/Scientists Might Have Quicker Fix to Predict Bluff Collapse

Scientists Might Have Quicker Fix to Predict Bluff Collapse

Mark Zumberge of Scripps Institution of Oceanography points to an optical strain meter that could be used to help predict whether coastal cliffs are about to fall. / Photo by MacKenzie Elmer

So, remember when I told you researchers were getting closer to predicting when Southern California beach cliffs are about to fall – hopefully avoiding the kinds of fatal injuries those bluff collapses have inflicted in years past?

At that time, “closer” meant Scripps Institute of Oceanography researcher Adam Young was still years off from uncovering a warning signal from a huge bank of data taken by a laser that measures weaknesses in the cliff.

Well, an answer could actually be much closer, if the California Legislature decides to throw money at it.

Young recently teamed up with another Scripps researcher, Mark Zumberge, a geophysicist whose fiber optic laser machines have helped detect ensuing earthquakes, volcanic eruptions and even nuclear missiles. That same technology, he hypothesizes, could be useful for knowing when a cliff’s about to crumble.

“There may be signals in the ground’s movement and groundwater that we may be able to detect prior to a failure,” Zumberge said.

In other words, he thinks he can measure tiny movements within the cliff caused by rain or groundwater that is widely considered to be a main trigger for bluff failures.

The tool he’s developed to do that is called an optical fiber strain meter. It uses the same fiber optic cable used to deliver high-speed internet to homes. This is how it basically works: Scientists bore a hole through the cliff from top to bottom. They attach the fiber optic cable at the top and stretch it to the bottom, so it’s taught. Then they shoot a laser light through the cable that is recorded 50,000 times per second. When the ground shifts, it causes the cable to move or stretch and the light moving through the cable can sense the change.

The laser generates a line on a graph back at the lab, much like an earthquake-measuring seismograph, and if the ground shifts, that line wiggles a little bit. That’s the signal scientists are looking for.

“We can sense that with a sensitivity of the diameter of a single atom,” Zumberge said.

An atom is so small, you could line up a billion of them across the end of a AAA battery. He’s essentially saying this instrument can sense really, really small movements.

Zumberge is using this same method to study when the Pacific Northwest might experience a devastating earthquake that could cause a tsunami big enough to decimate coastal towns. Up there, the big rock plates that make up the surface of the Earth are subducting. That means one rock plate is hitting another rock plate and being forced underneath it. About 300 years ago, the stress of that massive rock movement got so intense that it caused such an earthquake.

“The local governments there are already planning what they’re going to do to have buildings that are high enough,” Zumberge said.

And planning is precisely what cities along Southern California’s coast need to do as erosion takes more and more land out to sea.

Zumberge stressed, however, that scientists aren’t “promising that we’re going to have an early warning system through this. We’re promising what kind of early warning system might be feasible.”

But the Scripps team won’t be able to do this research without funding.

Assemblywoman Tasha Boerner Horvath, a Democrat who represents coastal North County, introduced a bill in March to put $2.5 million behind this specific effort. Lawmakers on the state Assembly’s Natural Resources Committee OK’d the funding March 25 and referred it to the state budget committee, but it still has many more hurdles to pass before the funding gets in the hands of scientists.

Until then, Scripps scientists can’t begin the study.

What’s Next for San Diego’s Biggest Power Contract?

Whether any power companies are going to challenge San Diego Gas and Electric for control of the city’s energy grid will be revealed when the city clerk opens bids on that contract Friday.

Weeks ago, I wrote that Mayor Todd Gloria already didn’t appear to have the votes he needs on the City Council to pass the terms of the contract he wrote, a fact revealed well after the contract was already out in the market.

That’s if four Council members stick to their guns and actually fight for the things they said they wanted in a series of memos written to the mayor’s office. That includes a much shorter contract term, something like five years instead of the 20-year total contract Gloria wants.

Some of those Council members also seem to be warming up to the idea of a publicly owned or government-owned power grid. That would mean the government would have to buy out SDG&E’s massive system of poles and wires and substations in order to take over.

One of Gloria’s first big decisions as mayor will be put to the test when the city clerk opens at a public meeting Friday.

A bit of history: Former Mayor Kevin Faulconer tried to get a new contract passed before he left office. But Gloria determined SDG&E (the only bidder after much ado over scintillating hints that other companies would also bid and give the city more negotiating room) didn’t meet the terms of Faulconer’s contract, canceled the process and wrote his own version.

I’ll Co-Host a Climate Talk at Scripps

Mark your calendars for April 29, when I get a chance to fire questions at my former professors and climate change experts at the UC San Diego Scripps Institution of Oceanography on a panel with Margaret Lienen, physical oceanographer and head of Scripps, and Benjamin Bergen, director of the UC San Diego Climate Action Lab.

You can register for that event here.

It will feature Tarik Benmarhnia, an expert on climate change and public health. He talked with me about how future heat stress will impact San Diegans differently based on where they live as the city contemplated Measure E, an effort to raise the building height limit in the Midway District.

The panel will also feature Mark Merrifield, an expert on sea-level rise who is developing tools for coastal California cities like Imperial Beach; Isabel Rivera-Collazo, who studies how past climate change impacted social identity of past human cultures and what that means for our future; and David Victor, director of many things including UC San Diego’s Deep Decarbonization Initiative, which is working with San Diego County on its zero-carbon climate plan.

In Other News

  • It’s that time again, when the Earth moves through the comet trail of C/1861 G1 Thatcher, sending dust and tiny bits of ice into our atmosphere – a natural light show called the Lyrids beginning April 16, peaking on Earth Day (April 22) and finishing April 25.
  • San Diego County is again exploring whether to join community-choice aggregation, a government-led authority that buys the region’s power. And San Diego Community Power, the CCA that includes San Diego, Chula Vista, Encinitas, Imperial Beach and La Mesa, is hella interested. (Union-Tribune)
  • A group of climate change advocates is going to score elected officials on their climate policies in a kind of report card.
  • Much like the Citadel of Minas Tirith, but not really at all, the great 400-foot smokestack above the Encina Power Station in Carlsbad is coming down. Once the region’s largest fossil fuel power plant, it was finally retired in 2018. (NBC 7)
  • A San Diego startup is taking its self-driving truck (albeit not electric, but supposedly lower-emission) company public. (Union-Tribune)
  • Some small stock holders in Sempra Energy – which owns San Diego Gas & Electric – want the company to align its goals with the Paris Agreement, designed to encourage countries to reduce their emissions. Shareholders will vote on the proposal May 14 but Sempra’s board of directors is already encouraging a “no” vote. (Union-Tribune)