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Transcript of Earthquakes
Earthquakes are caused by disturbances in the earth's crust. These disturbances are caused most often in strike-slip faults, when two plates are scraping past each other, their rocks catch and tension begins to build up. When the tension is released, the plates slip past each other, causing an earthquake.The focal point of the earthquake is where the earthquake happened, and the epicenter is where on the earth the earthquake will be felt. The focal depth is the distance from the focal point to the epicenter, and determines the magnitude of the earthquake. An earhquake with a deeper focal point, or a greater focal depth, will produce and earthquake with a lower magnitude, while an earthquake with a smaller focal depth will produce an earthquake with a greater magnitude.
P and S Waves: What are they?
Where Do Earthquakes occur?
Earthquakes occur at plate boundaries and faults. There are 3 different types of faults: strike-slip, normal and reverse. There are also three types of boundaries: convergent, divergent, and transform.The most common plate boundary that causes earthquakes is a transform boundary, where two plates are sliding past each other.
What are the Effects of Earthquakes?
Earthquakes can be devastating or they can not make a difference. Earthquakes with magnitudes of about 8.0 or higher have the power to collapse buildings or flip over cars. In Places like California have earthquakes daily but not all of them are felt.
How and Why Do Earthquakes Occur?
P and S waves, or primary and secondary waves, are waves that are emitted from the focal point of an earthquake. Primary waves can travel through solid and liquid material, and travel with a slinky-like motion. Secondary waves can travel through solid material, and have a constant motion.
How are Earthquakes Caused and Why do They Occur?
Two tectonic plates are slowly moving past each other at a transform boundary.
They catch on each other, since their surfaces are not even, and the tension builds between them.
The plates catch on each other, since they are not even, and as the stress builds, they snap in the direction that they were originally traveling. This causes an earthquake.
Opposite forces are pulling two tectonic plates apart along a divergent boundary.
The compression causes one or both plates to fracture, creating a reverse fault.
In this type of fault, the hanging wall increases in elevation or stays the same, and the foot wall decreases in elevation.
Hatillo, Puerto Rico
M6.4 - 57km N
M5.1 - 24km NNW
M6.5 - 33km W
When the two plates snap and slide past each other, one or both of the plates breaks due to the stress being put on it (them), and begins to slide, similar to the transform boundary.
The tension being caused by the divergent boundary causes one or both plates to fracture.
This fracture is a normal fault. In this fault, the hanging wall decreases in elevation, and the foot wall increases in elevation or stays at the same elevation.
Two tectonic plates are at a convergent boundary that is shared between them.
Earthquake Vocab Words
Focal Point-the location within the earth's crust at which the earthquake occurred.
Epicenter-the location on the surface of the earth's crust where the earthquake would relatively be located
Focal Depth-the distance between the epicenter and the focal point. Earthquakes with greater focal depth will have a lower magnitude, while earthquakes with a lower focal depth will have a higher magnitude.
How Are the Magnitudes of Earthquakes Measured?
Earthquakes are detected using seismographs. Seismographs can detect even the slightest movements in the earth's crust, which is marked by a series of markings. These markings are then translated into magnitude, which is measured by the Richter scale.