During the last week alone, the U.S. Geological Survey recorded 317 earthquakes in the state.
Most were relatively imperceptible, magnitude 4.0 or less -- the geologic expression of a perennially restless landscape that shapes the California character.
The Northridge quake was the first since 1933 to strike directly under an urban area of the United States. It occurred on a previously unsuspected blind thrust fault -- delivering a seismic uppercut to every building in the region -- and produced the strongest ground motions ever recorded in an urban setting in North America.
Almost half of the damage in the 1994 Northridge disaster involved wooden-frame buildings. Twenty-four of the 25 people who died in buildings during the quake were killed inside wood-frame structures, the Buffalo engineers said.
In the 6.9 Hanshin earthquake in Kobe, Japan, the following year, 6,400 people died -- almost all of them in wooden houses -- and economic losses were estimated at $200 billion.
As global urban sprawl spills into active seismic zones, the consequences of even a moderately severe earthquake have escalated dramatically.
"Northridge was a wake-up call," Filiatrault said.
"Suddenly, the engineering community is more interested in the performance of wood-frame buildings. "
lee.hotz@latimes.com
