A Surge of Earthquakes in Alaska Is Raising Red Flags
Since 2020, five earthquakes ranging from magnitude 7.2 to 8.2 have struck the southern coast of Alaska. It's not unusual for seismic activity to occur in this part of the state, as it runs along an active tectonic plate boundary called the Aleutian subduction zone. Still, seeing five large quakes within close range of each other in just five years has captured the attention of seismologists like Michael West, Alaska's state seismologist and director of the Alaska Earthquake Center. West told Gizmodo that the southern coast appears to be experiencing an earthquake sequence. While it's possible that Wednesday's quake was the last in this sequence, it's also possible that more large earthquakes—or even one huge one—could strike within the next few years, he said.
'Five earthquakes is enough to be statistically significant,' West said. 'This area is clearly undergoing a period of strain release while other areas of this particular boundary are—at the moment—a bit more quiet.'
Earthquakes occur when accumulated stress along the border between two converging tectonic plates suddenly releases, causing them to slip past each other. Sometimes, one earthquake is enough to relieve the stress on a particular section, but not always. It can take multiple quakes spanning several years to release a significant buildup of stress, which is probably happening on Alaska's southern coast.
Wednesday's quake occurred southeast of Sand Point, a small town in the Aleutian Islands. According to the U.S. Geological Survey, it resulted from strike-slip faulting—when two tectonic plates slip horizontally past each other—in the Aleutian subduction zone. Seismologists have been keeping a close eye on this part of the plate boundary since the 1980s, when they identified it as an area of accumulating tectonic stress, West said. It took another 40 years for that built-up stress to finally result in seismic activity.
'Starting in 2020, it was like, 'Okay, now it's time for this particular segment to do its thing,'' West said.
It's fortunate—and 'remarkable'—that none of the large quakes that have struck this area since 2020 have produced a tsunami, he added. Seismologists know the Aleutian subduction zone is capable of triggering devastating, Pacific-wide tsunamis. In 1946, for example, an 8.6 magnitude earthquake in this plate boundary caused a tsunami that traveled all the way to the shores of Antarctica and killed more than 150 people in Hawaii. The epicenter of that quake was located just 100 miles away from that of Wednesday's quake, West said.
The earthquake sequence currently unfolding in this part of the Aleutian subduction zone could lead to a few different scenarios, he explained. If Wednesday's quake released all the accumulated stress in this segment, seismic activity could stall out and remain quiet for decades. Alternatively, it could take several more magnitude 7 to 8 quakes—or a single magnitude 9—to release all the stress.
'The societal consequences are very, very different for those two different paths,' West said. Unlike the relatively inconsequential quakes Alaska's southern coast has experienced in the last five years, a magnitude 9 would be highly likely to produce a dangerous tsunami and damaging ground shaking. Fortunately, 'there are, and long have been, very strong preparedness efforts underway in these communities,' West said. 'Every community near here has been studied for its tsunami inundation potential.'
That said, 'we can always do more education,' he added. 'We've always got training to do to help people understand how to use that information, and how to do it quickly. You don't have much time [during] events like this.'
