A seismic station on the remote Farallon Islands is getting a major upgrade

In late January, seven engineers from the Berkeley Seismological Laboratory descended by helicopter to the Farallon Islands, a nearly treeless island chain 30 miles from San Francisco's Golden Gate, on an eight-day mission to upgrade one of the lab's remotest islands – However, most of them are critical seismic stations.

This station is one of a few stations in Northern California located on the western side of the dangerous San Andreas Fault and is vital to the University of California, Berkeley's 181-station seismic network, which is connected to the USGS and USGS networks. California Earthquake Early Warning System (CEEEWS) monitors earthquakes and provides data to warn Californians of seismic activity. The MyShake app, developed at UC Berkeley and sponsored by the California Governor's Office of Emergency Services (Cal OES), uses this network to give Pacific Coast residents early warning about potential shaking.

However, heavy rains and high winds affected the 30-year-old outstation on southeastern Farallon Island, the largest island within the Farallon Islands National Wildlife Refuge, a U.S. fish and wildlife sanctuary off-limits to the United States. Public and the largest seabird nesting site on the Pacific coast outside of Alaska. The ancient seismic sensors were placed in a rock pile for protection from the wind, but small seabirds called gray petrels appear to have burrowed for protection as well. Invasive house mice were nested in the electronic components of the sensors.

Berkeley Seismological Laboratory director Richard Allen and engineer Zach Alexie explain the importance of modernizing the Farallon Islands seismic station to improve the performance of the laboratory's Northern California network and earthquake early warning system along the Pacific Coast. (Video by Patrick Farrell, UC Berkeley)

Over the years, equipment maintenance has been sporadic, usually only possible with a six-hour round-trip boat trip across rough seas.

“This was one of the first instruments placed here when Berkeley started building the Berkeley Digital Seismic Network in the 1990s,” said Seismology Laboratory Director Richard Allen as he accompanied his crew on a survey of the old station. “It has been upgraded several times since then, but this is our opportunity to turn this site into a modern site where we have much lower noise levels and can actually detect all the earthquakes that occur in the area.”

On January 30, when Allen and the engineers arrived, the air was filled with the screaming of sea lions a stone's throw from the turbulent inlet. Their stay on the island was timed to avoid the upcoming nesting season for seabirds, such as petrels and Cassin's auks, whose nests completely surround the walkway where the station's cables are laid.

Southeast of Farallon Island, part of the Farallon Islands National Wildlife Refuge, looking south from the island's summit. Both houses are occupied by occasional visitors and, year-round, observers from Point Blue Conservation Science, a nonprofit group that has tracked the island's wildlife — seabirds and marine mammals — since 1968.

Robert Sanders, University of California, Berkeley

But they could not avoid bad weather. The worst storm of the winter hit during their stay, with winds reaching 75 miles per hour. The crew had to work in storm suits, while salt spray and rain caused their tools to rust within days.

“The Farallon site was always noisy anyway, because of storms and perhaps birds,” said Allen, a professor of earth sciences at the University of California, Berkeley. “The refurbishment — which is really the equivalent of a whole new station — will provide higher-quality data and more reliability.” And planetary science. “We don't want the station to go down.”

A much needed upgrade

The Berkeley Seismological Laboratory team has been upgrading seismic stations in the Northern California network over the past six years, in the process navigating around off-grid marijuana grows, repairing wires torn down by bears, and occasionally repairing vandalized equipment.

Engineer Zach Alexie talks with Seismic Laboratory Director Richard Allen about plans to replace old seismic sensors, buried under a pile of rocks for protection from wind, rain and animals, with modern sensors.

Robert Sanders, University of California, Berkeley

But the upgrade to the Farallon Islands station was, by far, the most unusual location with unique challenges. That was a crucial improvement, given the proximity of the San Andreas Fault to San Francisco and the densely populated Bay Area.

Earthquakes usually originate along a fault line, so pinpointing the epicenter requires sensors on either side of the fault, where four stations must detect the quake before triggering a warning through MyShake. ShakeAlert and CEEWS, which form the basis of MyShake, provide earthquake warnings to agencies and businesses throughout California. It has only had three false alarms out of 115 alerts sent since it began operating in October 2019.

Two of the false alarms were for earthquakes off Cape Mendocino, near Eureka, where the San Andreas Fault lies offshore without any monitoring stations nearby to pinpoint the exact location and magnitude. The other false alarm was on the California-Nevada border, where the Berkeley Seismological Laboratory has a few stations.

