Previous Question and Answer Session
The "Earthquake DOC" - July 2004
Thanks for asking these great questions!
Q1: Thank you for giving us an opportunity to ask questions. In reviewing earthquake information in So. Cal. I wonder why have there been so many people killed in the quakes, for instance the Dept. of Conservation (http://www.consrv.ca.gov/index/Earthquakes/qh_earthquakes_Calbigones.htm) reports that in the 1994 Northridge quake 61 people were killed, in the 1989 Loma Prieta quake 63 people died and 1971 San Fernando quake 65 people died.
I understand that it may be the magnitude of the quake but heaven forbid if we have that again as they are predicting - are we going to have less deaths? I am very worried especially since we live in N. Hollywood - near Northridge and San Fernando.
A1: Certainly, those earthquakes were devastating to the people of California in loss of life and property. Though any loss of life during a disaster is extremely regrettable, when you compare our loss of life and property in California to that in other areas of the world (http://neic.usgs.gov/neis/eqlists/eqsmajr.html), or even during previous earthquakes in our state (http://www.consrv.ca.gov/CGS/rghm/quakes/eq_chron.htm), it becomes clear that California is one of the leaders in understanding our earthquake environment and developing better building codes and guidelines.
There is no doubt we live in earthquake country. Because the recent earthquake prediction technique used for the desert region of southern California is still very incomplete and speculative, we shouldn't worry about WHEN a particular earthquake will occur...we should be more concerned about HOW to plan for and WHAT we should do during the next big earthquake; we should think less about prediction and more about preparedness.
As you are probably aware, earthquake hazards such as ground shaking, liquefaction, landslides, and fault rupture, by themselves, typically do not directly harm people; it is the structures we occupy on a daily basis...our homes, workplaces, schools, roads, etc...that will influence the earthquake's overall effect on us. We must better understand the design, location, and surroundings of our structures to determine the risk of injury we will face during an earthquake. The questions you need to ask include:
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How old are the structures I occupy?
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To what building code and/or level of construction were they built?
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Are these structures at risk to foundation or outside problems such as liquefaction or landslides?
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Will the building interiors (wall and ceiling hangings, book cases, etc.) be secure during an earthquake?
If you are concerned about the age, design, or location of a particular structure, check with your local building department or a geologist or structural engineer to determine your level of risk. We also have information regarding earthquake hazards for the North Hollywood/Northridge/San Fernando area, as well as other populated parts of the state, at the following website: http://gmw.consrv.ca.gov/shmp/index.htm
The other thing that we need to do is be PREPARED before, during, or after an earthquake. The information on the following website should help you prepare and protect yourself when an earthquake does occur: http://www.consrv.ca.gov/index/Earthquakes/qh_earthquakes_what.htm
As scientists and engineers, we continue to learn more from each earthquake that occurs. We have many programs at the California Geological Survey that help identify earthquake hazards and help improve locating and constructing buildings in California. To learn more about these programs, please visit the following website: http://www.consrv.ca.gov/CGS/geologic_hazards/earthquakes/index.htm
Q2: I grew up in Port Hueneme, Ventura County, California. I was very interested in the supposed "split" that occurred just northwest of Santa Monica in the (“10.5”) movie. Is there any justifiable reason to show a crescent shaped split in that area? As a native of "Gateway to the Channel Islands," I am aware of faults that run directly under those.
A2: No, there is no justifiable reason for a “split” in the area north of Santa Monica (nor anywhere else in Southern California for that matter) like they show in “10.5”…but you are right that there are active faults along the base of the southern Santa Monica Mountains, out to the Channel Islands, and in the Ventura Basin.
A “split” would not occur there because the crust in the area is under compression; that is the earth is being pushed together instead of pulled apart like they show in the movie. Because of this compression, the faults that exist in this area are predominantly either reverse or thrust faults…faults along which the earth on one side is forced up and sometimes over the other side of the fault. In this case, the Malibu Coast, Santa Monica, and Hollywood faults are the planes along which the Santa Monica Mountains are being forced upward relative to the low-lying valley area to the south.
Though we wouldn’t expect the earth to open up along these faults like they show in the movie, these faults are active and should be a concern for people living in the area. If you would like to know more information about these and other faults, the Southern California Earthquake Center (SCEC) maintains a good website for basic information: http://www.data.scec.org/faults/lafault.html. You can find out additional information about faults and earthquakes at http://www.consrv.ca.gov/CGS/geologic_hazards/earthquakes/index.htm.
P.S. (Not that it matters but…) If you have the “10.5” miniseries on tape, watch the last part again and you will see that the original location of the “split” starts in the Santa Monica area but in the final scene of the movie, when they show the newly formed island from above, Santa Monica is located near the center of the island…the “split” has moved to Carlsbad! Now that is some “special” effect!
Q3: In "10.5," the people who are scientists look for the fault apparently using things like ground-water levels, radon pockets, and gouge-proof. Are these things really used to find a fault?
A3: Yes and no. In some cases, there is a problem with the way they talk about them in the miniseries.
There are many things that geologists look at to find evidence of faulting in the field. A fault is a planar feature along which the rock and soil on each side move...this motion is what creates earthquakes. Sometimes this boundary acts like a barrier to ground water, where water backs up on one side, producing different ground water levels on each side of the fault. Also because of this barrier, radon gas can migrate up along a fault but when it has been used as a fault indicator, the results have not always been definitive.
Due to the grinding motion along the fault plane, the fault commonly contains fault gouge, which is clay and ground-up rock. However, it is important to note that the scientists in "10.5" incorrectly refer to this as "gouge proof" several times; it is possible that the screen writers read something like "gouge is proof of a fault" and made the jump to calling it "gouge proof."
