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Volume 101, Issue 1
Displaying 1-9 of 9 articles from this issue
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Excavation Study of the Umehara Fault, Central Strand in the Nobi Active Fault SystemAtsumasa OKADA, Mitsuhisa WATANABE, Masataka ANDO, Tameshige TSUKUDA, ...1992 Volume 101 Issue 1 Pages 1-18
Published: February 25, 1992
Released on J-STAGE: October 13, 2010
JOURNAL FREE ACCESSThe Nobi Active Fault System, one of the most active fault systems in Japan, is composed of a series of active faults extending 80 km in the NW-SE direction with en echelon arrange-ment. These faults display predominantly left-lateral displacement. In 1891, major strands within the system were ruptured during the great (M=a8.0) seismic event (the Nobi earthquake) of 1891. The magnitude of this event was extraordinarily large for normal intraplate earth-quakes.
In order to clarify the long-term behavior of the fault system, the activity of each segment or strand has been examined by geological and geomorphological methods. A section of the Late Pleistocene-Holocene sediments broken by one of the segmented faults (Umehara Fault) was studied to establish the timing of faulting mainly by trench excavation The results are summarized as follows:
(1) An accumulated displacement ensures that the Neodani Fault lying at the middle of whole length of the Nobi Fault System is the most active and longest strand. The Neodani Fault has ruptured at least, once every few thousand years with higher frequency than other strands.
(2) The entrenchment across the Umehara Fault provided recognition of the horizons on which paleo-seismic events had taken place on the fault zone. The six events were inferred within trench logs. The ages are 1891 A. D.(Event 1), 20, 000 y. B. P.(Event 2), 28, 000 y. B. P.(Event 3) and prior to 30. 000 y. B. P.(Event 4-6). The ages of Events 2, 3 and 6 are not conclusive.
(3) The recurrence intervals of the Umehara Fault between the last three events are over 10, 000 years, which are ten times longer than that of the Neodani Fault.
(4) Thus, other strands in this fault system are inferred to have been dormant even when the Neodani Fault ruptured. It is likely that very large earthquake seldom occurred in association with faulting not only along the Neodani Fault but also along the other less active strand such as the Umehara Fault.
(5) The 1891 Nobi earthquake was an extraordinarily large one. However, the record of the great Nobi earthquake should be used in evaluating future seismic hazards. especially in areas where long active faults are densely distributed.View full abstractDownload PDF (4478K) -
Atsumasa OKADA, Tokihiko MATSUDA1992 Volume 101 Issue 1 Pages 19-37
Published: February 25, 1992
Released on J-STAGE: October 13, 2010
JOURNAL FREE ACCESSThe Neodani fault to the north of Nagoya, central Japan, is a principal strand of the Nobi fault system. The fault moved primarily in a left-lateral sense during the great Nobi earthquake of 1891 (Magnitude 8.0). The maximum vertical and horizontal offsets are 6 m at Midori and 7-8 m at Naka, respectively. After reviewing previous works, we discuss new geomorphological and geological data bearing on the 1891 and earlier paleoearthquakes in the latest Quaternary: specifically we find that
1) The 1891 vertical offset was about 5 m at the western slope of Terayama which is located on the northwestern extension of the well-known Midori fault scarp.
2) The subsurface data show that the vertical offset of the base of the alluvial deposits beneath the Midori scarp is about same as that of the ground surface at the scarp, implying that the 1891 event was the first faulting event since the beginning of the deposition of the allu-vium. The radiocarbon date suggests that the alluvium is not older than 1, 000 years in age.
3) The lower river terrace, ca. 14, 000 years old, is displaced as 14 m vertically at Terayama in Midori where about 5 m vertical displacement occurred in 1891, and a stream incising the lower terrace on the fault line at Naka offsets ca. 28 m laterally where 7-8 m lateral displacement occurred in 1891. If the fault is characterized by the repeated occurrence of earthquakes of the same size, both the 14 m vertical offset at Terayama and 28 m lateral offset at Naka may be interpreted to be the result of 3 to 4 events occurring at average intervals of about 3, 000-4, 000 years since the formation of the lower terrace. The observation also indicates that the Neodani fault, at least in the central segment including Midori and Naka, has averaged 2m per one thousand years in the left-lateral slip rate in that period.View full abstractDownload PDF (5344K) -
Shuichi SHINOHARA1992 Volume 101 Issue 1 Pages 38-58
Published: February 25, 1992
Released on J-STAGE: October 13, 2010
JOURNAL FREE ACCESSThe purpose of this study is to consider types and distribution of main ports of fish landi ng in Japan through landed quantity by kind of fish. Main ports of fish landing are identified as 235 fishing ports with fish landing of more than 5, 000 tons in 1984, when Japanese fishermen caught the largest quantity of fish in the past (Table 1 and Fig. 1).
By means of factor analysis, twenty variables about landed quantity of 235 ports (Table 2) are summarized into seven factors (Table 3). Landing of large quantity of sardines or macker els or saury represented in the first factor is the most commonly chracteristic to the main ports of fish landing in Japan. The ports are classified into ten types, by means of cluster analysis based on seven factors, named from A to J (Fig. 2, Tables 4 and 5).
