Next here to the massive earthquake that woke up Alaska, sparking tsunami alerts all along Alaska, the entire west coast of the U.S. In kodiak, Alaska, people rushing to higher ground. You can see the traffic jam in the middle of the night. Those fears stretched all the way to Los Angeles. And tonight, we show you how the Earth shifted, how those plates moved that might have made all the difference. Here's ABC's kayna Whitworth now. Reporter: Sirens waking the residents of kodiak, Alaska, overnight. The entire west coast on alert. Please evacuate immediately! Reporter: Inside homes, people recorded the shaking. Oh, my gosh, it's an earthquake. Reporter: And then scrambling to get to safety. We're leaving base now. Reporter: With just five minutes to spare, many of kodiak's 6,000 residents rushing to a local high school. Despite the quake's 7.9 magnitude, the seventh largest ever recorded near Alaska, scientists say it could have been worse. The plates slid past each other. This will cause less uplift on the sea floor and there is less chance of a tsunami. Reporter: Had the fault line slid vertically, like this, there would likely have been a large tsunami. The quake occurred on the so-called ring of fire, a 25,000-mile stretch of seismic activity underneath the pacific ocean, where 90% of all quakes happen. So, let's get to kayna Whitworth with us tonight. And there's still concern this even, because there have been dozens of aftershocks. Reporter: David, the largest one was a 5.0. And while that tsunami warning was canceled early, authorities I spoke with say this is a good reminder to everyone that they should be prepared and know their evacuation route. David? All right, kayna Whitworth with us, thank you. And here in the east