Since 1990, nearly one million people have died from the impacts of earthquakes. Reducing those impacts requires building a local seismic ulture in which residents are aware of earth- quake risks and value efforts to mitigate harm. Such efforts include earthquake early warning (EEW) systems that provide seconds to minutes
notice of pending shaking. Recent events in Mexico
provide an opportunity to assess performance and perception of an EEW system and
highlight areas for further improvement. We have learned
that EEW systems, even imperfect ones, can help people
prepare for earthquakes and
build local seismic culture,
both beneficial in reducing
Public EEW systems are deployed in Japan and Mexico
and are being implemented
elsewhere around the globe,
including ShakeAlert in the
United States. Mexico’s EEW
system, SASMEX, was built
following the 1985 Michoacán
earthquake in which more
than 9500 people died. Seismic
sensors covering much of the
country provide alerts in select
cites. In Mexico City, roughly
12,000 pole-mounted speakers
can sound a siren to indicate that an earthquake is imminent. Alerts are also distributed by radio and television.
On 7 September, the magnitude (M) 8.1 Chiapas mainshock triggered the city’s sirens roughly two minutes
before shaking was felt. The quake had little impact in
Mexico City due to the 700-kilometer source distance.
The sirens were triggered again on 19 September by the
M7.1 Puebla earthquake, although the alert was not issued in Mexico City until approximately 5 seconds after
the widely felt P-waves arrived, due to the close proximity of the quake source to the city. The 23 September
M6.0 aftershock of the Chiapas mainshock activated
the system again. Most people in Mexico City, however,
did not feel shaking from this event.
After these events, we were deployed to Mexico City
by the Earthquake Engineering Research Institute
(EERI). Although considerable research and technology
underlie the seismic sensing capability, and SASMEX
has issued alerts for more than 150 quakes over three
decades, what has been missing—hence the focus of our
mission—is an assessment of public perception of the
system. These first major damaging earthquakes since
SASMEX was built provided a rare opportunity to learn
how people perceived and responded to EEW.
Our findings point to a collectively positive attitude
toward SASMEX, with the public generally accepting
of the technical limitations.
They show a greater tolerance for alerts associated with
little or no perceptible shaking
than for late or missed alerts.
Residents said that all alerts
provide an opportunity to
practice protective actions and
that hearing, seeing, or talking
about EEW helps build awareness of earthquake risk and
appropriate protective actions.
These findings are consistent
with surveys regarding EEW
in Japan done after the 2011
Tohoku-Oki M9.0 earthquake.
We draw several recommendations from our reconnaissance. EEW systems are
seen as being valuable despite technical limitations.
This should give us added
confidence to accelerate deployment of EEW systems
elsewhere. Also, EEW systems
should provide an initial alert that is as simple as
possible to prompt people to take immediate action.
Follow-up information from authoritative institutions
is needed in the seconds and minutes after an alert
is issued and shaking has subsided. A wide range of
media channels should be used. In addition, the warning information and messaging provided by all EEW
systems must be consistent and distributed widely. In
Mexico, information from the public SASMEX system
did not always align with information from the private
SkyAlert system. Importantly, an EEW system is only
as good as the likelihood that effective action is taken
to reduce harm. This means closely pairing EEW development with disaster preparedness research, education, planning, and policy.
– Richard M. Allen and
the EERI Reconnaissance Team*
Quake warnings, seismic culture
Allen is director
of the Berkeley
*Earthquake Engineering Research Institute Reconnaissance Team: Elizabeth S. Cochran, U.S. Geological Survey; Tom Huggins, Massey
University; Scott Miles, University of Washington; Diego Otegui, University of Dela ware.
SCIENCE sciencemag.org 01 DECEMBER 2017 • VOL 358 ISSUE 6367 1111
“EEW systems are seen
as being valuable despite