We often get the question, “What should I know about earthquakes?” We suggest becoming familiar with the following:
What is an earthquake?
An earthquake is a sudden slip in a fault, caused when stresses in the earth’s outer layer push the sides of the fault together. The friction across the surface of the fault holds the rocks together temporarily, until enough stress builds up and the rocks suddenly slip.
What is a fault?
A fault is a thin zone of crushed rock separating blocks of the earth’s crust. When an earthquake strikes on one of these faults, the rock on one side of the fault slips with respect to the other. Some faults have not shown signs they exist, so we will not know where they are until they produce a large earthquake. This is another reason why we must be prepared!
What is an aftershock?
Earthquakes come in clusters; the largest quake in a cluster is a mainshock. An aftershock is an earthquake that usually occurs near a mainshock. An earthquake large enough to cause damage will produce several felt aftershocks within the first hour. The only official short-term predictions for an upcoming earthquake are foreshocks, which are earthquakes that occur right before the mainshock.
What is magnitude?
Magnitude is the most common way of describing an earthquake’s size, measuring the amount of energy released by an earthquake, as indicated on the Richter scale.
What is the Richter scale?
In 1935, American seismologist Charles Richter developed a scale that measures the magnitude of seismic waves. The Richter scale displays the total amount of energy released by an earthquake. Its values typically fall between 0 and 9, with each increase of 1 representing a 10-fold increase in energy.
What does “seismic” mean?
Seismology is the study of earthquakes and of other earth movements, such as those caused by humans. The seismic focus or seismic origin is the point of origin of the earthquake within the crust. The resulting shocks are waves of energy that travel through earth and along its surface, called seismic waves, which may be recorded and measured by a seismograph.
What are the epicenter and hypocenter?
The epicenter of an earthquake is the point on the surface of the ground directly above where the earthquake begins. The hypocenter of an earthquake is the point below the earth’s surface where the rupture begins.
The information here is available in partnership between the American Red Cross of Greater Los Angeles and the Earthquake Country Alliance. The American Red Cross of Greater Los Angeles is a member of the Southern California Earthquake Country Alliance.
Tags: CDE, Community Disaster Education, disaster, earthquake, prepare, preparedness
