Figure 7. Variation of magnetic field Bm with distance R from an electro-kinetic source, for four combinations of crack size and channel frequency. (1) lc=1 m, f0=7.5 Hz; (2) lc=2 m, f0=0.751 Hz; (3) lc=5 m, f0=0.073 HZ; (4) lc=10 m, f0 =0.015 Hz. Parameter values are a=1, q=10-2, C1-C2=10-6 V/Pa, DT=1800 s, s=10-1/W-m and r=100 m. Remaining parameters from Table A1.