BY LARRY COLLINS
In Part 1 (SEPTEMBER 2005), we reviewed the effects of the Christmas 2004 Indian Ocean tsunamis that killed more than a quarter-million people and discussed how that catastrophe should be seen as a harbinger for potential future disasters affecting coastal zones in the United States and other nations vulnerable to tsunamis. Here, we will review what’s being done to prevent a similar loss of lives in the United States and other nations, including improvements in planning, warning, evacuation, and response capabilities for fire departments, the U.S. Coast Guard, lifeguard agencies, and law enforcement.
Many officials mistakenly assume they will always have several hours after a Tsunami Warning is issued to evacuate threatened populations to high ground. This, unfortunately, is not always true. Tsunamis caused by local earthquakes and underwater landslides can strike the coast within minutes, and the closer you are to the epicenter, the higher the chances that the largest and most damaging tsunamis will strike your location.
“The stated goals for getting warnings out in the Pacific are 30 minutes or more for a basin-wide event, 10 to 15 minutes for a regional event, and five minutes for a local event (near-source earthquake),” according to Laura Kong, director of the United Nations’ International Tsunami Information Center in Hawaii. (She was speaking at a tsunami preparedness seminar on February 8, 2005.)
But five minutes notice wouldn’t have been enough to save nearly 200 people killed on the northern Japanese island of Okushiri in 1993. Three minutes after a quake was felt there, waves reported as high as 93 feet swamped parts of the island. The Okushiri tsunami told Japanese officials that warnings of near-source tsunamis must be given and reacted to before three minutes passes after a major offshore quake. That is obviously a difficult (and perhaps unreasonable) target, but the Japanese experience is very telling about the potential for tsunami waves to beat the official warnings.
“In many areas where the Asian tsunamis hit, such local communications systems need to be improved,” said David Prior, an expert on geological hazards at Texas A&M University. “How can the warning system effectively alert people along the coast, especially if the earthquake and tsunami occur at night?”
Harry Woodworth, a meteorologist and tsunami researcher working out of the National Weather Services’ Mt. Holly (NJ) station, puts it this way on an educational Web site: “If you are in a coastal region and experience a large or lengthy earthquake, immediately head for higher ground. This IS your warning.”
TSUNAMI BASICS: A REVIEW
Contrary to some common perceptions, seismic sea waves aren’t simply “large waves” of the sort generated by wind, the turbulence of large storms, and other typical oceanographic and weather phenomena. In fact, tsunamis are very different (and hence far more dangerous) than wind-driven waves with respect to their inertia and their ability to sweep ashore for great distances. Whereas it’s true that tsunamis may be quite large in height, the true danger is related to the mass of energy that propels them through the ocean at great speeds.
The true deadly force behind tsunamis is based on several factors. First, they are generally caused by significant vertical movement of large blocks of the earth’s crust during earthquakes, or by the occurrence of large underwater landslides, or both. Unlike wind-driven waves, which generally affect just the top 20 to 30 feet of water, the energy of a tsunami is traveling at jet engine speeds through the water from the surface all the way to the bottom of the ocean. When such a mass of waterborne energy strikes the coast, it may suddenly raise the level of the sea and drive walls of water far inland, creating a sort of flash flood that can pick up ships and large buildings and carry them inland. Topographic features of coastal zones such as bays, inlets, and river mouths can multiply the force and reach of tsunamis.
Clearly, tsunamis don’t behave the same way every time, even in the same place, in part because different events create the surges of seawater.
Earthquakes, collapsing volcanoes, landslides above and below the sea surface-even the rare meteor strike-can all cause tsunamis, scientists say.
Not all quakes cause tsunamis. Also, as was the case in the Indian Ocean, not everyone affected by a tsunami feels the quake that spawned it. Teletsunamis, which travel at up to 500 miles per hour over thousands of miles, offer better odds for giving warning than local tsunamis.
CHALLENGES FOR FIREFIGHTERS IN EARTHQUAKE COUNTRY
As noted in Part 1, when large earthquakes strike earthquake-prone regions, it’s often standard practice for fire department units to respond through their jurisdictions to conduct “windshield surveys.” These are rapid visual and physical assessments of damage levels and major problems (or lack thereof) conducted while rolling “Code R” through the streets on predetermined routes to check the status of the most obvious life-loss hazards. The results of these damage surveys are reported and used by commanders and dispatchers to begin moving resources into the places with the worst impact.
