What is a mega-tsunami? Scientists sound alarm for US Pacific coast — could it happen and how far inland would it reach?

Mega-Tsunami Threat Cascadia Subduction Zone: The Cascadia Subduction Zone, stretching from Northern California to Vancouver Island, could trigger a catastrophic mega-tsunami if it ruptures. Scientists warn that a massive earthquake of magnitude 8.0 or higher could happen within the next 50 years, sending waves up to 1,000 feet toward coastal cities like Seattle and Portland.