Fresno geological expert explains what caused Anchorage earthquake
All earthquakes are caused by tectonic plates (pieces of Earth’s crust that move and collide).
The place where tectonic plates overlap is called a Subduction Zone.
Alaska sits right on top of one.
“It’s an area of known seismic hazard, so Earth scientists and anyone who knows much about earthquakes would know that that’s an area where we should expect one in the long-run. Of course, we never really know when they’re going to happen on a daily/hourly/weekly kind of basis,” said Christopher Pluhar, a professor of geology at Fresno State University.
The “Magnitude” refers to an Earthquake’s strength.
People can feel an earthquake once it reaches Magnitude 3, but the United States Geological Survey says damage doesn’t normally happen until Magnitude 4 or 5.
Today’s earthquake was a Magnitude 7.
Professor Pluhar says about 150 square miles near Anchorage experienced a high level of “Liquefaction”.
“That’s basically where ground that is not rock, but is sort of sediments that not what you would think of as dirt might lose its capacity to hold up structures, due to the shaking,” said Pluhar.
That leads buildings to sink in, and highways to buckle.
And right now people in Alaska have another thing to worry about: Aftershocks.
“Frequency of those aftershocks is going to decrease with time, but you can have aftershocks up to years afterwards. But most of it is going to happen in the next days, weeks,” said Pluhar.
The USGS aftershock forecast is predicting there will be between 84 and 610 magnitude 3 earthquakes coming.
And within the next week, the USGS says there’s an 88% chance of there being another magnitude 5 quake, and a 24% chance of a magnitude 6.
The Alaska Earthquake Center has reported over 150,000 earthquakes over the last five years. 31 of those were of magnitude 6 or greater.