Features of the Upper Mantle Around Japan as Inferred From Gravity Anomalies

Yoshii, Toshikatsu

doi:10.4294/jpe1952.20.23

Cited by 67 publications

(3 citation statements)

References 38 publications

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“…within the mantle. The residual anomaly due to the mantle had the same shape as that for Tonga, i.e., positive over the trench and island arc Yoshii [1972]. deduced gravity anomalies due to the mantle from a profile across the Japan trench at the latitude of northern Honshu.…”

mentioning

confidence: 68%

Gravity field of the Kuril-Kamchatka Arc and its relation to the thermal regime of the lithosphere

Коган¹

1975

J. Geophys. Res.

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Five gravity anomaly profiles across the Sea of Okhotsk and the Kuril island arc and trench and two profiles from Fiji to Tonga are presented and studied. The four profiles across the Kuril arc are similar and differ from the profile extending off southern Kamchatka. The contributions to gravity anomalies from the crust and mantle are investigated by means of continuous seismic refraction measurements along tracks coincident with the gravity profiles. The mantle gravity anomalies computed from various density models are positive over the island arc, trench, and adjacent Pacific basin and amount to at least +50 mGal. Gravity anomalies due to the mantle suggest the existence of a denser slab 50–60 km thick parallel to the seismic zone. The positive gravity effect of the slab appears to be balanced over the Okhotsk basin by the negative effect of the heated, less dense mantle. The local minimum of Bouguer anomalies occurring over the shoreward flank of the Kuril trench is rather insensitive to the density contrast adopted. The sediments measured seismically account for this Bouguer minimum. The gravity field over the Kuril and Tonga ridges supports the idea of reduced density under the volcanic chain. The local minimum of gravity anomalies associated with the northwestern boundary of the Okhotsk basin is probably related to the fault separating the Academy of Sciences rise from the basin. The ocean‐to‐continent trend of the free air anomalies in the Kuril area is unlike that in Tonga, which might be related to features of heat flow anomalies in the Kurils.

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confidence: 68%

Gravity field of the Kuril-Kamchatka Arc and its relation to the thermal regime of the lithosphere

Коган¹

1975

J. Geophys. Res.

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“…6, early arrivals at the Pacific Ocean side from Hokkaido to northern Kanto are probably due to that the wave velocity is relatively high in the upper mantle for this region as has been pointed out by many authors (for instance, KATSUMATA, 1960KATSUMATA, , 1970UTSU, 1967UTSU, , 1971UTSU and OKADA, 1968;KANAMORI and ABE, 1968;ICHIKAWA, 1969;MOLNAR and OLIVER 1969;NAGUMO et al, 1970;NAGAMUNE, 1971NAGAMUNE, , 1973YOSHII, 1972).…”

Section: Datamentioning

confidence: 83%

P waves to seismological stations in Japan from the underground explosion of November 6, 1971, at Amchitka Island.

Nagamune

1973

J,Phys,Earth

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“…The peculiarity of first-degree can be explained as follows: "Despite the shallower water depth, the Moho depth beneath the marginal seas with high heat flow, such as the Sea of Japan, is not very different from that beneath the western Pacific basin." YOSHII (1972aYOSHII ( , 1972bYOSHII ( , 1973 and SCLATER (1972a) considered that this is due to the hotter and lighter upper mantle with the thin lithosphere beneath the marginal seas. This thin lithosphere has been inferred from surface wave studies (KANAMORI and ABE, 1968;ABE and KANAMORI, 1970).…”

Section: Peculiarity Of the Marginal Seasmentioning

confidence: 99%

Upper Mantle Structure Beneath the North Pacific and the Marginal Seas

Yoshii

1973

J,Phys,Earth

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104

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"Residual gravity anomalies" , RGA, in the north Pacific are calculated from the explosion seismic results and examined as a function of the sea-floor age deduced from the geomagnetic anomalies.The RGA, which implies the mass anomaly in the upper mantle, increases systematically as the age increases; this suggests gradual cooling of the upper mantle away from the midocean ridges.The RGA in the Hawaii region, which is smaller than predicted by the standard RGA vs. age curve by about 100 mgal, implies hot material beneath this region. On the other hand, the RGA in the Parece Vela Basin is larger than predicted by the standard curve by about 100 mgal. This deviation can be expected if the upper mantle material beneath the marginal seas is of higher density than that beneath the normal ocean. The thickness of the "plate" inferred from the RGA is approximately proportional to the square root of the age.

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Features of the Upper Mantle Around Japan as Inferred From Gravity Anomalies

Cited by 67 publications

References 38 publications

Gravity field of the Kuril-Kamchatka Arc and its relation to the thermal regime of the lithosphere

Gravity field of the Kuril-Kamchatka Arc and its relation to the thermal regime of the lithosphere

P waves to seismological stations in Japan from the underground explosion of November 6, 1971, at Amchitka Island.

Upper Mantle Structure Beneath the North Pacific and the Marginal Seas

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