| transform boundaries | moderate and shallow earthquakes occur here |
| convergent boundaries | strong and deep earthquakes occur here |
| divergent boundaries | weak and shallow earthquakes occur here |
| P-waves | move back and forth; fastest; can travel through all material |
| S-waves | move like a snake; second to arrive; cannot go through liquid mass |
| surface waves | move ground up and down in circles; slowest; most destructive; feels like a roller coaster |
| elastic rebound | this causes earthquakes; the ground suddenly retains original shape |
| epicenter | the ground directly above where the earthquake occured |
| focus | the direct area of seismic activity |
| moho | seismic waves travel much faster upon reaching this area |
| shadow zone | area where no direct seismic waves can be detected |
| seismograph | an instrument that records seismic waves |
| seismogram | a recording of the shaking motion in earthquakes |
| seismic gap | a particular area along a seismic-active location where unusually few earthquakes have occured |
| gap hypothesis | the theory that areas where few earthquakes have occured are likely to experience aerious quakes in the future |
| seismology | the study of earthquakes |
| sunquakes | caused by solar flares; much stronger than our earthquakes |
| moonquakes | seismic waves last much longer than they do on Earth |
| marsquakes | some earthquakes, though seismographs often acted more like a wind gauge because of the wind |
| mass damper | a weight in the building roof that will counteract w/ building movement when activated |
| active tendon system | a weight in the building's base, similar to the mass damper |
| base isolators | these are in the base of the building; made of rubber w/ a lead core; absorb seismic waves to avert their travel through the building |
| cross braces | steel braces in between the floors that support the building during earthquakes |
| body waves | seismic waves that travel through the Earth's interior |
| surface waves | seismic waves that travel along the Earth's surface |
| time-distance graph | compares the distance between P waves and S waves |
| S-P time method | the common method used to find an earthquake's epicenter |
| Ritcher scale | tool used for measuring earthquake strength |
| 31.7 | the number of times greater energy an earthquake w/ one # greater magnitude releases than the lower |
| earthquake hazard | measures how vulnerable an area is to future earthquakes |