Friday, 11 March 2011

Are there more earthquakes in our days? Is the end of the world here?

Not even 24 hours have passed since the deadly 8.9 Mw earthquake in Honshu, Japan, and already conspiranoics, cranks and even some broadcasters are opening the door of the panic room in the internet: Are we having more earthquakes now than some years ago? Is the end of the world approaching? Is Gaia trying to get rid of us?

The answer to all these questions is a big NO.

As most of people know, an earthquake is the sudden slip on a fault, and the consequent instantaneous emision of energy in the shape of seismic waves that was previously accumulated in a fault. There are many reasons for that, and many different types of faults in many different parts of the world, but the Ring of Fire in the Pacific is certainly one of th most hazardous areas in our planet in terms of seismicity.

The USGS, even though is the national geological survey for the USA, registers earthquakes in all the planet and publishes statistics about them. So, are earthquakes from frequent lately? The answer is in the facts, as usual in this topics.

Take a look to these graphs, where the number of earthquakes, classified by number and per year, is depicted. It is clear and obvious that the frequence of quakes of magnitud over 7.0 stays pretty constant:

But, we may think: "Every year it seems that more people die because of natural catastrophes". Well, it may seem like that until we take a look to the statistics, and then this idea simply vanishes.
What happens is a mixture of not so natural phenomena.
  • In first place, we have instant communications around the whole of the planet. And this didn't existed before. We switch on the TV when we get up, and we see in the news in UK or USA or Finland what is happening at the moment in Japan, tens of thousands of kilometres away.
  • Secondly, the network of seismograph stations is more complete every year, and therefore the amount of earthquakes located is higher (and also the amount of smaller earthquakes detected. In 1931 there were 350 seismograph stations in the world. Today, there are more than 8000. Of course, that information is easily available and fills the media constantly. It is far more easy now to report an earthquake of 5.0 or 6.0 Mw, than it was in 1985. Note that the graphs DO actually show an increase, but this increase is more probably related to the number of registered earthquakes, and not to the actual seismic activity.
  • In the last years, big quakes have occurred in populated areas, being more relevant. Sumatra, Haiti, Chile, Japan... But do we care when an earthquake happens in the Aleutians? Hazard is not synonym of risk! Risk involves exposure of human lives, of economically valuable places.
And of course, the Mayans didn't predict anything!

Source of the graphs: http://earthquake.usgs.gov/earthquakes/eqarchives/year/graphs.php

33 comments:

Eunice said...

According to your graphs:

Earthquakes in:

1980-1989

6-6.9: 980
7-7.9: 101
8-9.9: 4
Total: 1085

1990-1999

6-6.9: 1339
7-7.9: 147
8-9.9: 6
Total: 1492

2000-2009

6-6.9: 1467
7-7.9: 131
8-9.9: 13
Total: 1611

Darren Baker said...

I don't believe that there has been a definite increase, but I sure would love to hear a defense against the previous comment. It would appear, according to your own cited graphs, that there HAS been an increase. Care to comment?

Jorge said...

What increases is the seismic record, not the number of earthquakes.

As I have already written in the article, the global network of seismographic stations expands every year, and that means that more earthquakes are registered. In past decades, earthquakes in remote regions wouldn't have been detected, or they would have been accounted as background noise if the process of triangulating their location was not accurate enough.

The record of earthquakes of different magnitudes increases in a linear fashion, and in the same proportion, which does not actually indicate an increase of seismic activity.

I'll try to show this correlation if I can obtain the needed data (number of station and their location per year).

Greetings

(Eunice, the graphs are not mine. At the end of the article is the link to the source, USGS).

Darren Baker said...

Jorge:

Thank you for your comment!

Ahh, I see - this is much like the increase in cancer rates being due in large part to the advancements in detection methodology. This nicely maps on to the increase in smaller quakes, but I don't believe that this would account for the increase in the 8 - 9.9 quakes, as these don't require sensitive seismometers. Is that just a statistical anomaly?

Darren

Jorge said...

I would think you are right, Darren. I would think that this deviations are not very meaningful.

I recommend reading that, from the USGS http://earthquake.usgs.gov/learn/topics/increase_in_earthquakes.php

The last sentence, I think it says it all:

"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. "

If a specific region of the world is specially active for some time, the statistics can change totally!

I am glad of have you as reader,

Cheers,

Jorge

danakil said...

