Puente Hills Thrust Fault: fatal quake history, behavior, continuity of slip rates and.. fracking

On Thursday morning at 7:42am, October 1, 1987, the Whittier area of Eastern Los Angeles was shaken by a M5.9 quake. This had been the strongest quake to hit so close to the downtown area since the memorable Sylmar quake in 1971. The Whittier Quake killed 4 people and did $360 million in damage.

Just M5.9 and it did so much damage and took 4 lives in eastern Los Angeles, back in 1987. Flash forward 27 years later, and another M5.x hit again, last night starting 9:09p and ending around 9:11p with a 3.4 and a 3.6 and then some 30 aftershocks - in La Habra, felt throughout Los Angeles county, and is believed to have occured on the Puente Hills Thrust Fault (yet to be confirmed, though).

It will be interesting to see what the next quake on PHTF is like.

Evolution of the Puente Hills Thrust Fault

scholar.harvard.edu...

This study aims to assess the evolution of the blind Puente Hills thrust fault (PHT) by determining its age of initiation, lateral propagation history, and changes in slip rates over time. The PHT presents one of the largest deterministic seismic hazards in the United States, given its location beneath downtown Los Angeles. The Los Angeles (LA) and Santa Fe Springs (SFS) segments are characterized by growth stratigraphy where folds formed by uplift on the fault segments have been continually buried by sediment from the Los Angeles and San Gabriel rivers. The Coyote Hills (CH) segment has developed topography and is characterized by onlapping growth stratigraphy.

scholar.harvard.edu...

Continuity of Fault Slip Rates

If slip rate does vary for a fault, it would have major implications for assessment of regional earthquake hazards. The Puente Hills blind-thrust fault beneath metropolitan Los Angeles is an excellent place to test slip-rate continuity because overbank deposits from the Los Angeles River have continually buried surface folds formed as a result of slip on the fault at depth. These syntectonically deposited sediments, commonly referred to as growth strata, provide a record of both uplift and time. We acquired a shallow seismic reflection image of the growth strata and used it to measure uplift of the fold crest to determine fault slip.

Fault slip rates over the past ~27 kyr (0.65-1.29 mm/yr) are comparable to the Holocene rate determined on the adjacent Santa Fe Springs fault segment (0.9-1.6 mm/yr) (Dolan et al., 2003; Leon et al., 2007) and the Quaternary average rates on the Los Angeles fault segment (0.60-1.13 mm/yr) (Shaw et al., 2002). The slip rate rapidly increases after this period, however, reaching a preferred slip rate estimate of 7.2 mm/yr between ~27ka and ~36 ka, the oldest date acquired by OSL at present. The slip rate then decreases to 0.44 mm/yr, slightly below the long-term Quaternary average. These preliminary results suggest a large (order of magnitude) deviation in slip rate on a 10-kyr timescale.

www.scec.org...

IIn a single magnitude 7 earthquake along the Puente Hills thrust fault, "USC would go up a meter or two relative to the area just south of the Los Angeles Coliseum. Downtown, and everything north of USC, would also be lifted by a meter or two." Adding to the bad news is the fact that the Puente Hills fault extends through the Los Angeles basin, a highly populated area made up of soft sediments that amplify shaking.

"This fault is in one of the worst places you could think of to put a fault of this size and geometry"

There's been a long history of OIL DRILLING & FRACKING in and around Puente Hills, CA. Could this past drilling have left the area prone to even larger future quakes?

www.whittierhillsoilwatch.org...

This is the fault that could eat L.A.,” seismologist Sue Hough told The Times in 2003.

This is interesting, thanks for posting it.

I was very little in 1971, and we lived in Whittier. I remember I thought a giant was shaking our house; my mom always described getting seasick looking out the windows at the street rippling like a wave.

In 1987, I lived in Fullerton, and remember all the damage that did.

Now my parents live in Carbon Canyon, and I find myself thinking "What the heck is wrong with my family? Why have we always sat on top of this fault line no matter how many times nature tries to shake us off???"

While the difference between a 5.9 and a 5.1 may seem to be minor, the energy released is about 16x. A full 1.0 difference is about 32x as much energy. So the recent quake isn't really in the same league as the older one. It's about 6% of the size of the older 5.9...... Caused by fracking? I seriously doubt it. Try caused by plate tectonics.

