There were about 2,000 bridges in the epicentral region of the Northridge quake.
As in the 1989 Loma Prieta earthquake, the implementation of hinge and joint restrainers is credited with preventing the collapse of many of the bridges in the epicentral region.
The literature provides a number of empirical relationships that model the intensity decay in varied regions of the world as a function of epicentral or hypocentral distance.
Mathematically, the attenuation of intensity is written as the difference between epicentral and site intensity.
The most simple energy attenuation model for spherically expanding waves is an inverse relationship based on the square of the epicentral
In the epicentral
region, team geoscientists mapped portions of the 80 kilometer surface rupture of the earthquake-generating reverse fault, and investigated sites experiencing vertical uplifts of up to 8 meters, numerous landslides (several with displacements of up to 100 meters), and other spectacular ground failures.
Geological Survey (USGS) installed a simple warning system that detected aftershocks in the epicentral
region and radioed a warning to Oakland, providing 12 to 20 seconds of warning for people working on the collapsed 1-880 highway overpass.
In the epicentral
region, the earthquake generated a fault rupture of 110 kilometers and ground shaking intensities of VIII to X on the Modified Mercalli Intensity (MMI) scale.
These measures may have an impact provided they are implemented immediately," Episkopou, the CEO of Epicentral
The local magnitude of some shallow earthquakes was calculated using shocks with epicentral
distances ranging between 10km and 300km as well as the magnitudes of some deep earthquakes with hypocentral distances ranging between 100km and 600km.
Comparing the two epicentral
regions, Ellsworth says, "instead of 125,000 living in the immediate area where the ground shaking was hardest, there will be 1.
It took a full 25 seconds for the strongest seismic waves from the Loma Prieta earthquake last October to reach San Francisco and Oakland, roughly 90 kilometers from the epicentral