Shimizu (Shizuoka Prefecture) and Yaizu are the ports of the type A, where frozen or processed fish, tuna, or skipjack are landed in large quantity. Choshi is the port of the type B, where the largest quantity of true sardine, chub mackerel and saury are landed. Kushiro is the port of the type C, where true sardine, saury, walleye pollack, salmon are landed in large quantity. The quantity of fish landing at Kushiro is the largest in Japan in 1984. Squid of the largest quantity in Japan are landed at Hachinohe, the port of the type D. Cod, flatfish, or sand lance are landed in large quantity at the ports of th e type E, whic include Wakkanai, Ishinomaki, Monbetsu, Abashiri and Matsukawaura. Main fish at the ports of the type F is fish in warm water such as horse mackerel and spotted mackerel. The ports of the type F contain Nagasaki, Hakata, Shimonoseki, Shiogama, Sakai, Karatsu, Matsuura, Makurazaki, Ushibuka, Kushikino, Ura and Akune. The type G involves 47 fishing ports, which are characterized by landing of shellfish or sea weed. The type H consists of Wakaura, Misaki, Kagoshima, Funakoshi (Ehime Prefecture), Mochimune, Fukaura, Tarumi, Usui and Uchiura. The characteristic of these ten ports is landing of high price fish such as yellowtail and so on. A lot of salmon are landed on the ports of the type I, whichi nclude Miyako, Nemuro, Kamaishi and Yamada. The other 152 ports of the type J ar e the averaged ports in the total 235 fishing ports.
There are areal and regional differences of the distribution between the types of the main ports of fish landing in Japan (Fig. 3). The types of the main ports can be classified into four categories of distribution:“warm water”“cold water”“warm and cold water” and “shallo w water”. Shimizu, Yaizu and Nagasaki are the typical main ports of the “warm water” category; Kushiro is the most typical port of the “cold water” category; Choshi, Hachinohe and Sakai are the typical main ports of the “warm and cold water” category; Wakaura is the most typical ports of the “shallow water” category. These eight ports are the most typical and important ports of fish landing in Japan. Based on the four categories of the distribution of main ports of fish landing, the coast in Japan can be divided into ten areas of fishing industry (Fig. 4).View full abstractDownload PDF (4420K) -
Kenji HAYATSU1992 Volume 101 Issue 1 Pages 59-70
Published: February 25, 1992
Released on J-STAGE: October 13, 2010
JOURNAL FREE ACCESSMyoko volcano, situated in the northern part of Central Japan, is one of the composit stratovolcanoes whose life histories have been studied in detail. In this paper, ten volcanic ash layers belonging to the central cone stage of Myoko volcano are described, and more detailed volcanic history of the central cone stage is compiled in connection with the informations already known.
The result are summarized as follows:(1) The central cone stage started ca. 5, 800 years ago. The central cone, Mt. Myoko, was almost built at the early time of the stage.(2) The youngest magmatic eruption of Myoko volcano took place ca. 4, 200 years ago, and produced pyroclastic flows and pyroclastic surges.(3) The youngest steam explosion of Myoko that was confirmed took place ca. 3, 000 years ago, and produced small pyroclastic surges.(4) For 1, 600 years between 5, 800 and 4, 200 years ago, a series of eruption whose ejecta were kept as an obvious stratum at the foot of Myoko volcano took place at the average rate of once for 200 or 300 years. After the violent eruption of ca. 4, 200 years ago, Myoko rapidly became less active, and the eruption in the similar scale took place only once or twice for ca. 4, 200 years up to the present.(5) The central cone stage was dominated mainly by the activity of dacitic magma, and coincided with the time when pyroclastic flows and pyroclastic surges were apt to be produced by explosive eruptions.View full abstractDownload PDF (2563K) -
Takahiro MIYAUCHI, Sayumi YAMASHITA1992 Volume 101 Issue 1 Pages 71-78
Published: February 25, 1992
Released on J-STAGE: October 13, 2010
JOURNAL FREE ACCESSA flight of late Quaternary marine terraces in the Tobi-shima Island, Northeast Japan, shows tilt toward the east. Uplift pattern of five paleoshorelines allows two modes of deformation to be estimated; chronic uplift marked in the southwestern part, and south-eastward tilting probably by cumulative seisimic crustal displacement.View full abstractDownload PDF (1761K) -
[in Japanese], [in Japanese]1992 Volume 101 Issue 1 Pages 79-81
Published: February 25, 1992
Released on J-STAGE: October 13, 2010
JOURNAL FREE ACCESSDownload PDF (618K) -
[in Japanese]1992 Volume 101 Issue 1 Pages plate1-plate2
Published: February 25, 1992
Released on J-STAGE: October 13, 2010
JOURNAL FREE ACCESSDownload PDF (659K) -
Excavation Study of the Umehara FaultAtsumasa OKADA1992 Volume 101 Issue 1 Pages plate3-plate4
Published: February 25, 1992
Released on J-STAGE: October 13, 2010
JOURNAL FREE ACCESSDownload PDF (1231K) -
Atsumasa OKADA1992 Volume 101 Issue 1 Pages plate5-plate6
Published: February 25, 1992
Released on J-STAGE: October 13, 2010
JOURNAL FREE ACCESSDownload PDF (1273K)
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