Reasons as to why there have been large earthquakes in Ecuador

Posted on January 5, 2017 • Filed under: Earthquake, Ecuador, Ecuador Emergency

temblor.net/By Gabriel Lotto – The April 16, 2016 Pedernales, Ecuador, earthquake was the latest in a string of large quakes that have repeatedly ruptured the Ecuador-Colombia subduction zone over the last 100+ years. The earthquakes kicked off in 1906, when a megathrust earthquake – estimated between M=8.5 and M=8.8 – ruptured the entire interface between the downgoing Nazca Plate and the North Andean Sliver (NAS), a small segment of the South American Plate.

Since 1906, there have been not-quite-as-huge-but-still-large earthquakes in 1942, 1958, 1979, 1998, and 2016, the last of which was probably very similar to the one in 1942. If you were sitting at the plate interface at the equator (0 degrees latitude), you would have seen the Nazca Plate slip past the NAS three times since 1906. Why have there been so many large earthquakes in Ecuador so close together in time? A team of geophysicists from Ecuador, Colombia, and France recently published a paper in Nature Geosciences that aims to answer that question.

Away from plate boundaries, Earth’s tectonic plates move at a steady speed with respect to one another. But where two plates meet, they often lock together, sticking to each other as stress builds up and then rapidly releases in an earthquake. Off the coast of Ecuador, the Nazca Plate moves at 47 mm/yr with respect to the NAS. The Ecuador-Colombia subduction zone is locked, and it should experience earthquakes that just barely account for that 47 mm/yr of long-term deformation. For example, an earthquake that slips 4.7 meters every 100 years would get the job done. But in Ecuador, things aren’t so simple…. Read Full Article

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