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Re: CHSRA may operate over "conventional" Metrolink trackage Palmdale to LA
Author: an AP reader
Date: 03-21-2011 - 14:26
There is a helpful interactive map of California earthquake faults here:
Cal Geo Survey 2010 Fault Map
If you zoom in around the Gorman/Lebec area, you'll see where the San Andreas fault (red line) slices east & west across I-5, then continues east along the escarpment where the Mojave Desert abuts the San Gabriel Mountains.
Gorman/Lebec seems to be the bulls-eye for several fault lines - the NE/SW trending North and South branches of the Garlock Fault (orange line) of the SA fault, as well as the Pine Zone Fault (green line) and the Frazier Mountain Thrust zone (purple line.)
Driving on I-5 thru that area, you'll see huge sedimentary mountain-sized blocks, once horizontal, tilted at various steep angles, due to earthquake activity over millions of years.
In just the past 200 years, there have been two significant earthquakes in that area: the 1857 Ft Tejon Earthquake (Magnitude 7.9) and the more recent 1952 Kern County Earthquake (Mag 7.5).
The epicenter of the 1857 shaker was actually in Chalome, near Parkfield, nearly 100 miles NW of Ft Tejon, yet it ruptured nearly 350 km with a slip of 4.5 meters and a vertical displacement of up to 9 meters in the Carrizo Plain area.
SECDC 1957 Ft Tejon quake
The 1952 Kern County EQ epicenter was much closer to the Grapevine - just 37 km south of Bakersfield. Several tunnels on the SP's Tehachapi route collapsed and rail lines shifted due to the quake.
1952 Kern County quake
IMO, the geological hazards for a HSR line over Tejon Pass, coupled with the political challenges of the National Forest lands and Tejon Ranch Company ownership, make it all but impossible to build the HSR in that area.
The Tehachapi route for the HS line is clearly the lesser of two evils.
Cal Geo Survey 2010 Fault Map
If you zoom in around the Gorman/Lebec area, you'll see where the San Andreas fault (red line) slices east & west across I-5, then continues east along the escarpment where the Mojave Desert abuts the San Gabriel Mountains.
Gorman/Lebec seems to be the bulls-eye for several fault lines - the NE/SW trending North and South branches of the Garlock Fault (orange line) of the SA fault, as well as the Pine Zone Fault (green line) and the Frazier Mountain Thrust zone (purple line.)
Driving on I-5 thru that area, you'll see huge sedimentary mountain-sized blocks, once horizontal, tilted at various steep angles, due to earthquake activity over millions of years.
In just the past 200 years, there have been two significant earthquakes in that area: the 1857 Ft Tejon Earthquake (Magnitude 7.9) and the more recent 1952 Kern County Earthquake (Mag 7.5).
The epicenter of the 1857 shaker was actually in Chalome, near Parkfield, nearly 100 miles NW of Ft Tejon, yet it ruptured nearly 350 km with a slip of 4.5 meters and a vertical displacement of up to 9 meters in the Carrizo Plain area.
SECDC 1957 Ft Tejon quake
The 1952 Kern County EQ epicenter was much closer to the Grapevine - just 37 km south of Bakersfield. Several tunnels on the SP's Tehachapi route collapsed and rail lines shifted due to the quake.
1952 Kern County quake
IMO, the geological hazards for a HSR line over Tejon Pass, coupled with the political challenges of the National Forest lands and Tejon Ranch Company ownership, make it all but impossible to build the HSR in that area.
The Tehachapi route for the HS line is clearly the lesser of two evils.
