What kind of boundary causes earthquakes

Seismometers are used to record the seismic waves produced by earthquakes. Relative arrival times of these waves is used to determine earthquake location. The extent of damage an earthquake causes depends not only on the magnitude of the earthquake, but also on local geology and on building techniques.

What causes earthquakes? Discovering Geology — Earthquakes. The structure of the Earth Seismic waves from large earthquakes pass throughout the Earth. The crust This brittle, outermost layer varies in thickness from about 25 to 70 km under continents and from about 5 to 10 km under the oceans. The mantle Below the crust lies the dense mantle, extending to a depth of km. Plate tectonic map of the world showing direction of movement. Divergent boundary Plates can move apart at a boundary.

A divergent, or constructive, plate boundary, where new material is produced at the surface. The Mid-Atlantic Ridge is a good example of a constructive plate boundary. You can see normal faulting at the surface where the Mid-Atlantic Ridge crosses Iceland. Convergent boundary Continental collisions result in the creation of mountains and fold belts as the rocks are forced upwards. A convergent, or destructive, boundary showing subduction of an oceanic plate under a continental plate.

A convergent boundary showing mountain formation where one continental plate crumples up and over another continental plate. They are associated with mountain ranges, such as the Himalayas or the Alps. Transform boundary Plates can move past each other in the same plane at a boundary. A transform boundary, where two plates slide past each other in the same plane.

Strike-slip faults occur at transform boundaries: for example, a system of strike-slip faults makes up the transform boundary of the San Andreas fault. Normal fault In a normal fault, the block above the fault moves down relative to the block below the fault. Reverse fault In a reverse fault, the block above the fault moves up relative to the block below the fault. Strike-slip fault In a strike-slip fault, the movement of blocks along a fault is horizontal.

You may also be interested in. Discovering Geology Discovering Geology introduces a range of geoscience topics to school-age students and learners of all ages. Earth hazards The Earth beneath our feet is constantly shifting and moving, and violently with catastrophic and immediate results. Earthquakes Earthquakes are among the most deadly natural hazards. Where do earthquakes occur? There is a very significant concentration of both shallow and deep greater than 70 km earthquakes in the northwestern part of Figure This is northern Afghanistan, and at depths of more than 70 km, many of these earthquakes are within the mantle as opposed to the crust.

It is interpreted that these deep earthquakes are caused by northwestward subduction of part of the India Plate beneath the Asia Plate in this area. This map shows the incidence and magnitude of earthquakes in British Columbia over a one-month period in March and April The string of small earthquakes adjacent to Haida Gwaii H.

How might these earthquakes be related to that one? Most of the earthquakes around Vancouver Island V. What is their likely origin? Some of the earthquakes in B. Which of the earthquakes here could fall into this category? Skip to content Chapter 11 Earthquakes. Exercise As the plates collide, the oceanic plate is forced beneath the continental plate. This is known as subduction. This happens because the oceanic plate is denser heavier than the continental plate.

When the plate sinks into the mantle it melts to form magma. The pressure of the magma builds up beneath the Earth's surface. The magma escapes through weaknesses in the rock and rises up through a composite volcano. Map of the Tectonic Plates - 67k Earthquakes can also occur within plates, although plate-boundary earthquakes are much more common. Less than 10 percent of all earthquakes occur within plate interiors. As plates continue to move and plate boundaries change over geologic time, weakened boundary regions become part of the interiors of the plates.

These zones of weakness within the continents can cause earthquakes in response to stresses that originate at the edges of the plate or in the deeper crust.

The New Madrid earthquakes of and the Charleston earthquake occurred within the North American plate.