Alaska Still Feeling Aftershocks From November Quake

The devastating earthquake that shook Anchorage and surrounding areas on Nov. 30, can still be felt weeks after.

Since the quake hit aftershocks are once again shaking Alaskans with nearly 3,000 counted as of the afternoon of Dec 6.

Some aftershocks can be significant events in their own right. According to the U.S. Geological Survey, five aftershocks measured 5.0 or greater on the Richter scale, 23 were 4.0, and 185 measured more than 3.0.

Alaska seismologist Mike West describes the Nov. 30 quake as the most significant to strike Anchorage since 1964. The tremor measuring seven on the Richter scale tore up roads, cracked buildings, and knocked out electric power and gas to more than 30,000 people.

When an Aftershock Is a Quake

According to the Anchorage Daily News, some Alaskans are wondering what the difference is between an aftershock and earthquake. Contrary to the widely held theory that when an earthquake hits, and another arrives one week later there are a total of two quakes it is not necessarily the case, Natalia Ruppert of the Alaska Earthquake Center told the Daily News.

“For an earthquake of this size, we expect the aftershocks to continue for a few months,” she said. “The rate of the aftershocks, however, will be going down with time.”

Earthquakes come in clusters, Ruppert said. The largest in the cluster—in the case the Nov. 30 shaker—is considered to be the “mainshock.”

Every subsequent shock that follows, until the seismic activity returns to pre-mainshock levels, is considered to be an “aftershock” related to the main event.

No major damage has been reported from any of the aftershocks.

The previous experience of the 1964 Anchorage earthquake shows a cluster of aftershocks lasted for more than a year, with a total of 11 recorded that measured more than magnitude 6.0.

The 1964 quake was 9.2 on the Richter scale, making it the ninth worst quakes in the top 10 recorded in history. Tsunamis from that event damaged cities as far flung as Crescent City, California—more than 2,700 miles south of the disaster. The Nov. 30 event is less severe by comparison.

Earthquakes Happen Often in Alaska

Alaska is normally seismically active. The Alaska Earthquake Center reported 723 tremors in the week of Nov. 19–25, with the strongest being a magnitude 5.7 shock near the Iliamna Volcano, about 100 miles southwest of Anchorage, on Nov. 21.

Alaskans are used to minor ‘rocking and rolling’ periodically. Most buildings are built strong enough to survive a fair-sized tremor, as the Nov.30 quake showed.

“The amount of infrastructure damage has been mitigated in large part by how we build things here and the level of preparation,” Anchorage Mayor Ethan Berkowitz told reporters after the quake.

Earlier tsunami warnings have already been cancelled in Anchorage and several surrounding communities.

Most gas and water leaks are patched-up quickly, and most residents have power restored by the end of the day.   

The longest-lasting damage was to roadways around Anchorage—and repairs are proceeding at a tremendous pace. Many highways that were torn apart on Nov. 30 were repaired completely less than a week later.

The Federal Highway Commission released $5 million in emergency funds to Alaska on Dec. 1, ABC News reported.  

Funds were released at the request of Alaska Gov. Bill Walker (I) and state transport commissioner Marc Luiken, ABC reported.

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