Good question. I don’t think a seismometer can give you a good proxy since the explosion was above ground. I mean, if you recorded a nearby quake you could compare it with that but …
There is a standard comparison for above ground explosions and that is equivalent pounds (or kilograms) of TNT. There are a lot of papers on that subject that Google will find for you. All the ones I looked at tend to be concerned with pressures > 1 PSI (6894 pa) because that is where you start to see some structural damage. Distances are usually within a couple of miles.
So if you had an RBoom, you might (*) be able to tell them an “equivalent pounds of TNT”.
My distant RBoom registered a peak pressure of 10,000 counts and that is about 0.18 pascals - so about 0.000026 psi. That pressure and distance would be a pretty big extrapolation of the curves shown in the papers I saw. For example, in this reference:
figure 6 shows at 10,000 feet you need 10^7 pounds of TNT for one psi peak pressure wave. Therefore 10,000 counts on the RB would require 260 pounds of TNT.
But I detected that same pressure at a 38.5 times that distance which would mean 57,000 times the weight of TNT.
I am quite sure that is not right. And the reason is, at that distance we no longer have the blast wave upon which all of this is based (see https://www.fema.gov/media-library-data/20130726-1455-20490-7465/fema426_ch4.pdf).
I don’t know where the blast wave stops and just plain old sound takes over but I am guessing it is within a few “wavelengths” where a wavelength is 1100 ft/sec times the duration of that first positive pressure transient.
Perhaps some experts in this area will show up and help us out.
BTW - the first reference has a section on leaking gas explosions.
(*) I say “might” because the peak may occur in a millisecond at close range and the frequency response of the RB is limited to 1/50th of a second. But you might catch most of it.