wavelength of seismic wave with a gaussian source
The Fourier transform of a Gaussian is a Gaussian.

If your signal is given by 

$$g(t)=\frac{1}{\sqrt{2 \pi \sigma^2}} \exp\left( -\frac{(t-t_0)^2}{2 \sigma^2}\right)$$

then your frequency spectrum is

$$G(f) = \exp(-2 \pi^2 \sigma^2 f^2),$$

where f is the frequency ($2 \pi \omega).$

I'l let you do the substitution with your particular numbers. Enjoy!


https://warwick.ac.uk/fac/sci/mathsys/courses/msc/ma934/resources/notes8.pdf
http://www.cse.yorku.ca/~kosta/CompVis_Notes/fourier_transform_Gaussian.pdf