Earthquakes and Movies

Lately, there has been quite a bit of press about the recent “San Andreas” movie. To me, this movie sets back the general public’s knowledge and understanding about how earthquakes create damage in Southern California.

Some basic stereotypes exist in the movie, many of which are completely false. Starting with the magnitude of the earthquake in the movie – No fault line in Southern California is capable of anything larger than about an 8.2. The only one truly capable of such an event, the San Andreas Fault, is also many miles from Los Angeles and is mostly separated from the Los Angeles Basin by the San Gabriel Mountains. Anything larger than a 9.0 is in the domain of “megathrusts” or subduction zones. In California, the only subduction zone is the southern end of the Cascadia Subduction Zone, which ends at the “Triple Junction” just offshore of Cape Mendocino. It last produced something close to a 9.2 or so in January 1700.

Tsunamis, especially ones of great height, are also not in the forecast for a large earthquake here in Southern California. Tsunamis are created by the large scale displacement of water, similar to sloshing in a bathtub. Move your hand below the water quickly, you create a wave on the surface. Usually, tsunamis that are related to earthquakes are caused by the movement of the fault itself, typically megathrust faults underneath the ocean. We just don’t have those in Southern California. Even the largest tsunami generated by such a fault may only be tens of feet high, certainly not hundreds of feet.

Big cracks just don’t open up in the land from earthquakes, certainly nothing like those represented in the movie. Fissures are created by earthquakes, however. These fissures are usually the result of settlement or fault movement. They aren’t that large either way.

Structural damage is also not going to be as great as represented. Mind you, a large magnitude earthquake centered in the Los Angeles Basin will do a great deal of damage. Water mains, sewer mains, gas lines, power lines, and other utilities will be compromised in many locations creating shortages and, in some cases, fires. Buildings may collapse or be damaged beyond repair. The underlying geology will determine some of the damage extent. The rest will be determined by building type and its susceptibility to seismic waves. Either way, the skyscrapers in Downtown Los Angeles won’t be toppling like trees anytime soon. I’d still stay away from the area after a major event though, as there would be an immense amount of glass and debris creating hazards for travel.

Keeping all this in mind, and also keeping with the theme that Southern California officials have been doing, use this opportunity to prepare yourself for a major earthquake. They can strike at any time and will create problems for all of us that live, work, and visit this region. The best way to survive a major catastrophe is to be prepared. Part of that preparation is to know your region, know the routes, and know where the problem areas may be following a major earthquake.

For further information, I highly recommend contacting your local Emergency Services agency in your city and county. They have a great deal of resources to help you prepare for an event like a major earthquake.

Looking for Graphic Design Help

I’m looking for help with graphic design. Specifically, I want to create a logo for this website, something to put on cards, e-mails, favicon, and anywhere else a logo should go (even this website). If you’ve got graphic design skills and are looking to do some free work, please contact us. We can use your help!

New Feature Coming Soon – Cucamonga Valley Wineries

As this website is dedicated to providing the best coverage possible for a wide variety of subjects, it is time for another expansion. This time, the wineries of the Cucamonga Valley will be covered. These remaining wineries are a part of the history of the area and of California winemaking. We expect to have this new page up and running in the next month or so. Stay tuned for updates.

Finding Old Highways – A Guide – Part 2

Concrete Paving

Concrete is a very durable material. It has many uses, though for our purposes – roadway surfaces, curbs, and sidewalks. Local roadways, such as concrete city streets, won’t be covered in this post. Bridges will be covered in a later post. This durability allows us to get either a relative date of when a roadway was paved or built to an absolute date when we find a date stamp.

  • Style of Paving
Short section of Roberts Rd that is now a driveway.
Short section of Roberts Rd that is now a driveway.
1920's paving near Osborne St. Note the widening work that was done on the right side. Looking west.
1920’s paving near Osborne St. Note the widening work that was done on the right side. Looking west.

As technology has evolved, so has concrete paving. The first concrete paving along State Highways was 10-12′ wide, usually not reinforced with steel. These roads were paved in one single slab of concrete. Roadways of this style were paved from around 1910 to 1915. After 1915, wider paving was used and was generally reinforced. Wider paving ran from 15′, 18′, and a “full” 20′. These are usually referred to as “Single Slab Paving”.

