Tsunami Warning Center Reference Guide
Summary for Tsunami Warning Center Staff

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. To accomplish this the center must be adequately staffed to have at least two watch standers available at all times, plus sufficient staff and resources for administration, research, outreach, and maintenance functions.

Earth Data Observations

  • Seismic data are needed to issue initial tsunami warnings.
  • Changes in sea level, as measured by coastal tide gages and deep ocean buoys, are used to confirm, track, and model a tsunami.
  • International seismic gage networks can be accessed and used for assessing the need for an initial tsunami warning.
  • A warning center should maintain access to multiple networks via multiple communications channels. This ensures that all earthquakes and sea level changes are captured, even in the event that a network or communications channel fails.
  • If a warning center has local tsunami potential, it may need to deploy and maintain additional seismic, tide, and deep ocean buoy instruments to augment international networks.
  • Subduction zones, where spreading oceanic tectonic plates dive beneath continental plates, create most earthquakes. For this reason, these zones are where most tsunamis are generated.
  • About ten percent of the energy of an earthquake goes to form seismic waves.
  • Seismic S (shear) waves travel through the body of the earth at about 60-70 percent the speed of P (compressional) waves. Thus the arrival of S and P waves at a location can be used to locate where and how deep an earthquake occurred.
  • Earthquake magnitude is a measure of the amount of energy released.
  • Most warning centers use the moment magnitude from P waves in their decision making process because it can be computed soon after the earthquake and it is fairly accurate.
  • Warning centers usually rely on broadband inertial seismometers because these instruments have large dynamic ranges.
  • The three most important considerations for installing a seismometer are (a) a location away from ambient shaking sources, (b) a bedrock base when possible, and (c) good thermal insulation to shield the instrument from large temperature fluctuations.
  • For a warning center to respond with a warning product within five minutes of an earthquake, the center must have access to twelve evenly distributed seismometers within a 900 kilometer radius (2 minute travel time) of the source area.
  • For interoperability with other centers, the USGS Earthworm software should be used to obtain and process seismic data.
  • The most extensive international tide gage network is the Global Sea Level Observing System (GLOSS), conducted under the auspices of the Joint Technical Commission for Oceanography and Marine Meteorology (JCOMM) of the World Meteorological Organization.
  • If a warning center must deploy seismic or sea level gages to address a local tsunami potential, the instruments should meet international standards, and the data made readily available to everyone.
  • There are several types of coastal tide gages, including float gages, pressure gages, acoustic gages, and radar gages. The latter are becoming the instrument of choice.
  • Multi-use platforms, those able to are the most sustainable.
  • To be of use in a warning system, tide gages should sample every 15 seconds. For teletsunamis a continuous tide gauge transmission cycle of every 5 minutes is acceptable. But for tsunami source regions within 100 kilometers (local tsunami) transmissions need to be every minute.
  • Computer software called TideTool is available for use in decoding, displaying, and manipulating tide gage data.
  • NOAA developed the Deep-ocean Assessment and Reporting of Tsunami (DART) buoy to improve tsunami warnings by overcoming many of the shortcomings of tide gage data, including incorrect estimates caused by local bathymetry, sheltering, and other local conditions.
  • The DART system consists of an anchored seafloor bottom-pressure recorder (BPR) and a companion moored surface buoy for operational communications.
  • DARTs provide standardized reports of sea level information measurements back to warning centers where the information is processed and used in models to produce revised and more refined estimates of the expected effects of a tsunami.
  • When a DART detects a tsunami it automatically shifts into event mode and transmits data more frequently.
  • Two-way communications with the DART is also possible.

Data and Information Collection

  • Warning centers have three main data and information collection requirements – collect seismic and sea level data, receive event impact information from government agencies and the public, and share data and products with other warning centers.
  • Critical seismic and sea level data must be received rapidly at warning centers to be of any use in the warning process. Thus, data collection communication programs are crucial to the success of the warning system.
  • Warning centers should use backup observational data networks and backup communications channels to ensure a robust warning program.
  • The primary data collection pathway is the WMO-administered Global Telecommunications System (GTS).
  • Messages on GTS may be alphanumeric, binary, or pictorial. All messages must conform to a pre-defined structure.
  • Sea level data is carried on GTS, but seismic data should be obtained via the internet and dedicated circuits.
  • Because there are so many data networks and communications pathways, warning centers need to automate data collection. At the same time, interrogation parameters for gages should be easy to modify on the fly during an event.
  • The International Federation of Digital Seismic Networks (FSDN), the USA-led Incorporated Research Institutions for Seismology (IRIS), and the International Monitoring System (IMS) of the Preparatory Commission for the Comprehensive Nuclear Test Ban Treaty Organization make up most of the very robust Global Seismic Network (GSN).
  • GSN data are available via the internet or via leased lines.
  • GLOSS (Global Sea Level Observing System) data are available via the GTS.
  • There are several meteorological satellites that can be useful for supplementing GTS connectivity. These include ISCS, EMWIN, SADIS, INSAT, RETIM-Africa, RANET, GMDSS, and the emerging GEONETCast.
  • DART buoys transmit sea level data to an Iridium satellite and eventually to the NOAA National Data Buoy Center, the National Weather Service Telecommunications Gateway (NWSTG), and the internet via GTS.
  • Pacific Tsunami Warning Center (PTWC) and West Coast/Alaska Tsunami Warning Center (WC/ATWC) can initiate an interrogation retrieval mode, or set the bottom pressure recorder (BPR) to Event Mode on NOAA DART buoys.
  • Warning centers should develop and test full and partial backup plans with another center.
  • The USGS Earthworm software is the de facto standard for seismic data and hypocenter parameter exchange.
  • Tide gage data is transmitted in one of three main formats – WMO BFR, WMO CREX, and non-WMO GLOSS coding.

