Taking this condition, in mind, we carried out detailed mapping of active faults and lineaments, and compared with their topographical, geological, seismological and tectonic settings, in order to develop a new technique to find potential seismogenic faults.The results obtained are as follows;1) Active faults and lineaments were not evenly distributed, and the dense zone is recognized along the Japan Sea while the sparse zone in the central part of the district. The active faults known before are mainly located in the dense zone (Fig.1).2) The lineaments mapped are mostly less than 10km long, and half of them strike to NE-SW or ENE-WSW and 30 per cent to NW-SE or WNW-ESE (Fig.2). NE-SW lineaments prevail in the western part of the district, and NW-SW lineaments are systematically distributed only in the western-most and eastern-most area of the district probably reflecting their tectonic setting under the present stress condition.3) Lineaments with poor topographical manifest were not commonly recognized by individual geologist, and were generally short, scattered, isolated, random in strike, and independent from geological structures. These lineaments will not be considered as potential seismogenic faults.4) Epicenters of the small earthquakes are characteristically distributed to the north of the backbone range probably coincided with the past volcanic front. On the contrary, the area to the south of the backbone range the seismicity is sparse, except for several swarms. These seismic condition well matches with the distribution of active faults and well-defined lineaments (Fig.3).5) Most of the active faults and lineaments follow the pre-existed geological faults that had moved opposite direction to the active faulting, indicating their inversion movements under the present stress field.6) Surface ruptures reported as earthquake faults associated with the 2000 Tottoriken-seibu earthquake are considered as results of subsidiary shallow-sheeted faulting spontaneously caused by stain release around the seismogenic faulting in depth, because many of them appeared spontaneously, and not always along rather well-defined lineaments. They are small in extent and displacement. Therefore, it is rather difficult for evaluate such minor surface fault ruptures, but such ruptures may not displace the surface in large extent.

著者

石関 隆幸 隈元 崇

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2007, no.27, pp.63-73, 2007-06-30 (Released:2012-11-13)

参考文献数

14

---

bility to the BPT model. As a result, we conclude that case (c) is the most realistic model by the AIC procedure.Also, we simulated the value by randomly selecting the event occurrence between the range of the recurrence interval and verified the variable estimated from the mean recurrence interval. As a result, the value 0.24 estimated from the four active faults or the value 0.42 estimated in this study is mostly smaller than the average value that can be practically estimated from data. Also, we show some case that is possible to estimate the variable more accurately by considering the probability density distribution of the event occurrence.

著者

木村 治夫 中西 利典 丸山 正 安藤 亮輔 堀川 晴央

出版者

日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2013, no.38, pp.1-16, 2013

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The Itoigawa-Shizuoka tectonic line (ISTL), which is located between the NE and SW Japan arcs, is one of the most major tectonic lines in Japan. The N-S trending Kamishiro fault located in the northern part of the ISTL active fault system is an east dipping reverse fault. Near the southern part of the fault, the alluvial fan formed by a river flowing toward the southeast is tilted to the west by faulting. To reveal shallow subsurface deformation structure above a depth of 5 m, we carried out ground penetrating radar (GPR) profiling along two survey lines, whose lengths are 50 m and 130 m, respectively, across the fault. The GPR data was collected by common-offset modes using the control unit SIR-3000 (Geophysical Survey System Inc.) and the 200 MHz antenna Model-5106(Geophysical Survey System Inc.), and the station spacing was 0.01 m. The depth converted GPR sections after careful data processing are very concordant with the geological section based on drilling and trenching surveys conducted near the GPR survey. The GPR sections show deformation structure of the fan deposits in detail. The vertical displacement of the top of the fan gravel deformed by the Kamishiro fault is over 3.0 m during the last faulting event.

著者

渡辺 満久 中田 高 水本 匡起

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2017, no.46, pp.9-15, 2017-03-31 (Released:2018-03-29)

参考文献数

17

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We found several faulted landforms and an active fault outcrop around the Minobu fault, Yamanashi Pref., central Japan. The Neguma fault may be a reverse fault dislocating a fan surface (not dated) ca. 13 m vertically. Fluvial terrace surfaces at Wada are classified into W1 to W5 surfaces in descending order. It is probable that the W3 surface was formed in the period of MIS 5 to MIS 4. The Wada fault cuts the Neogene and the overlying gravel distributed in almost the same height with the W3 surface. The dip and strike of the fault plane are N5゜E and 50-60゜W, respectively. The striations are plunging to the south at an angle of ca. 20 degree and blow. The relative vertical component is upthrown on the east side. These structures are indicative of left-lateral movement. The maximum accumulated left-lateral slip since MIS 5 to MIS 4 is 100 m at least.

