Report of Hydrographic Researches
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Contents
Entire documents
Preface
130th Anniversary Issue. (in Japanese), p.1
Special Articles
-
An Overview on the Recent Research and Development for Hydrographic Works. (in Japanese)
, p.3 -
Electronic Navigational Chart (ENC) Production of Japan and Its Correspondence. (in Japanese)
, p.19 -
Progress in Trajectory Prediction of Drifting Matter. (in Japanese)
, p.43 -
Challenges to Observe Sea Bottom Crustal Deformations with Acoustic Ranging Technique. (in Japanese)
, p.47
Original Papers
-
The Submarine Faults in Hakodate Bay. (in Japanese )
, p.59 -
A Source Model to Explain Crustal Deformations by Earthquake Swarm around Izu-shoto in 2000. (in Japanese)
, p.71 -
Improved Co-tidal Charts around Osaka Bay, Seto Inland Sea. - Influence of Coriolis force on the tidal distribution- (in English )
, p.85
Notes
-
Ocean Bottom Seismographic Observation at Fukutoku-okanoba Submarine Volcano. (in Japanese)
, p.101
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Abstracts
The Submarine Faults in Hakodate Bay.
Four faults 1 to 3 km in length were found off the western shore of Hakodate Bay. They are reverse faults with down throw to east, striking N-S to NNW-SSE roughly. They show an en echelon form trending in N-S direction. On the basis of their distribution and deformational features, these faults are considered to be the seaward extension of the active fault zone on the western margin of Hakodate Plain. This shows that the fault zone extends seaward to at least 10 km. It is probable that these submarine faults have been active in the Holocene.
( Text is Japanese )A Source Model to Explain Crustal Deformations by Earthquake Swarm around Izu-shoto in 2000.
We used GPS observations to obtain crustal deformations by volcanic activity of Miyake-jima and earthquake swarm around Izu-shoto since the end of June, 2000. The results showed movements extending in a northeast-southwest direction between Miyake-jima and Kozu-shima.
In this report, we carried out an inversion analysis of the GPS results and suggested a source model to explain observed crustal deformations. Although it is very difficult to decide a unique model because of few stations and partial locations of the stations, the proposed model is consistent with the GPS results. Results suggest that a dike of about 7-8m in width intruded between Miyake-jima and Kozu-shima.
In addition, the model is also consistent with results of dense GPS observations that was carried out at Kozu-shima in June, 2001.
( Text is Japanese )Improved Co-tidal Charts around Osaka Bay, Seto Inland Sea. -Influence of Coriolis force on the tidal distribution-
Using the equation of motion for tide and tidal current data around Osaka Bay, momentum balance of tidal waves are investigated and precise co-tidal charts are edited. Some distinctive characteristics are recognized in the charts such as nodal area of M2 tide shifted to the northern corner of Awaji-shima. These distributions are almost explained by the influence of Coriolis force on tidal current. In addition, generation of shallow water tide of M4 around Akashi-strait, which was first introduced by S. Ogura(1933), is quantitatively discussed based on tidal current data.
( Text is English )Ocean Bottom Seismographic Observation at Fukutoku-okanoba Submarine Volcano.
An ocean bottom seismographic (OBS) investigation was carried out to obtain seismic characteristics around Fukutoku-okanoba, one of the active submarine volcanoes on the southern end of the volcanic front of the Izu-Ogasawara (Bonin) arc.
Crustal structure was estimated by seismic refraction survey using an airgun and OBS system. First arrivals were hardly detected within an offset of 10 km in several record sections, although an airgun with large capacity of 4000 inch3 was used. This suggests that there are low wave speed materials and/or seismic wave attenuated zone beneath the topographically depressed region around Fukutoku-okanoba.
The seismicity in and around Fukutoku-okanoba region was low during the observation period from Jun. 28 to Aug. 1, 1999. Most of the hypocenters were located outside of the OBS array and they were distributed in the connected region between the Ogasawara Ridge and Mariana Ridge. Many micro earthquakes with monotonic frequency of 7-14 Hz, so-called long period event (LPE) popular in volcanic regions, were recorded at several OBSs but independently.
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