Last week California geology officials released an updated seismic activity map that includes more than 50 surface fault lines discovered over the last 20 years.

The last seismic map update was 16 years ago. The new maps are much more detailed, and have interactive digital versions that are linked to Google maps.

Since 1998, real estate agents and sellers are required to inform potential buyers if a property is within one of these active fault areas, according to the Natural Hazards Disclosure Act.

The Geologic Survey has also made detailed maps available for individual communities or property owners.

From an AP story on the new maps:

The more than 50 additional surface fault lines, among an estimated 15,000 faults in the state, are new to the statewide seismic activity map but have been mapped previously.

Some of these faults announced themselves long ago, including the system which unleashed the magnitude-7.1 Hector mine quake that rocked Southern California and neighboring states in 1999 but didn’t cause much damage because of the remoteness of its epicenter in the Mojave Desert.

Those faults were mapped within a few weeks but hadn’t been incorporated into California’s statewide map until now, he said.

The map, however, does not display faults like those that caused the 1994 Northridge quake that caused billions of dollars of destruction and dozens of deaths in metropolitan Los Angeles, or the 1983 quake that wrecked most of downtown Coalinga and damaged hundreds of homes in the Central Valley city.

Such faults aren’t on the map because they are “blind thrusts” with no surface rupture to depict.



1 Comment

Leave a Reply