The Marcus G. Langseth, a research vessel operated by Lamont-Doherty Earth Observatory, traverses the world’s oceans conducting marine seismic studies that contribute to new understanding of Earth systems. The ship typically spends half the year or more on research expeditions led by Lamont-Doherty scientists and colleagues from other research institutes.
A new method for detecting big landslides is allowing scientists to understand the dynamics of these elusive events almost instantly, without traipsing to remote mountains or scrambling up rugged peaks months, or even years, later. In a recent study in the journal Science, Göran Ekström and Colin Stark, geophysicists at Columbia University’s Lamont-Doherty Earth Observatory, have catalogued the 29 largest landslides since 1980 using satellite images and recordings from a global network of seismic instruments. A third of the avalanches are documented now for the first time.
The NoMelt project is more than just a seismic experiment; it also has an important magnetotelluric (MT) component. MT instruments measure natural magnetic and electric fields on the seafloor, allowing scientists to estimate the electrical conductivity of the underlying rocks. Conductivity is highly sensitive to tiny amounts of water and molten rock within the upper mantle and thus can help distinguish whether the mantle is “wet” (and thus easy to deform) or “dry” (rigid and plate-like).
Recovering OBS instruments from the ocean floor is always a tricky business, especially in our case; these instruments have been sitting beneath more than 3.5 miles of water for over a year. With cold, tired batteries powering the instruments’ acoustic transponders, communicating with them through miles of ocean currents amounts to a whispered conversation on a stormy night.
Today marks our sixth day aboard the R.V. Melville on a journey to a remote region of the Pacific to retrieve seismic instruments that have been quietly recording earthquake signals on the ocean floor for the past year. We have covered more than 2,600 km thus far but must cruise for another two and a half days before we reach the NoMelt project site.
On December 18, 2012, the Research Vessel Melville departed San Diego to recover remainder of the NoMelt instruments and data. The expedition includes two scientists from Columbia’s Lamont-Doherty Earth Observatory: Post-doctoral scientist Patty Lin and graduate student Natalie Accardo. Natalie is sending regular reports from the ship.
An important piece of earthquake-science history popped up a few weeks ago on Jeopardy!: “The Press-Ewing was an early seismograph, recording waves from these events. If you didn’t know a Press-Ewing from a French press, you were in luck. For $200, all you needed to know to formulate the question is what a seismograph measures. What is an Earthquake?
With round-the-clock shifts, there are precious opportunities for Santa to slip onto a research ship unseen. But slip in he did, leaving treats and gifts around the R.V. Langseth to brighten our day.
Over the first 22 days aboard the R/V Marcus G. Langseth, we’ve zigged and zagged our way over a 360×240 mile region of the Pacific plate, first dropping instruments to the seafloor, and then shooting airguns to them (see previous posts). The final step is to recover a subset of the instruments: 34 ocean-bottom seismometers [...]
The NoMelt experiment aims to image the structure of an oceanic plate, including its deepest reaches up to 70 km beneath the seafloor. One of our primary means to do so is to create sound (acoustic) waves in the ocean from the ship, and record those waves at receivers on the seafloor, after they have [...]