# EM: FDEM: 1D: InversionΒΆ

Here we will create and run a FDEM 1D inversion.

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 import numpy as np from SimPEG import (Mesh, Maps, Utils, DataMisfit, Regularization, Optimization, Inversion, InvProblem, Directives) import SimPEG.EM as EM import matplotlib.pyplot as plt try: from pymatsolver import Pardiso as Solver except ImportError: from SimPEG import SolverLU as Solver def run(plotIt=True): """ EM: FDEM: 1D: Inversion ======================= Here we will create and run a FDEM 1D inversion. """ cs, ncx, ncz, npad = 5., 25, 15, 15 hx = [(cs, ncx), (cs, npad, 1.3)] hz = [(cs, npad, -1.3), (cs, ncz), (cs, npad, 1.3)] mesh = Mesh.CylMesh([hx, 1, hz], '00C') layerz = -100. active = mesh.vectorCCz < 0. layer = (mesh.vectorCCz < 0.) & (mesh.vectorCCz >= layerz) actMap = Maps.InjectActiveCells(mesh, active, np.log(1e-8), nC=mesh.nCz) mapping = Maps.ExpMap(mesh) * Maps.SurjectVertical1D(mesh) * actMap sig_half = 2e-2 sig_air = 1e-8 sig_layer = 1e-2 sigma = np.ones(mesh.nCz)*sig_air sigma[active] = sig_half sigma[layer] = sig_layer mtrue = np.log(sigma[active]) if plotIt: fig, ax = plt.subplots(1, 1, figsize=(3, 6)) plt.semilogx(sigma[active], mesh.vectorCCz[active]) ax.set_ylim(-500, 0) ax.set_xlim(1e-3, 1e-1) ax.set_xlabel('Conductivity (S/m)', fontsize=14) ax.set_ylabel('Depth (m)', fontsize=14) ax.grid(color='k', alpha=0.5, linestyle='dashed', linewidth=0.5) rxOffset = 10. bzi = EM.FDEM.Rx.Point_b( np.array([[rxOffset, 0., 1e-3]]), orientation='z', component='imag' ) freqs = np.logspace(1, 3, 10) srcLoc = np.array([0., 0., 10.]) srcList = [EM.FDEM.Src.MagDipole([bzi], freq, srcLoc, orientation='Z') for freq in freqs] survey = EM.FDEM.Survey(srcList) prb = EM.FDEM.Problem3D_b(mesh, sigmaMap=mapping, Solver=Solver) prb.pair(survey) std = 0.05 survey.makeSyntheticData(mtrue, std) survey.std = std survey.eps = np.linalg.norm(survey.dtrue)*1e-5 if plotIt: fig, ax = plt.subplots(1, 1, figsize=(6, 6)) ax.semilogx(freqs, survey.dtrue[:freqs.size], 'b.-') ax.semilogx(freqs, survey.dobs[:freqs.size], 'r.-') ax.legend(('Noisefree', '$d^{obs}$'), fontsize=16) ax.set_xlabel('Time (s)', fontsize=14) ax.set_ylabel('$B_z$ (T)', fontsize=16) ax.set_xlabel('Time (s)', fontsize=14) ax.grid(color='k', alpha=0.5, linestyle='dashed', linewidth=0.5) dmisfit = DataMisfit.l2_DataMisfit(survey) regMesh = Mesh.TensorMesh([mesh.hz[mapping.maps[-1].indActive]]) reg = Regularization.Tikhonov(regMesh) opt = Optimization.InexactGaussNewton(maxIter=6) invProb = InvProblem.BaseInvProblem(dmisfit, reg, opt) # Create an inversion object beta = Directives.BetaSchedule(coolingFactor=5, coolingRate=2) betaest = Directives.BetaEstimate_ByEig(beta0_ratio=1e0) inv = Inversion.BaseInversion(invProb, directiveList=[beta, betaest]) m0 = np.log(np.ones(mtrue.size)*sig_half) reg.alpha_s = 1e-3 reg.alpha_x = 1. prb.counter = opt.counter = Utils.Counter() opt.LSshorten = 0.5 opt.remember('xc') mopt = inv.run(m0) if plotIt: fig, ax = plt.subplots(1, 1, figsize=(3, 6)) plt.semilogx(sigma[active], mesh.vectorCCz[active]) plt.semilogx(np.exp(mopt), mesh.vectorCCz[active]) ax.set_ylim(-500, 0) ax.set_xlim(1e-3, 1e-1) ax.set_xlabel('Conductivity (S/m)', fontsize=14) ax.set_ylabel('Depth (m)', fontsize=14) ax.grid(color='k', alpha=0.5, linestyle='dashed', linewidth=0.5) plt.legend(['$\sigma_{true}$', '$\sigma_{pred}$'], loc='best') if __name__ == '__main__': run() plt.show()