Written by Noel Jackson, Assistant Professor, University of Kansas
Day 2 is going according to plan. At around 12:30 am this morning four of our brave graduate students and apply-to-sail participants operated the CTD (Conductivity, Temperature, and Depth) instrument with the help of our awesome marine technician Ana.
These measurements will allow us to calculated the speed of sound through the water column, which is an important component of GNSS-Acoustic (GNSS-A) positioning. Our GNSS-A sites are critically important for measuring where the subdiction zone fault is locked and can rupture in a big earthquake, and how large the next great earthquake in Cascadia might be.
The winds died down and we were able to get Jason in the water this morning. We successfully placed 3 GNSS-A transponders on existing benchmarks at site NCB1. NCB1 had previously been occupied by transponders for 4 years, which were recovered before the end of their 5-year battery life. GNSS-A benchmarks are cleverly designed to be reoccupied by new transponders to continue the GNSS-A time series, which was our first operation on this cruise.
Map of Cascadia with GNSS-A sites and other points of interest marked.
The transponders are sent down on an "elevator", which is a platform with a float that controls the descent speed of the transponders through the water column and ensures that they land upright on the sea floor. Jason then cut the straps holding the transponders to the elevator, and carried each transponder to it's benchmark. We did find that some of the benchmarks had become home to some sea life - most notably, a lot of crabs! NCB1 has only been without transponders for a year, so we didn't expect the degree of sea life that would move in during that time. However, Jason was able to gently sweep away any sea life that needed to be removed to place our transponders.
Tonight we will transit to the Seafloor Optical Fiber Strainmeter (SOFS) site and begin operations at the strainmeters tomorrow morning.
Comments
Post a Comment