In the case of windshield surveys being conducted along the coast in potential tsunami inundation zones, and when resources being dispatched into these areas in response to reports of collapsed buildings, fires, trauma, medical emergencies, and haz-mat releases, firefighters and other public safety personnel (lifeguards, police officers, ambulance personnel, for example) will find themselves in immediate danger if a near-source tsunami catches them by surprise while the early and most dangerous phase of post-earthquake operations takes place. The danger is that personnel responding to fires, collapses, casualties, and hazardous-materials releases in quake-damaged coastal zones may be wiped out by surprise tsunamis.
This is exactly what happened in the earthquake that struck the Japanese Island of Okushiri in 1993. As residents evacuated the coastline for high ground in the dark of night, fires started by the earthquake lit up the city, and within three to five minutes a black wave swept into the city and destroyed burning buildings and fire engines alike. Several more tsunamis followed, destroying large sections of the city and killing more than 200 people, including many firefighters.
As explained in Part 1, we must reconsider the normal approach to post-earthquake response and damage assessment in regions subject to near-source tsunamis, including the central and southern coasts of California and Lake Tahoe, high in the Sierra Nevada Mountains, more than 150 miles from the ocean.
EMERGENCY SERVICES IMPACT
Post-tsunami search and rescue operations are likely to be difficult and dangerous, possibly requiring the use of swiftwater rescue teams and task forces, rescue divers, helicopters, rescue boats, and other special resources. Extensive damage to fire departments and other municipal structures, as well as infrastructure like roads and bridges, would probably be in some scenarios. The potential for live victims to be trapped, requiring specialized extrication resources, is significant.
Combined with the other land-based effects that typically occur during damaging quakes (i.e. collapsed buildings, freeway overpasses, and dams; multiple fires; the release of hazardous materials, for example), large tsunamis that strike the coast for periods ranging from minutes to hours (24 hours in some estimates) would clearly impede fire/rescue agencies’ ability to cope with the disaster.
PLANNING AND PREPARATIONS
With preparation, fire departments and other public safety agencies have the means to devise effective tsunami warning, evacuation, and search and rescue plans that will serve the public and responders well. One option is to establish multidisciplinary working groups to address this issue at the appropriate levels of government. Fire/rescue agencies in potential tsunami impact zones can seek technical advice from recognized experts who can accurately define the hazards that need to be addressed.
Effective public education programs that raise awareness of the dangers of near- and far-source tsunamis are needed. There’s a need for realistic warning systems that include not only signs posted in multiple languages but also the implementation of audible warning systems (i.e., sirens along endangered coastal zones) that conform to recognized standards. Such systems are now in place along the coasts of Oregon, Washington state, Hawaii, and northern California. A tsunami plan for a fire department in the potential impact zone might begin with recognizing that strong shaking in coastal areas should cause firefighters to immediately abandon fire stations and evacuate to high ground or to a safe distance from the coast (based, in part, on tsunami impact and inundation maps) and to initiate immediate public evacuation until the danger of a tsunami has been ruled out.
Such a plan should direct the local dispatch center to immediately check with authorities to determine whether the quake’s epicenter is offshore and to immediately transmit epicenter information to field units so they can react appropriately. If the epicenter is reported to be offshore, the dispatch center may have standard tsunami warnings and evacuation instructions to issue. But even if the quake is centered onshore, the potential for tsunamis resulting from underwater landslides should be recognized.
Tsunami plans should include appropriate cautions that prevent personnel from committing themselves to potential inundation areas until the danger of multiple waves has passed (a period of hours, according to some tsunami researchers). This will clearly cause a conflict in cases where fires have broken out, people are trapped in collapsed buildings, and mass-casualty situations occur within potential tsunami impact zones. The plan should take these factors into account and provide reasonable guidelines for personnel faced with such dilemmas.
The tsunami plan should recognize the advantage of using helicopters, inflatable rescue boats, and other special resources to conduct search and rescue in the wake of a tsunami. It might also include provisions for predeploying resources in anticipation of predicted tsunamis from distant sources.
