A magnitude 5.0 aftershock struck the Anchorage capitol area on the morning of New Year’s Eve—and ushered in two days filled with many more tremors.
That 5.0 was the strongest aftershock since the Nov. 30 quake.
Alaska has endured thousands of aftershocks since the 7.0 magnitude quake powerfully shook Anchorage and its environs on Nov. 30. This was the second-largest earthquake ever recorded in Alaska, and the most powerful since the record-breaking 1964 quake.
Reviewed magnitude is 5.0. Location is down on the south end of the rupture patch. It's closer to Anchorage than most, which could explain why it felt stronger to many. This now replaces Friday's M4.9 as the strongest aftershock since the night of Nov. 30.
— AK Earthquake Center (@AKearthquake) January 1, 2019
The 1964 quake measured 9.2 and the strongest to hit the United States in recorded history and the second strongest ever recorded on earth.
The November temblor was not as severe but still tore up roads all around Anchorage—and spawned aftershocks for days.
As of this morning, there have been just over 6,100 aftershocks from the November 30 magnitude 7.0, including about 40 at or above magnitude 4. As of this tweet, our statewide total for 2018 is at 51,612.
— AK Earthquake Center (@AKearthquake) December 27, 2018
In just the first week after the November quake, the United States Geological Survey (USGS) counted nearly 3,000 serious tremors. Another few thousand more in the next three weeks raised the total to more than 6,100.
Five aftershocks measured 5.0 or greater on the Richter scale, 23 were 4.0, and 185 measured more than 3.0, according to the USGS.
Those tremors had ebbed, and for the next three weeks, things were relatively more peaceful. Probably a lot of South-Central Alaskans had let the November earthquake fade into memory—until another magnitude-5 quake shook the region at 6 a.m. on Dec. 30.
Since the main tremor, the Alaska Earthquake Center detected more than 100 further aftershocks in the first two days of 2019.
A 4.2-magnitude aftershock hit just five miles outside of Anchorage just after 6 a.m. on Jan. 2. A 4.9 magnitude temblor hit 10 miles northwest of Anchorage on Dec. 27 but was 22 miles below the surface and did not create much of a stir in the city.
Did it wake you up?Magnitude 4.9 earthquake 8 miles NW of Anchorage at 5:21am.The largest aftershock since December 1st.
What Makes it an Aftershock?
The USGS defines aftershocks as “earthquakes that follow the largest shock of an earthquake sequence.” They are smaller than the mainshock and within one to two rupture length’s distance from the mainshock. Aftershocks can continue over a period of weeks, months, or years. “In general, the larger the mainshock, the larger and more numerous the aftershocks, and the longer they will continue,” USGS said on its website.
As KTVA reported, aftershocks can themselves trigger aftershocks—all of which are considered to have been caused by the major quake (the Nov. 30 event.)
A 5.0 earthquake is still arguably severe regardless of whether scientists blame it on an earlier quake.
Besides the aftershocks Alaska has its fair share of quakes. The Alaska Earthquake Center recorded 51,612 shocks in 2018 but many of them are simply overlooked.
For instance, a magnitude 6.1 quake hit about 61 miles off the coast of King Cove and 600 miles southwest of Anchorage. It was far out to sea and thus not near any major population centers, so little attention was given.
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