Acceleration: The change in speed per unit time (e.g., my car accelerates from 0 to 60 km/hr in 5 seconds, or 12km/hr in 1 second, or 12,000 m/hr in one second, or 3 1/3 m/s/s). Earths gravity has an acceleration of 9.8m/s/s.

Accelerometer: An instrument that measures the change in speed per unit time.

Active Protection System (APS): An accelerometer system internal to ThinkPad laptops that helps protect the internal hard drive from damage when shocked or dropped.

Aftershock: Any earthquake that occurs after a large earthquake (or mainshock) in the same vicinity. Usually after large earthquakes there are many aftershocks, which reduce in number gradually with time. Aftershocks can be dangerous because they can shake already damaged buildings. Aftershocks are one of the many reasons you should never enter a damaged building after an earthquake.

Bit: A binary digit of either 0 or 1.

Body Waves: A wave that travels through the interior of the Earth (a opposed to along the surface).

BOINC: Abbreviation for the Berkeley Open Infrastructure for Network Computing. This open source code provides an architecture that enables and standardizes distributed computing.

Byte: A unit of measure of information storage. One byte is composed of eight bits.

Central Processing Unit: (CPU) A logic machine that executes computer programs.

Core: (Computer): A linked logic chip making up one component of a Central Processing Unit.

CPU: Abbreviation of Central Processing Unit.

Dip: The angle from horizontal that a fault tilts into the Earth.

Distributed Computing: A computing architecture that divides portions of a calculation among many distributed computers. Parallel processing differs in that it runs programs on many processors of the same computer, not separate computers.

Earth: The third planet from the Sun. Earth is the largest of the terrestrial planet in the solar system.

Earthquake: the sudden release of a large amount of energy that is built up in the EarthÕs crust, which often takes the form as a shift or rupture along a fault.

Epicenter: The point at the EarthÕs surface directly above an earthquake (the map location of an earthquake).

Fault: A planar fracture or zone of fractures between two blocks that shows evidence of prior displacement.

Fracture: A breakage surface separating two sides of joint or fault.

Focal Mechanism: The direction and sense of slip on a fault plane for an earthquake. Focal mechanisms are often drawn on maps with a "beachball"-like symbol: . The black areas denote compression; the white areas denote dilation.

Foreshock: Any earthquake that is shortly followed by a larger earthquake in the same location.

Geology: The scientific study of the EarthÕs formation, evolution, and current composition.

Hypocenter: The location of an earthquake, including latitude, longitude, and depth.

Igneous: Describing a rock that formed by cooling from a magma.

Intensity: The measure of the effects of shaking at a place and time (See Mercalli Intensity Scale).

Internet: A global system of interconnected computer networks that exchanges data using the standardized Internet protocol (TCP/IP).

Isoseismal map: A map showing the distribution of intensity across a region for a given earthquake.

Joint: A breakage surface where no displacement has occurred from on side to the other.

Local Area Network: (LAN) A computer network covering a small geographic area (as opposing WAN).

Love Waves: Seismic waves that travel along the surface of the Earth causing horizontal ground motions.

Magnitude: General: The strength or scale of a measure. Seismology: A measure of the energy released in an Earthquake. Often measured on the Richter Magnitude Scale, Modified Mercalli Scale, or Moment Magnitude Scale.

Mainshock: The largest earthquake in any series of earthquakes.

MEMS: Abbreviation for Microelectromechanical systems. QCN uses MEMS accelerometers.

Mercalli Intensity Scale: A scale used to measure the intensity of an Earthquake by quantifying the observations of damage to man-made structures. Intensities range from I (instrumental) to XII (Catastrophic). Today a Modified Mercalli Scale is more commonly used.

Meter: A unit of measure in length.

Microelectromechanical systems: (MEMS) Mechanical machines with components on the scale of 1-100 micrometers, and with total dimensions on the order of 20 micrometers to a millimeter. The Quake-Catcher Network uses MEMS accelerometers.

Micrometer: One millionth of a meter.

Millimeter: One thousandth of a meter.

Metamorphic: Describing a rock that changed as a result of pressure, strain, or heat.

Moment Magnitude Scale: (Mw) A measure of seismic energy released from an earthquake that is more accurate than the Richter Magnitude Scale. An increase in one Mw corresponds to a 31.6 times increase in energy release. A Mw increase of two corresponds to a 1000 times increase in energy release.

