## Koenigsberger ratio

Anything about geophysics and geoscience: jobs, events, technical or general discussions ...
pharaaow
Member
Posts: 1
Joined: Tue Jan 25, 2022 6:50 am

### Koenigsberger ratio

I have some questions about the Koenigsberger ratio that relates induced and remanent magnetization in rocks. I have not had a chance to take a course in petrophysics and have a hard time finding detailed information online.

The general equation is easily found, I guess, but the details about assumptions, approximations and the induced field to use etc. is seldom explained.

Q = NRM / (K * H)
where NRM is the remanence in [A/m], K is the susceptibility in [SI] and H is the inducing field in [A/m].

What assumptions and approximations are used for this equation to hold?

I've often seen that H in the equation above, is approximated to 40 A/m (roughly 50265 nT), which simplifies the calculation. But is this approximation widely used and acceptable? It gives up to 10% error in for example northern Europe, if one compares with using IGRF values for the inducing field.

Furthermore, I was told that it is the inducing field at the time and location of sampling that should be used. However, I feel that is a bit odd and rather think it should be the inducing field at the time and location of measuring the magnetic properties of the rock sample, so that all values in the calculation correspond to the same time and location. So, what is the correct answer here?

I don't have oriented samples, so I'm generally not considering directionally dependent factors, however, it would be interesting to hear if also that plays a role in determining Q.

I would very much appreciate if someone could help shed some light on these questions!
Marie143
Silver Member
Posts: 18
Joined: Mon Mar 14, 2022 12:59 pm

### Re: Koenigsberger ratio

home renovation contractors dallas txThe equation assumes that the rock samples are homogenous and isotropic. That means that the magnetic properties of the rock samples are the same in all directions. It also assumes that the rock samples are single domain, meaning that the magnetic moments of the minerals are not aligned and are free to rotate in response to an applied magnetic field.It is also important to note that the equation is only valid for low-field measurements, and the induced magnetization is linear with the applied field. In summary, the Koenigsberger ratio is a useful tool for understanding the magnetic properties of rocks, but the assumptions and approximations made for the equation to hold must be considered when interpreting the results.