摘要:

We study the effects of present‐day glacial discharges and the growth of the Antarctic ice sheet on exciting the Earth' rotational axis. Glacial forcing could cause a maximum change in J2of about one‐third of the observed amount, for the Maxwell rheology and for Burgers’ body models with a long‐term, lower‐mantle viscosity greater than about 1023P. For transient rheologies the amount of excitation due to glacial melting decreases. Polar wander is not much excited by recent glacial melting for the various types of rheologies

ISSN:0094-8276    

DOI:10.1029/GL013i006p00533

年代:1986

数据来源: WILEY

摘要:

Since 1978 we have conducted extensive gravity surveys in Central Honshu, Japan, to establish 5,345 new gravity stations. The results are synthesized into a Bouguer anomaly map with the data from other sources. The map shows a distinctive belt of gravity gradient on the Pacific side of Central Honshu. This belt is about 300 km long and 30‐50 km wide, across which Bouguer anomaly changes by about 30‐50 mGals. Broad Bouguer high prevailing further oceanward of Central Honshu is sharply bounded by this anomaly belt. There seems to be no apparent correlation between this anomaly belt and the surface geol

ISSN:0094-8276    

DOI:10.1029/GL013i006p00537

年代:1986

数据来源: WILEY

摘要:

The effect depth‐dependent viscosity has on convective mixing and sampling (or degassing) of primitive mantle beneath ridges is explored in two‐dimensional models. Higher relative viscosities in the deep mantle decrease convection velocities and strain rates and prolong the residence time of material in the deep mantle. If the average viscosity of the lower mantle is at least 100 times the viscosity of the upper mantle, then some mantle material could have survived from very early in the earth's history. If, in addition, the depth of degassing under ridges has been less than 75 km, on average over earth history, then helium isotopic systematics are qualitatively consistent with whole mantle convect

ISSN:0094-8276    

DOI:10.1029/GL013i006p00541

年代:1986

数据来源: WILEY

摘要:

Wave equations that govern porous flow in a matrix and analogous equations for fluid conduits can be reduced to the Korteweg‐deVries equation in the limit of small perturbation

ISSN:0094-8276    

DOI:10.1029/GL013i006p00545

年代:1986

数据来源: WILEY

摘要:

Rayleigh and Love phase and group velocity dispersion measurements are performed along a purely african path between the Geoscope stations TAM and AGR, for the Leewards Isl. earthquake of March 16, 1985. This regional study is important as it brings deep‐seated structure information in a seismologically blank region of Africa. It enables to improve the spatial resolution of larger scale models. For periods longer than 160 s. and up to 250 s., the fundamental Rayleigh wave dispersion is in agreement with prediction by global models. For shorter periods, the results fall below this prediction, which is an indication of lithospheric S‐wave velocities lower than those of the models. The results are also compared with previous regionalizations. The Rayleigh second higher mode is extracted at AGR, and the phase velocity dispersion obtained in the period range 50‐140 s is in agreement with the theoretical dispersion for

ISSN:0094-8276    

DOI:10.1029/GL013i006p00547

年代:1986

数据来源: WILEY

摘要:

Measurement of the spatial decay of spectral amplitudes of the higher‐mode seismic surface wave train Lgindicates that in the Great Basin the apparent seismic quality factor,Q, is a function of frequency. Observations along a 300 km profile recording of a nuclear explosion yield the functionQ(ƒ)=206ƒ0.68over the band 0.3 ⩽ ƒ ⩽ 10.0 Hz. Similar analysis using numerous recordings of earthquakes along paths which provide a good average sampling of the Great Basin crust givesQ(ƒ) = 214(± 15)ƒ0.54(±0.09), for 0.3 ⩽ ƒ ⩽ 5.0 Hz. If the crustal sampling by Lgenergy from nuclear explosions (surface sources) is primarily in the shallow crust, as has been suggested, then these results indicate a greater frequency dependence of apparentQth

ISSN:0094-8276    

DOI:10.1029/GL013i006p00551

年代:1986

数据来源: WILEY

摘要:

The suggestion that the Earth is being bombarded by cometoids that subject it to an influx of 3×1011water molecules/cm²‐sec encounters severe aeronomical problems. There is a serious disposal problem for water molecules deposited near 100 km. The implications for Venus and Mars also present serious problems. It is argued that the proposable is untena

ISSN:0094-8276    

DOI:10.1029/GL013i006p00555

年代:1986

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/GL013i006p00559

年代:1986

数据来源: WILEY

摘要:

The question of ion heating at subcritical collisionless shocks is reviewed in light of newly proposed mechanisms.

ISSN:0094-8276    

DOI:10.1029/GL013i006p00561

年代:1986

数据来源: WILEY

ISSN:0094-8276    

DOI:10.1029/GL013i006p00563

年代:1986

数据来源: WILEY