Trans-dimensional Monte Carlo sampling applied to the magnetotelluric inverse problem

Author(s)

Eric Mandolesi, Nicola Piana Agostinetti

Abstract

The data required to build geological models of the subsurface are often

unavailable from direct measurements or well logs. In order to image the

subsurface geological structures several geophysical methods have been

developed. The magnetotelluric (MT) method uses natural, time-varying

electromagnetic (EM) fields as its source to measure the EM impedance of

the subsurface. The interpretation of these data is routinely undertaken

by solving inverse problems to produce 1D, 2D or 3D electrical

conductivity models of the subsurface. In classical MT inverse problems

the investigated models are parametrized using a fixed number of

unknowns (i.e. fixed number of layers in a 1D model, or a fixed number

of cells in a 2D model), and the non-uniqueness of the solution is

handled by a regularization term added to the objective function. This

study presents a different approach to the 1D MT inverse problem, by

using a trans-dimensional Monte Carlo sampling algorithm, where

trans-dimensionality implies that the number of unknown parameters is a

parameter itself. This construction has been shown to have a built-in

Occam razor, so that the regularization term is not required to produce

a simple model. The influences of subjective choices in the

interpretation process can therefore be sensibly reduced. The inverse

problem is solved within a Bayesian framework, where posterior

probability distribution of the investigated parameters are sought,

rather than a single best-fit model, and uncertainties on the model

parameters, and their correlation, can be easily measured.

Organisation(s)

Department of Geology

External organisation(s)

Dublin Institute for Advanced Studies

Journal

Journal of Physics: Conference Series

Volume

574

Pages

12132

ISSN

1742-6588

Publication date

01-2015

Peer reviewed

Yes

Austrian Fields of Science 2012

105102 General geophysics

ASJC Scopus subject areas

General Physics and Astronomy

Portal url

https://ucrisportal.univie.ac.at/en/publications/53d72a63-4505-42d1-84dc-680ed82419b0