In any case, if fracking could cause enough smaller quakes to happen that it would relieve pressure along a major fault, that would quite frankly be a good thing. They would be much smaller. It would certainly save lives and be a huge savings in property damage as well. Were there real science behind fracking releiving pressure along tectonic boundries, you would see fracking all along the San Andeas. Nonstop.

Oh, and the "big one" along the thrust fault will be about 5600x larger. This recent one, and even the 5.9, is nothing in comparison to a 7.5 to 7.6.

Wouldn't fracking (removing heavy oil out of recesses in the earth, leaving gaping open spaces once the water drains) create more areas in the crust for collapse once quakes hit?

Slips and slides along the faults is one thing in this seismic region. Los Angeles county (and the entire SoCAL coastline) is moving north toward SF and upward over the red of North America. (Rate of plate movement along the San Andreas fault - 1.3 inche seach year - is about how fast fingernails grow. But creating networks of pockets waiting to collapse?

These frackers obviously don't want to acknowledge that Los Angeles county is a BASIN with a thin crust as it is. Picture a 'rising basin of sand' over a mound that is north america. Fracking in that rising basin of sand in my limited knowledge of geology, makes sections of that 'basin of sand' to just crumble into each other as the basin we call Los Angeles, rises due to its seismic nature.

reply to post by gardener


This type of OP keeps me coming back to ATS. Novel, thoughtful predictions and well done posts.

Fracking is a new thrust of corporate predation on the complacent and delusional citizenry of the US. Destroying the oblivious worker bees with impunity.

Stand By, for Heavy Rolls!

Live California Earthquake Map

San Andreas Fault

gardener
Wouldn't fracking (removing heavy oil out of recesses in the earth, leaving gaping open spaces once the water drains) create more areas in the crust for collapse once quakes hit?

First: no, I'm not in the oil industry nor does my family depend on the oil industry. I did become a geophysicist by both education and employment but voluntarily left that behind to pursue a more personally interesting field: semiconductors.

It's a common misconception that oil is found in pools or lakes under the ground. That's not the case. Oil is trapped in solid rocks which allow the oil to seep slowly through them. Sometimes oil is trapped in more porous rocks where it can move more easily. Depending on the type of rock, and the porosity of the rock (the ability of water to move through them), one can either remove a larger or smaller percentage of the oil contained in the rock. In most cases, the vast majority of the oil remains trapped in the rock because the oil is too thick for the pores or the pores do not connect well enough for the oil to move.

If you have a sandstone honing tool to sharpen knives, you can see how this works for yourself. Add a drop of honing oil to it, and some of it will sink into the sandstone. That oil is very light -- much lighter than oil in wells. Anyway, most knife sharpening kits provide a fine Arkansas sandstone which is not very porous. So not much oil gets into the sandstone, but some does. This sandstone is like the rock that we find oil in -- and it's very difficult to get the oil out. Imagine trying to remove all the oil from the Arkansas sandstone and you will see the problem. It's not going to happen, but you can get some.

There is always pressure from the overburden (the rocks above weigh a great deal) and sometimes there is pressure from trapped gas too. Just like oil, gas can be trapped in the rock. Drilling a hole into the rock creates a space for the pressure to push the oil into. That happens more rapidly in formations with high porosity (fluid moves more easily) than low porosity (fluid moves slowly if at all). In all cases, some oil sticks to the rock and some of the pores clog up with oil. The rock layer itself does lose some density and will often be compressed a little by the overburden as the oil is removed. This is where subsidence after oil removal (same as water from water wells for drinking) comes from. If you return fluid, like water, there is less subsidence.

To get more of the oil out, there are only a couple of different things which can be done (cost is a big constraint). Sometimes hot water is injected to increase the pressure and improve the flow -- hot oil flows more easily than cold oil. Place a jar of oil in your fridge and see how this works yourself. The injections can also locally increase the pressure in the formation, repalcing the lost "drive" as the oil is removed. Pressure is important because only very high pressure (many thousands of pounds per square inch) can cause the oil to move. Oil does not like to move through rocks very much!