著者

島崎 邦彦

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2008, no.28, pp.41-51, 2008-03-31 (Released:2012-11-13)

参考文献数

62

被引用文献数

1

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A comparison of frequencies of large earthquakes between the observed and expected on the major active faults in Japan may suggest some underestimation of the occurrence rate of large events by the long-term earthquake forecasts. The main cause was thought to be the forecasts often anticipate a single large earthquake on a long fault zone, without assuming smaller earthquakes on segmented zones. However, the principal factor of the likely underestimation is that those events without enough evidence on fault zones cannot be evaluated by a trench excavation survey. Historical records show poor or no seismic surface rupture associated with a large earthquake with magnitude around 7 on some of the major fault zones.Recent improvements on interpreting aerial photographs have brought a detailed pattern of active faults and fault segments. Together with information on underground structures obtained from geological and gravity anomaly maps, the detailed feature of active faults may enable us to decipher behavioral fault segments without solely relying on paleoseismic records.Except for volcanic areas a short active fault on the surface should have a longer subsurface fault length within the earth's crust. The magnitude of earthquakes on such a fault is 6.9 or larger on JMA scale. This inference is based on reports on surface ruptures associated with large shallow crustal earthquakes in Japan. Only the 1945 Mikawa earthquake with magnitude 6.8 appears to be an exception to that no prominent surface rupture appears associated with earthquakes with magnitude 6.8 or smaller.

著者

土井 宣夫 越谷 信 本間 健一郎

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.1998, no.17, pp.31-42, 1998-12-29 (Released:2012-11-13)

参考文献数

40

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The geology at the northern and western margin of the Shizukuishi basin is composed of upper Miocene Yamatsuda Formation, Pliocene Masuzawa Formation, Plio-Pleistocene Tamagawa Welded Tuffs and units from Takakura and Iwate volcanoes, in ascending order. The geological structure of the margin is characterized by the Nishine fault system, which displaces these formations and units. The fault system, a set of west-dipping reverse faults, forms the topographic and geologic boundary between the Ou Backbone Range and the Shizukuishi basin, and it controls the vertical position of underlying units as well as Takakura and Iwate volcanic products. The vertical displacement of the Shibutami Welded Tuff, which is included in the Tamagawa Welded Tuffs and erupted between 0.7and 1.0 Ma, decreases to the north and south from an area where the tuff has been vertically offset some 300-400 m, for an average displacement of about 0.4 mm/yr. Slip occurred on the northern part of the fault system during the Iwate-ken Nairiku-hokubu earthquake of September 3,1998. The tuff is also displaced at least 250 m along the Matsuo fault for an average displacement of about 0.25mm/yr at the north of the Nishine fault system. This reverse fault strikes nearly parallel to the Nishine fault system and can be traced for 5 km.

著者

堤 浩之 後藤 秀昭 谷 美由起

出版者

活断層研究会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2004, no.24, pp.157-165, 2004

被引用文献数

1

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The Arima-Takatsuki fault zone consists of a series of ENE-trending right-lateral strike-slip faults along the northern margin of the Osaka plain. This fault zone is considered to have ruptured during the 1596 Keicho-Fushimi earthquake based on paleoseismic trench excavations across the fault zone conducted by the Geological Survey of Japan and numerous liquefaction features on archaeological sites in Kobe-Osaka-Kyoto areas. The surface offset during the earthquake was estimated to have been about 3 m based on offsets of rice-paddy dikes at two localities. In order to search for more data on the surficial slip during the 1596 earthquake as well as evidence for prehistoric earthquakes, we have interpreted large-scale aerial photographs and conducted geomorphic field investigations. We have identified several localities along the fault zone where geomorphic and/or artificial features are systematically offset about 3 m, confirming previous estimates of the surficial slip during the 1596 earthquake. Larger displacements of older geomorphic features also suggest repeated right-lateral slip on the fault zone in late Holocene time.

著者

岡田 篤正

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2012, no.37, pp.29-37, 2012-09-30 (Released:2016-03-16)

著者

野原 壯 郡谷 順英 今泉 俊文

出版者

日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2000, no.19, pp.23-32, 2000

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The horizontal strain rate caused by fault activity for the past several hundred thousand years was calculated using the latest active fault database. Features of fault activity at the scale of the Japanese Islands were estimated, and the results were compared with the strain rates that the pre-existing literature showed.<BR>The strain rate required using the latest active fault database resembles the strain rate requ ired using the pre-existing data on active faults in the Quaternary period (Kaizuka and Imaizumi,1984). The distribution of the strain rate required from active fault data resembles the distribution of the strain rate required from the GPS observations (Sagiya<I>et al</I>.,1999) in many regions, with the exception of the Pacific coast region. However the value of strain rate required from active faults data (10<SUP>-8</SUP>/year) is smaller than the value of strain rate required from the GPS data (10<SUP>-7</SUP>/year). In the region along the Ou Mountains, Northeast Japan, the value of strain rate required from the latest active fault data was nearly equal to the strain rate required from the geological section (Sato,1989).

