Finishing the Kodiak Seismic Deployment

This blog marks the successful completion of the Kodiak-based seismometer deployment. In Sunday we reached our last, farthest site – at a remote airstrip on the Alaska Peninsula, one of the closest places to the epicenter of the recent earthquake. The site featured a small grass runway and a small wilderness camp with about four summer inhabitants. When queried, they described being tossed out of bed by a M6.9 aftershock a couple of days ago, they were some of the closer humans to the aftershock zone.  We set up our standard instrumentation next to the airstrip and flew back to Kodiak, and then we are done! At least with the Kodiak-based deployment, the western team (led by the other Jeff) continues for a few more days. And, we have to return in the spring to collect the equipment and record the data. But for now, in Kodiak we are all packed up, gear is either being shipped home or stored, and the crew is traveling back to New York State, Colorado, and California.

The last station: a remote, but mowed airstrip made access easy. 
Dan and Geoff take a final selfie with the tarp-covered electronics box

It is worth saying a few words about what, exactly, we installed at each site. The seismograph consists of two primary components: a seismometer, or sensor, that is buried in the ground to sense small ground motions, and a data logger that converts the electrical signals from the sensor to digital bits, and stores them to a disk. They are connected by a thick cable, and powered by a bank of batteries – we use an air-alkaline technology that can power one seismograph for a year without need of extra sources like solar panels (not very useful in the Alaska winter). The other component is a GPS/GNSS antenna that is used to get precise timing, so we know exactly when signals reach each station. The whole dataset is recorded on a 60 Gb flashcard, which we do not access until the next time the site is visited. All of this tech has improved immensely and allow us to collect vastly better and more data – when I first did this, we used pens and ink on those paper drums, and had to visit them every day. 

The electronics box. The white box is the data logger, sitting on batteries separated by bubble wrap. The thick black cable goes to the sensor, and the thin black one goes to the GPS antenna. Gray cables are for power.  
Dan is using a compass to orient the sensor as close to north-south as possible. It is half-buried in the hole at his knees.

Once we recover the data, some checks and reformatting are done back home, then we deliver all of it to the IRIS Data Management Center, the main repository for seismic data. There, it can be easily accessed along with data from thousands of other seismometers, by anyone who is interested. Because of the high value of these aftershock data, all of it will be immediately available to anyone who wants it – the principle of open data is increasingly common to community projects like this. It helps speed up science by letting anyone with a good idea try it out, and makes sure the data are used as effectively as possible.

The July-August 2021 earthquake sequence, in white circles, and the response seismometers. Black boxes show the ones we deployed from Kodiak with our routes. The red boxes are being deployed next. 

That’s a wrap for now, from Kodiak! We will be back in late spring to see what we learned. It has been an adventure and rewarding to successfully mobilize a project this quickly, and we had much help. I would like to thank the program managers at the National Science Foundation for seeing the value in the project, the skilled support from the IRIS-PASSCAL Instrument Center, the Alaska Volcano Observatory, and the many people in Kodiak who have been understanding and very helpful. And of course, Enrique and Dan who mobilized so quickly! – Geoff


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