Off the U.S. Pacific Northwest coast, the 680-mile-long Cascadia subduction zone has produced giant earthquakes and tsunamis like the one that ravaged Japan last year--the most recent, in 1700. These quakes are thought to come every several hundred years. To help understand subduction processes along this zone, scientists at sea and on land are conducting the first-ever imaging of an entire plate-the Juan de Fuca-from the ridge where it is growing, to the trench where is diving under North America. Aboard the R/V Langseth and R/V Oceanus scientists will study how fluids, sediments and the structure of faults may influence the evolution of this seismic zone, and the frequency and power of earthquakes, as well as volcanoes that erupt inland.
We are a scientific team of 20 scientists currently aboard the R/V Langseth, acquiring seismic images of the Cascadia subduction zone. Through our work we hope to provide new insights on the position and structure of the plate boundary between the downgoing Juan de Fuca plate and the overlying North American plate.
Our sensors record the same seismic signals as the ocean bottom seismometers the R/V Oceanus deployed, and we will combine the data later. They can detect R/V Langseth signals up to 100 miles inland! This is something extraordinary, and difficult to believe until seen.
By Helene Carton As part of our study of the Juan de Fuca plate from its birth at the mid-ocean ridge to its recycling at the Cascadia subduction zone, the R/V Oceanus has the task of conducting Ocean Bottom Seismometer (OBS) operations and oceanographic measurements: this is done in close coordination with the R/V Langseth, [...]
Heading west from coastal Oregon we are able to make our initial seismic images beneath the seafloor continuously as we go. Where once our data would have been recorded on magnetic tapes only to be analyzed long after the expedition was over, thanks to the wonders of modern signal processing, we can now make images [...]
Yesterday we deployed one of the Langseth’s long cables equipped with listening devices and began the second phase of our survey which we have been awaiting with much anticipation.
In the research expedition now underway, we will investigate the Juan de Fuca plate before it disappears under North America to understand why earthquakes happen where and when they do within the Cascadia subduction zone off the Pacific Northwest. Our ship, the R/V Marcus G. Langseth, is one of 25 research vessels available to U.S. scientists for oceanographic research.
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