Filippo Biondi

Okay, okay.

Well, good.

Yeah, those were some of the tougher questions, I think, and you did a phenomenal job of answering them.

So thank you, thank you.

And then I guess just maybe just a couple more thoughts or questions kind of as we close out.

And I guess just for me, to help me understand the surface vibration conversation of measuring the surface vibrations and being able to

determine the density of the rock or the substance below for up to potentially a thousand meters or more than a thousand meters.

Yes.

How is it that... How does a surface vibration, something that's only happening at the very surface of the earth...

How does it distinguish between what it's measuring 10 meters below the ground from 500 meters below the ground?

Yes, absolutely.

I give you the answer of this.

It's called the fast Fourier response.

The fast Fourier response...

the fast Fourier transform is the particular algorithm that implements the digital Fourier transform and let's say the analog version the Fourier transform so let's say you have a oscillating phenomena a time domain oscillating phenomena here like that particular here

it means that if you have a sensor here we are speaking about seismic reflection tomography it's the same it measures the vibration here and you record these vibrations in the time domain

it means that on the horizontal axis you have the time on the vertical axis you have the energy like that it is not a sinusoid but it is a combined oscillation it means why combine it because you have if you do the spectrum so you perform the fourier transform of this time domain of this time domain oscillation

you will retrieve the so-called sources.

It means that you start finding

principal vibration, vibrational sources that are located underneath.