No doubt FM stations could be used but the TX radius is only about 100 miles. I might be wrong but I doubt this would be enough to triangulate the point of EM interference and in many places there would not be enough transmitters. Anomalous long range FM transmissions would be possible if the atmosphere was ionized (like sporadic E-layer transmissions) but it's a moot point whether the EM effects of that type are sufficiently regular in an already unpredictable earthquake environment. It's possible the low frequency approach may be more consistently sensitive, that is it may still work when there was no ionization necessary for the anomalous FM transmissions.
Of coarse, that's only speculation on my part. Again, this needs further scientific investigation, and again amateurs could be helpful. The FM band is 88-108MHz but the amateur bands of 50-54MHz (6m) and 144-148MHz (2m) could be used as a feasibility study (the characteristics of those bands ought to be close enough to evaluate the idea).
Of coarse, that's only speculation on my part. Again, this needs further scientific investigation, and again amateurs could be helpful. The FM band is 88-108MHz but the amateur bands of 50-54MHz (6m) and 144-148MHz (2m) could be used as a feasibility study (the characteristics of those bands ought to be close enough to evaluate the idea).