The Physics of Earthquakes

A Physics 212 Project


Plate Tectonics

Earthquakes are a product of different forces acting on the Earth’s plates, which is effectively what causes the plates to shift. The big question is what is causing all these forces that result in an earthquake. Plate Tectonics describes, in general, describes where these forces come from.

 

Previously there was a theory that concluded that the plate tectonics are caused by a convection process in which the cooler molten rock in the lithosphere to sink to the bottom, causing a convection process that drives the movement of the plates. Another theory of plate tectonics is a process called slab pull. This occurs because the newly created parts of the lithosphere rise up due to their density. After aging and cooling down, these lithosphere chunks sink back down. This process of constantly rising is what is believed to cause the movement of the plates. It’s important to note that this is just a theory and we are not entirely sure if this process causes the plates to move.

 

According to an article in Physics Today the plate motion is described as:

“The relative plate motion determined from these data is about 2–7 cm/year, which translates into a strain accumulation rate of approximately 3 × 10−7/y along plate boundaries. The strain also accumulates in plate interiors, but at a much slower rate of about 3 × 10−8/y or less. Since the rigidity of the crustal rocks is about 3 × 104 MPa, this corresponds to a stress accumulation rate of 10−2 MPa/y along plate boundaries, an order of magnitude less in plate interiors.”