In an age where managing the consequences of terrorist attacks (some involving weapons of mass destruction) has rightly become the national priority and where hurricanes, floods, and damaging earthquakes are constant concerns, it may be difficult to get worked up about the danger presented by tsunamis, which are clearly rare events in most coastal zones. Nevertheless, the potential life loss (including the loss of many firefighters and rescuers during post-earthquake and post-tsunami emergency operations) can no longer be denied in places recently identified as being vulnerable to near-source tsunamis.
Armed with this knowledge about the potential to lose firefighters, rescuers, and citizens during a near-source tsunami event, it’s incumbent on local fire department officials and other decision makers to develop a rational response plan that takes into account the need to warn and evacuate the public, to provide reasonable guidelines for firefighters and rescuers assigned to tsunami-vulnerable coastal zones, and to take advantage of the research being done by experts who can help quantify the actual risks. ■
• Tsunami Information Bulletin. A message issued by the West Coast Alaska Tsunami Warning Center (WCATWC) to advise participants of the occurrence of a major earthquake in the Pacific or near-Pacific area, with the evaluation that a potentially destructive Pacific-wide tsunami was not generated.
• Tsunami Warning Bulletin. Warning message issued throughout the Pacific based on confirmation that a tsunami posing a threat to the population in some or all of the Pacific coast regions has been generated. It will be followed by additional bulletins with updated information until it is cancelled.
• Regional Tsunami Warning/Watch Bulletin. Message issued initially by WCATWC. Based only on seismic information, it is sent to alert all participants of the possibility of a tsunami and to advise that a tsunami investigation is underway. Areas within zero to three hours from the estimated time of arrival of the first wave are placed in a Tsunami Warning status. Areas within three to six hours are placed in a Tsunami Watch status. It will be followed by additional bulletins until it is upgraded to a Pacific-wide Tsunami Warning or is cancelled.
• Near-field tsunami (also known as local tsunami). A tsunami from a nearby source, generally less than 200 km away. A local tsunami is generated by a small earthquake, a landslide, or a pyroclastic flow. This is the most serious tsunami hazard for Los Angeles County (1) because the wave heights are likely to be highest and the forces are likely to be the strongest (because of the proximity to the precipitating event), (2) because these tsunami waves can arrive in as little as three to 15 minutes of the event, and (3) because they may occur after a disastrously damaging coastal earthquake. They create another layer of disaster, threatening the public and responders to the earthquake, and complicate search, rescue, treatment, firefighting, and hazardous-materials management.
• Teletsunami (also known as distant-source tsunami). A tsunami originating from a distant source, generally more than 1,000 km away.
• Estimated time of arrival (ETA) of tsunami. Time of the tsunami’s arrival at some fixed location, as estimated from modeling the speed and refraction of the tsunami waves as they travel from the source. ETA is estimated with very good precision if the bathymetry and source are well known (less than a couple of minutes).
• Tsunami evacuation map. A drawing or representation that outlines danger zones and designates limits beyond which people must be evacuated to avoid harm from tsunami waves.
• Tsunami travel time. Time required for the first tsunami wave to propagate from its source to a given point on a coastline.
• Tsunami travel time map. Map showing isochrones, or lines, of equal tsunami travel time, calculated from the source outward toward terminal points on distant coastlines.
• Inundation line. Inland limit of tsunami inundation, measured horizontally from the mean sea level (MSL) line.
• Run-up. The difference between the elevation of maximum tsunami penetration (inundation line) and the sea level at the time of the tsunami attack.
■ LARRY COLLINS is a 25-year member of the Los Angeles (CA) County Fire Department (LACoFD). He is a captain, USAR specialist, and paramedic assigned to USAR Task Force 103, an LACoFD rescue company. He is assigned to Tsunami Planning committees for the LACoFD and the County of Los Angeles. He is a search team manager for the LACoFD’s FEMA/OFDA USAR Task Force for domestic and international disaster response and a USAR specialist on the “Red” FEMA US&R Joint Management Team, with deployments to the 9-11 attack on the Pentagon, the Oklahoma City bombing, the 2004 Florida hurricanes, and several national security events. He is author of the three-part book series Technical Rescue (Fire Engineering-Part 1, 2004; Part 2, 2005).