Last updated on July 4th, 2011
Are earthquakes around the world increasing, compared to the historical recorded ‘normal’? Some suggest yes, while others argue no due to technological advancements in earthquake detection and reporting – which is partly true – but mostly for lower magnitude quakes. Given that ‘large’ earthquakes seem to be occurring at a higher than normal rate, I thought that it would be worth data-mining the fatality statistics – to have a slightly different angle approach on the subject.
My data is sourced from the USGS (United States Geological Survey).
Before some of you immediately discount the results due to advancements in technology and data reporting during recent times compared to say, 50 years ago or further… consider this…
Similar to how recent technology has enabled more accurate accounting of small earthquakes compared to years ago, today’s communications technology has no doubt contributed somewhat to a higher number of reports of fatalities due to earthquakes around the world compared with years ago.
There is without a doubt some percentage of ‘skew’ in the numbers because of this. However, I would argue that the skew is somewhat slight when considering that strong-high magnitude earthquakes (and fatalities) are fairly easy to measure and account for – and have been, even 50 or 100 years ago.
In addition, although expected along tectonic boundaries, the random nature of where a large earthquake will occur, will affect the number of recorded fatalities. Logically, if a large quake occurs near a major city region, we will surely encounter higher fatalities. World population has also increased, thus increasing the odds of earthquake fatality (and all other fatalities for that matter…).
Nevertheless, it is interesting to look at historical data, while keeping in mind the known arguments for-and-against an increase in earthquakes or fatalities during recent times.
My instinct tells me that we are in a period of higher than ‘normal’ earthquake activity while looking at magnitude 5 or greater, and while looking at overall fatalities (given the arguments).
Curiously, the highest hit nations with regards to earthquake fatalities since the year 1900 are China, Sumatra, Haiti, Japan, Pakistan, Peru, Italy, Turkey, and Iran.
Earthquake Fatality Trend – 10 year intervals to 2011
As of the end of June, 2011, the world has already received the average (1) quake of magnitude 8 or greater, plus we’re 117% ahead for magnitude 7-7.9, 197% ahead for magnitude 6-6.9, and 212% ahead for magnitude 5-5.9 earthquakes as of percentages for day#174 of the year.
Given these interesting statistics, you may ask, what can I do about it? It’s out of my control…
You can take some preparedness precautions by storing some extra food and water (a ‘survival’ form of life-insurance), build a simple (or complicated) survival kit for you home or vehicle, or think about or make a disaster plan (where you would go – what you would do).
Remember, by failing to prepare, you are preparing to fail…
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It is extremely telling how the USGS ALWAYS will downgrade rather than upgrade the initial value. What does that tell you…
I have never witnessed the USGS upgrading the magnitude after-the-fact. I have been tracking all magnitude 5+ quakes for a year and a half, every day, and I can’t even tell you how many times they shift the magnitude downwards – sometimes a week later. Very odd indeed.
No, not odd – this just tells you something bout instrumentation, the number of the instruments (to low) and the weak points of automatic annotation of quakes. Why on earth should USGS have an interest in making quakes smaller than they are? The difference between a 7.4 and a 7.2 is rather small. They should be able to get more funding, when more serious quakes appear, I guess.
I believe you may have missed the point… that is, if USGS (or whomever) is nearly always needing to downgrade a quake (rather than a mixture of upgrades and downgrades), then the downgrade pattern itself presents an obvious pattern, wouldn’t you say? Although I don’t know… could it be the way that quakes are preliminarily measured, perhaps have a flaw? Then why not fix it? It’s just odd is all…
Not really odd. Initial reports are always “Preliminary”. Often the Magnitude is estimated by an automatic computer estimate. It takes a few days of study of all charts to give a more precise statement of magnitude. Both the Sumatra 1974 and the 2011 great quakes were given upwards results after the preliminary estimates,
Statistically, two Mag 9 events within a decade is an anomaly. Statistically also, it is apparent that geological events intertwine with solar events.
The Sun is in a state which scientists and astro-physicists are finding “interesting”.
And of course, the internet has made world wide populations more aware of events that would have never been reported pre-1990.
e.g. I know of a Volcano in West Sumatera which erupted in 1973 and emitted a CO2 cloud which annihilated an entire village’s population. There was only one survivor – hundreds died. You will never have heard of it. The Indonesian authorities in Jakarta have probably never heard of it. If this event happened today the whole world would know about it within hours.
You don’t learn statistics anymore, won’t you? Geological processes happen over very long periods – so looking at a single year and stating that we have 117% of the average quake is simply pointless. We should look at data over a few hundret years, before we are able to make such statements, unfortunately we don’t have this data. The other thing is, that when we assume a normal distribution its perfectly normal to have years which are above average and years which are below. The more extreme you get, the less likely the situation gets – have a look on the Gauss curve.
That there are some countries, which have a lot of fatalities due to poor (or non-existing) building codes and a very dense population (which is especially true for asia).
An example: The Aquila earthquake in Italy a few years ago reached 6.3 points on the scale. The town was almost completely destroyed, around 300 people where killed. In 2008 we had a quake of similiar strength here in Iceland just below the city of Selfoss – about 50km from Reykjavik. In Selfoss 2 houses had to be taken down afterwards, a handfull of people suffered injuries from glass – nothing more. In Reyjavik the quake still had 6.0 on the scale but nothing happened – we could clearly feel it. The difference? Strict building codes in Iceland.
