The general earthquake naming method is mainly based on the familiar neighborhood names where the epicenter is located, such as the 92 1 Chi Chi earthquake in Taiwan Province Province, which is named after Chi Chi because it is close to the epicenter. Another example is the 5 12 Wenchuan earthquake, which was also named after the epicenter of Wenchuan. Before the 20th century, the way to determine the epicenter was generally the geometric center method. Since the 20th century, with the gradual maturity of instruments and technologies such as seismograph, single station measurement and network measurement have been born. Compared with the three methods, because of the influence of the inhomogeneity of the crustal structure on the propagation of seismic rays, the network method has the highest accuracy and the geometric center method has the lowest accuracy.
Extended data:
Epicenter measurement method
1, geometric center method
Before the 20th century, when there was no instrument record, the epicentres of earthquakes were all macro epicentres determined according to the damage range, and they were the geometric centers of the extreme earthquake zone (the most severely damaged area near the epicenter). Because it is impossible to determine the exact range of the polar seismic belt, it usually causes errors.
2. Single determination method
Due to the different propagation speeds of various seismic waves in different areas and depths, the fast wave speed or diameter reaches the station first, and then other waves arrive one after another, resulting in time difference. The recorded epicentral distance, focal depth and time difference of various waves can be compiled into time distance curves and travel time tables suitable for various places.
When an earthquake occurs in a certain place, analysts can measure the time difference of various waves of the earthquake event from the seismogram, compare it with the compiled travel time table or calculate it by using the formula, and then get the epicenter distance. Then you need to determine the position. The initial amplitudes in two horizontal directions are converted into ground motion displacement, and the azimuth can be obtained by trigonometric function. When the azimuth and epicentral distance are obtained, the epicenter position can be easily found. This method is called single station determination.
3. Network determination method
When the epicentral distance is calculated by at least three seismic stations, the location of the epicenter can be determined by trilateration [4]. This method of measuring the epicenter with instruments is generally called micro-epicenter, which is called network measurement [1][ Note 5]. The specific method is to draw a circle on the map with three stations as the center and the epicentral distance of each station as the radius according to the corresponding proportion. Then, connect the intersections of every two circles, and the intersection of three chords is the calculated epicenter, and then convert the latitude and longitude [2].
Baidu encyclopedia-epicenter