China News Service, Beijing, September 4 (Reporter Sun Zifa) In the early morning of September 4, 10 years ago, an earthquake with a magnitude of 7.1 on the Richter scale struck Christchurch, New Zealand, causing two serious injuries and several others with minor injuries. The "zero death" phenomenon of strong earthquakes has caused widespread concern.
The Public Service Department of China Earthquake Administration recently organized seismic agencies and experts to review and summarize the 2010 New Zealand magnitude 7.1 earthquake. It pointed out that earthquake damage is highly uncertain and there will be overlooked problems. We should draw lessons from historical earthquake damage. , Continuously improve earthquake resistance, effectively prevent earthquake disaster risks, and reduce earthquake damage losses.
A series of effective measures to minimize the risk of earthquake disaster
New Zealand is located between the two major tectonic plates of the Pacific Ocean and the Indian Ocean, with frequent geological activities and very active seismic activities.
Historically, they were severely affected by earthquakes. In 1931, Napier City on the North Island and Wellington in 1942 experienced earthquakes of magnitude 7.9 and 7.2 respectively, causing a large number of casualties.
The Heilongjiang Provincial Earthquake Administration’s Mission Center stated that the 2010 Christchurch earthquake with a magnitude of 7.1 “zero deaths” is related to the large area of the earthquake-producing city, the scattered population, the earthquake occurred early on weekends, and the scarcity of people in crowded places such as shopping malls and schools. But it also shows the achievements of New Zealand in long-term earthquake resistance.
In the face of frequent and sudden earthquakes, New Zealand has long been committed to minimizing the risk of earthquake disasters. To this end, it has adopted a series of effective measures, including strengthening legislation in construction, and strict regulations on building safety standards and earthquake resistance. The quality of infrastructure construction is also equipped with complete supervision measures, and extremely severe punishment measures are taken for unqualified projects.
New Zealand also widely uses seismic isolation technology. As early as the late 1960s and early 1970s, special rubber pads were used for foundation isolation, and structural seismic isolation devices were successively used in some important buildings and bridges. , Effectively reduce the damage to the building caused by the earthquake.
In addition, New Zealand has always attached importance to disaster prevention and mitigation education, and has long promoted and popularized knowledge of how to identify and prevent disasters and conduct self-rescue and mutual rescue among all citizens, effectively raising the awareness of ordinary people in earthquake prevention and mitigation.
The Publicity and Education Center of the Heilongjiang Earthquake Administration believes that China is one of the countries with the most severe earthquake disasters in the world. The basic national conditions of China are the high intensity, wide distribution, high frequency and heavy losses of earthquakes.
At present, China’s earthquake disaster prevention capability is still relatively weak. This is one of the risk challenges that must be addressed on the road ahead. It is necessary to learn from the advanced experience of New Zealand and other countries to comprehensively improve the comprehensive prevention capabilities of the entire society against earthquake disasters, and strive to prevent earthquakes. Disaster risk is minimized.
New Zealand's seismic legislation, design and insurance experience are worth learning
The Shandong Provincial Earthquake Administration's Education Center believes that the “zero deaths” of the magnitude 7.1 earthquake in New Zealand 10 years ago were mainly due to factors such as New Zealand’s housing seismic legislation, global leaders in seismic design, and successful examples of the global earthquake insurance system.
In terms of housing seismic legislation, the New Zealand Building Act of 1935 was formally enacted. It was revised four times between 1965 and 1992. In 2004, the New Zealand Ministry of Building and Housing passed the “Building Act 2004” to implement the “New Zealand National Standard”, which means that small wooden houses are excluded. In addition, it is necessary to reinforce all the buildings in New Zealand at one time. The project is huge, the resistance is not small, and the controversy is high. However, the New Zealand government has implemented it forcefully in accordance with the law.
In terms of seismic design, New Zealand is the first country to develop and apply seismic isolation system design. This technology allows buildings to be placed on special bearings to avoid structural damage. New Zealand’s important buildings and bridges use structural isolation. Shock absorption device.
In terms of earthquake insurance system, the New Zealand earthquake insurance system is known as one of the most successful disaster insurance systems in the world. Its main feature is that the country establishes a multi-channel catastrophe risk diversification system in accordance with its national conditions in legal form, combining the government with the market Way to spread the catastrophe risk as much as possible.
“It can be said that it is not the earthquake itself that killed people, but the unsafe buildings.” The Shandong Provincial Earthquake Administration’s Mission and Education Center stated that as one of the most devastated countries in the world, China has to travel from home and abroad, including the New Zealand earthquake. We learned lessons from the earthquake disaster and continued to improve our earthquake resistance and disaster prevention and mitigation.
Special attention should be paid to buildings without obvious earthquake damage in safety appraisal after earthquake
In Christchurch, New Zealand, the magnitude 7.1 earthquake in September 2010 "zero deaths", but a few months later, in February 2011, another 6.3 magnitude earthquake occurred there, killing 185 people.
Why did the two strong earthquakes in the same area increase the loss and casualties when the magnitude was smaller?
Associate researcher Yu Shizhou of the Institute of Engineering Mechanics, China Earthquake Administration, pointed out that the factors closely related to the earthquake disaster include the magnitude of earthquake action, earthquake secondary disasters, distribution of disaster-bearing bodies, post-earthquake risk management and recovery and reconstruction.
In terms of earthquake action, comparing the ground motion records of these two earthquakes in the Christchurch area, the intensity of the surface acceleration recorded in the latter earthquake is much greater.
This is mainly due to the difference in focal depth and epicenter distance. The focal depth of the 2011 M6.3 earthquake was shallow and close to the epicenter.
Although the magnitude of the earthquake is small, the energy attenuation is much smaller than the previous one, which then affects the engineering structure, causing serious earthquake damage.
At the same time, the phenomenon of sand liquefaction caused by the magnitude 6.3 earthquake is widespread, causing cavities and collapse on the surface, and affecting the structural foundation to a certain extent, leading to the tilt and destruction of the upper structure.
In terms of the distribution of disaster-bearing bodies, the magnitude 7.1 earthquake in 2010 occurred in the early morning, while the magnitude 6.3 earthquake in 2011 occurred at noon. The urban population density varies greatly, which is one reason for the large difference in the number of casualties caused by the two earthquakes.
In just over 5 months, Christchurch suffered two strong earthquakes in succession, and the superimposed effect of earthquake damage on the engineering structure should not be neglected.
In terms of post-earthquake risk management and restoration and reconstruction, Yu Shizhou emphasized that in the post-earthquake safety appraisal work, special attention should be paid to buildings without obvious earthquake damage. Due to the decoration and decoration of houses, it is difficult to distinguish houses without obvious earthquake damage based on their appearance. The safety state of the structure requires the use of professional equipment and technical means to be identified in accordance with the requirements of the specification.
He said that the occurrence of a destructive earthquake is a small probability event, but the losses caused by it are huge.
Therefore, it is particularly important to analyze the earthquake damage of the earthquake that has occurred, sum up the experience and lessons, and take countermeasures, and it is also an important way to effectively reduce the loss of future earthquake disasters.
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Changtu Science Interpretation of the 7.1 magnitude earthquake in New Zealand in September 2010: the accident, inevitability and long-term worry behind the "zero death"
Photo courtesy of the Public Service Department of China Earthquake Administration