Gravity in the junction between the Japanese and the Izu-Bonin Islands.

Segawa, Jiro; Bowin, Carl

doi:10.4294/jpe1952.24.275

Cited by 5 publications

(4 citation statements)

References 14 publications

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“…It is interesting t o note, however, that a zone with significant negative free air gravity anomalies and topographic depression extends from the Hokkaido comer (Kuril-Japan junction) to the anomalous stress field region discussed above (Den ef al. 1971;Den & Hotta 1973;Segawa & Bowin 1976). Because the effects of body force are not included in our model calculation and the gravity anomaly is very sensitive to the uppermost part of the crust, our model fails to explain the distribution of the gravity anomaly.…”

Section: Discussionmentioning

confidence: 96%

“…Because the effects of body force are not included in our model calculation and the gravity anomaly is very sensitive to the uppermost part of the crust, our model fails to explain the distribution of the gravity anomaly. As interpreted by Segawa & Bowin (1976), underthrusting of a plate, especially at a junction of two adjoining trenches, is generally associated with local topographic depression and causes local mass deficiency. Future investigations of major earthquakes occurring at a junction would also provide more detailed pictures of such deformation of the continental lithosphere.…”

Section: Discussionmentioning

confidence: 99%

“…It has also been noted that certain other interesting geophysical phenomena are found near arc-arc junctions, such as negative travel-time anomalies of P-waves recorded at stations near the junctions (Aoki & Tada 1973), broad negative free-air gravity anomalies (Segawa & Bowin 1976), and unusual earthquake aftershock sequences (Kanamori 197 1). Moreover, the configuration of the Wadati-Benioff zone suggests that the subducting oceanic lithosphere is considerably deformed in the process of subduction near arc-arc junction (Aoki 1974;Moriya 1978).…”

Section: Introductionmentioning

confidence: 99%

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The effect of the contorted 'nose' of a subducting slab on the stress field in the continental lithosphere at an arc-arc junction

Minamino

Fujii

1981

Geophysical Journal International

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In the continental lithosphere, the stress field near the junction of two arc-trench systems often shows a different state from the regional trend. By assuming that the drag forces and nose-shaped contortion of the subducting slab control the state of stress in such a region, the vertical displacements and stress distribution in a continental lithosphere with a concave seaward boundary are calculated using a three-dimensional finite element method. It is also assumed that the drag is applied to a depth of about 60 km which is the depth limit of thrust-type earthquakes along the interplate boundary.It is demonstrated that the anomalous stress field resulting from the contorted 'nose' of the subducting slab extends inland some distance from the corner of an arc-arc junction. The area of anomalous stress field is characterized by surface upheavals and a stress regime conductive to strike-slip faulting, though the extent of this area depends on the model parameters. The degree of contortion, i.e. the width of the contorted 'nose' of the subducting slab, remains arbitrary even when appropriate restrictions such as the conservation of surface area and fixed meeting angle and dip angles of the two neighbouring subduction zones are made in symmetrical models. Applying the model to the Hokkaido corner, i.e. the junction of the Kurile and Japan trenches, the anomalous stress field appears in the south-eastem part of Hokkaido and coincides more or less with geophysical observations.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effect of the contorted 'nose' of a subducting slab on the stress field in the continental lithosphere at an arc-arc junction

Minamino

Fujii

1981

Geophysical Journal International

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“…After taking measurements using the Vening Meinesz pendulum apparatus (Matuyama, 1934;Kumagai, 1953), many gravity measurements around the Japanese Islands have been conducted using sea gravimeters, and some gravity anomaly maps have already been published (Tomoda, 1973;Watts, 1976;Segawa, 1976;Segawa and Bowin, 1976;Segawa and Tomoda, 1976;Watts et al, 1976;Stroyev, 1971;Tomoda and Fujimoto, 1982). The Hydrographic Department of Japan conducted detailed marine gravity measurements around Japan and published some 50 free-air gravity anomaly maps in a scale of 1:200,000 in the series of the Basic Map of the Sea over the continental shelf around Japan, and a free-air anomaly map in the vicinity of the continental shelf around Japan is compiled based on these data (Ganeko and Harada, 1982).…”

Section: Introductionmentioning

confidence: 98%

Gravity field around Japan — sea gravimetry by the Geological Survey of Japan

Ishihara

1983

Marine Geodesy

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Using a LaCoste & Romberg sea gravimeter, more than 60,000 gravity measurements were obtained from 11 research cruises around Japan, as conducted by the Geological Survey of Japan from 1974 to 1979. From the misties* of freeair anomalies the r.m.s. accuracy of the measurements was estimated to be 2.8 mgal (with the satellite navigation system and an EM-log) and 0.7 mgal (with a Doppler sonar system). From this result it was suggested that the observed gravity error was mainly due to the ship's velocity measurements. Mean free-air anomalies of 15' x 15', 30' x 30', and 1° x 1° were calculated using these measurements and compared with the previous data.A free-air anomaly map in the area of 22°N to 46°N and 123°E to 148°E was compiled based mainly on these data. The map fully covers four island arc and trench systems-the Northeast Japan, the Ogasawara (Bonin), the Southwest Japan, and the Ryukyu Arc and Trench-and they are associated with paired *In this paper a "mistie" is used in the meaning of a discrepancy in observed values at a track-line intersection.

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Marine gravimetry

Cochran¹,

Talwani²

1979

Reviews of Geophysics

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The first continuous shipboard gravity measurements were made just over 20 years ago on board U.S.S. Compass Island (Worzel, 1958) and, since about 1961, gravity measurements have been routinely made by several institutions as part of marine geophysical surveys. During the 1960's much effort went into developing and refining instruments and into understanding the mechanical and environmental factors affecting them. A major factor in improving the reliability of gravity measurements was the introduction in the late 196O's of satellite navigation systems which meant that accurate positions, speeds, and courses, all necessary to compute the theoretical gravity value and the Eotvos correction, could be obtained.

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Gravity in the junction between the Japanese and the Izu-Bonin Islands.

Cited by 5 publications

References 14 publications

The effect of the contorted 'nose' of a subducting slab on the stress field in the continental lithosphere at an arc-arc junction

The effect of the contorted 'nose' of a subducting slab on the stress field in the continental lithosphere at an arc-arc junction

Gravity field around Japan — sea gravimetry by the Geological Survey of Japan

Marine gravimetry

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