Sometime around 1923, longitudinal joints were added to the concrete paving. This created a “Twin Slab” roadway. This style persists today, though greatly changed. Early Twin Slab roadways had fewer expansion joints running across the lane. After around 1926, this problem was worked out by adding more frequent joints. By this time, each lane was a “standard” 10′. This standard remained until the late 1940’s when lane width started to widen to 12′.

  • Date Stamps
1948 date stamp on Olympic Blvd.
1948 date stamp on Olympic Blvd.

Contractors, either by requirement or pride, usually stamp the concrete roadway, curb, or sidewalk with a date stamp. These stamps vary in location, size, and information. Date stamps marked either the beginning or end of a days paving. As such, the stamp tended to be located near an expansion joint. A general rule with date stamps is “find one, you can find the rest”. This is mostly about the location. Some stamps are in the middle of a lane, some are to the side of a lane. The orientation also varies with stamps. The information contained in these stamps also varies. Early stamps just have the contractor and the date. Later stamps added the engineering station. Without going into too much detail, at this time, about engineering stations, the “zero” point is at the beginning of a road section or project. With little exception, I have had little success in finding a date stamp on Single Slab roadways. Twin Slab roadways are much better with stamps.

Using date stamps and styles as a guide, you can easily date a roadways construction to within a few years. There are other methods you can use, but these aren’t covered here. Some will be covered in later posts. Stay tuned for more posts. Bridges, Road Signs, and more will be covered over the next few weeks. If you have any questions, please post a comment or send me a message.

Finding Old Highways – A Guide – Part 1

When looking for old highways, there are many clues you can use to help discover where old highways ran. This will serve as a partial guide to finding those clues and figuring out the history of a roadway in California.

State Highways

When you are looking for clues if a roadway you are on is an old State Highway, there are a few things to look out for. Depending on the age and location, look out for Right of Way monuments. In California, these are small concrete blocks with a C on the side of them, facing the roadway. They tend to be at the fence line along roadways, at the same distance as the utility poles, or further out. How much they stick out also varies. Some are just a few inches above the ground where others are about a foot high. Look out for these monuments at the beginning or ending of a curve usually about 50-100′ from the centerline of the roadway (or former centerline).

Old C-Block State Highway Right Of Way marker from 1930.
Old C-Monument State Highway Right Of Way marker from 1930.

Other clues tend to be tougher to spot but can be very subtle in appearance. Roadways that were formerly paved with concrete instead of asphalt are usually cracked in a very specific way if the asphalt is old enough. Expansion joints in the concrete, potholes exposing the old paving, or a defined crack running near the roadway edge usually give this away. Older concrete paving was either 15′, 18′, or 20′ wide. Modern roadways are usually 24′ wide, with two 12′ lanes. Look out for this concrete at curves which appear to have been straightened.

Original alignment of the Ridge Route at Tejon Pass. These lanes were built in 1923 on top of the original 1919 Ridge Route concrete.
Original alignment of the Ridge Route at Tejon Pass. These lanes were built in 1923 on top of the original 1919 Ridge Route concrete.


On some roadways bypassed or abandoned after 1964, old postmile markers can be found. These markers are similar to the ones on current State Highways. On a current roadway with R mileage, look for old alignments in the area. R mileage indicates a realignment that took place after 1964, which is the point of “base mileage” for California State Highways.

This milepost was found near Whitaker Summit on old US 99. US 99 was gone legislatively in 1964 so Route 5 took over the numbering here. That is why it shows the mileage for I-5.
This milepost was found near Whitaker Summit on old US 99. US 99 was gone legislatively in 1964 so Route 5 took over the numbering here. That is why it shows the mileage for I-5.

Abandoned roadways are tougher to spot depending on the area climate. Drier climates tend to preserve older paving better than wetter climates. In some areas, the paving itself was removed after the roadway was bypassed. I have found a few sections of roadway relatively intact, complete with old striping, in Central and Eastern California. When the pavement has disintegrated or obliterated, you can look out for areas where there is less vegetation and distinct roadway grade. Sometimes old drainage culverts and bridges are left behind with nothing but dirt grade leading to them.


More paving, both lanes now visible.
More paving, both lanes now visible.

In any area, make sure to take plenty of photos if you find an old alignment. You never really know when the local jurisdiction will come along and either obliterate or repave the roadway. This is fairly common in Los Angeles County as I have found. The most recent loss has been the June 1933 three lane concrete in Gorman along old US 99 which was repaved in the past couple years. Document what you find as best as you can. Doing so will help to preserve the memory of these forgotten roadways for many years to come.

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