Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1785/0120180166

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Language：Japanese   Publisher：The Geological Society of Japan  

<p>We developed a new portable percussion piston corer for coring lacustrine and shallow-marine sediments from a frozen ice surface. The weight of the corer is less than 100 kg, and it can be separated into individual components. Therefore, the corer can be carried to remote sites using pack frames and allows coring to be undertaken in areas that cannot be reached with mechanical drilling equipment. The engine-driven percussion coring can obtain relatively coarse and hard sediments. The main body of the corer is composed of a transparent polycarbonate pipe with an external diameter of 76 mm, which allows us to check length and facies of the cored sediments immediately after coring. The polycarbonate pipe is suitable for preserving sediments and can be easily replaced in subsequent coring. The new corer is advantageous for lacustrine- and marine-sediment coring in extreme (cold) environments, such as Antarctica and high mountains, and may also be applied to a wide range of geoscientific fields.</p>

DOI： 10.5575/geosoc.2018.0065

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/2017JF004382

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

In order to mitigate landslide risks, monitoring of ground water is essential. Previous indoor experiments suggest that the self-potential approach has an advantage to establish the early warning system in performance to detect related signals and in cost. To evaluate results obtained from the previous indoor experiments, in situ measurements are required. To achieve this, we selected a test slope at Nishiikawa, Tokushima, Japan and we performed preliminary electrical resistivity exploration (ERT) and core-sampling. The results of ERT show that there are low resistive areas in shallow depth (&lt;3 m). The core-sampling results also indicate that there exists the structure which corresponds to slip surface. In addition, anisotropy in magnetic susceptibility was examined and the samples around the estimated slip surface region provide the oblate ellipsoid characteristics. These results of ERT and core analyses are consistent and make convince the identification of the slip surface. Based on these preliminary results, we set up the in situ self-potential observation at the slope and started measurements.

DOI： 10.1002/ecj.11967

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Language：Japanese  

DOI： 10.5026/jgeography.126.1

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1186/s40623-016-0560-8

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.tecto.2016.04.005

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：National Institute of Polar Research  

Scopus

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1007/978-3-319-09057-3_91

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Language：Japanese   Publisher：Japanese Society for Active Fault Studies  

<p>The 2014 M 6.7 Naganoken-hokubu earthquake was caused by movement of the Kamishiro fault located in the northernmost part of the Itoigawa-Shizuoka Tectonic Line (ISTL) active fault system, central Japan. We conducted a series of field research immediately after the earthquake to describe coseismic surface ruptures. Our description methods were: 1) field reconnaissance using pre- and post-earthquake airphotos; 2) quick measurement using staff; 3) topographic profiling using Auto Level and Total Station; and, 4) UAV and highpole SfM measurement. We identified 9-km-long coseismic surface rupture, most of which was located along the pre-existing surface trace of the Kamishiro fault. The maximum value of coseismic vertical offset was ca. 1 m or more, which was recorded at Oide in the northern part of the rupture. Based on comparison of the 2014 coseismic slip distribution with the long-term slip rate distribution, both 2014 slip amount and cumulative offset amounts of L2 and L3 terrace surfaces are larger in the northern end of the ruptures. This implies that the subsurface coseismic slip during pre-2014 earthquakes continued toward the north, similar to that during the 2014 earthquake. In addition, both coseismic slip and long-term slip rate becomes smaller toward the south, indicating that the Kamishiro area is one of the segment boundaries in the northern part of the ISTL active fault system. Further investigations of the 2014 earthquake and the Kamishiro fault are needed to understand formation of tectonic landforms, landscape development, or earthquake prediction model of active faults.</p>

DOI： 10.11462/afr.2015.43_149

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.geomorph.2012.11.001

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)  

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Language：Japanese   Publisher：SEISMOLOGICAL SOCIETY OF JAPAN  