“This is an amazing performance overall, but we are missing earthquakes all around the edges of the grid,” Allen said, stressing the need to update the location of the Farallon Islands.

A helicopter transports equipment to the island.

Robert Sanders, University of California, Berkeley

These efforts required so much equipment — including rock drills and cables — that seven round-trip helicopter flights from Half Moon Bay Airport were needed to deliver them and the crew. Between January 30 and February 7, engineers built the new Farallon station, tested sensors, and lived in one of two unheated houses on the island.

What they found on the island was a dusty rack of electronic equipment dating back to 1994, pushed to the side of what is now a busy carpentry shop, the only remaining part of the barracks that was built of rock and cement in 1905. Connected to sensors The large scale is out in the open a hundred yards away, hidden under a pile of rocks stuck together with spray foam. The holes in the foam contained feathers, attesting to the fact that birds had carved nests there over the years.

Rusty communications antennas and an old GPS Radome, a structure that protects the radar antennas from the weather, complete the station's network.

At the end of the team's mission, all of the old equipment except the seismographs encased in rocks was dismantled and returned to Berkeley.

Network for the next generation

Instead, the team installed two types of accelerometers – a powerful, sophisticated motion sensor, the focus of most seismic stations, and a broadband seismometer capable of detecting small earthquakes that often go unnoticed. These instruments are now mounted on cement foundations, packed with glass beads inside a protective aluminum cylinder and protected from wind and animals by shiny stainless steel boxes bolted to the rocks.

UC Berkeley crews worked with storm equipment throughout the stormy and rainy weather to complete the upgrade to the seismic station, including installing new antennas in the woodshop to send real-time data to the mainland.

Alvaro Median, University of California, Berkeley

The new GPS antenna for measuring horizontal movement rises six feet into the air, supported by four supports molded into granite. New cables were laid; New electronic equipment is now housed inside mouse-proof cabinets in the woodworking shop; A new antenna is seen above the store's roofline to send real-time data to a receiver at UCSF.

Jonah Merritt, who led the team, said that thanks to months of planning and great teamwork, “things went shockingly well.” “This has been the most involved project we've ever done, honestly.”

Berkeley Seismological Laboratory scientists are now calibrating the sensors and reviewing the data, part of a months-long commissioning process required before any station is operational.

The newly installed seismic sensors – a powerful motion accelerometer and a broadband sensor – are now protected from wind, rain and invasion by stainless steel tanks. The view from southeast of Farallon Island looking east.

Zach Alexie, UC Berkeley

The renovated Farallon station is among the last UC Berkeley stations to be upgraded, and because of the difficulty of access, it was the most expensive, costing an additional $90,000 for transportation above the typical cost of an upgrade on the mainland. Only four stations remain. All were funded by federal and state grants through the USGS and Cal OES. The entire ShakeAlert network of 1,675 stations from California to Washington is now 91% complete, and includes networks run by UC Berkeley, Caltech, the California Geological Survey and the USGS, as well as the University of Washington and the University of Oregon, Allen said.

The UC Berkeley network has also been enhanced to conduct basic research on global earthquakes and study increased motion along underground portions of the state's faults. One of the lab's main areas of interest is whether small earthquakes, called microseisms, can provide more information about the geometry of deeply hidden faults and, perhaps one day, identify areas most vulnerable to rupture in the near term, narrowing the window in which That an earthquake occurs. Expected from a generation to perhaps a decade.

The crew rebuilding the Farallon Islands seismic station poses for a photo. From left to right, Alvaro Median, Jeremy Kaplan, Dylan Sembalski, Zach Alexie, George Dorian, team leader Jonah Merritt, and Nick Stein.

Jeremy Kaplan, University of California, Berkeley

“All Berkeley stations have two sensors: a strong motion instrument and a broadband instrument,” Allen said. “This is good for earthquake early warning because now we have two sensors, and we're actually looking at the agreement of both sensors on an ongoing earthquake. The broadband sensor is a much more sensitive instrument, so it allows us to detect earthquakes of much smaller magnitude.” This feeds into the research goals, as “We can detect these small-magnitude earthquakes and use them to image faults and understand the statistical properties of earthquakes much more quickly.”

Allen said the seismic station upgrades ensure a robust early warning system in the future.

“We wanted to build a network not only for sensing earthquakes, but for the next generation,” he said.

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