China scientists look for ways to predict earthquakes from space.
Xinhua News Agency, Beijing, March 18th (Reporter Yu Fei, Yang Chunxue) More than 1,800 years after Zhang Heng invented the seismograph, scientists in China are using the satellite named after him to search for abnormal electromagnetic signals from space before the earthquake, trying to solve the problem of earthquake prediction and reduce the damage caused by natural disasters.
"Although we can’t predict earthquakes at present, we are working hard in this direction. I believe that in another 10 to 20 years, earthquake prediction is expected to usher in a breakthrough." Shen Xuhui, a researcher at the National Space Science Center of China Academy of Sciences, an academician of the International Academy of Astronautics, and the chief scientist and deputy chief designer of the "Zhang Heng-1" satellite program, said.
At 15: 51 on February 2, 2018, China successfully launched the electromagnetic monitoring test satellite "Zhangheng No.1" with the Long March II carrier rocket at Jiuquan Satellite Launch Center and entered the scheduled orbit. Xinhua News Agency (photo by Wang Jiangbo)
At the recent 35th National Symposium on Space Exploration, Shen Xuhui introduced the progress of "Zhang Heng No.1" launched in 2018 in five years: global geomagnetic field data and global low-frequency electromagnetic spectrum data were obtained; The world-leading global reference geomagnetic field model and cross-layer coupling propagation model of low-frequency electromagnetic waves are established, which have been evaluated by the International Union of Geomagnetism and High-altitude Physics and successfully selected for the calculation of the new generation of international geomagnetic reference field.
Earthquake prediction has always been a difficult problem in the world. The main reason is that it is difficult for scientists to accumulate enough destructive earthquake cases to form statistics and verify prediction methods and theories. In addition, it is difficult to detect the situation from the source to the surface by the existing technical means.
Satellite monitoring has broken through the limitation of traditional seismological research, and electromagnetic waves can spread from underground to space across circles. Statistics show that there is obvious correlation between space electromagnetic disturbance and earthquake occurrence. Scientists can expand their observation range to the global scale through satellites. On average, there are 18 earthquakes of magnitude 7 or above every year in the world. From the perspective of observation and collection of earthquake cases, "one year in the sky is equal to twenty or thirty years on the ground". Satellite monitoring allows scientists to carry out large-scale statistical research and provides a basis for testing various methods and models.
"Zhangheng No.1" is the first satellite of the space-based observation platform of China Earthquake Stereoscopic Observation System. It can give full play to the advantages of large dynamic, wide viewing angle and all-weather observation from space. By obtaining global observation data of electromagnetic field, ionospheric plasma and high-energy particles, it can carry out real-time monitoring of ionospheric dynamics and earthquake precursor tracking in China and its surrounding areas, make up for the shortage of ground observation and open up new ways to explore earthquake monitoring and prediction.
Shen Xuhui introduced that "Zhang Heng No.1" has observed about 60 earthquakes of magnitude 7 or above, nearly 600 earthquakes of magnitude 6 or above and tens of thousands of earthquakes of magnitude 5 around the world. "We found that as many as 80% of earthquakes with magnitude 6 or above had obvious precursor signals in the first half of the month, mostly in the week before the earthquake. Usually, the precursor signals detected by satellites do not appear directly above the epicenter and often deviate from the epicenter by hundreds of kilometers. "
Shen Xuhui admits that at present, a large number of precursor signals are found in the data after the earthquake, and only a few are found in advance. This is because the data processing is very complicated, and it is impossible to track the global data in real time with limited manpower and computing power.
He said that there is still a big gap between earthquake prediction and accurate prediction of time, place and intensity. To truly realize earthquake prediction, we must rely on the combination of seismology, electromagnetism, geodesy, geochemistry and other multidisciplinary means.
"But I am full of hope for the future. I think earthquake prediction can finally be realized. In another 10 years, we will accumulate massive observation data. With the development of information technology such as machine learning, big data and artificial intelligence, the computing power is becoming more and more powerful, which can carry out real-time data processing before the earthquake. In addition, we also need the interdisciplinary development of seismology and physics to study the ultra-high temperature and ultra-high pressure underground seismic source environment. " Shen Xuhui said.
In addition to earthquake monitoring, "Zhangheng No.1" has also become an accurate recorder of space weather activities, supporting the formation of space weather disaster monitoring and early warning capabilities and providing protection for communication and navigation environment management. For example, the geomagnetic storm that occurred in August 2018 was the strongest geomagnetic storm recorded since the launch of Zhang Heng-1. In addition, volcanoes, solar eclipses, tsunamis, storm surges, and magnetic anomalies in the South Atlantic have also been accurately recorded by "Zhang Heng No.1", showing its good application prospects in monitoring and early warning of space weather disasters, extreme weather disasters and volcanic activities.
Shen Xuhui introduced that China plans to launch the "Zhangheng No.1 02" satellite. This new satellite will realize 24-hour uninterrupted monitoring, and expand its observation range to the north and south poles of the earth, thus enhancing its ability to observe changes in the earth system. "The combination of 02 and 01 stars can realize the observation of a complete solar activity cycle for 11 years."
Zhang Heng-1 is the first star of China Geophysical Field Exploration Satellite Program. Shen Xuhui pointed out that in the future, this plan will continue to pay attention to the exploration of monitoring and early warning technologies for major natural disasters such as earthquakes, closely combine the themes of livable earth, global change and sustainable development, and promote the earth system science, especially the coupling process of the key spheres of the earth and its disasters and environmental effects.