An earthquake is the shaking and breaking from moving rock underneath the ground. Earthquakes cause many different actions one of them being cracking. It depends on the size of an earthquake to determine what will happen on Earth; for example, if it's a small one, there will just be shaking that some can't even feel. Some types of earthquakes can even shift mountains if they are powerful enough. Plate movements cause them to happen, and the resulting stress underground creates the conditions for an earthquake.

Seismic waves are vibrations that travel through the Earth after an earthquake happens. The types of materials under us is the reason whether or not the waves move slowly or fast. Seismic waves carry energy that travels through the Earth's interior and across the surface. The different types of seismic waves are different movements that each wave makes. For example P waves can expand the ground.

The focus is something underground, and it is the main thing that triggers an earthquake. The thing that's located under the focus is the epicenter. Another type of wave is a surface wave, and it travels mostly through water and causes severe ground movements. The scale that tracks the amount of damage is the Modified Mercalli scale. The scale is the best thing and most accurate compared to everything else they tried to use.

A seismograph is an instrument that measures and records earthquakes' seismic waves.  Magnitude gets smaller the farther away it is from an earthquake happening.  Geologist moniter earthquakes by measuring the seismic waves that they produce. They use a scale called the Richter scale to measure the small magnitude of earthquakes. When you see a number that is quoted its always the earthquake's moment magnitude.

To assign a certain magnitude to an earthquake, geologists use seismographs. This data allows scientists to estimate how much energy an earthquake really releases. Each increase in magnitude is 32 times more energy. An earthquake with 2 magnitude is gonna be less damage than one with 6.

An earthquake with a magnitude of 8 is very rare to happen and could be very harmful. During the 1900s, there were 3 earthquakes that had a magnitude of 9 or more, and not a lot has happened since. Geologists use seismic waves to locate the epicenter. Locating the epicenter can't be very helpful in predicting what will happen in the future.

P waves travel the fastest out of the three, followed by S, and last are surface waves. From looking at the P waves, you can read the graph to find the distance of the seismograph to the epicenter. When you find the distance, you can draw 3 circles to find the epicenter. Stress is a force that acts on a rock to change its shape or volume. Stress can cause rocks to do many things to earth.

Tension, compression, and shearing have all worked to shape the whole world. Tension is the stress that pulls on the crust and thins the rock in two opposite directions. The different stresses all do different things to the ground to create or break things. Rocks are very hard and stiff, and the movement of the plates can bend or fold them. The movements could be beneficial for some areas and harmful for others.

When there is enough stress that builds up, it can create faults in the rocks. Normal faults: the fault cuts through a rock at an angle, so one block of rock lies under the other.  The block of rock that sits over the fault is called a hanging wall. The rock that falls under the fault is called a footwall. When there is movement along a normal fault, the hanging wall slips under.