Geology & Geophysics News

Wildfires Threaten West Coast’s Seismic Network

A dense seismic network keeps vigil over the western United States, sensing quakes soon after they begin so people nearby can brace themselves. How do wildfires affect these guardians of the West Coast?

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As climate change increases the threat of wildfires, U.S. states are battling historic blazes. On the West Coast, the fires have put at risk several hundred seismic stations tasked with protecting citizens from the effects of earthquakes—nonseasonal but ever present scourges.

The network of seismic stations inform ShakeAlert, an earthquake early-warning system designed to give people enough time to drop, cover, and hold on before an earthquake’s waves roll through. Eliminating stations risks slowing these alerts.

“There is no one person tracking all seismic stations that may be affected by the fires,” said Kasey Aderhold, a seismologist with the Incorporated Research Institutions for Seismology (IRIS). Instead, several organizations oversee subsets of the network, monitoring the health of their charges by watching real-time data streams. “If data [are] coming in,” Aderhold said, “we are good. If the data connection flatlines, we investigate.”

Vulnerabilities

Wildfires attack seismic stations both directly and indirectly by excising them from the rest of the network. The sensors and electronics that record the quakes often withstand direct assaults, although Paul Bodin, a seismologist and network manager of the Pacific Northwest Seismic Network, noted that “if a fire wants to eat your station, it’ll find a way to eat your station.”

Often, the stations’ most vulnerable hardware—communications and power—may end up scorched. For example, newer stations have solar panels necessarily exposed to both sky and flame. Fire disables these stations until repairs can commence, explained Peggy Hellweg, an operations manager at the Berkeley Seismological Laboratory.

When wildfire indirectly incapacitates stations, “the telemetry,” said Bodin, “is particularly fragile.” Telemetry refers to instruments that determine how stations communicate data in real time—by Ethernet, satellite, cell, or radio. Fires can cause cell tower outages, temporarily decommissioning any connected stations by amputating the data feed. In such a scenario, stations typically come back online when power is restored.

If an off-line station doesn’t reappear in the data stream, said Hellweg, “we have to visit to see what the details are.” However, sending field personnel into hazardous situations like a wildfire, especially in the COVID-19 era, is not a good option, explained Bodin.

Fewer Stations, Less Coverage

“Sometimes stations are set up to daisy-chain or wheel-and-spoke back to a communication hub, often through low-cost radio connections,” explained Aderhold. “If a key data connection is severed…then it can be problematic for seismic monitoring.”

In 2015, this scenario played out in California’s Butte Fire, where, in addition to burned stations, a swath of stations lost their hub, said Corinne Layland-Bachmann, a seismologist at Lawrence Berkeley National Laboratory. Shortly thereafter, at the request of the U.S. Geological Survey, Layland-Bachmann calculated how the loss of these stations affected the health of the seismic network using a probability-based method that determines whether the network can detect small earthquakes. She concluded that by lancing these 28 stations from the network, the fire noticeably decreased the network’s ability to see tiny temblors, particularly in the wildfire-affected region.

Image centered on central California, outlined in black. Dark blue pixels indicate no change in magnitude of completeness, whereas red indicates the maximum change in magnitude of completeness, which is 0.8 magnitude unit. The color ramp changes from dark blue to light blue to green to yellow to orange to red. Stations eliminated because of wildfire are shown as white triangles. Latitude and longitude are noted on the y and x axes.
This image shows how the magnitude of completeness, a measure of how sensitive the existing seismic network is, changed after removal of 28 seismic stations (white triangles) because of wildfires. California’s state boundary is shown by a black line. Credit: Corinne Layland-Bachmann

For the Pacific Northwest, Bodin said, “I’m not worried about earthquake early warning and fires at this point.” He explained that in Washington, fires tend to rage in the east, which is less seismically active. Also, when stations receive upgrades, they “are armored against fire.” For example, replacing plants with gravel removes fuel for encroaching fires.

California, however, hosts fires that regularly cross active faults enveloped in dense instrumentation. “Every station missing in the network is a problem for earthquake early-warning [systems] because it will take longer to detect an earthquake with fewer stations,” said Hellweg. She argued that even small, undetected earthquakes matter. “Every measurement we make of an earthquake brings us another step forward in terms of understanding how they happen, why they happen, and when they happen and will help us in our ability to forecast earthquakes.”

For now, both Bodin and Hellweg agreed that they’ve been lucky, considering the historic infernos. Hellweg estimated that five to six of the stations she manages have been burned. She said, “Stations from other networks in the state have also been affected.” Likewise, Bodin guessed that between two and 10 stations of the several hundred under his watch have been affected by fire. “It’s a dynamic situation,” he said.

—Alka Tripathy-Lang (@DrAlkaTrip), Science Writer

Citation: Tripathy-Lang, A. (2020), Wildfires threaten West Coast’s seismic network, Eos, 101, https://doi.org/10.1029/2020EO150781. Published on 26 October 2020.
Text © 2020. The authors. CC BY-NC-ND 3.0
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