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Yahoo
4 days ago
- Yahoo
In world first, CCTV captures supershear velocity earthquake
Yahoo is using AI to generate takeaways from this article. This means the info may not always match what's in the article. Reporting mistakes helps us improve the experience. Yahoo is using AI to generate takeaways from this article. This means the info may not always match what's in the article. Reporting mistakes helps us improve the experience. Yahoo is using AI to generate takeaways from this article. This means the info may not always match what's in the article. Reporting mistakes helps us improve the experience. Generate Key Takeaways Earthquakes are violent events that alter the face of the planet. In many cases, those changes occur beneath the surface and only gradually become visible over thousands of years. Occasionally, however, an earthquake's effects aren't just felt—they're seen. It's even rarer to actually capture one of those moments on camera, but according to seismologists at Japan's Kyoto University, the footage highlights the first-known video of a strike-slip fault. Their analysis, published in The Seismic Record, has led to new findings based on real-time visual evidence of tectonic motion. The magnitude 7.7 event took place on March 28 along the Sagaing Fault with an epicenter near Myanmar's second-largest city, Mandalay. Although the initial rupture process lasted barely 80 seconds, it and numerous aftershocks were ultimately responsible for 5,456 confirmed deaths and over 11,000 injuries. Later evaluations indicated the quake was the second deadliest in modern history, as well as the most powerful to hit Myanmar in over a century. According to a separate group's paper published in the same journal, the southern portion of the rupture occurred at an astonishing 3.7 miles per second—fast enough to qualify as 'supershear velocity.' Amid the catastrophe, an outdoor CCTV camera about 74.5 miles south of the epicenter recorded a visceral illustration of its power. Over just a few moments, what at first looks like a single chunk of the ground appears to suddenly divide and horizontally shift past one another in opposite directions. Completely by accident, the camera recorded a direct look of a strike-slip fault, something previously analyzed by remote seismic instruments. To researchers at Kyoto University, the clip wasn't just a jaw-dropping scene—it was an opportunity to study a strike-slip fault using visual data. Geologists analyzed the brief video frame-by-frame to learn about the fault shift. Credit: KyotoU / Jesse Kearse 'We did not anticipate that this video record would provide such a rich variety of detailed observations,' corresponding author and geologist Jesse Kearse said in a statement. 'Such kinematic data is critical for advancing our understanding of earthquake source physics.' Kearse and colleagues utilized a technique called pixel cross-correlation to analyze the fault movement on a frame-by-frame basis. Their findings showed the fault slipped horizontally by 8.2 feet in only 1.3 seconds, with a maximum speed of about 10.5 feet per second. While the movement matched experts' existing knowledge of strike-slip ruptures, the short duration and speed were new developments. 'The brief duration of motion confirms a pulse-like rupture, characterized by a concentrated burst of slip propagating along the fault, much like a ripple traveling down a rug when flicked from one end,' Kearse explained. Additional examinations also proved that the slip path was slightly curved, confirming previous observations recorded elsewhere in the world. This means subtly curving strike-slips instead of totally linear ones may be the rule, not the exception. 'Overall, these observations establish a new benchmark for understanding dynamic rupture processes,' the study's authors wrote, adding that the video offers real-time confirmation of curved slip paths while helping 'deepen our understanding of the physical mechanisms that control rapid fault slip during large earthquakes.' Such discoveries may also help seismologists, geologists, and urban planners design more resilient architecture to ensure that when major earthquakes inevitably occur, their damage is minimized as much as possible.
Yahoo
4 days ago
- Yahoo
Ancient Canadian fault could produce major earthquakes in the future
The Tintina, a major geologic fault that extends 1,000 km northwestward across much of the Yukon Territory, was thought to have been inactive for at least 40 million years, but new research led by a team at the University of Victoria (UVic) finds evidence of 'numerous large earthquakes', suggesting additional earthquakes could occur in the future. The team used high-resolution images from satellites, airplanes, and drones. They found a 130-km-long fault segment near Dawson City, suggesting seismic activity in the Quaternary Period, dating from 2.6 million years ago to today. "Over the past couple of decades, there have been a few small earthquakes of magnitude 3 to 4 detected along the Tintina fault, but nothing to suggest it is capable of large ruptures," Theron Finley, recent UVic PhD graduate and lead author of the recent article, says in a statement. "The expanding availability of high-resolution data prompted us to re-examine the fault, looking for evidence of prehistoric earthquakes in the landscape." Canada's current understanding of earthquake frequency and risk is limited to the last couple of hundred years, the authors say, and it is comprised of data derived from Indigenous records, historical archives, and modern technology. 'However, for many active faults, thousands of years can elapse between large ruptures,' the authors say in a statement. Large or shallow quakes can rupture Earth's surface, creating a linear feature in the land known as a fault scrap. This feature, which can be hundreds of kilometres long, can remain for tens of thousands of years and provide insight into seismic activity in the area. They're notoriously difficult to detect, especially in Canada's dense forests. The high-resolution topographic data used in the study is one of the best ways to detect fault scraps. It revealed glacial landforms that formed about 2.6 million years ago were laterally offset across a fault scrap by 1000 metres. Some that are 132,000 years old are offset by 75 metres. 'These findings confirm that the fault has slipped in multiple earthquakes throughout the Quaternary period, likely slipping several meters in each event. What's more, landforms known to be 12,000 years old are not offset by the fault, indicating no large ruptures have occurred since that time. The fault continues to accumulate strain at an average rate of 0.2 to 0.8 millimetres per year, and therefore poses a future earthquake threat,' the authors write in a statement. Finley says future earthquakes on the Tintina fault could be major, exceeding a mangitude 7.5, potentially causing severe shaking in Dawson City, a community with a population of about 2,350 people. 'Compounding the hazard from seismic shaking, the region is prone to landslides, which could be seismically triggered. The Moosehide landslide immediately north of Dawson City and the newly discovered Sunnydale landslide directly across the Yukon River both show ongoing signs of instability,' the authors write. The research will be shared with local authorities, governments, and infrastructure planners to help mitigate risk. Earthquake frequency in Canada Small earthquakes are common in Canada, with the Geological Survey of Canada recording and locating an average of 4,000 earthquakes annually, or 11 per day, nationwide. Header image: Approximate location of the Tintina fault. Cheryl Santa Maria for The Weather Network.
