Why does the shock spread so far?, 5.5 magnitude earthquake in situ

According to the official measurement of China Earthquake Networks Center, at 2:33 on August 6, a 5.5 magnitude earthquake occurred in Pingyuan County, Dezhou City, Shandong Province, with a focal depth of 10 kilometers, and many earthquakes felt obvious.

What is the cause of this earthquake? What issues should be noted in the future? China News Network interviewed Xu Xiwei, founding director of the National Institute of Natural Disaster Prevention and Control and professor at China University of Geosciences, in this regard.

How to determine the cause of the Texas earthquake?

According to the quick report catalog of China Seismostation Network, there have been 8 earthquakes of magnitude 3 or above within 200km around the epicenter in the past five years, and the largest earthquake is this one.

Xu Xiwei analyzed to China News Network that, in terms of earthquake types, the earthquake that occurred in Dezhou this time belongs to a tectonic earthquake.

From the occurrence of earthquakes, Texas is not a place where earthquakes occur frequently. The North China Plain where it is located is located in the west of the Tanlu seismic belt. This area is not an obvious seismic belt, but a relatively weak place.

According to relevant data, the Tan Lu seismic zone is a part of the frequent earthquakes on the Tan Lu fault zone, distributed in a nearly north-south direction. The Tanlu Fault Zone starts from the Wuxue area in Hubei Province in the south, passes through Anhui, Jiangsu, and Shandong to the north, crosses the Bohai Sea, passes through the three northeastern provinces, and enters the territory of Russia, with a length of over 2400 kilometers in China.

Research has shown that the Tan Lu fault zone is located in a fault segment with strong compression and dextral torsion. Due to its high normal stress and shear stress, it is easy to accumulate the energy of large earthquakes and is often released in the form of destructive earthquakes, resulting in high seismic intensity and low frequency in this section. However, the recurrence cycle of such massive earthquakes in situ is generally long, even lasting several thousand years.

Why are there still tremors in areas far from the epicenter?

Xu Xiwei believes that people around or even at a slightly distant distance who have obvious tremors are also related to the earthquake occurring in the early morning.

Most people are in a state of sleep, and if it's not deep sleep, they will feel more pronounced after being shaken. If it happens during the day and most people are working, they may not necessarily feel it.

Will there be a greater risk of earthquakes occurring?

According to the news from the Seismological Bureau of Shandong Province, after the earthquake, the Seismological Bureau of Shandong Province quickly launched the Level II response according to the plan, and held a joint video conference with the China Seismological Bureau and the China Earthquake Networks Center Center. The three parties discussed the trend of the earthquake situation, and analyzed that it was unlikely that a larger earthquake would occur in the original epicenter area after the earthquake.

Xu Xiwei explained that there are significant differences between different sections of the Tan Lu fault zone. Strong earthquakes of magnitude 6 or above, major earthquakes, and major earthquakes are mainly concentrated in the middle section of the Tan Lu fault zone. The earthquake in Pingyuan County, Texas occurred on the western edge of the Tanlu Fault Zone. Although there are multiple faults in this area with unknown activity, it is currently believed that there are no significant earthquakes or large-scale active faults. Of course, some faults with relatively weak activity, but their seismic hazard is not very clear, and further exploration and identification of active faults are needed. Overall, the seismic hazard within the seismic zone is slightly higher, while in other areas it is relatively weaker.

Has China reached a period of frequent earthquakes?

Xu Xiwei introduced that earthquakes in China in the past 30 years have mainly occurred in the western region. Except for the Wenchuan earthquake in 2008, which occurred in the southern Longmen Mountain area of the Chengdu Plain, causing large-scale casualties, most of the other destructive earthquakes occurred in uninhabited areas.

After the Tangshan earthquake in 1976, North China Plain basically did not have earthquakes above magnitude 7, and was in a quiet period of earthquakes. In this situation, it is currently impossible to determine whether the entire North China region, especially the plain areas in the northern part of North China, has entered an active period.

What should we pay attention to after this earthquake occurs?

Xu Xiwei said that if the local houses are basically built according to the fifth generation seismic parameter zoning map, the damage to the houses should not be too severe after a moderate intensity earthquake occurs. Unless the old houses in rural areas have slightly poor seismic performance, or if the houses are excessively renovated, some furniture, lights, etc. inside may fall off and cause injuries.

Xu Xiwei stated that the earthquake that occurred in Dezhou has sounded an alarm for earthquake prevention and control work in the plain areas. He said that human casualties are caused by the collapse of houses. The quality of building construction should strictly follow the requirements of the fifth generation seismic parameter zoning map.

The China Earthquake Administration has formulated the fifth generation of China Seismic Parameter Zoning Map, which is a mandatory national standard that provides technical elements, basic regulations, and methods for determining seismic parameters in China. It is applicable to seismic fortification of general construction projects, as well as the preparation of social and economic development plans, land use plans, disaster prevention and reduction plans, environmental protection plans, and other related plans.

Xu Xiwei mentioned that in addition to buildings built across faults, if a strong earthquake of magnitude 6.5 or above occurs in the future, buildings built nationwide according to the seismic parameters of the fifth generation zoning map can crack and not collapse as long as they do not cut corners, effectively reducing casualties.

Secondly, Xu Xiwei also found that the water level of some dams and reservoirs around some cities in plain areas is higher than that of cities. He reminded that relevant departments should regularly inspect the safety of dams and reinforce old reservoirs according to requirements.

In addition, Xu Xiwei also stated that the detection of active faults in North China should be strengthened. Because the faults in North China are relatively hidden, many places are covered by Quaternary sediments, and human activities are relatively dense and intense. It is difficult to determine the location of active faults on the surface based on seismic geological and geomorphological indicators, and to scientifically and reasonably analyze and determine their seismic risk.

He suggested identifying active faults that may cause earthquakes and serious earthquake disasters, and having the planning department effectively avoid them during the planning and construction process to minimize the damage caused by earthquakes.