Two Big West Coast Faults May Strike Back to Back

Topic: Earth Science

Scientists studied deep sea sediment cores and found that two major earthquake faults on North America's West Coast may be connected. This means a big earthquake on one fault could be followed by seismic activity on the other, causing even more damage.

Two of the most closely watched fault systems on North America's West Coast are the Cascadia subduction zone and the San Andreas fault. A recent study suggests that these two faults can become synchronized, with a major earthquake on one fault potentially followed by seismic activity on the other.

The researchers studied deep sea sediment cores containing about 3,100 years of geologic history. They found striking similarities in the timing and structure of turbidite layers associated with the Cascadia and San Andreas fault systems. Turbidites are deposits that form when underwater landslides send large amounts of sediment rushing downhill.

The team identified three events during the past 1,500 years when Cascadia and the northern San Andreas appear to have ruptured within minutes to hours of each other. The most recent of those episodes occurred around 1700. This means that if a major earthquake were to hit one of these faults, it could be followed by another earthquake on the other fault, causing even more damage.

The possibility of closely spaced earthquakes has major consequences for disaster preparation. If both systems ruptured within a short period, multiple major metropolitan areas could be dealing with severe damage at nearly the same time.

Why It Matters

This discovery is important because it can help us prepare for and respond to natural disasters on the West Coast of North America. It's also a reminder that we need to think about how different parts of our planet are connected and how they can affect each other.

Key Facts

• The Cascadia subduction zone and the San Andreas fault are two major earthquake faults on North America's West Coast.
• A recent study suggests that these two faults can become synchronized, with a major earthquake on one fault potentially followed by seismic activity on the other.
• The researchers studied deep sea sediment cores containing about 3,100 years of geologic history.
• They found striking similarities in the timing and structure of turbidite layers associated with the Cascadia and San Andreas fault systems.
• The team identified three events during the past 1,500 years when Cascadia and the northern San Andreas appear to have ruptured within minutes to hours of each other.

Key Terms

Subduction zone

A region where one tectonic plate is being pushed beneath another.

Turbidite

A deposit that forms when underwater landslides send large amounts of sediment rushing downhill.

Synchronized faults

Faults that can become connected and have earthquakes at the same time.

Implications

This discovery is important because it can help us prepare for and respond to natural disasters on the West Coast of North America. It's also a reminder that we need to think about how different parts of our planet are connected and how they can affect each other.