1. Assuming that the source is underground, the seismic wave propagates in all directions at a constant speed after the earthquake, and the speed remains unchanged during the propagation.

2. It is assumed that the propagation speed of seismic waves in various media is equal.

3. Assume that the time difference in the earthquake area is zero.

Although the location of the earthquake cannot be accurately found by the above conditions, a model mechanism for accurately simulating the occurrence and prediction of earthquakes in space and time can be established, which is of great practical significance for earthquake prediction and prevention.

The source may be underground. After the earthquake, the seismic wave propagates from the focal point in all directions in a spherical way, which is a three-dimensional model structure in space and time.

Let the epicenter be at point M(x, y) and the focal depth be h km/s, and the time for receiving seismic waves at points E and H in the coordinate map is t seconds after the earthquake. As shown in figure 1, each observation point has the following equation:

e:？ ms=sqrt(( 1700-x)^2+(700-y)^2+h^2)=v*t

h:？ ms=sqrt((2900-x)^2+(900-y)^2+h^2)=v*t

d:？ ms=sqrt(( 1400-s)^2+(2200-y)^2+h^2)=v*(t+9 1)

g:？ ms=sqrt((2500-x)^2+( 1900-y)^2+h^2)=v*(t-92)

c:？ ms=sqrt((800-x)^2+( 1600-y)^2+h^2)=v*(t+ 185

Using matlab software to solve the above equations, we can get the epicenter location m, focal depth h and the time of earthquake occurrence.

Model solving

Write a program to solve the parameters in the equation with solve function. The plan is as follows:

'sqrt((2500-x)^2+( 1900-y)^2+h^2)=v*(t-92)','sqrt((800-x)^2+( 1600-y)^2+h^2)=v*(t+ 185)','x,y,h,v, t' s=solve('sqrt(( 1700-x)^2+(700-y)^2+h^2)=v*t','sqrt((2900-x)^2+(900-y)^2+h^2)=v*t','sqrt(( 1400-x)^2+(2200-y)^2+h^2)=v*(t+9 1)')

The solution results are as follows:

x=2200. 198 1？ kilometre (km)

y= 1398.8 1 14？ kilometre (km)

h=67.06 17？ kilometre (km)

v=3.0066？ Kilometers per second

t=284.9566？ second

From this result, it can be concluded that the epicenter was m (2200. 1 981.1398.814), the focal depth was 67.0 17km, and the earthquake occurred on April 9,1year.

Attached drawings:

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Can you solve these problems? The landlord gave too few points.