7 votes

California tsunami hazard area map

2 comments

  1. rosco
    Link
    Thanks for the link! I was interesting how much of yesterday's warning/evacuation area was inside the "No, outside tsunami area" sections. Will definitely refer back to this if we get another...

    Thanks for the link! I was interesting how much of yesterday's warning/evacuation area was inside the "No, outside tsunami area" sections. Will definitely refer back to this if we get another earth tickle.

    7 votes
  2. skybrian
    Link
    How Confusion Over California's Tsunami Warning Shows the Limits of US Forecasting (KQED) … … …

    How Confusion Over California's Tsunami Warning Shows the Limits of US Forecasting (KQED)

    According to Lori Dengler, an emeritus professor of geology at Cal Poly Humboldt, not much has changed about the U.S.’s tsunami warning system since a similar near-coast earthquake hit in 2005.

    “The entire West Coast from San Diego up to the Canadian border was put into a tsunami warning and a tsunami did not materialize,” she said. “[The U.S.] is still in the relative infancy or maybe toddlerhood of the tsunami warning world in terms of having the kinds of instrumentation offshore, having the kinds of models to forecast [their] impacts.”

    Dengler said there are a lot of shades of grey under that “warning” umbrella.

    “In Japan, they have three levels of tsunami warnings,” she told KQED. “They have a small tsunami, a medium tsunami and a big tsunami. In the U.S., we just have one level. We just have ‘warning.’”

    An earthquake that meets a prespecified set of standards based on magnitude, location and depth triggers a warning, no matter how close, or far, from the cut-off it is.

    The map of at-risk zones and guidance for a local response, when there’s a warning issued, is based on a model researchers designed for a worst-case earthquake event on that underwater Cascadia fault — “the big one” — Dengler said.

    Officials there say the decision was based on state guidance after the city received the blanket “warning” Dengler referenced.

    “The message indicated that a ‘Warning-level’ tsunami of at least 3 feet would hit the shores of San Francisco by 12:10pm, implying that Berkeley would likely be hit shortly thereafter,” spokesperson Matthai Chakko wrote via email. “Pre-existing state guidance indicated that such a tsunami could reach as far east as portions of 7th Street” and “prompted the City to issue an evacuation order for the affected area.”

    Other disruptions rippled throughout the bay: BART temporarily shut down service in its Transbay Tube, Salesforce Tower began an evacuation, and San Francisco warned coastal residents to move at least a block inland and avoid evacuation zones.

    Delger said that refining the national Tsunami Warning System would require investment in offshore instruments and more personnel.

    “There’s no way right now to pull the San Francisco Bay’s communities — Alameda, the Marin County part that’s on the bay — there’s no way to pull those communities out of the warning,” she told KQED. “The system is not set up now to do localized threats within Puget Sound, within San Francisco Bay, or really parsing the details of any of the coasts.”

    4 votes