"...the global network of seismographic stations expands every year, and that means that more earthquakes are registered."

a)Would you care to share the specific numbers that support this assertion?
b) Do you mean that the network is expanded in terms of reach or in terms of sensitivity?

"...The record of earthquakes of different magnitudes increases in a linear fashion, and in the same proportion, which does not actually indicate an increase of seismic activity."

Interesting conclusion. I would've thought that if the increase was mostly in the lower magnitudes, rather than uniform across the board, then it would be clearly explainable in terms of an enhanced detection system.

Furthermore, since (as you yourself point out) the increase seems uniform across all magnitudes, your explanation necessarily implies that a sizable number of big earthquakes went "undetected" in the 20th century--a somewhat difficult point to defend, IMO.

Anonymous said...

Judging from your own graph, earthquakes have increased dramatically over the past 30 years or so -- up by almost 40% a year.
Do you know how to read graphs and do basic math?

Sindi said...

i have just gone through all the usgs figures for the years 2000-now. here are the averages for 7.0+ earthquakes to today's date of 4/7/11:

averaged 1.24/month last 10 years
averaged 1.35/month last 5 years
averaged 1.47/month last 3 years
averaged 1.58/month last 2 years
averaged 2.08/month last 12 months
averaged 2.76/month this year.

so yes there are more 7.0+ earthquakes now and the pattern shows the incidence has been increasing steadily.

Jorge said...

Anonymous,

Firstly, please, moderate your tone. I am polite with everyone and I expect the same from others.

I have already said, in these comments and also in the article, that the network of seismographic stations increases, and therefore the number or earthaquakes registered increases. But that DOES NOT mean that the number of earthquakes increases.

Sindi,
Thanks for the calculation, but I say the same: the network increases in number, the detection too. Besides, it is not very significative to use the data of this year as many of the 7 plus earthquakes have been aftershocks of the big 9.0 of Japan.

Thanks four your visits.

Jorge said...

And, by the way, let's consider the earthquakes over 7 Mw. starting in 1995.

20, 15, 16, 12, 18, 15, 16, 13, 15, 16, 11, 16, 12, 17.

Where is the dramatic increase, anonymous? I insist, read the article before critisising it. I clearly said:

"Secondly, the network of seismograph stations is more complete every year, and therefore the amount of earthquakes located is higher (and also the amount of smaller earthquakes detected. In 1931 there were 350 seismograph stations in the world. Today, there are more than 8000. Of course, that information is easily available and fills the media constantly. It is far more easy now to report an earthquake of 5.0 or 6.0 Mw, than it was in 1985. Note that the graphs DO actually show an increase, but this increase is more probably related to the number of registered earthquakes, and not to the actual seismic activity."

Good day.

Anonymous said...

Thank you Jorge, it is good to have some reassuring common sense out there.

Jorge said...

You are welcome. Thanks for your comment and your visit.

Anonymous said...

Great site,as a person going thru the Earth Quakes in New Zealand, there is a lot of speculation and fear and its great to look to science!

Do you also think that what may appear to be a increase of deaths would also be due to the population increase?

Ie: areas that perhapas a 100 years ago had no real population are now a small thriving city, but 100 years ago it may of been hit regulay by quakes, but no deaths due to no lives there.

I dunno just my ideas:)

Thanks again

Angus

Jorge said...

I wouldn't say there is an increase in the death toll of earthquakes... I don't have numbers, but in the pass, quakes causing major destruction didn't have to be necessarily very powerful. Every eq is unique, anyway, and each of them happen in very different conditions, not only geologica, but also in terms of society, urban development, etc.

Thanks for the comment :-)

Edwin said...

Hi All,

This site looks we good to me simple but effective and people are nice too.

And I just want to share my personal experience. I'm in Markham, Ontario, Canada (about 30 mins north of Toronto Downtown). I has been working in the same building for the last 11 years and never had earthquake before but in the last 6 months it happens twice and in deed it was just happen 20 minutes ago (5.8)

Other than the number of earthquake (looks like it did not increase much) did anyone had idea what is the distribution looks like? I means the place that have earthquake happened, is more city area (I means the area is urbanized for more than 50 years) being affected? In other word the location of earthquake shifted from remote area to city (again, my definition of city is the area had been urbanized for more than 50 years not new development).

My through is if that is the case (the trend of more city being affected) then we may be running into trouble even the number of earthquake was not increased.

Thanks
Edwin

Anonymous said...

First, thank you for your analysis.

That said, I'm not sure I agree with the suggestion that the increase in earthquake activity is an artifact of more sensors in the field.

