ABSTRACT
Earthquakes are naturally occurring broad-banded vibratory ground motions that are due to a number of causes, including tectonic ground motions, volcanism, landslides, rockbursts, and manmade 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 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. The seismic waves generated by the rupture propagate long after the movement on the fault has stopped, however, spanning the globe in about 20 min. Typically, earthquake ground motions are powerful enough to cause damage only in the near field (i.e., within a few tens of kilometers from the causative fault) — in a few instances, long-period motions have caused
Steven Kramer
Charles Scawthorn
significant 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 km from Mexico City.
