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geoscixyz / em

Electromagnetic methods in geophysics - open educational resources.
http://em.geosci.xyz
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Peak time calculation not right in TDEM_Planewave_Wholespace app #537

Open jiajiasun opened 5 years ago

jiajiasun commented 5 years ago

Hi,

I was using the app TDEM_Planewave_Wholespace.ipynb to explore the peak time. I set conductivity to 1 S/m. And adjust the time to see when the peak reaches the depth of 400 m. peaktime

The app shows that it takes about 0.1 s for the peak to arrive at 400 m depth.

I also used the equation $t{max} = \frac{\mu\sigma z^2}{6}$ to calculate the peak time, which is $t{max} = 4 \pi 10^{-7} X 1 X400^2/6=0.0335 s, which is quite differnt from what the app shows.

Could anyone please explain what was going on here? Thanks!

sgkang commented 5 years ago

I thinks here the concept of peak time is bit mixed up. To figure out tmax we need to plot Ex as a function of time. Peak shown in the profile does not necessarily correspond to the peak amplitude at -400 m. Does this making sense?