If you look at the increase in activity from 1980-1989 vs. 2000-2009:

Magnitude 6 range quakes increased by 50%.

Magnitude 7 range quakes increased by 30%.

Magnitude 8 range quakes increased by 225%.

I don't think this is consistent with more monitoring equipment being put in place. For example, I wouldn't expect to see the magnitude 7 range quakes lagging behind.

I think the data is consistent with an increase in the number of larger 8 range quakes, which in turns has leads to an increase in the number of 6 range aftershocks.

Anonymous said...

Thank you, Jorge, for your anaysis. And thanks to others for pros and cons. As a non-geologist, I found this all very interesting, not an all black-and-white display of unchanging bench marks. I can tell you much about snowstorms in Minnesota but have no experience in earthquakes -- and satisfied to have it so.
Jim B.

Jorge said...

Thanks to the posters of new comments. I am about to go to the office and I don't have time to reply in depth, but...

- Jim, I am from NW Spain, where some seismicity is present. In one had I would have liked to have felt a quake (living now in SE England, that is very unlikely). In the other hand... I am fine like that!

- Anonymous user: Thanks for your visit and your observation. You are right that the increase of more than a 200%, but we are talking of an increase from 4 to 13. You can see how 2007 had 4 earthquakes larger than 8 magnitude and 2008 none. Clearly, some periods of time have to have more activity, and some others less, but we cannot say "There are more earthquakes now", as this statement implies a regular and consistent increase, which doesn't seem to happen. Surely there are cycles in the frequency, but more probably those are random cycles than a "global increase" of earthquakes, as earthquakes in different tectonic regions and regimes are totally independent from each other.

- Edwin, I don't think the earthquakes happen now more in urban areas, but we have more information, instantly, than we had before. If you check the USGS website you can see that every day there are several 6 to 7 magnitude earthquake, all around the planet, and most of them are not felt by any human.
But, if one happens in USA, it has a much more relevance than one occurred in Iran or Pakistan.

Work time, and I hope you are all right after this quake in Virginia!

J.

Omeezy said...
This comment has been removed by a blog administrator.
Jorge said...

I am sorry, Omeezy, but I don't tolerate this tone, so your message has been removed. When you decide to write with respect (the same respect I am using with you), you are very welcome to post here your ideas and opinions, but please, keep an eye on your language.

Thanks.

Anonymous said...

I was looking at the following web page
http://earthquake.usgs.gov/earthquakes/world/most_destructive.php

I thought it interesting that for the last 100 years there have been 11 earthquakes that took the lives of at least 50k per compared to the prior 1000 years of 11 earthquakes that did the same. Looks like a lot more lives taken over the past 100 yrs than the prior 1000 due to earthquakes.

Anonymous said...

just to clarify one thing about my last comment

when I said more lives over the past 100 than prior 1000 yrs, I was referring to on average ;-)

Jorge said...

Well, we are more and more people on this Blue Marble :-)

Anonymous said...

holl smokes

ommezy said...

are you still deleting comments from people that disagree with you? obviously all your little graphs are not accurate. don't use 24-7 news cycle as an excuse. newspapers have been around 200+ years.

earthquake activity is up!!!! No doubting it.

Jorge said...

I delete comments that include spam links or insult others. Full stop. If you do any of these, it is your fault, not mine.

In general, I am very busy to discuss with trolls.

Jorge said...

Besides, the "little graphs", are not mine, they have been produced by USGS. Please, inform yourself and read before you create your own little story...

Omeezy said...
This comment has been removed by a blog administrator.
Jorge said...

Omeezy, you are banned from this blog for insulting me. If you would read the comments of other people, you would see that I don't have any problem with other point of views. My only problem is your insults

I repeat, you are banned. Full stop.

Andy said...

@omeezy
"We are experiencing the dawn of unprecedent plate activity"

You have never been very interested in geology, right? You just like to read a few paranoid websites and convince yourself that all will end in December 2012, don't you?

For God's sake... stop saying silly things.

Pablo Neruda said...

Another 6.3+ earthquake in southern california... thats number 6 this year. most in last 100 yrs was 5.

Yet thee "author" of this blog continues to delete posts by those that disagree with him.

Lynn Trump said...

Earthquake seems to be a catastrophe that disaster recovery can be very difficult to achieve. I guess we should just cross our fingers and hope for the best.

Anonymous said...

Did anyone ever consider that earthquakes are judgments from the hand of Almighty God?