EARTHQUAKES: An analysis indicating increasing frequency and severity

As can be evidenced by a quick search of the ATS forums, earthquakes have recently generated a significant amount of member interest and quite warranted, concern. In fact, it's got to the point that almost ANY earthquake occurring ANYWHERE in the world now seems to rate it's own thread with many posters commenting on what seems like an apparent and significant rise in the number of earthquakes that have been occurring during the last few years.

The purpose of this thread is twofold ... firstly to examine the evidence for this widespread belief that earthquakes around the world are indeed, on the increase ... and secondly, to propose a hypothesis as to why this alleged increase in activity may be occurring.

Let me state right at the onset that I will NOT be considering HAARP as a candidate, despite the number of threads trying (unsuccessfully) to link HAARP activity to the recent spate of earthquakes. I have yet to see any kind of substantive, corroborative and consistent data being produced that definitively and unambiguously links such technology and identifies it as a confirmed source capable of manipulating tectonic plates and resulting in deliberate and targeted manmade earthquake generation.
Instead, I will be looking at earthquakes from the point of view that some (or many) are the indirect and accidental result of ongoing human activity taking place on the planetary surface.

So, lets start firstly by looking at the available evidence and attempting to determine if there has or has not indeed been a significant and unusual increase in earthquake activity over the last 4 decades. To determine the answer to the above, I'll be using data accumulated over that period by the United States Geological Survey (USGS) organization: www.usgs.gov
To make the analysis much more significant from a statistical point of view, I'll be examining USGS earthquake data pertaining ONLY to earthquakes of magnitude 6.0 or greater. The reason for this is twofold ... the majority of damage and casualties occur during earthquakes of such magnitude ... to reduce the amount of 'noise' from the vast majority of earthquakes that fall in the sub 6.0 category and that may tend to skew or dilute the data we're actually interested in.


In analyzing the USGS earthquake database, I've split the data into 3 groups, namely earthquakes occurring in the 6.0 to 6.9 magnitude range; those occurring in the 7.0 to 7.9 magnitude range; and those in the 8.0 and above magnitude range. The reason for this is to help identify any particular magnitude range that may for whatever reason be showing any significantly altered or abnormal earthquake activity.


In the following graph (Graph 1), I have summarized the USGS earthquake data to show any potential trend, whether increase or decrease, within the 6.0 to 6.9 magnitude range.

[atsimg]http://files.abovetopsecret.com/images/member/bcc8a234382d.jpg[/atsimg]

It's immediately obvious that there's a considerable and disparate difference in the number of earthquakes in any given year in the 2 decades prior to 1990 and the 2 decades post 1990. In fact, it's almost as if someone had flipped a switch in the year 1991, causing a significant increase in the number of subsequent earthquakes.
In fact, the difference between pre 1991 and post 1991 tallies highlights a statistically significant increase in the number of earthquakes of 40.5%.



In the following graph (Graph 2), I have summarized the USGS earthquake data to show any potential trend, whether increase or decrease, within the 7.0 to 7.9 magnitude range.

[atsimg]http://files.abovetopsecret.com/images/member/d3f4fd601436.jpg[/atsimg]

Obviously, as the magnitude range increases, we should expect to see fewer events occurring within this range and this is reflected accordingly.
Now looking at the above graph, 2 immediate points of interest stand out clearly. Firstly, in the decades prior to 1991, we can see what appears to be a relatively consistent decrease in the number of earthquake events occurring. From an initial maximum of 20 events, we quickly see a downward diminishing trend ending around the 4 / 5 event level.
But then suddenly (as in Graph 1) at the 1991 mark, we see a sudden and unexpected significant increase in events as if some kind of 'trigger occurrence' had taken place .. and from 1991 onwards, we see a slow but gradual increase in the number of events within this magnitude range.

In fact, the difference between pre 1991 and post 1991 tallies highlights a smaller (in comparison to the 6.0 to 6.9 range) yet still statistically significant increase in the number of earthquakes of 13.5%.



In the following graph (Graph 3), I have summarized the USGS earthquake data to show any potential trend, whether increase or decrease, within the 8.0 and higher magnitude range.

[atsimg]http://files.abovetopsecret.com/images/member/24fecac64289.jpg[/atsimg]

Once again, our expectation of even fewer earthquake events of this magnitude is reflected in the observed values.

Even taking the above into consideration, it is yet again apparent that the decades post 1990 show a statistically significant increase in earthquake activity, even at these catastrophic magnitude levels.
We can clearly see that there is more than a doubling of events in the post 1990 decades compared to pre 1990 decades. In fact, we have an increase of 111%.



Now having analyzed the available USGS earthquake data in compartmentalized magnitude ranges, lets combine the data from the above 3 graphs to show a summary of overall earthquake activity during the last 4 decades covering all magnitude events 6.0 and higher.

[atsimg]http://files.abovetopsecret.com/images/member/bed460ccf27e.jpg[/atsimg]

Looking at the above summary, it is plainly obvious that overall, earthquake activity was on a gradual decline in the decades prior to 1990 but then unexpectedly, in the year 1991, some kind of 'tipping point' was reached and the number and intensity of subsequent earthquakes in all magnitude ranges began a steady and statistically significant increase.
Amalgamating all the data from the 3 magnitude ranges still shows a consistent and undeniable trend of increasing earthquake activity as is obvious in the overall increase of 38%.


So, can we conclude that the 'feelings' and 'impressions' that many ATS members have regarding significant increases in earthquake activity is justified ?
From the above analysis, it appears that we can conclude that there is indeed strong justification for such a belief.

PREDICTION

Based on the observed trends, it is more than likely that earthquake activity will continue to increase over time and that based on the above clearly observed trends, the greater proportion of future major earthquake events will be seen to occur primarily within the 6.0 to 6.9 magnitude range. However, it would also appear that we will be seeing increasing numbers of events also occurring within the 7.0 to 7.9 and 8.0 and higher magnitude ranges, compared to what were observed to have happened in past decades.

Continued next post ...

Continued from previous post ...



In my OP, I mentioned that this thread had 2 purposes ... the 1st being to determine whether the frequency and severity of earthquakes really WAS on the increase and 2nd, what may be triggering or driving such an increase.

With regards to the 1st point, I think that has been answered in the affirmative.
We'll now move on to the 2nd point of this thread.



With earthquakes being a global, high energy phenomena, we need to look for possible explanations that are also on a global scale and that have the potential capability of interacting with the structure and stability of the planets crust.
Using this premise, we can further simplify by assuming that the earthquake trigger must be either terrestrial (i.e. planet based) or off planet.

Now many people hypothesize that the increase in earthquakes may in fact be due to increased solar activity interacting with the Earths surface by some unknown mechanism, quite possibly the result of ongoing sunspot activity.
However, I believe that we can discount such a possibility as we would require strong correlation between ongoing solar activity and earthquake frequency. Examining the decades from 1970 onwards on the following 2 graphs, such correlation is clearly not evident.
It should be safe to say that we can discount the sunspot hypothesis as the basis for the ongoing increasing earthquake activity.

[atsimg]http://files.abovetopsecret.com/images/member/bed460ccf27e.jpg[/atsimg]
[atsimg]http://files.abovetopsecret.com/images/member/4c3fb81c7716.jpg[/atsimg]


Lets instead look for a terrestrial based explanation.



Firstly, for those who may not be too clear on how the majority of earthquakes happen, lets take a quick look at a map of the Earth. The following global map shows that the crust of the Earth is actually broken up into numerous sections called 'plates' ... some large and others small.

[atsimg]http://files.abovetopsecret.com/images/member/286795aac669.jpg[/atsimg]

These plates are in constant contact with other neighbouring plates and exerting massive amounts of force on each other as they slip past or over each other. They average 80 kms (50 miles) in thickness and have a relative movement of just centimeters (inches) per year. Irrespective of the minute amounts of movement taking place, the interaction between these plates frequently generates enormous amounts of energy which often is released in the form of earthquakes at these interaction points.
So as can be readily seen, the entire crust of the Earth is under continuously changing stress levels as these plates move and jostle one another. However, the overall planetary crust stress levels is maintained at equilibrium levels by the relative movement and repositioning of these tectonic plates, allowing the dissipation of any major stress buildup.

Now based on the above explanation, it should be readily apparent that any localized changes to, or alterations of stress patterns in a given area of the planetary crust will not remain localized but instead will be transmitted through the plates in an attempt to smooth out or dampen these stress changes. If this 'transmitted' stress encounters a plate area that is already experiencing increased levels of local stress caused by normal plate movement, then it could conceivably act as a 'trigger' causing the release of the built up energy in the form of an earthquake. And depending on the amount of pent up energy released, will determine the magnitude of the resultant earthquake.
So as can be seen, the earthquake 'trigger' (the transmitted stress) can theoretically have its origins far removed from the actual observed earthquake event. Therefore a stress event on one side of the planet could conceivably trigger an earthquake on the opposite side of the planet, purely due to stress forces being transferred from plate to plate until a location is reached that is capable of releasing these stress forces.


So what could affect localized areas of the Earths crust in such a manner that large stress forces could be generated ?
The answer to that is human activity.
Since the beginning of the industrial revolution, human society has become more and more dependent on various resources which can only be extracted from the Earths crust; resources such as crude oil, coal, iron, copper, aluminium, etc, etc ... and as the years go by, the demand for these resources continues to grow at an ever increasing rate.
Now as these various resources are usually concentrated in various specific locations within the Earths crust and their removal MUST have an impact on that local areas crustal stress configuration. If you're thinking that we're only talking miniscule amounts of material being removed compared to the overall size of the Earths crust and that it couldn't possibly have any significant impact on the overall stress configuration of the entire crust, lets use crude oil extraction and try to estimate the amount of material that has so far been removed from the Earths crust.

Lets use statistical data compiled by Energy Information Administration (IEA) section of the US Department of Energy (DOE). They provide detailed statistics, data, analysis on resources, supply, production, consumption for all energy sources on a global basis.
We'll examine the global extraction of crude oil during the period 1960 to 2008.

www.eia.doe.gov...

The number of barrels of crude oil extracted per country for each of these years is supplied and a simple calculation shows that during that 48 year period, an approximate total of 978 BILLIONS of barrels of crude oil were extracted/removed from the Earths crust.
Fine, but whats this mean as a quantity that we're more familiar with ?
Ok, lets convert those barrels into metric tonne equivalents ... note that 1 metric tonne = 1000 kgs.

1 barrel of crude oils weighs approximately 140 kgs (depending on the type of crude oil).

So 978 billions of barrels is the equivalent of approximately 137 BILLION metric tonnes of weight (mass) removed from the Earths crust.

I can't even begin to picture what such an incredible amount of material must look like. I tried to find the weight of Mount Everest to use as a comparison but unfortunately was unable to do so. But irrespective, 137 billion metric tonnes is a mind-boggling number !

And thats just for crude oil removal. Now factor in the billions of tonnes of coal, iron, copper, aluminium, etc removed from the Earths crust during that same 48 year period and the quantities become literally astronomical in size.

It wouldn't be so bad if the crustal modifications were limited to only the removal of vast quantities of material in various locations but we also have to realize that we're also adding incalculable amounts of artificial weight in many locations by way of our cities and infrastructure. Take mega cities such as London, New York, Paris, Tokyo, etc, as prime examples. I doubt if anyone would be capable of exactly determing just how much weight the material that these cities are made from (buildings, streets, houses, suburbs, roads, etc) is adding to the crust in their immediate vicinity. Again, this sort of weight must easily run into the trillions of metric tonnes and bear in mind that just as little as a 100 years ago, the majority of this additional weight did NOT exist in these locations.



Continued next post ...

Continued from previous post ...


So just by going about our normal day to day, year to year business of building and maintaining our human society, we're inadvertently modifying the stability of the Earths crust and generating significant artificial stress levels on many crustal points around the world. These artificial stress levels can't be maintained indefinitely ... they have to be dispersed and dissipated and one mechanism that the Earth has in place to deal with such contingencies is by way of generating earthquakes to relieve these crustal stress points.



Even with the above in mind, I'm more than certain that many of you will still find it hard to believe that human activity can have any kind of impact on the stability of the Earths crust or on the Earth itself. To show that such thinking is fallacious, lets use a very recent example of minor crustal modification on just one tiny place on the Earths surface to demonstrate how seemingly small changes can affect the entire Earth.

Recently, there was a significant earthquake occurrence just off the coast of the Maule Region of Chile on February 27, 2010. This earthquake registered a magnitude of 8.8.
As well as the local devastation, seismologists have estimated that the earthquake was so powerful that it may have shortened the length of the day by 1.26 microseconds and moved the Earth's figure axis by 8 cm or 2.7 milliarcseconds.

So how did such a very localized event (compared to the entire Earths surface) have the ability to modify the rate at which the entire planet revolves ?

All revolving/rotating objects such as the Earth have what's reffered to in physics as a Moment of Inertia value. Essentially, the Moment of Inertia of an object about a given axis describes how difficult it is to change its angular motion (rotation) about that axis. Therefore, it encompasses not just how much mass the object has overall, but how far each bit of mass is from the axis. The farther out the object's mass is, the more rotational inertia the object has, and the more force is required to change its rotation rate.
So in the case of the Chile earthquake, we had an occurrence whereby sections of the local ocean floor subsided (sank) by just a few meters. This subsidence meant that that particular section of the crust was now ever so fractionally closer to the center of the Earth and the Earths rotational axis.
Because the angular momentum of a rotating object is conserved (Law of Conservation of Angular Momentum), this minuscule reduction in the Earths radius at this point meant that the Earth had to speed up its rate of rotation to compensate ... and therefore the length of the day decreased by an estimated 1.26 microseconds.

To get a better mental image of this process, picture an ice skater starting a spin. At the beginning, her arms are outspread and she's rotating fairly slowly. But as she brings her arms in closer to her body and her axis of spin, her rotation rate rapidly increases.

So the slight subsidence of the Chilean ocean floor was equivalent to the skater pulling in her arms and in both cases, the rate of rotation MUST increase to compensate for the change in radial mass distribution.

Therefore the Chilean earthquake gave us a very real and practical demonstration how apparently small and localized changes to the crustal structure can have repercussions that affect the entire planet.
So it shouldn't be surprising that removing or altering massive amounts of material at various locations and repositioning such material in other different locations MUST by the very nature of how the planet copes with crustal stress management have some kind of impact on not only the frequency of earthquakes, but also on their individual severity.

reply to post by tauristercus


It's the incoming brown dwarf. It's obvious. It's geological stress exerted from an extra-terrestrial dense body. It's gravity and a grave situation. There! I've said it all in three lines.

mclinking

Actually, the average number of earthquakes of 7.0 and greater has not changed much in the past 100 years. If anything there appears to be a downward trend in frequency.
[atsimg]http://files.abovetopsecret.com/images/member/9f995b9df942.png[/atsimg]
(For data from 1973 to 2009 I used this (1973 is as early as it goes): Source
For data from 1900 to 1972 I used this: Source)

While the apparent spike in lower magnitude earthquakes looks impressive, it can easily be attributed to an increase in the ability to locate these earthquakes. You'll also recognize that it coincides with the advent of the internet.

There are several reasons for the perception that the number of earthquakes, in general, and particularly destructive earthquakes is increasing.

1) A partial explanation may lie in the fact that in the last twenty years, we have definitely had an increase in the number of earthquakes we have been able to locate each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications.

In 1931, there were about 350 stations operating in the world; today, there are more that 4,000 stations and the data now comes in rapidly from these stations by telex, computer and satellite. This increase in the number of stations and the more timely receipt of data has allowed us and other seismological centers to locate many small earthquakes which were undetected in earlier years, and we are able to locate earthquakes more rapidly.

earthquake.usgs.gov...

[edit on 4/6/2010 by Phage]

reply to post by Phage


I notice that you concentrated your response ONLY on the magnitude ranges that have the smallest number of events per year, namely magnitude 7.0 and higher and completely ignored the 6.0 to 6.9 magnitude range where statistically far more events occur than in the upper magnitude ranges.

As I've shown, there has been a 40.5% increase in earthquake events (6.0 to 6.9) in the 2 decades post 1990 compared to the 2 decades pre 1990. We're looking at an increase in events in this magnitude range of an additional 800+ earthquakes .... not just 10 or 20 or 100 or even 200 ... but an increase of over 800 additional 6.0 to 6.9 magnitude events.

reply to post by tauristercus

No. I addressed that. Here it is again:

While the apparent spike in lower magnitude earthquakes looks impressive, it can easily be attributed to an increase in the ability to locate these earthquakes. You'll also recognize that it coincides with the advent of the internet.

There are several reasons for the perception that the number of earthquakes, in general, and particularly destructive earthquakes is increasing.

1) A partial explanation may lie in the fact that in the last twenty years, we have definitely had an increase in the number of earthquakes we have been able to locate each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications.

In 1931, there were about 350 stations operating in the world; today, there are more that 4,000 stations and the data now comes in rapidly from these stations by telex, computer and satellite. This increase in the number of stations and the more timely receipt of data has allowed us and other seismological centers to locate many small earthquakes which were undetected in earlier years, and we are able to locate earthquakes more rapidly.

earthquake.usgs.gov...

Large magnitude earthquakes are more easily located than lesser ones. Our ability to locate lesser earthquakes has increased in the past twenty years.

In case you missed the link, here's more:

The NEIC now locates about 12,000 to 14,000 earthquakes each year or approximately 50 per day. Also, because of the improvements in communications and the increased interest in natural disasters, the public now learns about more earthquakes. According to long-term records (since about 1900), we expect about 18 major earthquakes (7.0 - 7.9) and one great earthquake (8.0 or above) in any given year. However, let's take a look at what has happened in the past 32 years, from 1969 through 2001, so far. Our records show that 1992, and 1995-1997 were the only years that we have reached or exceeded the long-term average number of major earthquakes since 1971. In 1970 and in 1971 we had 20 and 19 major earthquakes, respectively, but in other years the total was in many cases well below the 18 per year which we may expect based on the long-term average.

[edit on 4/6/2010 by Phage]

More information from USGS themselves -

The USGS estimates that several million earthquakes occur in the world each year. Many go undetected because they hit remote areas or have very small magnitudes. The NEIC now locates about 50 earthquakes each day, or about 20,000 a year.

As more and more seismographs are installed in the world, more earthquakes can be and have been located. However, the number of large earthquakes (magnitude 6.0 and greater) has stayed relatively constant.

Are Earthquakes Really on the Increase?

We continue to be asked by many people throughout the world if earthquakes are on the increase.Although it may seem that we are having more earthquakes, earthquakes of magnitude 7.0 or greater have remained fairly constant.

A partial explanation may lie in the fact that in the last twenty years, we have definitely had an increase in the number of earthquakes we have been able to locate each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications.

In 1931, there were about 350 stations operating in the world; today, there are more than 8,000 stations and the data now comes in rapidly from these stations by electronic mail, internet and satellite. This increase in the number of stations and the more timely receipt of data has allowed us and other seismological centers to locate earthquakes more rapidly and to locate many small earthquakes which were undetected in earlier years.

The NEIC now locates about 20,000 earthquakes each year or approximately 50 per day. Also, because of the improvements in communications and the increased interest in the environment and natural disasters, the public now learns about more earthquakes. According to long-term records (since about 1900), we expect about 17 major earthquakes (7.0 - 7.9) and one great earthquake (8.0 or above) in any given year

earthquake.usgs.gov...

earthquake.usgs.gov...

reply to post by tauristercus


Wow Taur I am really surprised at your results. This settles one thing for me if nothing else. You can be counted on to strive for the truth. So aside from your usual thoroughly informative thread, I commend you for your honesty. I appreciate this thread alot Sir. So Thank you, very much.

Phage

When you use the internet as a reason for a rise in the number along with saying we can detect more quakes. The reasons why do not change the end result. As for any earthquakes that we never detected before, well maybe they were there. Maybe not.

[edit on 6-4-2010 by randyvs]

reply to post by randyvs

When you use the internet as a reason for a rise in the number along with saying we can detect more quakes. The reasons why do not change the end result. As for any earthquakes that we never detected before, well maybe they were there. Maybe not.

By the same token you could argue that there are now less earthquakes - you can argue either way purely because we don't have the same datasets from which to argue "now" against "then" as we're getting soooo much more recorded data from more remote areas and more enhanced records from known hotspots.

So, purely because the data for "now" shows more quakes we can't say it's more as we don't know what to compare it to...

I suppose one could get more of a feel for any increase/decrease by isolating data from a set of recorders that have been monitoring the same regions for a lengthy amount of time and examining that instead?

Originally posted by grantbeed

More information from USGS themselves -

The USGS estimates that several million earthquakes occur in the world each year. Many go undetected because they hit remote areas or have very small magnitudes. The NEIC now locates about 50 earthquakes each day, or about 20,000 a year.

As more and more seismographs are installed in the world, more earthquakes can be and have been located. However, the number of large earthquakes (magnitude 6.0 and greater) has stayed relatively constant.

Unless I'm really missing something ... I don't consider an increase of 800+ mag 6.0 to 6.9 earthquakes in just a 20 year period as having stayed relatively constant.
Anyone can (as I have done) check the USGS database themselves and do the maths. A 40.5% increase in 2 decades is a serious large increase. And remember that earthquakes within this 6.0 to 6.9 magnitude range have the potential to inflict serious damage.

reply to post by tauristercus

Unless I'm really missing something

I think you are missing the fact that most of the article I quoted talks about how they can detect way more of these quakes than before due to a heck of a lot more seismic stations.

IMHO this plays a big part in the figures.

Actually , how can we really say either way whether there is an increase or decrease if so many parts of our experiment are changing.

The only way to make any solid statement on this is to use the same equipment for a very long time and then tell us the results. This simply does not exist.

Originally posted by grantbeed
reply to post by tauristercus

 

I think you are missing the fact that most of the article I quoted talks about how they can detect way more of these quakes than before due to a heck of a lot more seismic stations.