The M_jma 7.2 (M_w 6.9) Iwate-Miyagi Nairiku earthquake struck mountainous regions east of volcanic front in northern Honshu. To understand the relation between coseismic surface deformation and the seismogenic faulting and to have lessons in the long-term earthquake forecasting, we have performed urgent field investigations immediately after the main shock, while fragile structure and surface geomorphic features were fresh. More than 13 fault-rupture observations suggest that the estimated total length of the tectonic ground breakages reaches &sim;20 km even though their locations are spotty rather than continuous along the entire trend. Contractional features such as thrust fault exposures, flexure, tilting, and buckling deformations predominate on the rupture zone, which is consistent with the reverse faulting under the WNW-ESE compressional stress field in northern Honshu. Such shortening features as well as vertical displacements were visible on cultural features such as concrete, asphalt paved roads, sidewalks, guardrails, drainage ditches, and rice paddies. Amounts of vertical offset and horizontal shortening measured using such cultural piercing points are mostly smaller than 50 cm (&sim;1 m of net slip). Fractures with such small slip, in turn, would not have been noticeable and may reflect the spotty distribution of the ruptures. Meanwhile, near the southern end of the rupture zone, fault structure and slip sense become complex and measured offsets are exceptionally large. We found a E-W-striking &sim;1-km-long continuous rupture involved with 4-to-8-m dextral and 2-to-4-m vertical offsets of a paved road, trails, and rills near a massive giant landslide at the northern rim of the Aratozawa dam reservoir. Terrestrial LiDAR (Light Detection and Ranging) measurements together with our field observations reveal typical features of strike-slip faulting such as mole tracks, fissures, pressure ridges, bulges, and shutter ridges as well as the offset rills and ridges. Detail mapping of the ruptures suggests that this strike-slip dominant fault is a lateral ramp or tear fault that connects two distinct NNE-trending thrust faults, although we cannot rule out the possibility of a large mass movement due to gravitational force to induce such large displacements without suffcient geodetic and geologic data. The mapped zone of the ruptures approximately locates along the central part of the surface projection of a &sim;40-km-long west-dipping source fault and associated aftershock zone. It also well corresponds to an asperity estimated from seismic and geodetic inversions, particularly southern end of the ground breakage zone. However, from the viewpoint of the long-term predictability, the surface fracturing occurred where none of active faults was previously mapped. Although several active geomorphic strands are likely to have reoccupied with the 2008 event, they are more spotty than the 2008 ruptures. Thus it would not have allowed us to properly evaluate size of the shock and entire extension of the rupture.

DOI： 10.4294/zisin.62.153

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1785/0120080310

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1785/0120070204

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1130/G25028A.1

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1029/2007JB005300

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1785/0120070073

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1186/BF03353152

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1186/BF03352869

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.yqres.2006.09.003

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Language：Japanese   Publisher：Japanese Society for Active Fault Studies  

The Yugamine fault,10 km in length, is in the north-central part of the Atera fault zone. We studied Holocene activity of the Yugamine fault through a trenching survey. We excavated a trench across the scarplet on the L 1 terrace at Obayashi district. Some humic layers and fluvial gravels are exposed on the trench walls. The Yugamine fault has cut through these layers to form a linear depression on its NE side. From the structural evidence along the fault plane and angular unconformity, we recognize at least four faulting events in this trench.

DOI： 10.11462/afr1985.2007.27_201

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Language：Japanese   Publisher：Tokyo Geographical Society  

