A Cascadia earthquake will spell trouble for Portland's water supply. But is there any way to know how bad the shaking will be? Divers explore the protected Bull Run Lake, source of Portland's water, in search of evidence from past earthquakes that could shed light on how big the "big one" will be for the Portland area.
Copyright 2021 EarthFix. To see more, visit .
Scientist collecting core samples from Bull Run lake
/