著者

200万分の1活断層図編纂ワーキンググループ

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2000, no.19, pp.3-12, 2000-03-31 (Released:2013-03-22)

参考文献数

16

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We compiled a totally new 1: 2,000,000 active faults map of Japan based on the digitized GIS data of active faults in the scale of 1: 25,000 by Active Faults Map Working Group (1999).The new map differs from the existing active faults maps of Japan in t wo points. One is the definition of active faults and the other the scale of base maps. We defined active faults as faults that have repeatedly moved during the late Quaternary with intervals of one thousand to ten thousand years forming distinctive fault-related tectonic features on the earth surface. The Research Group for Active Fault Studies (1980,1991) and other previous studies commonly defined active faults as faults that repeatedly moved during Quaternary and are the potential sources for future earthquakes. Therefore, our criterion is stricter for recognition of active faults than those used for the previous mapping. The other difference is accuracy in mapping of active faults; our map is based on the active faults map data in scale of 1: 25,000 while others mostly based on much smaller scale data. Through our mapping, some faults previously recognized as active because of existence of Quaternary faults were not treated as active if these faults are not associated with fault-related tectonic features on the ground. On the other hand, many faults are newly found as active by our detailed photo-interpretation.We assembled active faults about 140 fault groups based on the f ollowing criteria; 1. Faults more than 10km long in dimension,2. Isolated from the neighboring faults at least 5 km apart, and similar type of faulting, strike and sense of faulting. We compared the active faults map with geoloic map to know their characteristic occurrence of faults. We prepared maps for type, activity, and density of faulting to know the regional characteristic of active faulting in Japan. We also examined the possibility of occurrence of new active faults and expansion of faults based on the mode of cumulative slips distribution along their traces.

著者

池田 安隆

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.1996, no.15, pp.93-99, 1996-11-29 (Released:2012-11-13)

参考文献数

28

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Faulting and other surface deformations in recent geologic time are essentially relevant to understanding present-day tectonic processes, which in turn are a key to scientific, not empirical, earthquake prediction. Geologic records are indispensable because instrumentally observed records, such as geodetic measurements and microseismicity, are not sufficient in time to cover a whole cycle of strain buildup and release in a orogenic zone.Rheological structure of the Japan arc b ased on explosion seismology, heat-flow measurements, and laboratory experiments indicates that the western half of central and northern Honshu, including continental slopes on the Japan Sea side, is mechanically very weak; only the upper 15 kilometers of crustal rocks behaves elastic, and ductile lower crust is underlain directly by asthenospheric mantle. This zone of weakness was rifted and stretched during the early Miocene back-arc spreading event, and coincides broadly with the distribution of active faults. Since late Miocene time up to the present, the Japan arc has been subjected to east-west compression due principally to the westward convergence of the Pacific plate at Japan trench at a rate as high as ∼90 millimeters per year.If the megathrust at the Japan trench is locked, the plate convergence is to be ac c ommodated mainly in this zone of weakness. Actually, geodetic observations in the last 100 years have revealed that strain accumulation rates over the mechanically weak zone are on the order as high as 10-7 per year. However, geologically observed strain rates, based on slip rates on active faults and folding rates, are one order of magnitude lower than the geodetic rates. A possible explanation for this discrepancy between short-term (geodetic) and long-term (geologic) observations is that the strain accumulated in the last 100 years at abnormally high rates is likely to be released by slip on the megathrust at Japan trench, which would produce big earthquake(s) with magnitude 8 or greater. Only a fraction of plate convergence may be accommodated within the Japan arc as long-term deformation.Whether or not the above scenario is real, the process of strain buildup and release in the Japan arc-trench system is unique, and should be understood with more geologic, as well as geophysical, observations.

著者

千田 昇 竹村 恵二 松田 時彦 島崎 邦彦 池田 安隆 岡村 眞 水野 清秀 松山 尚典 首藤 次男

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2003, no.23, pp.93-108, 2003-06-30 (Released:2013-03-22)

