Oh they know where the underground magma flows are, they just don’t know where or how it will crack out of the surface crust rocks. That’s why Leilani Estates was such a stupid place to build… right on top of a known rift zone and magma chamber that cracked open and flowed lava in the area as recently as 1955.
The big earthquakes apparently broke an underground dike in the plumbing and allowed the summit lava AND eruptive Pu’u O’o vent to both drain lower down the rift ridge underground. The present eruptive area became swollen and cracked with new lava pressure coming in from upslope areas.
Today the earthquake swarm is moving eastward, more downslope along the rift towards Cape Kumukahi. That area out at the eastern tip near Kapoho last broke open in 1960 and flowed to the ocean. An easterly migration downslope of the eruption would be a good thing, as it is sparsely populated and direct lava flow away from the subdivisions on the north side of the ridge…. where I happen to be.