Other potential evidence of a fault includes: 1) sudden changes of rock type (other than bedding planes), soil type, and vegetation type across a boundary; 2) offset drainages; and 3) sudden changes to topography such as an abrupt mountain front or a long mound in relatively flat terrain. The typical method that geologists use to locate faults and figure out how old they are (faults with movement in the past 11,000 years are considered "active") is to dig a trench across them to look at them in the subsurface.
The following website describes a CGS program that identifies and maps active surface faults, and delineates zones around them that require further investigation before building there (http://www.consrv.ca.gov/CGS/rghm/ap/index.htm).
Q4: I have a question regarding the 10.5 movie on NBC. Where would California actually split if it did happen the way the movie explained it.
A4: Hopefully you aren't looking for information to buy up "beach-front" property somewhere...just kidding.
Seriously now, when we Californians talk to people from other parts of the country about earthquakes, they always ask...joking or not...about when California will be "falling off" into the ocean. The "10.5" miniseries shows part of southern California, from San Luis Obispo to the vicinity of Carlsbad, north of San Diego, becoming an island. As we talked about in our "geo-logical" movie review for "10.5" (http://docsharepoint1/cgs/EarthquakeDOC/EQ-Movie_Reviews/Pages/NBC-10.aspx), California falling off into the ocean or becoming an island is the single biggest misconception about California geology. I'm sad (or happy) to say that it will never happen.
The San Andreas fault, the commonly misconceived "culprit" for such an event, is a transform fault that forms the boundary between the Pacific plate, to the west, and the North American plate, to the east. The trace of this fault starts south of the Imperial Valley, cutting diagonally across the state through the middle of the Transverse Ranges before it heads north where it ends near Cape Mendocino (ftp://ftp.consrv.ca.gov/pub/dmg/pubs/sp/Sp42.pdf).
The key thing to remember about the San Andreas is that it is a right-lateral strike-slip fault, with the land to the east is moving south relative the land in the west...the motion along the fault is lateral, not apart. As a matter of fact, there is even an element of compression along the boundary that continues to keep the two plates together. The movement along this plate-boundary fault is very slow, about 35mm per year. To put it into perspective, about 14-million years from now, Los Angeles and San Francisco might become suburbs of one another...if both cities still exist (imagine the traffic!).
So, the bottom line is that there is no way for California to fall off into the ocean or for part of it to become an island, like in the miniseries "10.5." (Having said that, if I were writing a science fiction movie like "10.5" I would break up California along the San Andreas fault...don't quote me on that, I will deny saying it!)
Q5: How would you compare the realism or "science" in the 1974 movie "Earthquake!" to that of the miniseries "10.5"?
A5: Well, in our research to write a movie review for "10.5" we went back and watched the movie "Earthquake!" (during a couple lunch breaks) and a CGS geologist wrote a movie review for that as well (http://www.consrv.ca.gov/CGS/EarthquakeDOC/EQ-Movie_Reviews/Earthquake!-(1974).htm). In that 1974 movie, Los Angeles is hit by a large earthquake less than halfway through the movie; the rest of the movie is spent following the principal characters as they try to survive in the aftermath.
Except for a few scientific falsehoods including a seismologist predicting the "Big One" (which we can't do), the overall realism of "Earthquake!" is significantly better than that of "10.5." As a matter of fact, some scenes in "Earthquake!" could be used to help educate people about what to expect and what not to do during or after an earthquake. There are several other good facts listed in the "Earthquake!" movie review...check it out. Some of my favorite facts include: 1) ground shaking causing old unreinforced masonry buildings like the mission to crumble; 2) people using elevators after earthquakes can get "injured"; and 3) my personal favorite: running into a house after an earthquake with a lit cigarette in your mouth might be hazardous to your immediate health!
Overall, the movie "Earthquake!" is a more realistic look at what we can expect from an earthquake in California (and some of the '70s outfits are really groovy too!).
Q6: Maybe you can explain something to me about the "10.5" movie? Why were the nuclear bombs used to hold the fault together placed at such shallow and exact depths like 324-feet? What good would that do with such a big fault?
A6: This is a very good observation. Beyond the fact that nuclear weapons can't be used to "fuse" a fault together, you are right that they would certainly not have an effect on a fault that is tens of kilometers deep...or one that is (impossibly) 700-kilometers deep like the one in the movie. We talk more about nuclear weapons and earthquakes in our movie review (http://www.consrv.ca.gov/CGS/EarthquakeDOC/EQ-Movie_Reviews/NBC-10.5.htm).
To answer your question directly, a nuclear weapon would not fuse a big fault.
Q7: About that "10.5" movie, can cars be swallowed up in quicksand like they showed?
A7: A car would not be swallowed up like they showed in the miniseries. If you noticed, the type of dirt used in that scene was composed of dry sand and gravel. Typical quicksand-like sinking during an earthquake is caused by liquefaction. Liquefaction occurs in loose, saturated sand where, due to ground shaking, the pressurized ground water forces its way upward reducing the water's support on the sand grains, which can cause things on the surface to sink.
This type of hazard can cause damage to the foundation of buildings by settling different amounts under the foundation.
Q8: Can you please tell me a website where I can find information and pictures about earthquakes?
A8: The "Earthquake DOC" has provided a list of Web page links for additional earthquake information at the end of this page. Many of the Web sites provide earthquake related images for downloading. Don't forget to browse their linked Web site suggestions as well. You will find a wealth of earthquake information. Please check back with the "Earthquake DOC" if you have any questions.