Tsunami Detection

  • Analyzing and prominently displaying earth data observations in the operations area is a core function of a warning center.
  • Warning centers require a variety of hardware, software, computer applications, and communications capabilities to analyze seismic data and detect tsunami signals in sea level data.
  • Assessing the impact of a particular tsunami requires scientific expertise and professional on-the-job experience. Thus it is not advisable to fully automate a tsunami warning system.
  • Warning center internal local area networks (LAN) may be connected to public wide area networks (WAN) like the internet. When this is the case the center should make sure that firewalls and other security measures are in place to protect the integrity of their networks.
  • Some warning centers use personal computers and some variant of the Windows operating system. Other warning centers use RISC workstations and UNIX/Linux-based operating systems. Both configurations have advantages and drawbacks.
  • Both Windows and UNIX/Linux approaches require redundancy and attention to security.
  • Warning centers should strive to standardize hardware, operating systems, and software applications. This will facilitate exchange of expertise between warning centers.
  • Warning centers need software applications that perform the following: collect, process and database seismic and sea level date in real-time; auto-monitor data for exceedence of critical thresholds; computation of derived parameters from observational data; display of data and derived parameters (situational awareness); dissemination of text and graphic products.
  • TideTool is a good sea level data processing program.
  • USGS Earthworm is a good base processing architecture for seismic data.
  • Warning centers can greatly reduce the chances of needing service backup from another center by deploying redundant communications, hardware, and software systems.
  • A well-coordinated and fully supported maintenance program is critical to the success of a warning center.
  • A center should establish and use an Engineering and Maintenance Reporting System (EMRS) to track all maintenance activities and effectively manage the center’s programs.
  • The USGS has a publication to assist with the installation of seismic sites. The Public Seismology Network website has posted maintenance manuals for many brands of seismometers.
  • UNESCO-IOC has published several training guides on the installation and use of coastal tide gages. Residence courses are taught by the Proudman Oceanographic Laboratory in the UK, with course materials available at the PSMSL training page.

Tsunami Warning Decision Support

  • Decision support programs include warning, watch, and advisory criteria, situational awareness techniques, tsunami wave models, and inundations models.
  • Thresholds for initial seismic-based warning and watch products are generally based on earthquake location, depth, and magnitude.
  • Due to coastal bathymetry, demographics, and distance from source regions, some warning centers may have different criteria for different parts of their area of responsibility (AOR).
  • Tsunami history and pre-event modeling are taken into account along with observed tsunami wave amplitudes in forecasting the extent of damage expected.
  • Centers should strive to adhere as closely as possible to the generally accepted bulletin threshold values recommended by IOC.
  • EarlyBird and EarthVu software packages were developed at West Coast/Alaska Tsunami Warning Center (WC/ATWC) to assist watch standers in maintaining situational awareness.
  • Warning centers should have an active research and development program since the center can often best address local problems.
  • Warning center research and development falls into three broad categories: earth science, data processing, and social science. Thus a center should have a staff that is a mix of oceanographers, seismologists, computer programmers, and network/communications experts.
  • A research & development program at a warning center creates an atmosphere of progress, and collaboration with other institutions can help keep the center on the cutting edge of new technology and techniques.
  • Developing better wave forecasting models and better inundation models may improve warning center products and services.

Warnings and Other Forecast Products

  • Once an earthquake has been analyzed and a decision made on its expected impact, a warning center must produce and deliver one or more products to government agencies, the media, the public, and others that will be affected by the event.
  • To avoid confusion, centers should strive to adhere to internationally agreed upon names and contents of public products.
  • A warning is for an event where a damaging tsunami is imminent or likely to strike a center’s AOR.
  • A watch is issued when a damaging tsunami may affect the AOR at some later time (hours in the future).
  • An advisory is issued when a non-destructive tsunami may produce strong currents or waves in harbors or along beaches.
  • Information statements are issued by warning centers to inform emergency management officials and the public that an earthquake has occurred. In most cases statements are issued to indicate that there is no threat of a destructive tsunami in the AOR.
  • All products should include appropriate WMO headers, earthquake information, and when possible, tsunami information, including arrival times for earthquakes with magnitudes greater than 7.0.