Excavating a pit across a small up-hill facing fault scarp on a mountain slope could be a paleoseismological tool for intramontane active faults, which usually lack suitable sites for traditional trenching. We tested this method on the Daguchi fault, north of Lake Biwa, southwest Japan, a typical short strike-slip fault in a mountainous region. Our test excavation at the Kurokoyama site on the southern subsegment of the fault, together with a re-interpretation of our previous excavation at the Daguchi site on the northern subsegment, allow us to obtain some constraints on the surface-faulting history of the fault. The timing of the most recent event is estimated to be 450-1050 cal. y.B.P. (900-1500 A.D.), whereas that of the penultimate event is poorly constrained : 1500-7300 cal. y.B.P. or prior to 5000-7300 cal. y.B.P., depending on different interpretations of the infilled fissure exposed on the pit wall. For either interpretation, our result is consistent with estimates from a previous paleoseismic study by Sugiyama and Yoshioka (1999), but the presence of other stratigraphically unidentifiable events cannot be ruled out, given the lack of piecing layers across the main fault in our pits, as well as their trench. The principal reason for the poor age control is an unexpected lack of peaty sediments at the Kurokoyama site, which is probably related to a high sedimentation rate and an unusual sedimentation process due to rapid soil creep on the mountain slope. Although application of this method might be limited on a mountain slope with rapid soil creep, which is commonly implied by the downslope bending of tree trunks as it is at the Kurokoyama site, our test excavations suggest that pit excavation on a mountain slope basically works as a paleoseismological tool in mountainous regions.

DOI： 10.5026/jgeography.114.5_724

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Language：Japanese   Publisher：Japanese Society for Active Fault Studies  

Pit excavation across a small uphill-facing fault scarp on a mountain slope could be a paleoseismological tool for active faults without suitable sites for traditional trenching. We tested this method on the Neodani fault, which is one of causative faults for the 1891 M 8.0 Nobi earthquake. We found an unnatural small uphill-facing scarp on a mountain slope just along the trace of the fault and decided that the scarp should have tectonic origin. However, pit excavation across it, radiocarbon ages from the pit, and following additional investigation on historical documentations reveal that it is probably one of ruins of a&ldquo; shishigaki&rdquo; (man-made protection wall against damage to crops by wild animals), which was built during the late Edo period (1804-1810 A. D. ). With the knowledge of a shishigaki, we would have previously recognized that the scarp was not a tectonic one: key observations are presence of level land along the scarp that used to be a paddy field (now woods), and common lack of recognizable vertical offset of a mountain slope across the scarp. As ruins of a shishigaki are reported to be widely distributed in all Japan except for Hokkaido and Tohoku regions, great care should be exercised with them in recognizing small fault scarps on a mountain slope.

DOI： 10.11462/afr1985.2004.24_95

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Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publisher：Tokyo Geographical Society  

Trench excavation is a less effective paleoseismic investigation for intramontane active faults because there are fewer good trench sites along them. We propose a new method called &ldquo;pit excavation on a mountain slope&rdquo; to determine the timing of the latest events of such faults. This method is carried out across a small uphill-facing fault scarp preserved on a mountain slope. Sediment trapped by the scarp should provide good information concerning the timing of the latest event.<BR>We applied the method to the northern segment of the Daguchi fault, one of the short rightlateral active faults in the Nosaka Mountains, north of Lake Biwa, southwest Japan. The rupture history of the segment has remained unknown because no good trench site exists along the fault trace. However, our precise geomorphological mapping revealed the presence of a 1 m-high uphill-facing fault scarp preserved on a mountain slope, and therefore we carried out a pit excavation across the scarp using man power. A very clear fault and 75 cm-thick trapped sediments were observed on the pit wall. Since these sediments showed neither displacement nor deformation associated with surface faulting, we interpret that they were all deposited after the latest event. For more accurate age control, we identified species and portion for wood fragments from the sediments. Unfortunately, all samples except those that could not be identified were parts of Cryptomeria japonica, Chamaecyparis obtusa Endl. or Cupressaceae, which can live for hundreds or even thousands of years : this means a possible large offset between deposition and radiocarbon age for these samples, leading to less accurate age control. However, some of them were from the outermost trunk, for which we can regard radiocarbon age as the deposition age in consideration of the very small catchment area of the pit site (several hundreds of m²). Based on the radiocarbon ages of the outermost trunk samples, the initiation of sediment trapping or equivalently the timing of the latest event is estimated to be about 1500 years ago (5th to 7th century AD).<BR>Our investigation on the Daguchi fault successfully revealed the accurate timing of the latest event, supporting the effectiveness of our new method. However, some problems remain unsolved, including application of the method to other faults, especially those with long dormancy, and necessity of a crosschecking excavation on a historically ruptured fault.

