The EGL has landed

Samer and I arrived in San José, Costa Rica on February 19^th. After picking up our 11 comically large and heavy cases of geophysical equipment (pictured below) from the airport, we headed to grab the rental car.

The first day of our stay was spent sorting out logistics while staying at the most gorgeous hotel, Gran Casa Universitario. The project co-lead, Darcy Cordell, arrived the day after and once we secured a second rental car, we began preparing to head out to our study area, the Nicoya Peninsula. Along the way, we also secured the generous help of two Costa Rican locals. The first is a geology student at the University of Costa Rica, Luis Salas, and the second is the muscle of our team, Gabriel León. We all made the four-hour journey to our destination of Santa Cruz, Costa Rica, which is centrally located on the Nicoya Peninsula. After a day to settle in, we set out to start deploying MT receivers.

We were lucky enough to have an amazing project collaborator, Carlos Ramírez, who scouted the sites for our MT deployments so that we could save time in the field (thank you, Carlos!). The ideal site for collecting MT data should be far from any large electrical signals since these saturate the highly sensitive electric and magnetic sensors and create too much “noise” in the data. Common sources of noise include powerlines, electric fences, pipelines, ground vibrations (such as being close to a highway), the passage of vehicles (basically large hunks of moving iron), and electric trains. The presence of a noise source obscures the natural electromagnetic field signals (in a future post I will go into more detail about where this signal originates)  and thus makes it almost impossible for us to image the subsurface. Lucky enough for us, Costa Rica is not a densely populated region which means fewer power lines and more potential sites.

We set out for our first deployment on February 22^nd  and thanks to Carlos’s scouting, we ended up with an amazing site nestled in a remote farmland. We spent around two hours on the first deployment, allowing plenty of time for everyone on the team to become familiar with the workflow of MT deployment. After a twenty-minute test run of the receiver, the preliminary data recorded looked promising, meaning low noise interference.

After this, we quickly moved on to our next deployment, where we were met with a long string of gated farmland. After making it through the multiple pasture gates, we encountered a few setbacks involving cows, wasp stings, and accidental trespassing. Once these were resolved, we settled on a site located near the far end of the farm.

After our breezy and spoiled experience at the first site of the day, this site proved to be not only a huge tripping hazard due to large holes and cracks in the dry ground but also made for very difficult digging in the rock-solid dry soil.

This site is intended to be a longer-term deployment, meaning we will leave the site out to collect data for around a week rather than two to three days. Even after all our issues, we did manage to have a successful deployment with no further hiccups. This was celebrated with juice boxes before heading out for the day.

February 22nd progress update:

Our second day of deployments had similar success! The first site was also located on a cattle farm, and we were met by lots of parrots, a starfruit tree, and a genuine cowboy on horseback who pointed us to where our next site would be. While this site was closer to powerlines than our two sites from the first day, it was still located far enough away to avoid overpowering the natural signal. The second site of the day was similar to the first and went even quicker, setting a new record deployment time for this trip of only one and a half hours from start to finish! The end of this day was celebrated with fresh coconut water from a roadside stop. These two days of mostly smooth deployments are encouraging as our goal is to deploy a total of 40+ MT sites before our fieldwork ends on March 20th.

February 23rd progress update: