Is it true that a series of small earthquakes help prevent a large eartquake?

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In summary, it is true that a series of small magnitude earthquakes help prevent a large magnitude eartquake, although this effect is usually not enough to prevent a major earthquake from happening. Additionally, it is important to realize that fault systems are rarely a linear thing and aftershocks are a way to readjust the stresses within the rupture zone.
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kaleidoscope
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Is it true that a series of small magnitude earthquakes help prevent a large magnitude eartquake? Aren't earthquakes basically independent events from a statistical point of view?
 
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Yes it is true, usually. Smaller earthquakes let out some of the pressure built up along a fault line.

The amount of slippage depends on the force integrated since the time of the last slippage. If a fault sticks for a very long time, for whatever reason, the amount of energy released will be greater as energy released is proportional to distanceXmass of the moved plate.
 
  • #3
My knowledge of plate tectonics and related areas isn't really that great, but I would think that a series of small earthquakes could prevent a larger one if it allows the stress between the two plates to be released gradually instead of all at once.
 
  • #4
Interestingly, when there is slippage between points A and B on a fault, additional stress builds up along the fault just beyond points A and B. You can imagine this as just inside points A and B there has been some movement, but just outside no movement, and this difference in movement in a solid body produces shear strain.

I think this is the usual cause of afterschocks, which are smaller earthquakes following a larger one.
 
  • #5
H2Bro said:
Yes it is true, usually. Smaller earthquakes let out some of the pressure built up along a fault line.

The amount of slippage depends on the force integrated since the time of the last slippage. If a fault sticks for a very long time, for whatever reason, the amount of energy released will be greater as energy released is proportional to distanceXmass of the moved plate.

I think we are going to need to see some peer-reviewed research posted here, before we can make statements like this. I used to believe that what you say is true, but then I read in a credible paper that it is not true. I'll see if I can find that paper, but if you have mainstream research showing that minor quakes help to prevent larger ones on the same fault, I'd like to read it.

(I live on the Hayward Fault in Northern California, BTW...)
 
  • #6
Unfortunately what I learned in Grade 11 Geology did not come with provided peer reviewed articles, so I can't give you direct source on that.

It's possible what they teach in school is wrong.
 
  • #7
I think I found where I learned that it is false -- at the USGS website:

http://earthquake.usgs.gov/learn/topics/megaqk_facts_fantasy.php

USGS said:
You can prevent large earthquakes by making lots of small ones, or by "lubricating" the fault with water

FICTION: Seismologists have observed that for every magnitude 6 earthquake there are about 10 of magnitude 5, 100 of magnitude 4, 1,000 of magnitude 3, and so forth as the events get smaller and smaller. This sounds like a lot of small earthquakes, but there are never enough small ones to eliminate the occasional large event. It would take 32 magnitude 5's, 1000 magnitude 4's, and 32,000 magnitude 3's to equal the energy of one magnitude 6 event. So, even though we always record many more small events than large ones, there are far too few to eliminate the need for the occasional large earthquake. As for "lubricating" faults with water or some other substance, if anything, this would have the opposite effect. Injecting high- pressure fluids deep into the ground is known to be able to trigger earthquakes—to cause them to occur sooner than would have been the case without the injection. This would be a dangerous pursuit in any populated area, as one might trigger a damaging earthquake.
 
  • #8
What I'm seeing from this site:

http://seismo.berkeley.edu/outreach/faq.html#smalleqs

Indicates that preceding earthquakes do relieve pressure along a fault, however most cases there are an insufficient number of them to significantly postpone the larger quake that follows.

Just goes to show that if intuition were at all accurate, we wouldn't need science.
 
  • #9
H2Bro said:
Interestingly, when there is slippage between points A and B on a fault, additional stress builds up along the fault just beyond points A and B. You can imagine this as just inside points A and B there has been some movement, but just outside no movement, and this difference in movement in a solid body produces shear strain.

I think this is the usual cause of afterschocks, which are smaller earthquakes following a larger one.

be a little wary of what you are posting ;)

The aftershock sequence is use to define the rupture zone of a quake
The areas outside that zone where stress has been transferred to is where you can look to the probability of future events that will occur usually well before the "return period' of the zone that has just ruptured.

Aftershocks are basically the readjusting of stresses within the rupture zone. You need to realize that fault systems are rarely a simple single plane that slips. and that the system is most likely made up of multiple large and small faults. All of these intertwined faults can produce aftershocks as the stresses are released within the area.

Dave
 
  • #10
If you haven't already read this, six Italian scientists have been convicted of involuntary manslaughter because they were "criminally mistaken" in "falsely reassuring" people that major earthquake is unlikely after series of some low-level tremors.
 
  • #11
manojr said:
If you haven't already read this, six Italian scientists have been convicted of involuntary manslaughter because they were "criminally mistaken" in "falsely reassuring" people that major earthquake is unlikely after series of some low-level tremors.

There is a long thread about this in the General Discussion forum. Please keep discussions about this subject in that thread:

https://www.physicsforums.com/showthread.php?t=646127

Thank you.
 

1. What is the theory behind a series of small earthquakes preventing a large earthquake?

The theory behind this idea is that by having a series of smaller earthquakes, the built-up stress and energy in the Earth's crust is released in smaller increments rather than all at once, reducing the likelihood of a larger earthquake occurring.

2. How do scientists measure the effects of small earthquakes on preventing larger ones?

Scientists use a variety of methods to measure and analyze the effects of small earthquakes on preventing larger ones. This includes using seismometers to detect and track seismic activity, studying fault lines and other geological features, and analyzing data from previous earthquakes.

3. Is there evidence to support the claim that small earthquakes can prevent larger ones?

While the theory of small earthquakes preventing larger ones is widely accepted, there is still ongoing research and debate about the extent of their effectiveness. Some studies have shown a correlation between small earthquakes and a decrease in the likelihood of larger ones, while others have found no significant impact.

4. Can artificially induced small earthquakes have the same effect as natural ones in preventing larger earthquakes?

There is some evidence that artificially induced small earthquakes may have a similar effect in releasing built-up stress in the Earth's crust. However, this method is still being researched and there are concerns about the potential risks and unintended consequences of intentionally triggering seismic activity.

5. Can the occurrence of small earthquakes be used to predict when a larger earthquake will happen?

While some patterns and trends have been observed in the occurrence of small earthquakes before larger ones, there is no reliable method for predicting the exact timing or magnitude of a future earthquake based on small earthquake activity. Earthquakes are complex and unpredictable events, and multiple factors must be considered in any prediction attempts.

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