# Understanding the response using a widget¶

The EM response from the above circuit model can be written as

Let I=0 \(^\circ\) and D=90 \(^\circ\) of the Loop2 shown in
Fig. 98. For this case, we consider a loop-loop EM survey
with the geometry of EM-31 (3.66m Tx-Rx offset), and the body (Loop2) is
embedded 3 m below the surface. Fig. 99 shows complex response
function (**Plot1**), easting line at 0 m-northing (**Plot2**), plan maps of
real and imaginary part of the EM data with the loop-loop EM survey when
\(\alpha\) =0.31. **Plot2** clearly shows how coupling is changing
depending on relative location and orientation of three loop system. **Plot3**
and **Plot4** illustrate plan map of EM data we could possibly obtain by
acquring multiplie lines. Following considers different orientation of the
body (Loop2), which will generate different coupling effects on the measured
EM data.

Fig. 100 shows same figures, but with different I and D of body (Loop2): I=-90 \(^\circ\) and D=0 \(^\circ\). Shape anomalous response is significantly different due to the different coupling among three loop system. Especially, the peak anomaly at the center has positive sign. Fig. 101 shows the case when I=0 \(^\circ\) and D=0 \(^\circ\). This is null-coupled case where there is no primary flux passing the area of Loop2, hence measured reponse is zero everywhere.

If you want to play with loop-loop EM survey click below:

Todo

Link to Python app for three-loop system

Use plot function in sphinx to plot above figures (?)