Other times the porosity isn't very good or the pores get clogged up. The rock can then be fractured around the drill hole by applying a high pressure fluid. The heavier the fluid, the easier it is to make it high pressure (gravity helps do the work). In many cases some material, something like a sand, will be added to the fluid to help prop open the fine cracks. Sand does not help make the fluid heavy (it's light) so there are other "engineered" materials which can be used but they are usually more expensive. Anyway, the fractures do not extend very far from the borehole, but there can be 10 or more boreholes in the same surface well if there is enough oil to make it worth drilling that many.

Now, we do expect some bulk movement due to subsidence. If any of the overburden, or the oil bearing formation cracks in a major way, there can be a small EQ. Because fracking mostly occurs in the immediate neighborhood of the borehole, the only way that fracturing could influence a fault would be to add lubrication along the fault itself. Large EQs require "breaks" possibly hundreds of mile long..... so influencing a major fault isn't a local thing at all. Also, keep in mind the formation we are taking the oil out of is already saturated with a fluid (oil) -- and oil is a lot better lubricant than mud or water.

It is still possible, at least theoretically, and a correlation with local small EQs has been claimed to have been observed. I don't know of any experiments though where the conditions were controlled to start and stop local, small EQs at will by adding and removing fluid. Any other claim which is based merely on timing or number of events over a short history (not hundreds or thousands of years of equally sensitive observation) is just someone's theory.

Many oil bearing formations do have oil trapped against an old, local fault of some type and limited extent. It would be very difficult to decisively know, without an experiment, that a small EQ in the area of such a well was due to fracturing the rock as opposed to subsidence or even natural EQs. Most oil fields are not near faults with large historical EQs and there is not even a short seismic history to refer to. We can get suspicious, but if we are paying more close attention or adding a seismometer because there is fracking in the area we can easily mistake natural occurrences from fracking related occurrences of EQs. The only way to know for sure is to do an experiment where small EQs can be started and stopped at the will of the experiment. Physics doesn't favor fracking as a possible "cause" of an EQ big enough to do much damage, but it also doesn't totally rule it out either. I'd personally suspect subsidence first if there is no prior history. Then again, faults exist because something in the past caused the fault to form..... so no prior history even over a hundred years is less than meaningful evidence per se. You need to know something about frequency of occurrence, and magnitude distributions, to know what you think you are observing is rare.

I have no doubt speculation is rampant about fracking, but the reality is most people passing on these stories have no clue. The few who might have the knowledge of the basic science (a geophysicist but not a geologist or hydrologist) could easily have other motivations or a grudge against a particular company. I don't follow this area because it's mostly uneducated nonsense, so I can't point to individual cases or people. But I'm well aware that there has been, since the 1980's, an almost continuous contraction (reduction) in the total number of geologists and geophysicists in US companies through mergers and decline of exploration -- read, lots of jobs lost due to layoffs. Alternative jobs for geologists and geophysicists, who are no longer wanted by the companies, usually pay much less and often are environmental in nature. These then, are a natural source of opponents of fracking. I'd check the credentials and read between the lines before blindly believing a theory that is not published in the journals. And without an experiment providing statistically significant evidence, I'd consider any journal publication very weak evidence -- basically speculative theory only. Not real science, yet, despite the claims.

reply to post by BayesLike

nice post about fracking for oil, without all the usual emotional drama

Thanks @muzzy for linking this thread in the 2014 Quake Watch thread

gardener
Wouldn't fracking (removing heavy oil out of recesses in the earth, leaving gaping open spaces once the water drains) create more areas in the crust for collapse once quakes hit?

The gaps left behind are often extremely small and are not "empty" in the sense of a vacuum. Some other fluid, or the same fluid with less pressure, has to replace the oil or gas which has been removed. Some compaction can occur in some formations but it usually isn't a lot in any one place. Although if it is hundreds of feet thick, the compaction might be noticeable over the years as an elevation change.

Think of the reservoir as something like a wet concrete block or wet brick. You can't see the "holes" unless it is damaged -- but they are there. It can be looser, like some sandstones, but it is still rock. Some sandstones, though, do look more like bricks than not.