On March 11 last year, an earthquake and tsunami occurred in the northeastern region of Japan, which led to a nuclear accident. This not only caused a huge disaster in the area, but also affected the entire world. This lesson also made many coastal countries aware of the importance of strengthening tsunami warning and forecasting. At an international conference held in Sendai, Japan last month, officials of the Japan Meteorological Agency stated that the existing disaster warning system still has some problems, and the accuracy of the tsunami forecast needs further improvement. The data is double-edged sword The Japan Meteorological Agency established a tsunami warning system in the 1940s. It has invested heavily in R&D and equipment for decades. The country is divided into 66 tsunami forecast areas. After the earthquake, the Meteorological Agency has to report the earthquake intensity within 3 minutes and report the tsunami height in about 5 minutes. Therefore, under normal circumstances, emergency management personnel can more effectively predict how the tsunami will penetrate thousands of kilometers of sea surface and hit the coast. In the afternoon of March 11, 2011, just as soon as the earthquake struck, the Meteorological Agency issued an alert in the shortest possible time: A magnitude 7.9 earthquake occurred off the coast of Miyagi, where a 6-meter-high tsunami might have occurred. The neighboring Iwate, Fukushima must be ready to meet at least 3 meters of high waves. However, an hour and a half later, when the tsunami wave reached the Kesennuma in the northeast, it reached 9 meters, far exceeding the forecast of the Meteorological Agency. The wave swept the coast off a 20-meter-high wave that washed away all the defensive facilities along the northeast coast. About 15,000 people died in this tsunami. According to reports, some people did not retreat to the high ground because the forecasted wave height was too low and they thought it was not dangerous. Only 1031 people died in Kesennuma, and hundreds of people were missing. Sato Kenichi, an official at Kesennuma who is responsible for issuing warnings, said that if one can know the true height of the tsunami, the loss may be even smaller. "We will send stronger alerts to ensure that people retreat to higher places." At the Sendai International Conference, the Japan Meteorological Agency’s Shang Hengchiu pointed out that the existing earthquake and tsunami warning system worked well for earthquakes with a magnitude of less than 8 but could not measure a larger earthquake. As a result, it was estimated that the earthquake intensity was 7.9, but The actual earthquake intensity reached 9 levels, exceeding the upper limit of 10%. Construction of submarine cable network Japan will soon invest 402 million US dollars to build a more advanced seafloor sensor network system to improve the early warning capabilities of the coastal tsunami. This is an expansion of a plan that began in 2004 with the goal of improving early warning capabilities. This is very difficult and may only have a few minutes of reaction time. "Historically, about 95% of the tsunami victims were killed in local or near-zone tsunamis," said Laura Kong, director of the International Tsunami Information Center (Honolulu, Hawaii, USA). The new network, which is regarded as a "safety net," will closely monitor the east coast of Japan and will be controlled and operated by the National Institute of Earth Sciences and Disaster Prevention (NIED) in Tsukuba. It is planned to be completed in March 2015. The head of the network development team, Junzawa Kanazawa, said that the system consists of 154 subsea observation stations, each equipped with a seismometer and a pressure gauge to sense the passing tsunami. The observation stations are connected together by optical cables and form six ellipses. Each ellipse extends to the coast and is far apart from each other. Even if a ground station or a cable is damaged by a tsunami, the entire system can still operate normally. There is already a large fiber optic cable network in the Nankai Trench area in southern Tokyo. The NIED's submarine sensors will be located between the coastline and the seismic source, here the Pacific Plate subduction zone, while North Japan is on the upper plate. After the NIED network is built, when the tsunami propagates from the deep sea to the continental shelf, it can detect changes in pressure caused by it, and alert the people on the shore 5 minutes to 20 minutes in advance. The Japan Meteorological Agency also plans to install three submarine sensors across the Cascadia stratum submerged zone to monitor the tsunami that has passed through the open seas, as a supplement to the cable network system. These data are not transmitted through the optical cable. The sensor will transmit the sound signal to the nearby buoys and relay the information to the geostationary satellite via the relay station. Installing a buoy will be faster than laying a cable network and will be in place this year. These buoys will be integrated with the existing Tsunami Deep Sea Assessment Report (DART) buoy network system. Keep an eye on the next wave of tsunami According to experts’ predictions, the Cascadia strata submerged zone may have a large earthquake within a few decades. Scientists and emergency managers all over the world are making unremitting efforts to improve tsunami reconnaissance and system early-warning capabilities to prevent a repeat of tragedy. The U.S. Tsunami Deep Ocean Assessment and Reporting System originated from a failed early warning in 1986. Eddie Bernard, former director of the National Oceanic and Atmospheric Administration’s Pacific Ocean Environmental Laboratory (PMEL), who designed the system, said that the Aleutian Islands After the 8.0-magnitude earthquake, people on the Hawaiian seaboard and other low-lying coastal areas all evacuated, causing losses of 40 million U.S. dollars. However, when the tsunami reached the surface, it was only 15 cm high. In 1997, the Congress funded the preparation of the tsunami disaster reduction plan. Bernard also completed his research on the development of deep-sea tsunami sensors. The DART buoy sensor is like a sentinel at sea, monitoring the tsunami from distant earthquake sources. It usually threatens Hawaii. In the United States, 40 buoys are distributed in the Pacific Rim and the Atlantic Ocean. In other countries, there are 14 in the Pacific and Indian Oceans. Countries can share almost all data. At a meeting held by PMEL in January this year, Japanese and American scientists discussed how to filter out the interference of seismic waves from the sensor data and make the sensors more fault-tolerant. Wesley Titov, a tsunami model designer at PMEL, said: “We can place the sensor at a distance of only 5 minutes from the seismic source. Once the wave reaches a DART sensor, it takes 5 minutes to 10 minutes. Only half of the entire wave can pass, and the height of the tsunami can be measured." Currently, the United States hopes to move some of the DART buoys closer to the source of the earthquake - along the Cascadia submergence zone and other areas. Titov said that the warning center will combine the DART data and the coastline space model to more quickly predict the height of the waves. “In a matter of half an hour, a high-quality forecast can be made to show which area is flooding. This can help emergency management personnel make decisions, which areas need emergency evacuation, and when people are urged to transfer to the highlands.†(Reporter Chang Lijun Comprehensive external power) Armored Door,Steel Door,Security Door Steel Door,Toilet doors,Wood Door Co., Ltd. , http://www.steeldoors-manufacuturer.com