Q4 EARTHQUAKES

Seismology

• comes from the Greek word “seismos.”

Seismology

• study of earthquakes and seismic waves.

Seismic Waves

• vibrations generated sudden energy releases from earthquakes.

Body Waves

• travel through the Earth’s interior.

Body Waves

• a type of wave that has higher frequency than surface waves.

Surface Waves

• travel through the exterior of the Earth’s crust.

P-Waves

• also known as primary waves.

P-Waves

• compressional waves.

S-Waves

• also known as secondary waves.

S-Waves

• these waves happen after the first change of ground.

S-Waves

• slower, but solid waves.

Love Waves

• made by Augustus Edward Hough Love in 1911.

Love Waves

• cause the worst damage to buildings and roads during an earthquake.

Love Waves

• have long wavelengths and travel on the ground horizontally, causing them to twist from side to side—they also have the greatest amplitude.

Rayleigh Waves

• predicted by John William Strutt & 3rd Baron Rayleigh.

Rayleigh Waves

• slowest seismic waves.

Seismograph

• a device that records the waves.

Seismometer

• detects the seismic waves.

Earthquake

• sudden violent shaking of the ground, due to pressure released by the movement.

Earthquake

• within Earth’s crust or volcanic action.

Earthquake

• by sudden energy release.

Earthquake

• associated with the faulting of rocks.

Aftershocks

• a sequence of earthquakes that happen after a larger mainshock on a fault.

Aftershocks

• occur near the fault zone where the mainshock rupture occurred and are part of the "readjustment process” after the main slip on the fault.

Tectonic Plates

• also known as “Lithospheric Plates.”

Tectonic Plates

• massive irregularly slab of solid rocks.

Plate Boundaries

• edges of tectonic plates, composed of many faults.

Hypocenter

• where the earthquakes’ rupture starts.

Epicenter

• the point where an earthquake or an underground explosion originates.

Pacific Ring of Fire

• the haven of most volcanoes.

Faults

• known as fractures or discontinuity.

Slip

• motion & direction of the fault.

Dip

• angle of the fault.

Foreshocks

• mild tremor preceding the violent shaking.

Earthquakes

• stress increases along faults while they slip past each other.

Deformation

• result of stress, the change to the shape of the rock.

Plastic Deformation

• deforms like clay, involves no earthquakes.

Elastic Deformation

• like a rubber band, causes earthquakes.

Fault

• break in Earth’s crust and where earthquakes occur.

Convergent Boundaries

• are also reverse faults.

Divergent Boundaries

• are also normal faults.

Transform Boundaries

• are also strike-slip faults.

Convergent Boundaries

• powerful and frequent earthquakes, occurring as tectonic plates collide and one slides beneath the other.

Divergent Boundaries

• where plates pull apart and are common but generally smaller and shallower than those at convergent zones, caused by tension as magma rises and new crust forms.

Transform Boundaries

• cause frequent, often powerful, shallow earthquakes as tectonic plates slide horizontally past each other, building stress that's suddenly released, creating faults.

Earthquake Zones

• where a large number of faults are.

Magnitude

• measures size & strength of an earthquake.

Magnitude

• measured using Richter Scale, named after Charles Richter (American Seismologist) in 1935.

Reverse Fault

• when a rock mass in the crust is pushed up relative to the other rock mass due to compressional force.

Normal Fault

• when a tensional force acts on rocks, one rock mass moves downward relative to the other forming a normal fault.

Normal Fault

• generally occurs in a place that is relatively high such as a plateau.

Transform Fault

• produced when a rock mass on one side of a fault slides past the other. the most famous of this type of fault is the Andreas Fault from the USA.

Active Faults

• in which all shallow earthquakes occur.

Active Faults

• active in plate boundaries where plates bump into or move away from each other.

Inactive Faults

• areas that have not displayed seismic activity for thousands of years.

Intensity

• measures the observed effects of an earthquake.

Intensity

• measured by the Mercalli Intensity (MMI) Scale, from Guiseppe Mercalli (Italian Seismologist) in 1902—this classifies earthquake effects into 12 grades.