Paul Whitmore, NOAA/NWS West Coast/Alaska TWC, July 25, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA

Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 1

Paul Whitmore, NOAA/NWS West Coast/Alaska TWC, July 25, 2007UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07)

U. Washington Tsunami Certificate ProgramCourse 2:

Tsunami Warning Systems

Session 1Tsunami Warning System Overview and

Seismic Data Acquisition

July 25, 2007 1:15-2:45pm



Outline

Part 1 – TWS Overview

• Tsunami Warning Systems– History

– Philosophy

• Challenges

• Warning Center Functions

Part 2 – Seismic Data Acquisition

• Seismometry

• Networks

• Station Distribution

• Exercise



Part 1 - Tsunami Warning Systems - History in the United States

• 1949 Honolulu Observatory established– Co-located with existing Magnetics Observatory

– Used data sent via teletype from seismic observatories

– Established in time for major tsunamis of the 50s/60s

• 1967 Alaska Tsunami Warning System established– Followed tsunami destruction due to 1964 Gulf of Alaska earthquake

– Originally 3 centers; later combined into 1.

• 1968 Pacific Tsunami Warning Center established– Officially expanded scope of Honolulu Observatory to other nations



Tsunami Warning System History in the United States



Tsunami Warning Systems

• Non-U.S. Centers– Japan

– Russia

– French Polynesia

– Chile

• Systems developing as a result of 2004 Indian Ocean Tsunami– For example; Australia, Thailand, Indonesia, …

– Caribbean

• Conclusion– Devastating Tsunami leads to Establishment of a Tsunami Warning

Center



Tsunami Warning System - Philosophy

• Main Purpose– Issue Warning prior to wave impact on coast– Protect life and property from tsunami hazard by providing tsunami

information and warning bulletins to the Area-of-Responsibility

• Problem– Wave usually can not be observed prior to impact at near locations

• Answer– Issue warning based on associated phenomena (ground shaking and

displacement – seismic data) which triggers the wave

• Problem– There is not a direct correspondence between the ground shaking and

tsunami impact

• Reality– Warnings are often issued with no ensuing wave.



Tsunami Warning Systems – What is it?



Tsunami Warning Systems – Basic components

– Tsunami Warning Centers

• Acquire Data

• Process and Analyze

• Disseminate Information

– Communication Pathways

• Robust

• Multiple

• Tested

– Local Emergency Response

• Ready to Respond through planning and exercises

• Receive Warnings from TWC

• Disseminate to local populations

• Provide public education



Tsunami Warning Systems – Challenges

– Can not monitor phenomena prior to nearest impact

– Warning communications to those at highest risk

– Hazard definition

– Local emergency response

• Rare events at any given location

• Many threats for which to prepare

• Short response time

• Poorly educated public



Tsunami Warning Centers

• Data acquisition– Seismic

– Sea level

• Process and Analyze– Initial processing based on seismic data

– Decision’s based on processed data and protocols

– Post-process seismic data

– Analyze sea level data in conjunction with historic and pre-computed models

• Disseminate Information– Use all available emergency alert systems

– Evacuation decisions made by state/local authorities



Tsunami Warning Centers - Data Acquisition

• Seismic– Virtual network

– Multiple data paths

– Redundancy



Tsunami Warning Centers - Data Acquisition

• Sea Level– Virtual network

– Satellite data transmission

– Many formats

– Many instrument types

– Coastal tide gages and DART



Tsunami Warning Centers - Data Processing– Seismic

– Sea level

– GIS – Data bases

– Forecasting

– Message/graphic generation



Tsunami Warning Centers - Data Processing

• Seismic data processing– Initial processing

• Location

• Depth

• Magnitude

– Post-processing

• Refine Magnitude

• Moment tensor (~ 15 minutes)

• Mantle magnitude determined




• Sea level– Display

• Strip-chart view

• Detail view

– Analysis

• De-tide signal

• Low pass filter

• Measure tsunami




• GIS and data bases– Overlay historical data

– Compute tsunami travel times

– Create web graphics

– Interface forecast models




• Forecasting– Assimilate observed tsunamis into

pre-computed models– Adjust models based on

observations– Use forecast to dictate

supplemental messages– Observations can also be

compared with historical data to forecast impact




• Message Generation– Based on source parameters

• Text products generated automatically

• Conform to NWS and WMO standards

– Graphics generated by GIS

• Experimental



Tsunami Warning Centers – Disseminate Information

• Message Dissemination– Primary

• National Warning System• NOAA Weather Wire• NWS gateway• FAA system

– Secondary• Email• RSS• FAX• SMS messaging• Web site• USGS



Tsunami Warning Center - Staffing

• WC/ATWC– 9 Watchstanders– 1 IT specialist– 2 Electronics technicians– 1 Admin Support– 1 Director– 1 Deputy Director

• Center staffed 24x7x2• Staff activities

– Day-to-day operations– Scenario training– Communications testing– Development projects– Outreach



Tsunami Warning System - Summary1. Tsunami warning centers and systems historically have been developed

in response to devastating tsunamis.

2. Tsunami warning systems are different from most natural hazard warning systems in that the phenomena itself can not normally be observed prior to impact.

