For years I've suggested radio amateurs set networks up to investigate this. The advantage of this is that there are many of them and they are spread over a diverse area.
The strength of carriers on certain bands could be monitored like a sort of mesh network and
changes in signal strength etc. that would likely be the signature of a pending earthquake could be quickly identified.
The strength of carriers on certain bands could be monitored like a sort of mesh network and changes in signal strength etc. that would likely be the signature of a pending earthquake could be quickly identified.