Gizmodo
5 days ago
- Gizmodo
Myanmar's Devastating Earthquake in March Split the Earth at ‘Supershear Velocity'
On March 28, Myanmar was rocked by a 7.8 magnitude earthquake that claimed over 5,000 lives and caused damage even in neighboring countries. In a study published July 10 in The Seismic Record, seismologists confirmed previous research indicating that the southern part of the large earthquake's rupture, or fracture, took place at astounding speeds of up to between 3.1 and 3.7 miles per second (5 to 6 kilometers per second)—at supershear velocity. This likely played a role in the earthquake's devastating impact. When an earthquake strikes, the first seismic waves to propagate from the epicenter are P waves, fast-moving waves that compress their way through all kinds of material but do not cause a lot of damage. Then come the S waves, or shear waves, which are slower but cause highly destructive perpendicular motion. Simply put, when parts of an earthquake's fault rupture at supershear velocity, it means that the speed of the break along a particular stretch of the rupture was faster than the speed of its S waves. In moderate earthquakes, rupture velocities are usually between 50 and 85% of S-wave velocity. Myanmar's earthquake occurred along the Sagaing Fault, which runs north-south through Myanmar. The fault is strike-slip, meaning two tectonic plates slide horizontally against each other. The Sagaing Fault's strike-slip movement in March was clearly captured in potentially first-of-its-kind footage showcasing an expanse of land suddenly moving forward relative to the viewer. The natural disaster saw around 298.3 miles (480 km) of the Sagaing Fault rupture or 'slip,' which is extremely long for a strike-slip rupture of this magnitude, according to the seismologists. By studying seismic and satellite imagery, they determined that the rupture had 'large slip of up to 7 m [23 feet] extending ∼85 km [52.8 miles] north of the epicenter near Mandalay, with patchy slip of 1–6 m [3.3–19.7 feet] distributed along ∼395 km [245.4 miles] to the south, with about 2 m [6.6 ft] near the capital Nay Pyi Taw.' A seismic station near Nay Pyi Taw registered ground motion data that were 'immediately convincing of supershear rupture given the time between the weak, dilational P wave first arrival and the arrival of large shear offset of the fault' at the station, UC Santa Cruz's Thorne Lay said in a Seismological Society of America statement. An offset is the ground displacement that occurs along a fault during an earthquake. 'That was unusually clear and convincing evidence for supershear rupture relative to other long strike-slip events that I have worked on.' The Sun Might Be Influencing Earthquakes, Scientists Say Lay and his colleagues suggest that the supershear velocity, as well as the rupture's strong directivity (the piling up of S waves in the direction of the fault line as the rupture spreads) toward the south, might have caused the earthquake's widespread damage. While the Sagaing Fault frequently causes large earthquakes, the one in March involved a stretch of the fault between the cities of Mandalay and Nay Pyi Taw that has been quiet since 1912. 'Longer histories and better understanding of fault segmentation and geometry are needed to have any guidance for future event activity, but I would not expect the central area to fail again before a long period of rebuilding strain energy,' Lay added. While it is impossible to predict earthquakes with any kind of precision, earthquake early-warning (EEW) systems provide last-minute but still crucial warnings of incoming seismic events by sending out electronic alerts that travel faster than seismic waves. While many seismic regions don't have the necessary infrastructure for such systems, the smartphone-based Android Earthquake Alerts (AEA) system has recently proved to be as efficient as traditional seismic networks.
