USGS: Quake Early Warning System

7/25/2019 USGS: Quake Early Warning System

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How Warning Can IncreaseSafety and Prevent Damage

Even a few seconds of warn-

ing can enable actions that protectpeople and property. In the time be-

tween receipt of an alert and arrivalof damaging shaking, the followingactions can be taken:

Human Responses

schoolchildren, drop, cover, and

hold on; turn off stoves, safelystop vehicles.

safe locations.

dentists, and others stop deli-cate procedures.

firehouse doors, personnel

prepare and prioritize responsedecisions.

Automated responses

doors, shut down productionlines, secure chemicals, place

sensitive equipment in a safemode.

slow or stop trains to preventderailment.

power stations and grid facilities

from strong shaking.

0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 > 80

100 KILOMETERS50

50 MILES

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0

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Earthquake Hazard Levels

Percent of 1g shaking with2-percent probability of beingexceeded in 50 years.

M8

M9

M8

Minutes of warning

Major fault lines

Scenarioearthquakeswith magnitude

Seismic sensor

EXPLANATION

1

M8

showing the amount of advance warningtime that might be available from a system

like ShakeAlert for several plausible future

earthquake scenarios. Those scenarios

include magnitude 8 (M8) quakes on the

San Andreas Fault with epicenters in

northern and southern California and an M9

quake on the Cascadia Subduction Zone

with an epicenter offshore of northernmost

have as much as several minutes warning

before shaking waves from those quakes

struck them. The map also shows the

regional variation in the level of earthquakehazard in terms of the intensity of shaking

(as a percentage of g, the acceleration

of gravity) having at least a 2-percent

probability of being exceeded in a 50-year

period (from 2014 USGS hazard map). The

network of seismic (earthquake) sensors is

population centers. Illustration modified

from Allen (2013).

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How Does ShakeAlert Work?

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Why ShakeAlert EmphasizesIntensity, not Magnitude

The shaking you feel isdescribed by earthquake intensity

rather than magnitude. High in-tensities are what cause damage

in earthquakes.

Intensity

caused by earthquake waves

at a particular location -

single earthquake

Magnitude

amount of energy released in

an earthquake

area) of fault rupture

others, 2003) rapidly show the

distribution of intensity after anearthquake (http://earthquake.usgs.

gov/earthquakes/shakemap/).You can also report the

ground shaking you experienced

to help create intensity mapsthrough Did You Feel It (http://earth-

quake.usgs.gov/earthquakes/dyfi/).

Will the West Coast have anEarly Warning System Before or

After the Next Big Quake?

warning systems built them after a

devastating earthquake.Japan invested $600 million in

such a system after the 1995 Kobeearthquake killed 6,400 people.

Today, Japans system allows everycitizen to receive advance alert of

earthquake ground shaking from

Thanks to this system, no trains

derailed in the 2011 magnitude 9.0Tohoku earthquake, and according

to a poll in Japan, 90 percent of thecitizens think the system is worth

2013).

Other countries that built sys-tems after devastating earthquakesinclude:

Earthquake killed 87,587 people)

Earthquake killed 2,415)

Earthquake killed 17,127)

City Earthquake killed 10,153)

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Diagrammatic maps showing

northwestward spreading of ground shaking

(red and yellow) generated by theM7.8

ShakeOut scenario earthquake centered in

the Imperial Valley of southern California.

The times shown are times after the start

of the earthquake rupture at the epicenter

(white star). This scenario was part of

a comprehensive earthquake exercise

conducted in the State of California in 2008

(Perry and others, 2008).


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P-wave

On your screen: ShakeAlert

1

2

Real-time tracking of seismic waves from quakes epicenter.

Your current location tracked by GPS.3

Seconds remaining before seismic waves reach you.4

Expected intensity of quake at your current location.5

Estimated magnitude of quake.6

7 Intensity scale.

Real-time tracking of the fault rupture (updates intensity).

S-wave

1

2

3

4

5 6

7

A user of ShakeAlert receives a message like this on the screen of his computer. The

message alerts the user to how many seconds before the shaking waves arrive at their

location and the expected intensity of shaking at that site. The shaking intensity follows the

by everyone, people find it difficult to stand, and structures may suffer some damage. Thewarning message also displays a map with the location of the epicenter, the magnitude of

the quake, and the current position of the P and S waves. In this example, the alert is for the

ShakeOut scenario earthquake (Perry and others, 2008).

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References

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http://dx.doi.org/10.3133/fs2014308

ISSN 2327-6932 (online)

ISSN 2327-6916 (print)

For more information contact:

U.S. Geological Survey

Earthquake Hazards Program

Earthquake Early Warning

http://earthquake.usgs.gov/research/

earlywarning/

or

Erin R. [email protected]

This Fact Sheet and any updates to it

are available online at:

http://pubs.usgs.gov/fs/2014/3083/

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USGS: Quake Early Warning System

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