Open source software for simulations and inversions of airborne electromagnetic data Lindsey Heagy, Seogi Kang, Rowan Cockett, Doug Oldenburg & the SimPEG Team June 19, 2018 

context 

building for researchers ● Flexibility to experiment ○ Prioritize organization and flexibility ● Integration of information ○ Geologic ○ Multiple physics ● Reproducible and transparent 

● Modular: building blocks ○ organized in a framework ○ pieces available to manipulation ● Declarative: express intent ○ write what you mean ○ looks like the math ● Extensible: new research ○ quantitative communication ○ built in feedback loops ● Open: for the future ○ reproducible ○ opportunities for collaboration building for researchers 

building for researchers ● Modular: building blocks ○ organized in a framework ○ pieces available to manipulation ● Declarative: express intent ○ write what you mean ○ looks like the math ● Extensible: new research ○ quantitative communication ○ built in feedback loops ● Open: for the future ○ reproducible ○ opportunities for collaboration 

6 inversion 

(Cockett et al., 2015) 

Implemented in Python! framework 

forward simulation Survey: Data collection and geometry Physics: PDE to solve 

finite volume 

create a mesh 

discretize & solve continuous discrete 

framework 

Data Misfit Regularization Inverse Problem inversion elements 

inversion as optimization 

16 (does it work?) 

a few questions ● Understanding responses ○ How does magnetic permeability or chargeability affect my data? ● Survey design ○ Which system should be used to excite / detect the target of interest? ○ Would adding another receiver orientation improve detection / recovery of the target? ● Inversion ○ Where is a 3D inversion needed? ○ Can a parametric inversion be used? 17 

example: conductive plate 18 

example: conductive plate 19 

20 conductive plate: current density 

21 conductive plate: magnetic flux 

fields, fluxes and data Current density Magnetic flux 

inverse problem 23 subject to mlower < m < mupper 

framework 

what is your model? ● Subsurface log conductivity ● 1D, 2D, 3D voxel model ● Parametric model ● … 25 ● Need to map to forward simulation mesh ● Keep track of derivatives for inversion 

1D inversion ● Model: 1D subsurface conductivity at each sounding location ● Forward simulation mesh: 2D cylindrical mesh ● Recent developments: SimPEG EM1D ○ includes lateral and spatial constraints 26 

2D voxel inversion ● 2D model (tensor mesh) ● Forward simulation mesh: 3D tensor mesh ○ Map 2D section to 3D space 27 

2D parametric inversion 28 

2D parametric inversion ● 6 parameters describing model ● Forward simulation mesh: 3D tensor mesh ○ Map parameters to 2D mesh à fill 3D space 29 

building for researchers ● Modular: building blocks ○ organized in a framework ○ pieces available to manipulation ● Declarative: express intent ○ write what you mean ○ looks like the math ● Extensible: new research ○ quantitative communication ○ built in feedback loops ● Open: for the future ○ reproducible ○ opportunities for collaboration 1D inversion 2D inversion Parametric inversion 

framework ● Electromagnetics: ○ FDEM, TDEM, EM1D (analytic) ● Vadose zone flow ● Gravity ● Magnetics ● DC / IP ● EMIP 31 In one consistent, modular framework 

open development versioned, peer reviewed, issue tracking 32 docs.simpeg.xyz tested available for industry, academic use 

coming soon… 33 ● Large scale problems with OcTree meshes and domain decomposition ● Efficiency improvements including parallelization ● Joint and cooperative inversions with petrophysical information ● … 

contributing 

Thank you! 35 simpeg.xyz slack.simpeg.xyz github.com/simpeg-research/heagy2018-aem This work is licensed under a Creative Commons Attribution 4.0 International License > pip install SimPEG