Dissemination and Notification

  • Dissemination refers to the process of physically getting the message to partners and customers, while notification refers to the understanding of the received message by these partners and customers.
  • National and local emergency management officials and other government, academic, and private sector individuals usually play major roles in educating the populace.
  • Warning centers also play a significant and crucial role in the outreach and education effort.
  • Warnings are primarily the responsibility of local governments.
  • Warning systems require a national partnership between government and industry. The media play a particularly critical role in warning dissemination.
  • Most warning delivery (dissemination) systems require government products as input (the message), but are manufactured, operated, and owned by private industry and individuals. In other words, the government provides the authority for the warning system, but the private sector provides the mechanisms for getting the warnings out as fast as possible to as many people as possible.
  • Dissemination should be automated to increase efficiency, decrease errors, and make optimum use of redundant communications pathways. Warning centers should limit dissemination channels to a manageable number, and use GTS as the primary channel. Secondary communications pathways like GEONETCast, EMWIN, and RANET should also be used.
  • Centers should establish ways to confirm that its main partners and customers receive critical messages. Communications channels should be tested routinely. Problems should be fixed immediately.
  • The Emergency Managers Weather Information Network (EMWIN) is a low cost satellite and internet delivery system available to everyone for display on their PC. EMWIN covers North and South America, the Caribbean, and much of the Pacific Ocean.
  • The Radio and Internet Technologies for the Communication of Hydro-Meteorological and Climate-Related Information (RANET) is a collaborative effort between government and non-government organizations to get information to rural and remote populations around the world.
  • RANET’s success is due to scalability, local ownership, and the fact that it is a multi-purpose system. RANET is organized at the country level, usually through the NMHS.
  • Two of the main international satellite communications systems are SADIS (UK) and INSAT (India).
  • Led by the USA, Europe, and China, the emerging UN-sponsored GEONETCast program will provide a global collection and distribution system via a network of satellites.
  • GEONETCast is a truly global dissemination system by which environmental in situ, airborne, and space-based observations, products, and services from contributions to the GEOSS (Global Earth Observation System of Systems) are transmitted to users through a global network of communication satellites, using a multicast, access-controlled, broadband capability.
  • GEONETCast uses commercially available technology and provides cost-effective solutions with easy-to-implement terminals, which are widely used for direct-to-home digital television.
  • Notification refers to the comprehension of a received message by the target audience, who then take appropriate actions.
  • The tsunami warning process consists of the warning center communicating with people at risk and emergency responders in advance of or during a hazardous event.
  • The success of a warning is measured by what actions people at risk take.
  • Warning messages should use terminology that is consistent across time for a given hazard, and compatible with the terminology used for other hazards. Thus, centers should create and store standard formats for their text messages and oral messages.
  • The "public" is not a homogeneous entity. Households, businesses, government agencies, NGOs, etc., vary in size, demographics, geographic location, and economic resources. Warning centers 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.
  • Community preparedness refers to having plans in place to respond properly to a warning. Community preparedness can be accomplished through programs like TsunamiReady.
  • A center’s outreach and education program must recognize that there are two categories of constituents—partners that assist in the warning process, and customers who rely on the center for timely and accurate products.
  • The goal and focus of outreach should be to educate the public and other groups about tsunami safety and preparedness, and to promote the center’s tsunami warning program.
  • During actual events a center should have a designated Public Affairs Officer to coordinate responses to the media and others.
  • The USA TsunamiReady program is an organized way for centers 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, and 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 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.
  • Additional training materials are available through the ITIC web site.

Community Connections

  • Tsunami warnings can be effective only if the audience receives and understands the warning.
  • Community partnerships, developed before an actual event, can help create a warning system that is effective in reaching the public.
  • Staff at warning centers must establish trusted relationships among international partners, government agencies, community leaders and organizations, businesses, and local citizens.
  • Partnerships with the media are required for an effective warning system. A good partnership with the media is essential to an outreach and education program before an event, and to strengthen the primary communications channel during an event.
  • Effective education and outreach must be based on a thorough understanding of the processes individuals go through when they make decisions about modifying their personal behavior, for example, deciding to evacuate.
  • Existing communication channels and strategies can be used to quickly and effectively reach target audiences. The most effective outreach efforts use existing channels in the community.
  • The key stages of persuasive communication are awareness of the risk, understanding of the potential impacts, acceptance of their need to respond to warnings, and the behavior change that includes taking action to prepare for events and to evacuate if necessary.
  • No one message can reach everyone in a community. Messages and message delivery strategies must be specialized and diverse at the same time.
  • A key step in developing community partnerships is to identify what community planning activities are already taking place and to get the warning center involved. At initial meetings, present what the warning center does, why it wishes to partner, and what the organization might gain from the partnership.
  • Warning centers can use a simple communication model to help establish local strategies for effectively distributing warnings to the public. Key components of the model are establishing credibility of the message source, designing an appropriate message for the audience, selecting a proper communication channel, clearly defining the audience for the message, and a method for audience feedback that includes questions, comments, and suggestions.
  • Warning centers should work with local governments to define the types of audiences present in the community, and then design outreach for these groups.