SEA Currents: Robert C. Seamans
March 17, 2017
New Zealand on the Move
42°48.5’ S, 174°12.5’ E
Ship’s Heading & Speed
170° at 3 knots
Force 4 winds, clear skies, 6-7 foot waves from the North
New Zealand is a country with a very active geologic history. The country sits at the convergence of the Australian Plate and the South Pacific Plate. The movement of these plates over time created the mountain ranges and geologic features that New Zealand is famous for. Another result of this movement is that the country experiences almost constant seismic activity. Last November, an earthquake near the Kaikoura Peninsula changed the bathymetry and topography of the region, raising portions of the land and seafloor several meters along the fault.
Early this morning, we sailed a transect near the Kaikoura Peninsula to try to find any shifts in the bathymetry resulting from this event. To do this, we used our CHIRP bottom profiler. The CHIRP, mounted on the hull of the ship, sends a pulse of sound straight down into the ocean (similar to sonar on a submarine). The sound bounces off the bottom and is received by the instrument. One of our computers takes the signal and converts the data into an “image” of the bottom. Unlike a depth sounder, we can tune the CHIRP to read the bottom in any location, including depths deeper than 4000 meters. Its pulse can also penetrate the seafloor and tell us some information about the sediment composition.
We sailed over the fault for a few hours, before turning and sailing back offshore to the South East. Did we manage to find any sections of the seafoor changed by the earthquake? We may have. As is usually the case with science, only more data analysis and time will tell.
P.S. To friends and family, I hope you are surviving the weather back home in New England. I will see you all soon!