Geoscience Reference
In-Depth Information
provides content about what to do using language that allows a person to visualize the re-
sponse (e.g., “Climb the nearest slopes until you are higher than the tallest buildings” instead
of “Evacuate to higher ground”). It also informs people when they should start and complete
the recommended protective action, which groups are in harm's way and must take action,
and how protective actions will reduce pending consequences of inaction. Effective warning
message style is simply worded, precise, authoritative, and non-ambiguous, even when discuss-
ing uncertainty in forecasts (e.g., “We cannot know exactly how high the tsunami will be when
it reaches our shores, but all experts agree that it is likely high enough that everyone should
evacuate now”). Accurate messages are critical because information errors confuse people and
affect their response to a pending disaster. Consistent messages (both consistent internally and
across messages from different sources) are needed to reduce the public's choices regarding
risk. The protective action to be taken and changes from previous messages need to be clearly
explained (Mileti and Sorensen, 1990).
To date, the committee is not aware of any previous efforts to formally review the
messages from the TWCs relative to evidenced-based approaches from the social and behav-
ioral sciences. The current and future warning messages of both the TWCs and the NWS would
both beneit from review and improvements based on the latest social and behavioral sciences
about how and why such messages inluence the behavior of people at risk and from being
rendered consistent with this knowledge base.
The committee reviewed the standard messages that are composed and delivered by the
TWCs and observed that several of the principles for effective warning-message content and
style have not been followed. For example, the information statement issued at 12:57AM on
February 27, 2010 (see Box 3.5), does not clearly identify who needs to take action because
it describes the affected area twice using different descriptions (listing individual West Coast
states by name once and then referring to the U.S. West Coast once). Although most informa-
tional statements of the WC/ATWC were issued when the earthquake was too small to gener-
ate a tsunami, this statement was more like a preliminary statement that at the end said to
stay tuned for more. The message was also ambiguous and internally inconsistent—it stated
“A tsunami is not expected” at one point and then later stated “A tsunami has been generated
that could potentially impact the U.S. West Coast/British Columbia and Alaska.” Recommended
actions for states to take were largely absent in this message, except for the last sentence,
which encouraged people to see the warning center website. A true warning message includes
required next steps; therefore, this message was more of an alert of a physical process.
With regard to providing recommendations for required actions, the committee recognizes
the limitations placed on the TWCs. Because of existing laws, the TWCs, as part of the federal
government, cannot order evacuations. Therefore, unless new national policies are implemented,
the TWCs are limited to what they can say for recommended next steps and oficial warning
messages will continue to lack speciicity with regard to what protective actions need to be
taken. Agreements have been made in certain states (Hawaii and Washington) where warning
messages issued by the TWCs can automatically trigger sirens, but only in cases where tsunamis
are expected to arrive within minutes of generation. In all other cases, however, it is the respon-
sibility of county emergency managers, in close consultation with state emergency managers,
