Meltdown!: The Nuclear Disaster in Japan and Our Energy Future
TSUNAMI The sudden upward movement of the top plate creates a huge tsunami A bulge of water about 180 km 110 mi wide begins traveling toward the Tohoku coast In the deep ocean a tsunami can travel at the speed of a jet plane It travels slower in shallower regions As the tsunami reaches shallow water near the Tohoku shore it slows and water piles up even higher The giant wave begins surging onto the closest land about 72 km 45 mi west of the epicenter about 10 to 20 minutes after the quake An hour later it reaches the major city of Sendai where it begins flooding the airport Most Japanese coastal towns have walls to keep them safe from tsunamis But this one is higher than the walls can handle At some narrow inlets it reaches as high as 39 m 128 ft It roars ashore It uproots trees knocks buildings off their foundations and carries cars and trucks in rivers of trash In some locations it rolls inland as far as 10 km 6 mi Loss of life and property is astonishing The tsunami damages or destroys roads railways a dam and more than 125 000 buildings Property damage may be more than 300 billion More than 5 300 people are injured and more than 23 300 are dead or missing Most of the damage and casualties are the result of the tsunami
PREPARATION SAVES LIVES The Tohoku quake is extremely powerful registering 9 0 on the Richter scale the most common measurement of earthquake intensity Only four earthquakes since 1900 have released more energy Yet the loss of life in Japan though large was much less than in serious quakes in other parts of the world For example the 7 0 earthquake that struck Haiti in 2010 released only a thousandth as much energy and did not cause a tsunami Yet it was more than ten times as deadly More than three hundred thousand people died In 2005 a 9 1 earthquake under the Indian Ocean near Aceh on the northern tip of Sumatra Indonesia triggered a tsunami similar to the one that struck Tohoku The Aceh tsunami was also ten times as deadly as Tohoku It killed more than 230 000 people on Sumatra on other Indonesian islands and in neighboring countries EARTHQUAKE TSUNAMI
Why do so many fewer people die in Japan Two words preparation and warning The Japanese are the most prepared people in the world when earthquakes and tsunamis strike And they have warning systems that alert them in time to seek safety Most of the Haitian deaths were caused by collapsing buildings In Japan most of the buildings survive the earthquake with little or no damage But even where buildings suffer damage most people escape injury because of Japan s earthquake warning system Meanwhile out in the ocean a system of undersea sensors and floating communication buoys called DART Deep ocean Assessment and Reporting of Tsunamis detects the early signs of a tsunami It takes nine minutes to collect and compare enough readings Then DART sends a warning to a communications satellite which relays the message to a receiver on the ground
In the hardest hit areas the tsunami alerts arrive about fifteen minutes ahead of the deadly wave That isn't much time but the Japanese people respond quickly when tsunami warning sirens blare Many cities and towns such as the fishing village of Ofunato in Iwate Prefecture have clearly marked escape routes with signs in Japanese and in English Tens of thousands of Tohoku inhabitants lose their homes but escape to higher ground How Earthquake Warning Systems work Japan's earthquake warning system uses ground motion detectors called seismometers The system takes advantage of the fact that every earthquake sends out two kinds of vibrations These are called primary and secondary waves or P waves and S waves The P waves are sound waves with such a low pitch that they can be felt but not heard They pass through Earth without causing damage They often go unnoticed They are called primary because they travel faster and arrive first As soon as a seismometer senses a P wave it sends out an alert Before the damaging secondary waves arrive people get messages on cell phones televisions and special radios that turn on automatically Cities and towns closest to the epicenter get the least warning In the Great Tohoku Earthquake the coast of Miyagi Prefecture near Oshika has only about ten seconds between the alert and the shaking People in Tokyo 370 km 230 mi from the epicenter have nearly a minute to take action People on the lower floors of buildings get out Doctors stop surgeries People get out of elevators Drivers move their cars to the roadside EARTHQUAKE TSUNAMI MELTDOWN 11
