ABSTRACT
Earthquakes are naturally occurring broad-banded vibratory ground motions, due to a number of causes, including tectonic ground motions, volcanism, landslides, rockbursts, and man-made explosions, the most important of which are caused by the fracture and sliding of rock along tectonic faults within the earth’s crust. For most earthquakes, shaking and/or ground failure are the dominant and most widespread agents of damage. Shaking near the actual earthquake rupture lasts only during the time when the fault ruptures, a process that takes seconds or at most a few minutes. e seismic waves generated by the rupture propagate long aer the movement on the fault has stopped; however, spanning the globe in about 20 minutes. Typically earthquake ground motions are powerful enough to cause damage only in the near eld (i.e., within a few tens of kilometers from the causative fault)—in a few instances, longperiod motions have caused signicant damage at great distances, to selected lightly damped structures, such as in the 1985 Mexico City earthquake, where numerous collapses of mid-and high-rise buildings were due to a Magnitude 8.1 earthquake occurring at a distance of approximately 400 kilometers from Mexico City.