IMHO this plays a big part in the figures.

Actually, re-reading your earlier quote

As more and more seismographs are installed in the world, more earthquakes can be and have been located. However, the number of large earthquakes (magnitude 6.0 and greater) has stayed relatively constant.

actually confirms that the above is misleading to say the least.

We have them making a statement that despite the many, many more installed seismographs installed around the world, the number of large earthquakes has remained fairly constant.

And yet I have clearly demonstrated an increase of 800+ magnitude 6.0 to 6.9 earthquakes in a 20 year period. I would most certainly NOT describe that as remaining 'relatively constant'.

reply to post by tauristercus

As more and more seismographs are installed in the world, more earthquakes can be and have been located. However, the number of large earthquakes (magnitude 6.0 and greater) has stayed relatively constant

I see how this can be mis-interpreted, but I think it means, in more recent times, since the introduction of this new equipment.

If it doesn't mean this, then yes, you are correct.

I don't dispute your numbers at all. I am merely providing evidence from the same source you have.

If indeed these quakes have increased, then why is it that larger quakes have not? (which account for way more damage and death). I of the thinking that if quakes have increased, then surely it should be across the board and not just a particular range on the scale.

But surely, all that your data shows is that the number of earthquakes that have been RECORDED has increased. In fact, to me, your graphs clearly demonstrate the effect technology has had on our ability to locate and record earthquakes.

The number of larger ones has remained stable - in that for every XX quakes there are XX larger ones and that relationship is stable.

A rise from 350 stations detecting quakes to over 8,000 is really a key element you can't ignore, as others above have stated.

Also, large earthquakes are generally more destructive, but our rapid urbanization of the planet means a 5.0 can be just as destructive - i.e. a 5.0 in a poorly constructed city could kill thousands but an 8.0 in the desert might injure just a few desert rats.




[edit on 6-4-2010 by MoorfNZ]

[edit on 6-4-2010 by MoorfNZ]

If it doesn't mean this, then yes, you are correct.

reply to post by grantbeed


Well since this study is in no way incorrect then this study is............

of 800+ magnitude 6.0 to 6.9

The numbers are way to high. there is only one conclusion and that is as
Taur has stated the members are correct. We are not imagining this rise in earthquakes.

[edit on 6-4-2010 by randyvs]

reply to post by randyvs


Well if you are indeed correct, then maybe the thread should be titled 6.0-6.9 earthquakes increased, because as per the figures, nothing else has significantly increased in the time that we have had greater amounts of seismic equipment.

Originally posted by grantbeed
reply to post by tauristercus

 

If indeed these quakes have increased, then why is it that larger quakes have not? (which account for way more damage and death). I of the thinking that if quakes have increased, then surely it should be across the board and not just a particular range on the scale.

Good question but the answer that springs immediately to mind is that as stress begins to build up at specific locations (see my OP regarding massive amounts of material being relocated), this stress is swiftly conducted away from that location and dispersed across neighbouring tectonic plates. This means that there is a greater likelihood that the stress will be managed by the triggering of an earthquake somewhere in the world and that unless circumstances conspire to prevent this release and allow the stress points to build, then the probability is that the resultant earthquake will fall somewhere in the lower magnitude ranges such as 6.0 to 6.9 or even less ... which is exactly what we see to be the case. It's only under very unusual circumstances that the stress buildup might be allowed to continue until it results in a 7.0 or higher quake.

reply to post by tauristercus


Makes sense what you say. I think you should send a link of your findings to USGS and ask their opinion. This would be very interesting!

Originally posted by MoorfNZ
A rise from 350 stations detecting quakes to over 8,000 is really a key element you can't ignore, as others above have stated.

I'm not ignoring that fact ... simply questioning whether our earthquake detecting technology was really that much more inferior in the 70's and 80's compared to post 1990.
Even in the 60's, the world had become a very crowded and small place and magnitude 6.0+ quakes would rarely go unnoticed or unreported.
So the huge discrepancy when comparing the 2 decades prior to 1990 with the 2 decades following 1990 still doesn't explain that massive increase of 800+ increase of 6.0 to 6.9 magnitude earthquakes.

If we had the technology to put man on the moon in the late 60's, we darn well had the technology to detect and tally accurately 6.0+ magnitude earthquakes in that same time period !
Heck ... we were even monitoring Soviet nuclear detonations half way around the world back in the 50's and 60's ... so yes, the accuracy and technology to detect such earthquakes has been around for a long time.