The USGS reports for volcano hazards are included within the ALgermissen hazard maps for quakes. They present a range with the worst damage zones clearly mapped. YET, all the People in charge of issuing building permits and approving plans for development seem to have their heads up their asses and issue approvals and permits just the same(almost always without any information that the officials may have from the geologists reports). Ive been involved in several insurance claims cases for these "acts of god" claims and the insurance companies are pushing back on coverage since the late 80's.
If a volcanism risk exists, proving that "We dint know" transferred several cases from the insurance carriers to the developers (Whose own insurance companies pushed back since many of them were the same damn carriers that sold policies to the homeowners).
So often the best defense for a homeowner whose suffered a catastrophic loss in a known hzard area is a heads up version of;
"Well why the hell did you sell me a policy if I was expected to know the hazard"? (That's gotten the planning boards and county engineers inb=volved in the cases besides the insurance carriers)
"Why did you keep this a secret from me?"