ANAHOLA — Hundreds of sediment core samples have been collected from Anahola Valley this month by researchers seeking to peer into the future by piecing together data about tsunamis from Hawaii’s past. The samples, some of which measure more than
ANAHOLA — Hundreds of sediment core samples have been collected from Anahola Valley this month by researchers seeking to peer into the future by piecing together data about tsunamis from Hawaii’s past.
The samples, some of which measure more than a dozen feet long, tell a story that’s 2,000 years old.
A layer of beach sand sandwiched between muddy peat, for example, suggests that perhaps it was lifted from Anahola’s beaches by a giant wave and then deposited in the valley sometime around 1946, said Bruce Richmond, a Santa Cruz-based research geologist for the U.S. Geological Survey of the Pacific Coastal and Marine Science Center.
That would make sense, he said, because that’s the same year that an Aleutian earthquake spawned a tsunami wave that ripped across the Pacific, killing 156 people in the Hawaiian Islands.
In some of the samples, Richmond said researchers have identified a similar layer of sand farther back in time. This break in the muddy peat might eventually help scientists build on the short historical record of tsunami events in the islands.
The samples are still being analyzed.
“It takes us a decade or more to put some of these stories together,” said Richmond, speaking to a small group at the Anahola Clubhouse. “Something brought that sand in to that wetland.”
He added, “We’re pretty excited about what we’ve been finding here.”
The event was hosted by Kalalea/Anahola Farmers Hui, Ka Hale Pono and Kukulu Kumuhana O Anahola.
The Anahola land managed by the Department of Hawaiian Home Lands where samples were taken represents one of many sites in Hawaii where USGS scientists are sampling their way back in time. Similar samples have also been taken on Oahu, Maui and on the Big Island, where there are hundreds of small earthquakes erupting every day.
Anomalies in the sediments samples, such as the small layers of sand mixed in with muddy peat found on Kauai, lend clues that scientists can study to uncover important pieces of the puzzle, such as the magnitude of past tsunami events and an estimation of the frequency of tsunami events over time. Ultimately, the goal of all this work is to try to answer the question: What’s the likelihood of another tsunami event in Hawaii?
Whether tsunamis are likely to happen in specific locales every 400 years or every 1,000 years, for example, is an important and largely missing part of the equation, Richmond said.
“Because they are rare events, to understand how big and how often they occur you need a lot of records,” he said.
Japan has by far the longest record of historical tsunamis, and as a result, Richmond estimates it is the country that’s best prepared.
“Our goal is to not let natural disasters tear down communities,” he said. “We want to use scientific research to better understand hazards and forecast disasters.”
Though Hawaii’s historical tsunami record is largely incomplete, communities themselves can play a large role in reducing loss of life in a future tsunami event by educating themselves and making others equally aware of what to do if one hits. Namely: Get to higher ground away from the coast.
“You should be prepared as a family and as neighbors,” Richmond said. “What are you going to do if? Don’t worry, but be prepared.
“Civil service is there, but the earthquake will be there first. You have to be prepared yourself before the sirens go off.”
