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Time Critical Studies

What do scientists do when earthquakes start happening on the seafloor?

Recently, a group of scientists had to figure out the answer to that question. In the spring of 2008, offshore sensors detected a strong earthquake swarm – a series of similar earthquakes happening one after the other in the same place – offshore of the state of Oregon on the Juan de Fuca tectonic plate. The location of these earthquakes puzzled the scientists because they happened in the middle of the plate, not near the edge or between 2 plates where earthquakes are normally located. An earthquake swarm like this could be caused by magma flowing up from deep inside the Earth to the seafloor, cracking the Earth's crust as it travels, and leading to an eruption of lava on the seafloor. The only way to find out if this is what happened was to get on a ship and head out to the location of the earthquakes with some sensitive equipment that could detect changes in the water column that would indicate that an eruption had happened. However, it was important for scientists to get out to the earthquake location as quickly as possible, otherwise the trail of evidence would be cold.

Time critical studies map

Figure 1. Locations of the earthquakes as circles, and the black line shows the track that the ship traveled during the response cruise. Stars mark where the scientists took measurements of salinity, temperature and depth. Elevated temperatures, or a higher-than-normal amount of particles in the water could indicate that an eruption has taken place recently on the seafloor.
Image credit: NOAA Vents Program

So that is exactly what the scientists did. A group of six scientists mobilized themselves and their equipment and were heading out of Newport, Oregon on the ship R/V Wecoma within weeks after they first learned about the earthquakes. In a bit of good luck, while the ship was out at sea, another earthquake swarm was detected – this one in an area called the Gorda ridge, near the southern edge of the Juan de Fuca plate. The ridge marks the boundary between 2 plates – the large Pacific plate and the small Gorda plate. The scientists onboard the Wecoma were able to change their plans and head over to investigate after taking measurements at the location of the first earthquake swarm.

The map (Figure 1) shows the locations of the earthquakes as circles, and the black line shows the track that the ship traveled during the response cruise. Stars mark where the scientists took measurements of salinity, temperature and depth. Elevated temperatures, or a higher–than–normal amount of particles in the water could indicate that an eruption has taken place recently on the seafloor.

The scientists were disappointed not to find any evidence of a seafloor eruption on their cruise, but they are still working back on shore to analyze the water samples that they collected in more detail. They hope to be able to crack the case of what happened during the Juan de Fuca plate's very active spring, and will be ready to go to sea when the Juan de Fuca plate starts to rumble once again.