参考文献数

11

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The writers describe the location and active mode of a fault (Funai fault) lying concealed under the town area of Oita City, by analyzing lots of the drilling survey, the reflection method and the Geo-slicer investigation.The Funai fault is the eastern part of“Beppu bay south coast fault group”, which com p osed of the Horita-Asamigawaa fault, Beppu bay south coast fault and Funai fault, extended from west to east with extension about 20km.The very position in Oita plain is considered from Kasugaura to the south of Maizuru bridge located at the left bank of Oita river.It was c o nfirmed in the drilling survey, and the amount of vertical displacement of the K-Ah volcanic ash layer in a main fault is 16m at the Funai castle traverse line. According to existing bore hole data, the maximum amount of displacement of the Funai fault is 18m to the west of Funai castle. The average rate of vertical displacement after the K-Ah volcanic ash (6,300 years BP) is 2.2-2.5m/1000 year, and the Funai fault is estimated one of the A class active faults in Kyushu.The latest activity of the Funaifault is thought to be time between before 1,540yBP dated at the lower part of the uppermost mud layer which does not show the displacement and after 2,350yBP dated in the peat layer in upper sand and gravel bed which shows displacement.The problem in the future is the clarification of the fault continuation to the further east, and it is necessary to elucidate accurate distribution and the activity history of the concealed faults lying under whole the Oita plain.

著者

太田 陽子

出版者

Japanese Society for Active Fault Studies

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2010, no.32, pp.57-72, 2010

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This paper summarises the results on active fault studies obtained mainly by the author's work during the last 10 years. The 1999 Chichi earthquake makes a turning point for active faults study. Many international and interdisciplinary works have been carried out for active faults studies, in which the author has participated in the field of geomorphological study of active fault. Her main contribution is a discussion on the close relationship between the 1999 surface trace and preexisting active fault, estimation of tilt rate and relation between the main fault and subsidiary fault, the possible segmentation based on trenching data (Chelungpu Fault), finding some new active faults and discussion of their implication for the geomorphic evolution, as well as seismotectonic significance (Tunglo Fault System and Touhuanping Fault, northwest Taiwan). Ongoing works on the reverse faults in southwestern Taiwan, are briefly summarized, including significant effect of rapid denudation, that may cause underestimation of length of active faults.

著者

池田 倫治 柳田 誠 西坂 直樹

出版者

日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2012, no.36, pp.31-44, 2012

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The Mw 7.1 (GNS Science) earthquake (Darfield earthquake) occurred near Christchurch, New Zealand on 4 September 2010. The earthquake happened in the area where active faults had not recognized previously, produced the ground surface rupture (Greendale fault). We surveyed the mode of occurrences of the Greendale fault on 8 days after the Darfield earthquake. Measured dextral and vertical displacements along the fault are ~ 4.2 and ~ 1.5 m (predominantly southern parts up), respectively. The both slip components are distributed roughly symmetrically along the west fault segment. However, the maximum displacement points are perhaps different between dextral and vertical sense based on the survey results. The fault is roughly E–W strike, characterized by many Riedel fractures that show shapes of mole tracks accompanying main dextral displacements. Few active faults had recognized previously on Canterbury plain near Christchurch, whereas distribution of active faults and folds had cleared in the Pegasus Bay area where locates in the eastern part of the Christchurch. Moreover, there are records of a few paleoearthquakes (M>5) near Christchurch and in Pegasus Bay. These data would have been clues to forecast existence of blind active faults on Canterbury plain.

著者

谷山 尚

出版者

一般社団法人 日本活断層学会

雑誌

活断層研究 (ISSN:09181024)

巻号頁・発行日

vol.2015, no.42, pp.35-53, 2015-03-31 (Released:2015-12-23)

参考文献数

29

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A distinct element method analysis was carried out to examine the deformation of unconsolidated overburden subjected to a high dipping oblique normal basement fault displacement. About 4 million spherical particles were used to model the overburden overlying a basement fault which has a dip angle of 60 degrees. Effect of normal fault component and strike slip fault component on the deformation of the overburden was investigated. The deformation was affected by both normal fault and strike slip fault component of the basement fault. Very steep high strain zones developed in the middle and lower part of the overburden and while they were formed on the footwall side of the basement fault in the case of a large normal fault component, they were formed on the hanging wall side of the basement fault in the case of a large strike slip fault component. Near the surface, in the case of a large normal fault component, large deformation mainly due to the horizontal compression was observed on the hanging wall side and it was followed by high strain zones on the foot wall side caused mainly by the horizontal extension. En echelon high strain zones were observed on the hanging wall side of the basement fault in the case where a strike slip fault component was large mainly because of the strike slip fault movement and partly because of the horizontal compression caused by the normal fault movement of the basement fault. When a normal fault component and a strike slip fault component were of the same magnitude, high strain zones almost parallel to the basement fault developed on both sides of the basement fault trace and between them high strain zones striking obliquely to the basement fault trace were formed. The angle at which high strain zones in the overburden strike to the basement fault trace was very small in the case of a large normal fault component and the result showed the possibility of a right step pattern if normal fault displacement with a slight right lateral strike slip fault component was applied to the overburden.