DOI： 10.5026/jgeography.111.5_747

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Language：Japanese   Publisher：Japanese Society for Active Fault Studies  

Surface rupture with maximum right-lateral displacement of 150cm and length of about 1 lkm was observed during the 1943 Tottori earthquake of Mw: 7.0, which struck the eastern Tottori prefecture, southwest Japan. We compiled all the previous reports and papers regarding the surface rupture associated with the earthquake as precise location maps (Appendix 1) and a data table (Appendix 2). We also showed the slip distribution along the surface rupture (Fig.3).<BR>The trace of the 1943 surface rupture exhibited the large step and quite sinuous geometry compared with other strike-slip surface breaks. This observation probably means that the causative fault for Tottori earthquake is at the infant stage on its way of evolution based on the Wesnousky's fault evolution model (Wesnousky,1988). Most of the surface rupture during the earthquake occurred along the geomorphologically detectable active fault (Shikano-Yoshioka active fault system). Thus, we can recognize the possible surface faulting event around the epicentral area based on recent understanding of tectonic geomorpholgy. However, the length of the subsurface seismogenic fault is underestimated by the presently proposed method (Odagiri and Shimazaki,2000) and this sh ould lead to crucial underestimation of the seismic moment and also strong ground motions. The method to estimate the lengt h Df the seismogenic fault must be reestablished.

DOI： 10.11462/afr1985.2002.21_73

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Language：Japanese   Publisher：Japanese Society for Active Fault Studies  

Surface-rupturing earthquakes tend to cause larger damage than earthquakes without surface rupture (Takemura,1998). However, the degree of damage during an earthquake is largely influenced by population, surface geology and strength of houses in the epicentral area. I calculated the index valueIby eliminating the effects of population, surface geology and strength of houses from compiled damage data of 37 earthquakes occurred intraplate Japan during the past 115 years:I=D/(j&sdot;k&sdot;D₇) whereDis number of collapsed houses during an earthquake, D₇, is calculated number of collapsed houses when a point source of moment magnitude Mw: 7.0 (depth: Okm) is assumed at the epicenter, j is a coefficient of calibration for population chang e through time, and k is a coefficient of calibration for strength change of houses through time. A damage estimation program by National Land Agency of Japan is used for the damage calculation.<BR>Ivalues for surface-rupturing events are expected to be at leas t a factor of ten larger than those for events without surface rupture in the range of Mw: 6.4-6.6 which is an over-lap zone of both types of events. The difference of depth to the upper edge of the seismogenic fault between both types of events possibly explains this observation. However, I interpret it to suggest that source property changes when rupture cuts free surface and this might cause larger damage.<BR>All of the earthquakes ofI>0.5 are surface-rupturing events except ones which occurred beneath alluvial plains. Since all of surface-rupturing events occurred by movements of geomorphologically detectable active faults, I can empirically conclude that earthquake with large potential to cause great damage always occurs on geomorphologically detectable active fault except one beneath alluvial plain.

DOI： 10.11462/afr1985.2001.20_23

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Language：Japanese   Publisher：Tokyo Geographical Society  

