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Abstract

An analysis of the steady-state heat conduction model for the Earth's crust and the upper mantle revealed that the main difficulties in the downward continuation of subsurface geothermal measurements q were connected with an estimation of the heat flow density q"SUB M" at the Moho boundary and of the source distribution f. Solving the steady-state heat conduction equation numerically by means of finite differences (finite elements), we can describe the relation between q, q"SUB M" and f by a linear algebraic system. To overcome the non-uniqueness and instability, a least squares approach is suggested to solve these systems. Bounds for the square-means of the unknown parameters q"SUB M" and f are introduced, whereby it is possible to find solutions with appropriate mean properties. A two-dimensional geothermal profile crossing Central Europe is used to demonstrate this method. The difficulties in estimating reasonable mantle heat flow density and optimal heat source models from geothermal measurements only are pointed out.-Authors