While coastal residents have a fairly high level of knowledge about tsunami hazards in general, many residents do not know the warning signs for tsunami and do not know how much time they would have to evacuate following either a tsunami warning or a strong offshore earthquake.
The survey was conducted last spring by Matthew S. Davis, Ph.D., professor of psychology at Dominican, in partnership with the Marin County Sheriff’s Department Office of Emergency Services (OES). The survey was designed to provide a baseline measure of residents’ awareness of tsunami hazards and knowledge about actions that would need to be taken if a tsunami warning were issued. This information is being used to help guide county officials as they design public education campaigns regarding tsunami preparedness. The OES has several Marin public education sessions planned: the first gathering is set for Monday, February 26 at the Stinson Beach Community Center.
In May 2006, Davis mailed 650 surveys to residents of Muir Beach, Stinson Beach, Bolinas, and Dillon Beach. The surveys focused on four key areas: the relative importance of tsunami risks compared to other risks; knowledge of tsunami hazards and protective measures; perceptions of risk and levels of disaster preparedness; and various demographic items.
A significant majority of residents knew that an earthquake or an underwater landslide either off the California coast or anywhere in the Pacific Ocean could trigger a tsunami. However, many residents do not know the warning signs that could signal an approaching tsunami. For example, when asked if other than hearing an official tsunami warning, there were any other ways to tell that a tsunami could be approaching the coastline, 72 percent replied yes. However, when asked to provide specific examples of warning signs of an approaching tsunami, only 2 percent knew that feeling an earthquake at the coastline could signal a tsunami’s approach while only 49 percent noted that receding waters are a precursor for a tsunami.
"Residents of Marin’s coastal communities are vulnerable to tsunami, and by better educating them about the warning signs of a tsunami and the proper actions to take if a warning is issued, we can help to prevent loss of life,” said Dr. Davis.
The survey revealed that relatively high numbers of people don’t know how much time there might be between an official tsunami warning and/or feeling a strong quake and the arrival of a tsunami.
In the event of a distant-source event generated in places such as Japan or Alaska, several hours warning time is likely, and the Pacific Tsunami Warning System is in place to alert at-risk populations, said Davis. This will allow time for an organized evacuation away from low-lying coastal areas. However, when residents were asked how much time they would have before the potential tsunami arrived, 38 percent of respondents said they did not know, while 37 percent believed they would have only 30 minutes before the tsunami arrived.
“Not understanding that a distant-source tsunami will take several hours to reach our coastline could create panic and dangerous actions during an evacuation of the coast,” noted Dr. Davis.
In contrast to such a distant-source event, a strong underwater earthquake occurring close to the northern California coast could generate a tsunami that could reach the shore in only 15 to 30 minutes.
When survey respondents were asked how much time they might have to take appropriate actions if they felt a strong earthquake while at the beach, 53 percent correctly answered that they had less than 30 minutes to take appropriate actions. However, 39 percent responded that they did not know how much time they had to evacuate, which Davis feels is cause for concern.
The survey found that most residents knew the best actions to take in the event of a tsunami warning, such as moving to higher ground, going inland as quickly as possible, avoiding coastal areas for several hours, and listening to the radio for official advice. However, 10 percent of the respondents incorrectly stated that they should scan the ocean and watch for sea waves and six percent noted that they would remain indoors.
The survey reveals that more must be done to educate coastal residents about tsunami risks. A significant majority of respondents cited various forms of the media (television, radio, newspapers or magazines) as their source of information regarding preparedness information, but a surprising 43 percent said they have received no information on tsunami risks and preparedness at all.
Posted January 25, 2007