In a few studies, researchers used ground penetrating radar to detect hidden crevasses in alpine regions. Since the cavity of the crevasse refracts and reflects differently than the surround snow, the ground penetrating radar can determine the location of crevasses.
Why isn't this practice expanded and more widely used. It seems possible to design an autonomous drone which has a ground penetrating radar and then map out highly trafficked regions that are known to contain hidden crevasses. Over a course of weeks and months, it should be possible to completely map out the trafficked regions and publish maps of where crevasses are located. Periodically, the snow bridges over the crevasses could also be collapsed with some kind of charge dropped by the drone.