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1984 M5.6 Sutton Earthquake: A Look at Alaskan Seismicity

on November 29, 1984, a magnitude 5.6 earthquake struck near Sutton, Alaska. While moderate in size,the event occurred within a complex tectonic region and provides insights into the ongoing deformation and seismic hazards of Southcentral Alaska. This earthquake, and the broader seismicity of the region, are linked to the interaction between the Bering microplate and the southern Alaska block.

tectonic Setting and Regional seismicity

Southcentral Alaska is a seismically active region due to its location along the convergent boundary between the Pacific and North American plates. The Denali Fault, a major strike-slip fault, dominates much of the tectonic activity in the region. However, a diffuse zone of seismicity exists between Cook Inlet and the Denali Fault. This zone is increasingly understood as a deformation zone resulting from the interaction between the Bering microplate to the west and the southern Alaska block to the east.

This deformation zone is characterized by a series of predominantly thrust faults, indicating compression. The 1984 Sutton earthquake occurred within this zone, and a larger, historical earthquake – a magnitude 7.0 event in 1943 – is also believed to have originated within this same band of seismicity.The presence of these events highlights the potential for meaningful earthquakes in this area.

The Bering Microplate and Southern Alaska Block

The Bering microplate is a relatively small tectonic plate situated between the North American and Pacific plates. Its interaction with the larger southern Alaska block creates a complex stress regime, leading to the observed pattern of seismicity. The movement and interaction of these blocks contribute to the ongoing deformation and earthquake risk in Southcentral Alaska. Understanding the dynamics of these plates is crucial for assessing seismic hazards.

Details of the 1984 Sutton Earthquake

The earthquake struck at 16:26:38 AKST (alaska Standard Time) on November 29,1984. Its epicenter was located approximately 25 miles (40 km) northeast of Anchorage, near Sutton, Alaska. The earthquake had a depth of approximately 8.7 miles (14 km). While the magnitude was moderate, the shallow depth contributed to felt effects over a wide area, including Anchorage and the Matanuska-Susitna Valley.

Reports indicated moderate shaking in Anchorage, with some minor damage reported, including cracked plaster and fallen objects. The earthquake did not trigger any significant landslides or tsunamis.the USGS event page provides detailed information about the earthquake, including seismograph readings and reported felt effects.

Implications for Seismic Hazard assessment

The 1984 sutton earthquake, along with the broader pattern of seismicity in the Cook Inlet-Denali fault zone, underscores the importance of ongoing seismic monitoring and hazard assessment in Southcentral Alaska. The potential for larger earthquakes within this deformation zone necessitates continued research into the region’s tectonic processes.

Key Takeaways

• The 1984 M5.6 Sutton earthquake occurred within a complex deformation zone between the Bering microplate and the southern Alaska block.
• This zone is characterized by thrust faults and has a history of moderate to large earthquakes, including a M7.0 event in 1943.
• Understanding the interaction between the Bering microplate and the southern Alaska block is crucial for assessing seismic hazards in southcentral Alaska.
• Continued seismic monitoring and research are essential for mitigating earthquake risk in the region.

frequently Asked Questions (FAQ)

Q: Is another large earthquake likely in the Sutton area?

A: Given the historical seismicity and the ongoing tectonic activity, the potential for another significant earthquake in the region exists. However, predicting the exact timing and magnitude of future earthquakes remains a challenge.

Q: What is the Bering microplate?

A: The Bering microplate is a small tectonic plate located between the North American and Pacific plates. Its interaction with the surrounding plates contributes to the complex seismicity of