Extreme Science: The San Andreas Fault
How California is predicting and preparing for the inevitable
Watch The Earth Open And Close During Japan’s 2011 Earthquake
Over 18,000 people were killed by a magnitude 9.0 earthquake and subsequent tsunami that struck Northeastern Japan on March 11, 2011. The earthquake lasted six minutes, and had over 250 aftershocks. A...
Quicksand
Quicksand is a colloid hydrogel consisting of fine granular material (such as sand or silt), clay, and water.Quicksand forms in saturated loose sand when the sand is suddenly agitated. When water in t...
Extreme Science: The San Andreas Fault
How California is predicting and preparing for the inevitable
Watch The Earth Open And Close During Japan’s 2011 Earthquake
Over 18,000 people were killed by a magnitude 9.0 earthquake and subsequent tsunami that struck Northeastern Japan on March 11, 2011. The earthquake lasted six minutes, and had over 250 aftershocks. A...
Hypocenter
The hypocenter (literally: 'below the center' from the Greek: ὑπόκεντρον) refers to the site of an earthquake or a nuclear explosion. In the former, it is a synonym of the focus; in the latter, of gro...
Aftershock
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated ...
Seismic wave
Seismic waves are waves of energy that travel through the Earth's layers, and are a result of an earthquake, explosion, or a volcano that gives out low-frequency acoustic energy. Many other natural an...
Blind thrust earthquake
A blind thrust earthquake occurs along a thrust fault that does not show signs on the Earth's surface, hence the designation "blind". Such faults, being invisible at the surface, have not been mapped ...
Tornillo event
A tornillo event is a low-frequency seismic event associated with volcanoes. The term, which means "screw" in Spanish, was coined in the mid-1990s at the Observatorio Vulcanológico y Sismológico de Pa...
S-wave
A type of elastic wave, the S-wave, secondary wave, or shear wave (sometimes called an elastic S-wave) is one of the two main types of elastic body waves, so named because they move through the body o...
Lake breakout
Lake breakout is a geological term that refers to the collapse of a (usually high-altitude) lake. High-altitude lakes tend to form in volcanic craters – where they are called crater lakes –...
Coal mine bump
A coal mine bump (also called a bump, a mine bump, or a mountain bump) is a seismic jolt occurring within a mine, often due to the explosive collapse of a wall or one or more support pillars, sometime...
Thrust fault
A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. The...
Fault mechanics
Fault mechanics is a field of study that investigates the behavior of geologic faults. Behind every good earthquake is some weak rock. Whether the rock remains weak becomes an important point in dete...
Aseismic creep
In geology, aseismic creep is measurable surface displacement along a fault in the absence of notable earthquakes. An example is along the Calaveras fault in Hollister, California. Streets crossing th...
Receiver function
A receiver function technique is a way to model the structure of the Earth by using the information from teleseismic earthquakes recorded at a three component seismograph.A teleseismic P-wave will gen...
Slow earthquake
A slow earthquake is a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake. First dete...
Mohorovičić discontinuity
The Mohorovičić discontinuity ([moxorôʋiːt͡ʃit͡ɕ]), usually referred to as the Moho, is the boundary between the Earth's crust and the mantle. Named after the pioneering Croatian seismologist Andrija ...
Epicenter
The epicenter, epicentre /ˈɛpɪsɛntər/ or epicentrum is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originate...
Love wave
In elastodynamics, Love waves, named after Augustus Edward Hough Love, are horizontally polarized surface waves. The Love wave is a result of the interference of many shear waves (S–waves) guided by ...
Sand geyser
A Sand Geyser or Sand Fountain is a geologic phenomena which occurs in association with earthquakes and other seismic events. In the geologic record, these are seen as clastic dikes.
Brittle–ductile transition zone
The brittle-ductile transition zone is the strongest part of the Earth's crust. For quartz and feldspar rich rocks in continental crust this occurs at an approximate depth of 13–18 km (roughly e...
Infrasound
Infrasound, sometimes referred to as low-frequency sound, is sound that is lower in frequency than 20 Hz (hertz) or cycles per second, the "normal" limit of human hearing. Hearing becomes gradual...
Peak ground acceleration
Peak ground acceleration (PGA) is a measure of earthquake acceleration on the ground and an important input parameter for earthquake engineering, also known as the design basis earthquake ground motio...
Thrust tectonics
Thrust tectonics or contractional tectonics is concerned with the structures formed, and the tectonic processes associated with, the shortening and thickening of the crust or lithosphere.
In areas...
Maximum magnitude
An important parameter in the calculation of seismic hazard, maximum magnitude (expressed as Moment magnitude scale) is also one of the more contentious. The choice of the value can greatly influence ...
Meizoseismal area
The meizoseismal area in an earthquake is the area of maximum damage. For example, in the Charleston, South Carolina, earthquake of 1886, the meizoseismal area was an area about twenty by thirty miles...
Induced seismicity
Induced seismicity refers to typically minor earthquakes and tremors that are caused by human activity that alters the stresses and strains on the Earth's crust. Most induced seismicity is of a low ma...