Earthquakes and tsunamis Flashcards
What is an aftershock
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock.
What is an earthquake?
a sudden violent shaking of the ground, typically causing great destruction, as a result of movements within the earth’s crust or volcanic action.
What is an Epicentre?
the point on the earth’s surface vertically above the focus of an earthquake.
What is the Elastic Rebound Theory?
an explanation for how energy is spread during earthquakes. As rocks on opposite sides of a fault are subjected to force and shift, they accumulate energy and slowly deform until their internal strength is exceeded.
What is a faultline?
line determined by the intersection of a geological fault and the earth’s surface
What is a focus?
The location where the earthquake begins (underground). The ground ruptures at this spot, then seismic waves radiate outward in all directions.
What is a magnitude?
a number that characterizes the relative size of an earthquake.
What is a mega thrust?
A sudden slip along a fault between a subducting and an overriding plate, resulting in a major earthquake.
What is the Mercalli Scale?
a twelve-point scale for expressing the local intensity of an earthquake, ranging from I (virtually imperceptible) to XII (total destruction).
What is a minor shock?
an earthquake that occurs before a larger seismic event (the mainshock) and is related to it in both time and space.
What is the Richter Scale?
A logarithmic scale used to express the amount of energy released by an earthquake. Its values typically fall between 0 and 9
What is a seismic wave?
a wave of energy that is generated by an earthquake or other earth vibration and that travels within the earth or along its surface.
What is a seismograph?
an instrument that measures and records details of earthquakes, such as force and duration.
What is a tsunami?
giant waves caused by earthquakes or volcanic eruptions under the sea.
2) Why do Earthquakes happen?
Firstly, they can be linked to explosive volcanic eruptions; they are in fact very common in areas of volcanic activity where they either proceed or accompany eruptions.
Secondly, they can be triggered by Tectonic activity associated with plate margins and faults. The majority of earthquakes world wide are of this type.
What is the origin of an earthquake?
The origin of the earthquake the focus.
Since this is often deep below the surface and difficult to map, the location of the earthquake is often referred to as the point on the Earth surface directly above the focus. This point is called the epicentre.
What determines the extent of the damage caused?
The strength, or magnitude, of the shockwaves determines the extent of the damage caused.
What two main scales exist for defining the strength?
Two main scales exist for defining the strength, the Mercalli Scale and the Richter Scale.
What is meant by: ‘Earthquakes are three dimensional events’?
the waves move outwards from the focus, but can travel in both the horizontal and vertical plains.
What are tectonic earthquakes?
Tectonic earthquakes are triggered when the crust becomes subjected to strain, and eventually moves.
The theory of plate tectonics explains how the crust of the Earth is made of several plates, large areas of crust which float on the Mantle.
Since these plates are free to slowly move, they can either drift towards each other, away from each other or slide past each other. Many of the earthquakes which we feel are located in the areas where plates collide or try to slide past each other.
What does the theory of plate techniques explain?
The theory of plate tectonics explains how the crust of the Earth is made of several plateslarge areas of crust which float on the Mantle.
Since these plates are free to slowly move, they can either drift towards each other, away from each other or slide past each other. Many of the earthquakes which we feel are located in the areas where plates collide or try to slide past each other.
Which theory explains the process of these earthquakes?
The process which explains these earthquakes, known as Elastic Rebound Theory
