Why is there no earthquake in Hainan?

In fact, there are frequent earthquakes in Hainan, but everyone doesn't know that there are earthquakes almost every month on Hainan Earthquake Information Network, but the magnitude is very small, about 1. -3, so everyone said there was no earthquake.

The largest earthquake was located at the bottom of the bay from Dongzhai Port, qiongshan district, Haikou City to Puqian Town, Wenchang City. It was caused by the land subsidence into the sea caused by a major earthquake in the Wanli period of the Ming Dynasty (1605). At that time, about 100 square kilometers of land, ***72 villages slowly sank into the sea for about 3 to 4 meters, which is rare in the world. Every May and June, when the sea ebbs, you can see the ruins of villages in the sea by boat.

According to the existing historical records

And modern instrument records show that from 1466 to 1990, there were 3 earthquakes with magnitude above 4.8 in Hainan, and from 1969 to 1990 * *, there were 26 earthquakes with magnitude above 3.0. Historically, the ocean

Most destructive earthquakes in southern province are distributed in Qiongbei area. Among them, there were 20 earthquakes with surface wave magnitude above 6, and the largest one was 1605 Qiongshanta earthquake with magnitude 7.5, which caused the ground to sink into the sea and 72 villages to sink.

Qiongbei Town and its vicinity have caused extremely heavy casualties and house damage, with the epicenter intensity of 10 degree, which is the highest intensity earthquake in South China. Neighboring areas have also been damaged to varying degrees. Guangdong, Guangxi, Hunan, etc

Some areas were also affected by the earthquake.

The earliest recorded strong earthquake in Hainan Island was an earthquake of magnitude 5 on March 2, 2005165438, and the largest was June 65438+July 65438+June 7, 2005.

Magnitude earthquake. If only the main earthquake is counted and the aftershocks are not counted, by the end of 1990 * *, there will be 10 earthquakes with magnitude above 5, the earliest felt earthquake is the Qiongshan earthquake of 1466, and more than 70 felt earthquakes have been recorded by the end of 1990 * *.

(excluding aftershocks). Since the end of 1969, a modern seismic network has been built in Hainan Island. Up to 1990, * * recorded more than 900 earthquakes, including 55 earthquakes with magnitude above 3 and 4 earthquakes with magnitude above 4. The largest earthquake was 5.2 in the sea area 50 kilometers southeast of Lingshui on February 20th.

China's southeast coastal seismic belt starts from Fujian coast in the east and reaches Beibu Gulf in the west, and Hainan Island is located in this seismic belt.

The southwest end of Hainan Island has a seismogeological structural background of strong earthquakes. The most striking feature of seismic activity is the uneven distribution of time and space, and the time distribution is characterized by alternating calm and active fluctuation.

The spatial distribution of seismic activity in Hainan Island and offshore areas is also uneven, and the destructive strong earthquakes with magnitude above 5 on land are mainly distributed in the northeast of Qionghai. In the nearby sea area, it is also the northeast of Qionghai, followed by the continental slope in the southeast of Qionghai and the north in the southwest of Qionghai.

Bay basin edge and other places. The general pattern is strong in the north and weak in the south, strong in the east and weak in the west.

Scientists and technicians point out that earthquake prediction is one of the biggest problems in contemporary science. The practice of earthquake prediction in China for more than 30 years shows that only

Under favorable conditions, some earthquakes can be predicted to some extent. For a long time to come, it is inevitable to make false reports and conceal them. The main reasons are as follows: First, it is quite difficult to directly detect the focal depth. In recent years,

There is almost no breakthrough in the past ten years, but the physical process of earthquake occurrence is still being explored; Second, the uncertainty or complexity of the relationship between precursory phenomena and earthquakes is observed, that is, there is no abnormal phenomenon anywhere.

Must appear before the earthquake, there is no abnormal phenomenon that will inevitably lead to the earthquake once it appears; Thirdly, the repetition period of strong earthquakes in the arranged precursor network is longer, that is, there are fewer opportunities to practice-know-practice again. this

Some cases show that it is a long and arduous process to explore earthquake prediction.