how can you determine the focus of an earthquake?

Question

geology

Answer 1

It is done with simple physics.
Earthquake stations record the earthquake and the time it was detected, geologists draw a radius from each station and where those radii meet is the center of the earthquake.

There are many earthquake monitors in areas that are prone to them. Since the general location of the earthquake is known and the time of the event is known then you check the readings of the other sensor stations. Since the geology in the area is known the scientists know how long it takes to feel an earthquake movement through the ground. The earthquake monitors also track the time when the event is recorded so you use Newton's formulas to calculate the distance.

While an earthquake can shift a plane of rock, it still starts at a specific and single point. This point is where the stresses on the rock, at that point, reach the breaking point for that rock.

To plot the exact location of the earthquake you use the distance formula to find the possible radius. That radius is the measurement that it would take for an earthquake to be detected. They will pretend that the earthquake happened at the monitor station and then see the distance it's shock waves could have traveled during the time it took to actually feel the earthquake at that station. This creates a circle of an exact radius. The scientists will draw this radius around the monitor station. Draw several radius around several monitor stations and the epicenter (earthquake’s origin) is where the circles intersect.

Finding how far down the earthquake happened is more difficult, but the principle is the same. The geologists draw a radius perpendicular to the surface of the earth and where the radii meet is the location of the earthquake's source.

The hard part is that a wave will travel at different speeds through different material so if you don't know what material is underground and where it is then your calculations will be off. Geologists use ground core samples to determine what type of rock is present, the depth at which it is present, and where its edges are so they can make these calculations.

If the exact time of the earthquake is not known then the geologists uses an offset factor from the station that first detected it to find the epicenter.

Nuclear weapons and other huge explosions generate waves like an earthquake would so this same system can be used to determine where a nuclear explosion took place.

Answer 2

With multiple seismographs. It is called triangulation.

Answer 3

Wave patterns and triangulation?