What’s Shaking Alaska?! Welcome to your weekly seismic update from across the state, brought to you by the Alaska Earthquake Center, where we monitor ground shaking 24/7.
Over the past week, we recorded about 310 earthquakes. Three were reported as felt, and the largest was a magnitude 4.8 on November 8th in the western Aleutians.
After an earthquake is widely felt, people often ask us how long the shaking lasted. They also share how long they experienced shaking, which can vary greatly. After the October 30th magnitude 5.4 earthquake near Seward, reports ranged from 10 to 30 seconds. And, according to our seismic sensors, they were all correct.
What influences how long you might feel shaking during an earthquake? First, how big the rupture is, a magnitude-5 fault-length rupture is typically less than 2 miles. The magnitude 9.2 Great Alaska Earthquake ruptured over a 500-mile length in five minutes.
Read More: Magnitude 5.4 Earthquake Shakes Kenai Peninsula, Alaska
From the rupture, seismic energy travels in all directions. The closer you are to the source, the more substantial and more immediate the shaking feels. The material your building is on matters, too. Unconsolidated sediment traps seismic waves and will shake for longer than bedrock.
Resource to learn about these and more influences on how you feel shaking https://earthquake.alaska.edu/how-long-does-earthquake-last