Network: An interconnected group or system of computers.

Open Source: A software development methodology that provides accessibility to the source code.

Parallel Computing: A form of computation in which many calculations are carried out simultaneously over many processors on the same computer by dividing a large problem into many sub-sections.

P wave: (Primary Wave) A compressional seismic wave. A wave that compacts material in the direction of propagation.

QCN: Abbreviation for Quake-Catcher Network.

Quake: Short for earthquake.

Quake-Catcher Network: A distributed computing network aimed at recording earthquake motions measured on MEMS accelerometers.

RAM: Abbreviation or Random Access Memory.

Random Access Memory: A temporary data storage used for rapid data retrieval. Usually measured in megabytes or gigabytes.

Rayleigh Waves: Waves that travels along the surface of the Earth in a circular or elliptical motion. Similar to the motion of ripples on the surface of water.

Richter Magnitude Scale: A local measure of seismic energy released in an Earthquake. A base-10 logarithmic scale obtained by calculating the maximum amplitude of a seismic record on a Wood-Anderson seismometer. A 5.0 magnitude is 10 times larger than a 4.0. A 3.3 is 10 times larger than a 3.2, and so on. Richter Magnitude Scale is out-dated.

Rock: A naturally occurring solid mass of minerals. Rocks take three forms; igneous, sedimentary, and metamorphic.

Sedimentary: Describing a rock that formed through deposition of previously formed rocks.

Seismology: the scientific study of earthquakes and the propagation of vibrations through the Earth.

Seismic: Pertaining to the study of earthquakes and the propagation of waves through the Earth.

Seismic Waves: Vibrations that propagate through the Earth, usually resulting from earthquakes. There are several categories of seismic waves: body waves, and shear waves. There are two types of body waves: P waves, S waves. There are two general types of surface waves: Rayleigh waves & Love waves.

Seismometer: An instrument that measures and records motions of the ground, including vibrations and displacements from earthquakes. Seismometers usually digitally record the measurements.

Seismograph: Is an instrument that measures and draws the motions of the ground, including vibrations and displacements from earthquakes. Seismographs are generally older versions of seismometers.

Server: A computer dedicated to running applications that provide responses to other computers when contacted by another computer.

Solar System: All celestial bodies gravitationally bound to the Sun.

Significance: A measure of the current shaking to the noise in the last minute. Significance is useful for detecting strong new motions.

Star: A massive luminous body with sufficient mass and heat to undergo thermonuclear fusion. Stars give off large amounts of energy in the form of light.

Strike: The horizontal direction marking the orientation of a fault.

Strike-Slip: Strike-slip faults are vertical (or nearly vertical) fractures where the blocks have mostly moved horizontally. If the block opposite an observer looking across the fault moves to the right, the slip style is termed right lateral; if the block moves to the left, the motion is termed left lateral (see image).

Strong-Motion Seismometer: A low-sensitivity sensor that has resolution to +/- 0.001 g (1 g is 9.8 m/s2). These sensors only record local or regional earthquake vibrations, and are much less expensive than high-gain instruments like broadband sensors. QCN sensors vary between +/- 0.001 g to 0.04 g.

Sudden-Motion Sensor (SMS): An accelerometer system internal to Apple laptops that helps protect the internal hard drive from damage when shocked or dropped.

Surface Waves: Waves that travel along the surface of the Earth (as opposed to through the interior).

Sun: The star at the center of the solar system.

TCP/IP: Standard Internet Protocol Suite: Transition Control Protocol and Internet Protocol. This is a standard protocol used to transmit information over local area networks and the Internet.

Teleseismic: An adjective meaning that an earthquake observation was made 100 km or more away from the epicenter.

Triangulation: The process of determining the location of a point (or earthquake) given angles between known points (seismometers) and the unknown point. If you close your eyes, your ears and brain can automatically triangulate where things are when they make noise Š seismic networks do the same thing.

USGS: Abbreviation for the United States Geological Survey.

United States Geological Survey: A scientific agency of the United States government that studies the landscape, natural resources, and natural hazards pertaining to the United States.

WAN: Abbreviation for Wide-Area Network.

Wide-Area Network: (WAN) A computer network covering a wide geographic area.