EQ Quiz

• Amplitude


  Maximum deviation from mean of centerline of a wave
• Aftershock


  One of a series of smaller quakes following the main shock of the earthquake.
• Core


  The central part of the earth below a depth of 2,900 kilometers. It is thought to be composed of iron and nickel and to be molten on the outside with a central solid inner core.
• Crust


  The lithosphere, the outer 80 kilometers of the earth’s surface made up of crustal rocks, sediment and basalt. The general composition is silicon-aluminum-iron.
• Deflection


  The horizontal or vertical displacement of a member due to the application of external force.
• Deformation


  Permanent distortion due to seismic forces.
• Depth of Focus


  the depth of the focus or hypocenter beneath the earth’s surface commonly classes Earthquakes: Shallow (0- 70 kilometers), intermediate (70-300 kilometers), and deep (300-700 kilometers).
• Displacement 


  Lateral movement of the structure caused by lateral force.
• Drift


  Horizontal displacement of basic building elements due to lateral earthquake forces.
• Epicenter


  The point of the earth’s surface directly above the focus or hypocenter of an earthquake
• Fault 


  A fracture plane in the earth’s crust across which relative displacement has occurred. (Location of slippage between the earth’s plates).
• Normal Fault


  A fault under tension where the overlying block moves down the dip or slope of the fault plane.
• Strike-Slip Fault (or lateral slip) 


  A fault whose relative displacement is purely horizontal.
• Thrust (Reverse) Fault


  A fault under compression where the overlying block moves up the dip or slope of the fault plane.
• Oblique-Slip Fault 


  A combination of normal and slip or thrust and slip faults whose movement is diagonal along the dip of the fault plane.
• Faulting 


  The movement which produces relative displacement of adjacent rock masses along a fracture.
• Fault Zones


  The zone surrounding a major fault, consisting of numerous interlacing small faults.
• Focal Depth 


  Depth of the earthquake (or hypocenter) below the ground surface.
• Focus (of an earthquake) or Hypocenter 


  The point at which the rupture occurs; (It marks the origin of the kinetic waves of an earthquake).
• Hypocenter or Focus


  The point below the epicenter at which an earthquake actually begins; the focus.
• Frequency 


  The number of wave peaks or cycles per second. The inverse of Period.
• Intensity 


  A subjective measure of the force of an earthquake at a particular place as determined by its effects on persons, structures and earth materials. Intensity is a measure of energy.
• MM (or Modified Mercalli) scale


  The principal scale used in the United States today. It is based on observation of the effects of the earthquake MM-I thru MM-XII (MM-I = not felt, MM-XII = damage nearly total).
• Landslide 


  Earthquake triggering land disturbance on a hillside where one land mass slides over the other.
• Liquefaction 


  Transformation of a granular material (soil) from a solid state into a liquefied state as a consequence of increased porewater pressure induced by vibration. Normally solid soil suddenly changes to liquid state (usually sand or granular soil in proximity to water) due to vibration.
• Magnitude 


  A measure of earthquake size which describes the amount of energy released.
• Moment Magnitude 


  is the measure of total energy released by an earthquake. It is based on the area of the fault that ruptured in the quake. It is calculated in part by multiplying the area of the fault’s rupture surface by the distance the earth moves along the fault.
• Richter Magnitude Scale


  A measure of earthquake size which describes the amount of energy released. The measure is determined by taking the common logarithm (base 10) of the largest ground motion observed during the arrival of a P-wave or seismic surface wave and applying a standard correction for distance to the epicenter. (Each unit of the Richter Scale represents a 10 times increase in wave amplitude. This corresponds to approx. 31 times increase of energy discharge for each unit on the Richter Scale.)
• Seismograph


  A device, which writes or tapes a permanent, continuous record of earth motion, a seismogram.
• Tsunami


  A sea wave produced by large area displacements of the ocean bottom, the result of earthquakes or volcanic activity. (Tidal wave caused by ground motion.)
• Body Wave 


  Seismic waves within the earth.
• Longitudinal Wave 


  Pure compressional wave with volume changes.
• Love Wave 


  Surface waves that produce a sideways motion.
• Rayleigh Wave


  Forward and elliptical vertical seismic surface waves.
• P-Wave 


  A type of body wave; the fastest waves traveling away from a seismic event through the earth's crust, and consisting of a train of compressions and dilatations of the material (push and pull).
• S-Wave 


  Secondary wave, or Shear wave, sometimes called an elastic S-wave, produced essentially by the shearing or tearing motions of earthquakes at right angles to the direction of wave propagation.
• Surface Wave 


  Also known as L-waves; a seismic wave that follows the earth's surface only, with a speed less than that of S-waves.
• Wave Length


  The distance between successive similar points on two wave cycles.
• Richter magnitude scale


  most common standard of measurement of earthquakes.
• Charles F. Richter


  Invented Richter magnitude scale.