Why a recent earthquake didn't wreak havoc, despite its power
The Unseen Impact of a Powerhouse Earthquake: A Closer LookIn an episode of *CBS News*, investigative reporter Patrick Keough explained that while an 8.8 magnitude earthquake off Russia's coast triggered tsunamis all the way to the U.S., experts like seismologist Harold Tobin highlight why such massive earthquakes might not leave as much devastation as their power suggests.
Understanding Tsunamis
First, it's important to understand how tsunamis occur. They are periodic waves of water that can cause significant flooding and destruction. A tsunami is typically generated by underwater displacement, often caused by earthquakes, volcanic eruptions, or volcanic activity in the surrounding area. These events can push water from deep regions to shallower areas, creating a series of pulses as water rushes forward.
The 2010 Chile Earthquake's Tsunami Incident
In 2010, the Chile earthquake, with its magnitude of 8.4, triggered tsunamis that destroyed much of what is now Chile and parts of South America. The largest tsunami ever reported had a width of over 50 miles and affected populations across Chile, Bolivia, and Peru. These events were caused by the seafloor's sudden subsidence due to the earthquake, displacing water on the seafloor into shallower waters.
The Role of Tsunami-Generating Earthquakes
Tsunamis are not solely the result of large earthquakes. Their intensity depends on factors like the depth of the seafloor, the size and location of the displacement event, and the proximity of the coast to the seafloor. For instance, an earthquake 60 miles away could still generate a tsunami if the seafloor is deep enough.
Harold Tobin's Insights
Seismologist Harold Tobin has written extensively about the relationship between earthquakes and tsunamis. He emphasizes that while large earthquakes can cause tsunamis, their power and destructive potential are often overshadowed by the localized nature of these events. Tsunamis affect coastal areas because they require a specific amount of ground displacement to trigger movement in water, which then causes the displacement of water into shallower regions.
The U.S.'s Impact on Tsunamis
In 2017, an earthquake off the Pacific coast of California and Mexico caused tsunamis that destroyed over 35 cities. The U.S., with its vast coastal landscape, experienced minimal destruction because tsunamis are localized effects generated during their generation in specific areas. The proximity to multiple tectonic plates and the depth of the seafloor played a significant role in preventing widespread devastation.
The Physics Behind Earthquakes and Tsunamis
The power of an earthquake is measured by its magnitude on the moment magnitude scale (MMS), which ranges from 0 to 8. An 8.8 earthquake has immense potential energy, but tsunamis are localized because they result from displacement in a specific area rather than global earthquakes.
Comparing Earthquakes and Tsunamis
While tsunamis can be devastating, their power is often underestimated due to their localized effects. A magnitude 8.8 earthquake can cause tsunamis with the potential for significant damage, but the specifics of how these events impact coastal areas differ from the broader power outputs of large earthquakes.
Conclusion
In summary, while powerful earthquakes can generate tsunamis, these events are not inherently more destructive than their source energy. The localized nature of tsunami generation, combined with the specific conditions in a region (such as proximity to multiple tectonic plates and depth), often result in minimal overall destruction compared to the magnitude of the earthquake itself. Understanding these relationships is crucial for assessing the potential impacts of earthquakes on coastal areas and improving public safety measures.
------
