Earthquakes Sudden shaking and vibration of the ground caused by movement of the earth along a fault

Earthquakes occur due to the elastic rebound theory

When movement is initiated along a fault seismic waves radiate outward from the focus Which are recorded using seismographs

There are three types of seismic waves P waves – Called primary waves, these are the fastest traveling waves S waves – Called secondary waves arrive next, and can not travel through liquid Surface waves – Are the slowest of the three and only travel along the surface

P waves are analogous to sound waves in air (except P waves are 14 times faster), they are compressional waves S waves are types of shear waves Surface waves are similar to water waves

An earthquake epicenter is located using the time interval between the arrival of the fist P and S wave The time interval between them depends on how far they have traveled from the focus. The longer the time interval the further they have traveled Readings from three seismograph stations are required to pinpoint the epicenter

The size of an earthquakes is measured by assigning a Richter magnitude, which depends on the amplitude of ground movement

Earthquakes are highly destructive and are often responsible for loss of life

When an earthquake occurs offshore, a tsunami may be generated When an earthquake occurs offshore, a tsunami may be generated. These travel ~800 km/hr and can be higher than 20 meters when they hit land

Earthquakes can not be accurately predicted by humans To mitigate damage should enforce building codes and encourage public education