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Volume 55 (2001)
- Issue 6 Pages 321-
- Issue 5 Pages 263-
- Issue 4 Pages 197-
- Issue 3 Pages 129-
- Issue 2 Pages 69-
- Issue 1 Pages 1-
Volume 55, Issue 4
Displaying 1-8 of 8 articles from this issue
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Shimosa Daichi Reseach GroupArticle type: Article
2001 Volume 55 Issue 4 Pages 197-198
Published: July 25, 2001
Released on J-STAGE: July 14, 2017
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Haruto Kodera, Masao Sugita, Yutaka Mitani, Naoto Saito, Fossils Rese ...Article type: Article
2001 Volume 55 Issue 4 Pages 199-200
Published: July 25, 2001
Released on J-STAGE: July 14, 2017
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Research Group for Debris Flow Disaster in the Rokko MountainsArticle type: Article
2001 Volume 55 Issue 4 Pages 201-216
Published: July 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSKobe and Ashiya Cities are situated on an alluvial fan and plain in the southern foot of the Rokko Mountains, western Japan. Talus debris from the mountains was produced due to collapse, which was triggered by the Hyogoken-Nambu earthquake. This area has experienced at least three strong earthquakes attacked, such as the ones in 1596, 5-6th century and 6300 years ago. We consider here whether there is an increase of debris flows after earthquake activity. The ages of debris flow and flood deposits were obtained from archeological data. Flood and debris flow deposits were recognized at archeological survey sites, and ancient sedimentary environment was estimated from outcrop investigations. Debris flow and flood deposits were found to often overlie earthquake induced sand dykes, indicating that flood events occur after earthquake. It is significant that debris flow and flood deposits show a tendency to increase after the earthquakes. Moreover, the main accumulation space shifted from alluvial fan to lowland about 1,000 years ago. Therefore, the talus debris of the Rokko Mountains is transported easily by debris flows due to heavy rains after the Hyogoken-Nambu earthquake, and accumulates on the alluvial plain.View full abstractDownload PDF (3194K) -
Nobuyuki Takahama, Tomio OtsukaArticle type: Article
2001 Volume 55 Issue 4 Pages 217-226
Published: July 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSThe authors identified six stratigraphic horizons of preserved deformation structure by ancient liquefaction (liquefaction structure) that have occurred since 24,000yrs, in loam and black soil layers in the Karasu River region, Gunma Prefecture, central Japan. Loam and black soil layers intercalate several dated pumice layers from the Asama Volcano, which is situated about 30km west of the study area. Ancient liquefaction structures reveal that the liquefied material penetrated upward into the pumice layer and blew out, covering younger pumice layers. The occurrence of ancient liquefactions based on their stratigraphic horizons in the pumice layers from youngest are as follows: 1) between 1108 and 1783AD., apreviously unkown historical earthquake, 2) 818AD., [Kanto-Shokoku earthquake, >M7.5], 3) after 10.000yrs BP., 4) between 16,000 and 14,000yrs. BP., 5) slightly before 20,000yrs. BP., and 6) slightly after 24,000yrs. BP. An earthquake, which occurred after 10,000yrs BP. triggered the large-scale Takasaki mudflow (deposit) and the reactivation of the Yudonosan mega-landslide. These ancient liquefactions and related phenomena in the Karasu River region may have a close relationship with the Karasugawa Tectonic Line or the north segment of the Fukaya Fault System, which bound the southwestern margin of the North Kanto Plain.View full abstractDownload PDF (3125K) -
Sadao HirakosoArticle type: Article
2001 Volume 55 Issue 4 Pages 227-239
Published: July 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSDuring the Winter of 1993 and the Autumn of 1995, the writer had been making observations about the nesting activities and the burrows of Procambarus clakii (Girard) in the rice field of fallow state. The rice field is located in the central Kanto Plane, Shimosudo, Gyoda City, Saitama Prefecture. The rice field are used to be tilled at the opening of every Spring, irrigating by water with the depth of 10-15cm. And it has been used to be draining during the Autumn and Winter. So the writer made observation during these draining period of the rice field. The writer surveyed the distribution and the morphological features in the field, and architectural characters on the 20 replica specimens of burrows made by gypsum pouring into the burrows. All of the writer's specimens constructed of single burrow with one opening and a few chambers, some of which have chimney at the opening. Considering from their architectural and morphological features, the writer classified them into three types as follows. Type A: Cylinder-like burrow with diameter 2.5-6.0cm, extending to the depth of 59-104cm, nearly vertical to the plane of rice field, twisting slightly on the way, inflating at the base bordered by a flat plane. Type B: Most of them are inclined to the plane of rice field with 60-70 degrees, extending to the depth of 9-14cm. Base of them are generally widening laterally with the form of chamber, a few of which are globular. Type C: They consist of the upper burrow of Type B and the lower burrow of Type A, which extend from the base of the former. The writer supposed that the process of the formation of the above three types of burrows as follows. Type B was made by the active life of crayfishes under the water level during the Spring and the Summer. And when the rice field commenced the drain state, animals excavated to the deeper position of the water level to escape the dry condition. They may take rest at the basal chamber during the Winter. Type A may be the product of these behavior of animals. Some animals used Type B as secondary burrows and excavate the new burrow from the base of the former. So type C may be the product of these behavior of animals. In conclusion, the writer's three types of burrows might be formed by the nesting behavior of Procambarus clarkii (Girard) influenced by the environmental change of the rice field in one year.View full abstractDownload PDF (3758K) -
Hajime Sakai, Katsuki KurokawaArticle type: Article
2001 Volume 55 Issue 4 Pages 241-246
Published: July 25, 2001
Released on J-STAGE: July 14, 2017
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Haruto Kodera, Masao Sugita, Yutaka Mitani, Naoto Saito, Fossils Rese ...Article type: Article
2001 Volume 55 Issue 4 Pages 247-252
Published: July 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSDownload PDF (1413K) -
Ryuichi Yashima, Kazuo Ohtake, Yoshitaka NagahashiArticle type: Article
2001 Volume 55 Issue 4 Pages 253-257
Published: July 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSDownload PDF (860K)
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