Tsunami Detection Improves
|Mar 18, 2011|
Despite the incredible damage wrought by the March 11th Great Tohoku earthquake and tsunami which struck the Pacific Coast of Japan’s Honshu Island, and which appear to have taken the lives of at least 14,000 people, the fact is that many more could have died.
Tsunami detection systems put in place since the Indian Ocean tsunami of 2004 appear to have been vastly improved, helping save the lives of multitudes in Japan and other area.
Fears in the immediate wake of the disaster were that unknown numbers of people could die on the islands and atolls that dot the Pacific Ocean and beyond as the teletsunami (as long-distance tsunamis are known) rolled across the Pacific Ocean. Only one person died, a 24-year-old man foolish enough to try to photograph the wave near the mouth of the Klamath River at the upper tip of Northern California. The damage has been limited to property and some livelihoods although colonies of albatrosses nesting on Midway Atoll have suffered badly. Despite earlier fears, there has been nothing on the scale of the damage caused by the local tsunami in Japan.
While mourning the victims of the local tsunami and hoping for the quick restoration of normalcy for the millions displaced, we must take a moment to recognize the achievements of the scientists who have worked hard to improve global detection and monitoring systems and issue warnings, and the first responders who conducted effective evacuations and thus saved countless lives.
The earthquake occurred at 14:46 Japan Standard Time near the Pacific coast of Japan’s Honshu Island. The first tsunami warning was issued just six minutes later, at 14:50 by the Japan Meteorological Agency (JMA), an extraordinary achievement which suggests a direct link between the signals from the sensors and the public warning system, excluding human decision making in the middle.”
The Pacific Tsunami Warning Center in Hawaii issued its first warning in 14 minutes back in 2004. Given the many weak links in the warning chains back then, the warning didn’t reach all of the countries, with devastating results. Some 230,000 people died in 14 countries. In the current tsunami, the warning center produced the alarm within nine minutes.
The additional resources poured into tsunami detection have paid off. At the warning center in Hawai’i, a qualified geophysicist looks at the data from the sensors before issuing the warning. Thus the process cannot take less than nine minutes. But the 2011 tsunami experience may tip the scales in favor of the automated Japanese approach.
Local tsunami risk reduction
For many in the coastal towns of Japan, no warning could have been fast enough. For Iwate Prefecture, the Japan Meteorological Agency’s model noted that a three-meter wave had already arrived by the time the warning was issued. For Miyagi Prefecture, six-meter waves were predicted within 10 minutes, and for Fukushima prefecture, in 20 minutes.
Four minutes was heroic, but still not enough. For Miyagi and Fukushima, they estimated 10 and 20 minutes for the six- and three-meter waves to hit. Clearly, there was no human way the sirens or cell broadcasts could have been activated in time for the people of Iwate to run; no way could orderly evacuations have been organized.
Did sirens and mobile phones give warnings to the people of Miyagi and Fukushima prefectures in the 10-20 minutes that remained? This would not be a high priority for Japanese disaster-risk-reduction professionals at this moment, but it is a question that must be answered if we are to learn from this tragedy to reduce the risks of tsunamis everywhere.
Countries vulnerable to local tsunamis, where faults lie very close to the coasts, will have to appreciate that the risk cannot be eliminated, but only managed. Perhaps this is the single most important, and humbling, lesson we learn from Japan. Excluding the option of moving people away from the coast, the key elements of risk reduction will have to be intelligent land-use planning, enforcement of resilient building codes, and mandatory insurance.
Insurance is the most sensible method of managing risk. Here, the high premiums that will attach to the higher-risk land will reinforce land-use rules and building codes. Yet, if people live and work in such areas, the government has a responsibility to help save their lives from a tsunami.
The answers here lie in preparedness (“Your feet are your warning; if you feel an earthquake run for high ground”) and contingency planning at the household level (in the minutes that are available community action is less effective). It appears that the Japanese authorities have done a good job on these aspects though of course one can always think of improvements.
Teletsunami risk reduction
Many more countries are vulnerable to teletsunamis. All disaster management authorities in ocean littoral states can receive the alert and warning notices issued by the Pacific Tsunami Warning Center and from the Japan Meteorological Agency. Even ordinary people can register for these messages. In my experience the two have come more or less simultaneously. This suggests that, sensibly, the meteorological agency has a special procedure for earthquakes likely to trigger local tsunamis in Japan, while it follows the standard procedure of issuing a warning after assessment by a geophysicist in other cases.
Some seismic waves travel through the earth and reach sensors anywhere in the world more or less at the same time. Therefore, theoretically, detection and monitoring can be done in one location for the whole world. In reality these activities are duplicated. Tsunami-detection buoys transmit data through satellite, meaning that they arrive more less seconds apart in different locations depending on how many hops are needed. But clearly the four- and nine-minute warnings that were issued by the two agencies on the Mar. 11 were based solely on earthquake data, not data from tsunami-detection equipment.
It is when it comes to interpretation that national centers are important. Setting off sirens and cell broadcasting warnings will cause people to evacuate, but they can also trigger mass panic, cause heart attacks in a subset of the populace, and disrupt normal life.
Tsunami prediction is an inexact art and false alarms can have major negative consequences. Only national political authorities can make the call on issuing evacuation orders. This is what concerned professionals and media must focus on, not on whether each country has its own tsunami detection and monitoring buoys.
On the basis of monitoring the performance of national authorities responsible for public warning around the Bay of Bengal, we can see a lot of room for improvement in the step of interpreting the data and issuing alerts and warnings. For example, Sri Lanka’s mobile networks are equipped to issue localized cell broadcast warnings (e.g., different messages for vulnerable coastal areas and for inland areas). Yet the whole process of communicating government orders to the mobile operators and even the conventional media is not automated and not done on the basis of standard templates. This leaves room for error and causes delay. The very action of who makes the final decision on evacuation orders is not clear, with governments not always speaking in one voice.
The government can issue warnings, but it is the general public that must act. In Japan, the media coverage shows that the preparedness training imparted from school days had good effects. In story after story, one hears of survivors who dropped everything and ran to high ground, in most cases simply because of the earthquake and not based on official warning. The land was flat and the sea walls a futile defense against the terrifying power of the roiled ocean. In addition, the earthquake had caused the land to drop by two feet, allowing the tsunami to go further inland. There is little defense against a wall of water in these conditions other than a prepared people.
For teletsunamis, contingency planning should be at community and organization levels, with periodic checks to see if the plans are current, because those needing special care change from year to year. Various forms of drills and exercises, especially for community leaders and first responder, are essential. Much of this should be voluntary, but in locations such as hostels and hotels with transient populations unfamiliar with local conditions, mandatory standards should be enforced.
The Great Tohoku Earthquake teaches us that the Japanese authorities had very good procedures for reducing risks that paid off, even if the casualty figures that will exceed 10,000 suggest otherwise. The Japanese authorities should not be judged on absolute numbers of deaths, but on how many died as a percentage of the vulnerable. By this criterion, I am sure they will come out ahead of the governments whose people died in the 2004 Indian Ocean Tsunami.
These deaths will not have been in vain if political authorities, professionals, and media in all countries vulnerable to tsunamis use this opportunity to learn from Japan’s (and other Pacific countries’) experience in 2011 to improve performance in the “last mile” of the warning chain, especially with regard to government decision-making re evacuations, the use of the best-available public warning technologies such as cell broadcasting, and preparing people to understand and act in ways that reduce risk.
Rohan Samarajiva, Chair & CEO, LIRNEasia, is an expert on early warning systems for natural disasters. He is currently in Sri Lanka. He can be reached at firstname.lastname@example.org