Tsunami Warning Center Reference Guide
Summary for Local Decision Makers

Overview

  • An "end-to-end" tsunami warning system (TWS) consists of several interrelated components. A TWS begins with international earth data observations, and culminates with local officials and individuals taking appropriate actions to protect lives and property.
  • The heart of a TWS is its warning center. A full-service center must provide accurate and timely warnings to coastal populations 24 hours per day, 7 days per week.

Earth Data Observations

  • The first component of the end-to-end warning system consists of earthquake observations taken by seismometer networks.
  • Additional earth data observations needed for an effective TWS are networks of instruments that detect changes in sea level, i.e., track the tsunami wave. These are coastal tide gages and deep ocean buoys.
  • The refinement of initial seismic-based warnings with data on sea level changes can greatly increase the credibility of warnings by decreasing false alarms.
  • International seismometer and sea level networks are usually sufficient for tele-tsunami events, e.g., tsunamis generated by earthquakes far from the area of interest. However, areas prone to "local tsunamis" may require additional local sensors since warnings must be issued much faster for nearby tsunamagenic zones.

Data and Information Collection

  • A second system component is the continuous collection of the earth data observations at warning centers with minimum delay from time of observation to receipt. Communications are the lifeblood of a tsunami warning center. All aspects of operations, from collecting data to disseminating warnings to developing community connections, depend on effective communications.
  • Data from international networks are often available in real-time through the internet and/or satellite. Data from locally deployed networks often require alternate communications paths such as land lines, cell phone, or radio.
  • To ensure data is available at critical times the system should provide for receipt from multiple networks via multiple communications channels. This helps ensure that no important events will be missed.

Tsunami Detection

  • The third component is the TWC's ability to process the received earth data into information for use in assessing the potential that a tsunamagenic event has occurred. To accomplish this, a warning center must detect and analyze earthquakes in the center's ocean basin. Earthquakes that are stronger than established thresholds should activate the center's tsunami investigation procedures.

Warning Decisions

  • Initial tsunami warnings are based solely on seismic data.
  • Once a tsunami's existence and its amplitude have been forecast, a separate system must assess the potential impact of the tsunami. This prediction sub-system should have an appropriate historical database, with potential inundation areas under different scenarios of tsunami occurrences.
  • False alarms, e.g., when a warning is issued but a destructive tsumami does not occur, can be reduced if decision support computer programs are developed to refine initial seismic information.
  • This fourth component of the end-to-end warning system, decision support, includes models of tsunami wave height, models of coastal inundation, and programs that keep warning center personnel aware of any important events detected by the earth data observations.

Warnings and Other Forecast Products

  • Effective warnings for an event are a crucial fifth component in the end-to-end system. Centers should strive to adhere as closely as possible to internationally established product formats and names. Products should be clear, concise, and contents coordinated with local officials well in advance of any events and should not create confusion.

The internationally accepted types of forecast products include the following. Note that these product definitions have been updated since the original publication of the reference guide (page 7-1):

    • Warning (a destructive wave will strike)
    • Watch (a destructive tsunami is possible)
    • Advisory (minor inconveniences due to a non-destructive wave or currents is likely)
    • Information Statement (an earthquake that is not expected to generate a tsunami has been recorded)

Dissemination and Notification

  • Product dissemination processes should take advantage of all technologies available and should be automated as much as possible to speed the warning process. Whenever possible, there should be redundant communication paths to ensure the receipt of critical earth data observations at the tsunami warning center and complete dissemination of warnings from the center.
  • A center needs to work closely with local officials to ensure constituents on the beach have multiple ways of receiving warnings and understand what to do before, during, and after an event.
  • Warning centers must proactively develop positive relationships with partners that assist in the dissemination process and customers that depend on accurate and timely warnings from the center.
  • The entire warning system should be periodically exercised to ensure that crucial components are operating successfully and constituents are capable of making optimum use of timely warnings. Communications channels should be tested routinely.
  • National and local emergency management officials and other government, academic, and private sector individuals play major roles in educating the population. Tsunami warning centers also play a significant and crucial role in the outreach and education effort.
  • Warnings are primarily a local government responsibility.
  • Centers should establish ways to confirm that their main partners and customers receive critical messages.
  • The Emergency Managers Weather Information Network (EMWIN) is a low cost satellite and internet delivery system available to everyone for display on their PC.
  • The "public" is not a homogeneous entity. Households, businesses, government agencies, NGOs, etc., vary in size, demographics, geographic location, and economic resources. Local Emergency Managers should identify ways that population segments differ in their perceptions, access to warning channels, reactions to message content, and problems they may encounter when attempting to take protective actions.
  • During actual events a warning center should have a designated Public Affairs Officer to coordinate responses to the media and others.
  • The USA TsunamiReady program is an organized way to assist communities with their efforts to set up their warning operations, evacuations plans, and public education efforts. TsunamiReady creates baseline standards that must be met, encourages consistency in educational materials, increases public awareness and community pre-planning.
  • The Coastal Community Resilience (CCR) program uses the NOAA Community Vulnerability Assessment Tool (CVAT) to help communities maintain an optimal balance between community development, coastal management, and disaster management.
  • The most comprehensive training aid for warning center outreach efforts is the UNESCO/IOC International Tsunami Information Centers (ITIC) "Tsunami Teacher" program. Tsunami Teacher consists of an Information and Resource Toolkit. A feature of the Tsunami Teacher Toolkit is the ability to customize training modules for different audiences.