3. Tsunami Warning Systems consist of:

1. Tsunami Warning Center

2. Message Communication Paths

3. Emergency Response Organizations

4. Tsunami Warning Centers basic functions are:

1. Data Acquisition

2. Data processing and analysis

3. Message Dissemination



Part 2 – Seismic Data Acquisition

• Seismometer– An instrument which records earth

vibrations

– Converts ground shaking energy into an electrical signal

– Extremely sensitive

– Output is proportional to ground displacement, velocity or acceleration depending on instrument

– Moving coil around magnet generates current

– Modern seismometers use electronic force feedback to gain wide spectral response

– Signal is normally digitized on site



Similar to our eyes not seeing the entire electromagnetic spectrum in sunlight, seismometers only “see” a portion of earthquake energy.

(USGS slide)



EQ

UIV

AL

EN

T E

AR

TH

PE

AK

AC

CE

LE

RA

TIO

N (

20

LO

G M

/SE

C

2 )

PERIOD (SECONDS)

More than one seismometer is

necessary to “see” the entire

earthquake energy spectrum (USGS

slide)



Seismic Data Acquisition

• Seismometer installations– Desired site characteristics:

• Low cultural noise levels

• Reliable source of power

• No vandalism

• Ability to “see” communications satellite

• Bedrock at or near surface

• Long term permitted site

• Easy accessibility for maintenance

• No overlap with other networks

– Data transmission

• Private VSAT

• Satellite internet

• Dedicated circuits

• Radio



WC/ATWC Seismometer vault at Middleton I., Alaska



Seismic Waves

• Seismology Basics– Three basic types of waves generated

by earthquakes

• Primary (P)

• Secondary (S)

• Surface

– P waves are sound waves traveling through the earth (the fastest wave)

– S waves travel about 60% as fast as P waves

– Surface waves area a little slower than S waves

– More energy is transmitted in S and Surface waves than P waves



Seismic Waves

• Body Waves – travel through the earth– P Waves

• Sound Waves

• Particle motion in the direction of propagation

– S Waves

• Particle motion perpendicular to the direction of propagation

• Generally caries more energy than the P wave

• Surface Waves – travel around earth’s surface– Rayleigh Waves

• Elliptical motion in direction of propagation

• Size of ellipse related to wave period

• Dispersive – peak velocity at about 50s period

– Love Waves



Seismic Networks

2004 Sumatra earthquake

recorded on several stations of

the IRIS Global Seismic Network (USGS slide)



Seismic Networks

Tsunami Warning Centers use available networks to create virtual global networks

• Global networks– IRIS Global Seismic Network– CTBTO

• National networks– US NSN– Canadian network– Etc.

• Regional networks– S. California Seismic Network– Pacific Northwest Seismic Network– Etc.







IRIS Global Seismic Network







Seismic Data Transmission

• Redundancy is the key– Use redundant path to critical networks

• No single path is 100% reliable

– Create virtual network out of overlapping regional networks

• Reduces dependency on any one network and its server

– Utilize two data import computers

• Each connects to a network through a separate path



Seismic Data Acquisition at the WC/ATWC



Seismic Network Density for Tsunami Warning Systems

• Seismic network variables which influence TWC response time– Station Density

• X stations within Ykm from a given location– Station Uptime

• Percentage of time station is operating– Data Latency

• Length of time it takes for signal to arrive at center– Data quality

• Broadband versus short period

• These values are the main factors which control a tsunami warning center’s response time

• Response time is the length of time it takes after an earthquake origin to issue a message




• Seismic Network requirements for a Tsunami Warning Center to issue a message within five minutes– Station Density

• 12 evenly distributed stations within 900km of source (2 minute P-wave travel time)

– Station Uptime

• 80% station uptime

– Data Latency

• Up to 30s latency

– Data quality

• Broadband, digital signal




• Given the station requirements on the previous slide, a warning timeline response is:– 150s to record signal on 9 to 10 stations

• Based on 12 stations within 900 km of epicenter with 80% station uptime and up to 30s latency

– 60s to record enough signal after the P to determine magnitude

• Using the Mwp moment magnitude technique

– 30s extra for analyst review

• Need well-trained and experienced analysts

– 60s to compose and review appropriate message

• Must be automated message generation




• Warning Response Timeline can be compressed by:– Increasing station density

– Reducing data latency

– Reducing station downtime

– Decreasing analyst process, review and message generation time

• There is a limit to decreasing response times– Large earthquakes have source process times of over 100 seconds

– There is an increased danger of false alarms as analyst review time decreases





Seismic Data Acquisition - Summary

1. Seismic data are critical to operations at tsunami warning centers

2. Broadband data provides a more realistic view of earthquake source properties than band limited data

3. Many networks are available to feed seismic data to tsunami warning centers and the amount of available data is increasing.

4. Redundancy is important for seismic data feeds so that a TWC is not left blind by the outage of one network

5. The density, quality, and reliability of seismic data controls a tsunami warning center’s response time



Seismic Data Acquisition: References

USGS Seismology and Tsunami Warnings Training Course – CD - 2006

Documents

Paul Whitmore, NOAA/NWS West Coast/Alaska TWC, July 25, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA