California Quakes and Hawaiʻi

Jul 24, 2019

Earlier this month, central California was rocked by a pair of powerful earthquakes. While there was no impact on Hawaiʻi, the islands make up the third most seismically active state in the country. And that brings up a pair of questions: can California quakes affect Hawaiʻi — and is there a way to get any early warning of something that may impact our state?  

As the seismic network manager for Hawaiian Volcano Observatory, Brian Shiro keeps a close eye on earthquakes. He says the possibility of a west coast quake triggering a tsunami in Hawaii depends on where the shaking is.

“The good news about the tsunami risk for Hawaiʻi from California is that it’s low. Even the great 1906 San Francisco earthquake produced a tiny tsunami only a few inches high that barely made it out of the San Francisco Bay Area. The reason for that is most of that motion is horizontal, not vertical. California doesn’t have the type of faults, at least not by the ocean, that can produce that vertical motion. Up in the cascades area, near Oregon and Washington, British Columbia, that’s another story. There’s a subduction zone there, where one plate dives beneath another, and all those earthquakes that happen are the type that can make a tsunami , including a large ocean-crossing tsunami.”

The Pacific Tsunami Warning Center would alert residents to any tsunami generated by a remote earthquake. 

As for early warning systems for earthquakes, they have been in use in Mexico City since 1993, and in Japan since 2007.  Just this past January, Los Angeles became the first U.S. city to roll out an earthquake early warning alert application for cell phones. 

Shiro says although there’s no funding now to provide early warnings in Hawaiʻi, some work has been going on.

“In Hawaiʻi, there was a study commissioned a few years ago by the telescopes on Mauna Kea to study the feasibility here. We found out that yes, it is possible, to have some seconds of warning in Hawaiʻi as well, with moderate improvements to the monitoring network.”

Shiro says Hawaiʻi already has lots of seismic monitors in place, because of our volcanoes.

“We do have the national volcano early warning system, known as NVEWS, which was recently authorized by Congress and signed into law by the president. We’re going to be expanding our monitoring of the volcanoes quite a lot. That expanded monitoring will have the side benefit of giving extra warning to people for earthquakes.”

Shiro says such a system could provide 15 to 30 seconds of warning, which could allow people to stop driving, utilities to shut off generators or close gas lines, and observatories to clamp down telescope mirrors, as examples, to save lives and reduce economic impact.