The Haiti quake had something around 7.0 and killed around 316.000 people – the japanese quake from 2011 was even 9.0 with a few hundret people killed by the quake (the tsunami is a different part of the story). Again peoples lives where saved by strict building codes on Japan and lost due to non-existing in Haiti.
You are correct in everything you have said in this comment. It is an interesting exercise nonetheless, to look at the quake statistics in a narrow window. I tend to do what interests me 😉 I’m certainly not claiming to be a geologist or a professional in this field. I do it for fun.
Your examples of quake fatalities are right on, and as I said within the post, fatalities are largely about the odds of where the quake occurs. Still, it’s fun to look at the data once in a while.
Michael is right about the quality and enforcement of building codes being a reason for high/ low fatalities, however it goes farther than that. As you mentioned, the world’s population has increased dramatically over the last century and this has had the effect of pushing the poor of the world into living in areas that are more dangerous to live in than they normally would opt for(e.g. steep slopes, areas susceptible to landslide and flood etc). You will see a greater number of deaths in poorer countries with large populatons than you will in countries such as Japan and New Zealand which are on the Pacific’s ‘ring of fire’, but have greater wealth.
Christchurch (NZ) recently had some major aftershocks following our devastating ones in September and February. Many previously damaged buildings fell, and the liquifaction and flooding started all over again. Thankfully no major injuries this time. They have had thousands of aftershocks in this whole periods, some quite large. The 2 last week were originally reported as 5.2 and 5.9, but were re-estimated at 5.6 and 6.3, due to closer reading of the hundreds of seismographs all over Christchurch. I notice that the USGS website is not reporting the increased values. The estimates were based on a few “key” readings, but the others showed a different picture.
When looking at the statistics of how many earthquakes there have been, perhaps we should not be counting aftershocks? The original 7.2 last September in Christchurch set off a whole lot of new faults and the place has been rocking and rolling ever since. They have just counted their 7,000th shake! While this may skew the stats, should it really be considered an increase in earthquakes, or just one big one that won’t quit? Exactly the same is happening in Japan – watching the USGS list they seem to have major ones quite regularly, that are all just the earth re-settling after the huge one.
On a different note – the New Zealand Government have just released a list of over 5,000 homes which will have to be abandoned, as the land under them is too unstable to be rebuilt on. These sections will be purchased by the Government and turned into parkland, probably for decades. All are beside the Avon River, and all have liquifaction and flooding. Water and sewage lines have been destroyed and will not be reinstated for decades. A further 10,000 homes are still under evaluation, and may also have to be abandoned.
And the shaking continues…
I’ve been thinking about earthquake sizes and frequencies on and off since the Japan Quake now, about the same time that I chanced upon this blog, and my (long-dormant) mathematical brain re-assures me that variations from year to year are more than likely statistically insignificant, as Michael suggests in his comment.
However, is there any tool that might suggest an upward trend? I would stress “suggest” rather than “prove” because of the short time over which the data has been recorded and published.
Would a rolling 5 year or 10 year average be of any use? In a normal distribution with a small amount of data, that should fluctuate up and down, but if activity is increasing, then that should be reflected to some extent. Or is the data 100 years ago too sparse and unreliable (with regards to unreported events) even for that?
(By the way, if anyone can point me to the raw data (number of recorded earthquakes of each magnitude each year), I’m happy to have a go at producing the graphs!)
This is the list of earthquakes where I sourced my data regarding fatalities.
http://earthquake.usgs.gov/earthquakes/world/historical.php
I designed one of the graphs within the article to show 10 year ‘chunks’ of fatalities while looking for a pattern in that way. There are lots of variables, and rational reasoning to shoot down the ‘suggestions’ from the graphs, as some have already pointed out here, but it is still interesting to look at and think about.
Yes, the data is certainly interesting.
It is a rainy afternoon here, so I’ve had a look at some data for earthquakes of 7+ magnitude since 1900. The results are here, and while it looks like the number of big earthquakes is on a slight upward trend (see 20 year average), it is certainly not as high as it has been in the 1940’s.
https://docs.google.com/leaf?id=0Byy4vfbjfqG0NzI1MzNiYzctNzc1Mi00NjY3LWIzNmMtOWFiMTNlNmZjZWEx&hl=en_US&authkey=CL3amdsH
Data Sources:
http://planb4.com/library/statistics/earthquakes_7_up.html
http://www.johnstonsarchive.net/other/quake1.html
If it carries on raining, I may start looking at correlation between the number of large earthquakes and the number of fatalities!
For those interested in the Christchurch, New Zealand area, here is an interactive map detailing earthquakes and locations as they happened. It takes a little while to go through and a few seconds to start.
http://www.christchurchquakemap.co.nz/
The earthquake in Italy in 1909 caused more than 120.000 casualties, not 80.000 as in your graph.
@Dario de Judicibus, I sourced my data from the USGS. Here is the link for the EQ you’re referring to…
Apparently 72,000 deaths:
http://earthquake.usgs.gov/earthquakes/world/events/1908_12_28.php