Have you ever wondered just what went in to going from ground shaking detected by a seismometer to a located earthquake available for viewing online? In this week’s Yellowstone Caldera Chronicles, we trace the path from the ground in Yellowstone to your web browser!
What Goes into Operating the Yellowstone Seismic Network?
Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week's contribution is from Jamie Farrell, assistant research professor with the University of Utah Seismograph Stations and Chief Seismologist of the Yellowstone Volcano Observatory.
At 6:34 am (12:34 UTC) March 30th, 2014, a magnitude 4.8 earthquake struck Yellowstone about 3 miles NNE of Norris Geyser Basin. This event is the largest earthquake to hit Yellowstone in over 30 years. It was well recorded by the Yellowstone Seismic Network (YSN) that is operated by the University of Utah Seismograph Stations (UUSS), a founding member of the Yellowstone Volcano Observatory (YVO). One of the closest stations to record the earthquake was station YNR, located about 4 miles to the south of the epicenter, near Norris Geyser Basin.
Seismometers come in many flavors. Accelerometers are better for recording large earthquakes close to their occurrence, since they don’t go off scale easily. Broadband and short period seismometers, however, can go off scale if the shaking is too large for the instrument to handle—from either a large earthquake, or from a smaller earthquake recorded at a station that is very close by. If this happens, we don’t get all the information that we would need to fully characterize the ground shaking. YNR has both a broadband seismometer and an accelerometer. In the broadband recording, the shaking was too much for this instrument and the signal is “clipped,” or not fully recorded. The accelerometer (sometimes called a strong-motion instrument), however, stayed “on scale” and recorded the full ground motion.
Because earthquakes can happen almost anywhere in the Yellowstone region, and can be both very small (below M0!) and quite large (like the M7.3 I 1959), the YSN is made up of a variety of instrument types. And in many places, like YNR, there are multiple instrument types at the same location.
So seismic stations of a variety of types record ground motion at Yellowstone. But how do the data of the YSN get from the stations in the field to the earthquake recording system at the UUSS? This happens via the telemetry network. This often-forgotten part of a seismic network is probably the most important and time-consuming component. Since the YSN is a monitoring network, the data need to be flowing in near real-time. This involves a large array of antennas, radios, cell modems, satellite dishes, and internet links, as well as a sophisticated computing system that can ingest the data and automatically identify, characterize, locate, and send out notifications about the earthquakes as they happen.
Because Yellowstone is such a remote place with severe winters, keeping the telemetry system up and running takes quite a bit of effort by the field techs who are the unsung heroes of seismic networks. In order to have a robust telemetry network, UUSS makes sure that there are many different data paths, so that if one path goes down, it doesn’t knock out the entire network at once. This ensures that, for the most part, data will be flowing even if the whole network isn’t fully operational.
In Yellowstone, UUSS has worked hard over the past decade to upgrade the YSN to a modern digital seismic network. However, much of the old analog telemetry network has been retained to provide a backup data stream in the event that the digital network goes down (or vice versa).
Another part of a seismograph station worth discussing is the power system. Most stations in Yellowstone are solar powered with batteries to store energy and operate the station at night or during heavy overcast conditions, although there are a few stations on AC power that are located near buildings and other infrastructure. For remote stations, the solar panels are carefully hidden from view and are placed as to get the most direct sun and the least amount of snow/ice buildup in the winter.
In order to get good radio connections, many stations are located on mountain tops (including the two main data collection sites on Mt. Washburn and Sawtelle Peak), where wind and ice buildup are particularly harsh in the long winter months. For a few of these stations, air-cell battery backups have been installed in case the solar system cannot provide enough power to keep the station running. Even with all of these measures, a few stations always go down at some point during the winter until the sun comes out long enough to melt the ice off the panels and charge the batteries. During these shorter down periods, data are stored locally at the station and back-filled when the telemetry is reestablished. If the power is out for too long, however, data will be lost. UUSS field engineers work hard during the summer months to make sure that everything is up and running and ready for the upcoming winter to minimize the times where stations might be down.
And it’s not just the weather that might impact seismic stations. Yellowstone is home to a variety of large and small animals, some of which are very curious…and hungry! Seismic stations need to be hardened to protect against animals that might wonder what a telemetry cable tastes like.
Most YSN stations are located on federal (National Park and National Forest) land, but a few have also been installed on private land. Each station on federal land requires a separate permit that needs to be initially applied for and then renewed after a few years. For equipment on private land, agreements are reached with individual landowners and must be reworked whenever the land ownership changes hands. This is yet another facet of operating the YSN and that requires additional time and resources to make sure the stations stay up and running.
Finally, as the data come into the University of Utah servers and earthquakes are automatically identified and located, a team of seismic analysts reviews every single earthquake to make sure the location and magnitude are as good as they can get. If you are curious about when and where earthquakes are happening in Yellowstone, you can visit the UUSS website at https://quake.utah.edu. The data are also sent to the U.S. Geological Survey to be distributed on the National Earthquake Information Center website as well.
Now, the next time you look at a seismic trace of an earthquake in Yellowstone (or anywhere in the world for that matter), or you see a story about a new swarm happening in the Yellowstone region, you know about all the hard work that went into making sure those data were available!