Photography & Video GRAPHICS
Infographic

Building a quake warning system

Scientists are expanding a quake sensor network that would eventually give the public a heads up before shaking arrives. Several grants since 1997 beefed up Southern California’s system — from about 20 stations in 1994 to more than 400 today. More sensors and funding are needed to complete the West Coast early warning network: California needs about 720 more stations, many in the north. Oregon and Washington need to increase their number from 224 to 550.

San
Francisco

Napa

Oakland

Berkeley

Epicenter

Strong shaking begins

Initial shaking

Strong shaking
begins to hit
San Francisco

Early earthquake
warning system
sends out alert

Quake begins

13.1 seconds

5.1 seconds

Zero seconds

10 MILES

Eight-second warning for San Francisco

How seismic stations work

Data and
power
conduit

9.5 feet
max.

Vault
cover

Landscape
bricks

Sensors

Concrete
base

Concrete
base

Recorded data is
transmitted to a central
location using cellular
and radio technology
in real time.

A prototype early earthquake warning system in
August provided San Francisco eight seconds of
warning that shaking from the Napa earthquake
was coming.

A system of seismic
sensors and a data
logger that detects and
records ground shaking
is placed in an
underground vault lined
with concrete and
high-density plastic.

Radio
antenna

GPS
antenna

Solar
pannel

Ground
shaking

Battery

Sources: California Integrated Seismic Network, Caltech and U.S. Geological Survey, UC Berkeley Seismological Laboratory; OpenStreetMap & Contributors.
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