Showing papers by "Sean C. Solomon published in 1975"

Some aspects of core formation in Mercury

Abstract: An evaluation of existing theories on the existence of the planet's metallic core is presented. Topics considered are: (1) magnetic fields; (2) surface geology; (3) cosmochemical models.

Mare Volcanism and Lunar Crustal Structure

Abstract: It is pointed out that the concept of hydrostatic head, the height to which a fluid at a given pressure will rise in a gravitational field, can be usefully applied to magmatic liquids and to a number of problems in volcanology For the moon, hydrostatic head arguments are an essential ingredient to explanations of mascons and of the scarcity of farside maria In the reported investigation, simple hydrostatic concepts are extended to synthesize results from experimental petrology, lunar chronology, thermal history models, seismology, and gravity Attention is given to a scenario for early lunar history, the density of lunar rocks and basaltic liquids, the thickness of the lunar crust, the source depth of mare basalt versus time, hydrostatic considerations with respect to the occurrence of high-titanium and low-titanium mare basalts, the structure of mascons, and the extension of the concepts of hydrostatics to the parent liquids of other basaltic rocks returned from the lunar surface

Inversion Schemes for Surface Wave Attenuation and Q in the Crust and the Mantle

Abstract: Summary Seismic wave attenuation, or Q-', is one of the parameters traditionally used to distinguish lithosphere from asthenosphere. As a means of inverting surface wave attenuation measurements to obtain Q-l as a function of depth, a classical linear inverse problem, we introduce a set theoretical approach. The set theoretical approach includes both the square matrix inverse and the linear programming method, which agree in concept but differ in that the constraints consist of mean or extreme hyperplanes, respectively. The set theoretical approach to inverting attenuation observations has two advantages: (1) The lithosphere thickness may be readily estimated using a geometric visualization of the square matrix inverse, which identifies the feasibility of a solution. (2) The approach allows more strict regulation of solution parameters than does the least square inverse, which often leads to a negative solution for inaccurate and sparse attenuation data. We apply the set theoretical approach to inverting the measured attenuation of Love and Rayleigh waves in western and eastcentral United States. Identifying the base of the lithosphere as the depth at which Q- ' increases sharply, we obtain lithosphere thicknesses of 80+20km and 130+30km in the two regions, respectively. Q-' in the asthenosphere is about a factor of 2 greater beneath western than eastcentral United States. A decrease in Q-' with depth in the lithosphere is resolvable in both regions.