Archive for March 6th, 2010

Earthquake at sea

Saturday, March 6th, 2010

Now we know what a p-wave from an earthquake feels like while at sea. We were sailing peacefully when the whole ship began to rattle. It was brief, but immediately after, our onshore correspondent informed us that the ground was shaking in Haiti, estimating a magnitude of 4.6.  The physical shaking would have been a direct result from the propogation of a p-wave (primary wave) resulting from surface movement.  Now that surface conditions have changed we have to start our mapping all over again…(just kidding!)

Surveying continues as we try to delineate fault scarps and fill in nearshore areas where shallow subsurface faults most likely transverse. We were successful collecting one gravity core and one multi-core today in an area where we believe the sediment is a debris flow resulting from the recent Earthquake. Visually, at least 2 events are apparent in these cores. We will process the sediments for grain-size and short-lived radionuclides when we return to New York. Grain-size is important for understanding the energy of a system. Larger and denser grains require more energy to be transported, so a landslide resulting from an earthquake would potentially transport larger grains than are commonly deposited in this environment.

Picture descriptions:

We are sailing pretty close to land, so have been able to see some more detail of coastal features and scenery.

Image captured while sailing adjacent to marine terraces, fossil coral reef platforms that have been recrystallized to limestone. They are above sea level due to a likely combination of tectonic uplift and sea level fall (~4 m higher 4,000 years ago).

Image of a fishing sailboat that has been interested in our activities the last few days.

The Endeavor cook, Amanda, displays a dangerous assortment of nightly snacks. This isn’t even all of it.

Scientists at work (Cecilia McHugh and Nano Seeber).