Solid Earth Parameters Modelling

Figure. Iceberg floating In sea (a good example for isostatic equilibrium). Isostasy is a term derived from Greek language meaning equal pressure. This is an alternative view of Archimedes’ principle of hydrostatic equilibrium. According to this principle a floating body displaces its own weight. A mountain chain can be compared with an iceberg or a cork floating in water, or in proper term floating in the mantle. According to the isostasy principle lighter Earth's crust is floating on the dense underlying mantle. The principle of isostasy states that the gravitational equilibrium between the Earth’s lithosphere and asthenosphere is such that the tectonic plates float at an elevation, which depends on their thickness and density. When a certain area of the lithosphere reaches the “state of isostasy”, it is said to be in isostatic equilibrium. The depth at which isostatic equilibrium prevails is called the compensation depth.

Different methods can be used for estimating Moho parameters i.e crustal thickness and crust-mantle density contrast e.g. seismic and gravimetric methods. We developed a gravimetric-isostaic model to determine Moho parameters (cf. Sjöberg 2009, Bagherbandi 2011 and Bagherbandi et al. 2013). According to gravimetric-isostatic models, the topographic mass surplus and the ocean mass deficiency are compensated either by a variable crustal thickness or density. Isostatic equilibrium is described by means of the isostatic gravity anomalies which should theoretically be equal zero, provided that the refined Bouguer gravity anomalies are isostatically fully rebalanced by the corresponding gravitational attraction of compensating masses. Moho parameters can be used in different geophysical and geodynamical applications such as sub-crustal stress determination, etc.

 

Figure. Crustal thickness using gravimetric-isostatic model with a resolution of 1x1 arc-degree. Unit: km. Credit: Bagherbandi et al. (2013)

Figure. Estimated crust-mantle density contrast determined by combination of seismic and gravimetric-isostatic models. Unit: kg/m3. Credit: Sjöberg and Bagherbandi (2017)

Published by: Camilla Nordin Page responsible: Gunilla Mårtensson Updated: 2019-05-27
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