Shownin Fig. 4 are 2Dresistivity cross-sections derived by inversion of
the four sets of data measured along L2 that are shownin Fig. 3. Theoverall
RMS-misfit of these models to the measured data is 4.3% for 20/01/2005,
1.8% for each of 12/03/2005 and 26/02/2006 and 3.1% for the final series of
measurements on 18/01/2007. For all four sets of measurements it can be
seen that the upper 3–5 m of the tephra barrier is modelled as having a
high resistivity of 500–2000 Ωm. For the first set of measurements the
bulk resistivity beneath this high resistivity surface is around 50–60 Ωm,