The Mitoke active fault system (MAFS) is about 50 km long with a NW-WNW strike in the western margin of the Tamba Mountains, and is generally characterized by an uplifting of the northeast side accompanied by a left-lateral slip. The MAFS is composed of many active faults and is one of the largest active fault system in the northern Kinki district. The Tonoda fault is situated in the central part of the MAFS and is about 15 km long. Based on a study of the fault topography, the Tonoda fault acted with an uplifting northeastern side and a left-lateral slip during the late Quaternary period. A paleoseismological study was requested due to the lack of evidence on which to base on evaluation of earthquake risk.<BR>To clarify the age of the latest event and intervals of events of the Tonoda fault during the late Quaternary, trenches were excavated across the fault scarplet at Sekibayashi where this fault cut river terraces with a NW trend.<BR>The results of this study can be summarized as follows:<BR>This fault is a reverse fault with northeastern side up-thrown and fault planes dips about 80&deg; to the north. Based on differences of geologic section and fault striation, this is accompanied by a left lateral slip.<BR>1) The vertical displacements of depositional surfaces of Li and L2 terraces are 5 to 9m and 1.9-3m respectively, based on drilling and trenching data. This fault is characterized by a average vertical slip rate of 0.1-0.3m/1, 000 years during the late Quaternary period.<BR>2) At trench B, three faulting events were identified since 11 ka. The latest event was dated to be 1, 950-2, 310y. B. P.(A. D. 100-B.C. 395), that is from the Middle Yayoi to Latest Jomon period. The second and third latest events were dated to be 5, 500-7, 500y. B. P, and 8, 500-10, 710y. B. P. The average reccurence interval of faulting is estimated to be about 3, 740 years. A much older faulting event from 17, 000-22, 000y. B. P. was only identified at trench A because of the poor resolution for a paleoseismicity analysis.

DOI： 10.5026/jgeography.109.73

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Publisher：Tokyo Geographical Society  

DOI： 10.5026/jgeography/109.1_plate7

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Language：Japanese   Publisher：Tokyo Geographical Society  

DOI： 10.5026/jgeography.108.276

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Publisher：Springer Nature Singapore  

DOI： 10.1007/978-981-19-1150-7_3

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Publisher：Springer Nature Singapore  

DOI： 10.1007/978-981-19-1150-7_10

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Language：Japanese  

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Language：Japanese   Publisher：National Institute of Polar Research  

DOI： 10.15094/00013477

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Language：Japanese   Publisher：The Institute of Electrical Engineers of Japan  

In order to mitigate landslide risks, monitoring of ground water is essential. Previous indoor experiments suggest that the self-potential approach has an advantage to establish the early warning system in performance to detect related signals and in cost. To evaluate results obtained from the previous indoor experiments, in-situ measurements are required. To achieve this, we selected a test slope at Nishiikawa, Tokushima, Japan and we performed preliminary electrical resistivity exploration (ERT) and core-sampling. The results of ERT show that there are low resistive areas in shallow depth ( < 3 m). The core-sampling results also indicate that there exists the structure which corresponds to slip surface. In addition, anisotropy in magnetic susceptibility was examined and the samples around the estimated the slip surface region provide the oblate ellipsoid characteristics. These results of ERT and core analyses are consistent and make convince the identification of the slip surface. Based on these preliminary results, we set up the in-situ self-potential observation at the slope and started measurements.

DOI： 10.1541/ieejfms.136.297

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Language：Japanese  

J-GLOBAL

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Language：Japanese  

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Language：Japanese   Publisher：The University of Tokyo  

We present new, high-resolution seismic reflection data (2000 Inabe River profile) acquired across the forelimb and backlimb of Kuwana anticline to further image its subsurface geometry. A seismic source (mini-vibrator) and 150-channel digital telemetry recording system were used in an off-end configuration with the nearest receiver adjacent to the source to record seismic waves from deeper reflection points. A 15-m source and geophone spacing give a 7.5-m CMP (common midpoint) spacing on the final section. The nominal CMP stacking fold had 75 traces. We also suppressed coherent noise by repeating source points 5-10 times. After data processing including surface-consistent statics, velocity analysis, normal moveout (NMO) correction, residual statics, CMP stack, and migration, the section was finally depth-converted using stacking velocities. Reflectors imaged on the seismic profile illuminate that fluvial terraces folded across the forelimb and backlimb are consistent with the subsurface structure of the fold imaged in a seismic section, providing insights into the kinematic solution of the underlying active wedge thrust.

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Other Link： http://hdl.handle.net/2261/8152

Language：Japanese   Publisher：海洋出版  

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Language：Japanese   Publisher：実業公報社  

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Language：Japanese   Publisher：海洋出版  

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Language：Japanese   Publisher：四国総合研究所  

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Language：Japanese   Publisher：歴史地震研究会  

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