Rapid inversion of data from 2D resistivity surveys with electrode displacements

Geophysical Prospecting - Tập 66 Số 3 - Trang 579-594 - 2018
M.H. Loke1, Paul Wilkinson2, Jonathan Chambers2, Philip Meldrum2
1Geotomosoft Solutions 115 Cangkat Minden Jalan 6 Gelugor Penang 11700 Malaysia
2British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK

Tóm tắt

ABSTRACTResistivity monitoring surveys are used to detect temporal changes in the subsurface using repeated measurements over the same site. The positions of the electrodes are typically measured at the start of the survey program and possibly at occasional later times. In areas with unstable ground, such as landslide‐prone slopes, the positions of the electrodes can be displaced by ground movements. If this occurs at times when the positions of the electrodes are not directly measured, they have to be estimated. This can be done by interpolation or, as in recent developments, from the resistivity data using new inverse methods. The smoothness‐constrained least squares optimisation method can be modified to include the electrode positions as additional unknown parameters. The Jacobian matrices with the sensitivity of the apparent resistivity measurements to changes in the electrode positions are then required by the optimisation method. In this paper, a fast adjoint‐equation method is used to calculate the Jacobian matrices required by the least squares method to reduce the calculation time. In areas with large near‐surface resistivity contrasts, the inversion routine sometimes cannot accurately distinguish between electrode displacements and subsurface resistivity variations. To overcome this problem, the model for the initial time‐lapse dataset (with accurately known electrode positions) is used as the starting model for the inversion of the later‐time dataset. This greatly improves the accuracy of the estimated electrode positions compared to the use of a homogeneous half‐space starting model. In areas where the movement of the electrodes is expected to occur in a fixed direction, the method of transformations can be used to include this information as an additional constraint in the optimisation routine.

Từ khóa


Tài liệu tham khảo

10.1190/1.2335575

10.1046/j.1365-2478.1999.00139.x

10.1016/j.geomorph.2010.09.017

10.3997/1873-0604.2013002

Daniels R.W., 1978, An Introduction to Numerical Methods and Optimization Techniques

10.1190/1.1442813

10.1111/j.1365-2478.1979.tb00961.x

10.1046/j.1365-246x.1998.00555.x

10.1111/j.1365-246X.2004.02190.x

Golub G., 1996, Matrix Computations

10.1144/qjegh2011-028

Jennings A., 1992, Matrix Computation

J.H. Kim 2014

10.1190/1.1444877

10.1111/j.1365-2478.1996.tb00142.x

LokeM.H.2000.Topographic modelling in resistivity imaging inversion.62nd EAGE Conference & Technical Exhibition Glasgow Scotland Extended Abstracts D‐2.

10.1071/EG03182

LokeM.H.andDahlinT.2010.Methods to reduce banding effects in 3‐D resistivity inversion.16th European Meeting of Environmental and Engineering Geophysics Zurich Switzerland Expanded Abstracts A16.

10.1016/j.jappgeo.2013.02.017

10.3997/1873-0604.2013025

LokeM.H. WilkinsonP.B.andChambersJ.E.2016.3‐D resistivity inversion with electrodes displacements.ASEG‐PESA‐AIG 25th Geophysical Conference and Exhibition August 21–24 2016 Adelaide Australia Extended Abstracts 809–813.

10.1111/j.1365-2478.1990.tb01859.x

10.1007/s10346-013-0409-1

10.1190/1.1443692

Press W.H., 1992, Numerical Recipes in C

10.1190/1.1443127

10.1190/1.1442649

10.1190/1.1443571

Schwarz H.R., 1973, Numerical Analysis of Symmetric Matrices

10.4133/JEEG5.3.45

Silvester P.P., 1990, Finite Elements for Electrical Engineers

10.3997/1873-0604.2013057

10.3997/1873-0604.2013060

10.1016/j.jappgeo.2015.07.003

10.1016/j.geomorph.2015.10.027

10.1111/j.1365-246X.2010.04760.x

10.1093/gji/ggu483

10.1093/gji/ggv329

10.1002/2015GL067494

10.1046/j.1365-2478.2000.00210.x

10.3997/1873-0604.2003001

Thông tin
Thông tin xuất bản

Geophysical Prospecting

Tập 66 Số 3

579-594

Thông tin tác giả