Earthquakes Are Not Increasing In Frequency, page 2

reply to post by muzzy

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The strict accuracy of the current data is not really important. A missing earthquake here or there isn't going to change the results enough to show a trend.

What is important is that you are working with incomplete historical data and drawing statistical conclusions from it. You are using pre-filtered catalogs. If you're interested, here is a summary of all recorded 7+ earthquakes from 1900 to 1999.
planb4.com...

Here is a graph I made a while ago using that data and data from USGS from 1973 forward. (I have not updated it)

If anything, it shows a downward trend. The middle of the 20th century was much more active than the present.

This can be debated forever.

I personally believe that access to the internet is just raising awareness of what normally was not reported.

For me a really good program for looking at worldwide earthquakes is this one.

bingweb.binghamton.edu...-Eruptions

A person can visualize on a world map all earthquakes that have happened since 1960.

You can see volcanic eruptions too.

Fifty years is a pretty good period of time for studying the frequency of quakes.

Take the time to download and install this program.

reply to post by Phage

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I just don't follow your reasoning.
You say I am using incomplete and filtered data and you quote USGS but they themselves have incomplete data.

On that link it says "Statistics were compiled from the Earthquake Data Base System of the U.S. Geological Survey, National Earthquake Information Center, Golden CO"
1975 ~ 21 quakes
so where were the other 6?

reply to post by muzzy

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I don't know how I can explain it any other way than I have. You are comparing a dataset which is incomplete to a dataset which is less incomplete. You are not comparing apples to apples. It is inevitable that more earthquakes are seen in the more complete dataset because it returns earthquakes which do not appear in the less complete database. It does not mean that there is a higher frequency of earthquakes.

You're right, the summary is not accurate. I shouldn't have used it without knowing how it was derived. In fact, the transition seems to be visible in my graph. That demonstrates my point. Within a given dataset, which should be self consistent, no trends appear. It is when a jump is made from one dataset to another that this happens.

reply to post by Phage

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So where is the data that that list is taken from? The links on theat page go around in a circle back to NAOO search page, and its back to what I have got already.
If USGS are not releasing all the data then why?

41 quakes in 1943 above 7 is way beyond the combined data umbers available from all sources (at least on the internet).

It can only be bad news if they are holding back information.

I'm going to carry on researching back into history with my project anyway, its been interesting finding out about earthquakes before my time, and gives a better sense about where to expect them in the future.

reply to post by muzzy

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You may be interested in this. I just discovered it though it has apparently been available since January 2009. It is a very detailed catalog, providing information about the source catalogs and the magnitude scales used.

A quick check shows that it cooincides quite well with the worldwide search catalog from USGS, generally matching the values. It also is provides an idea about what is involved with determining magnitudes.

For example; an earthquake which shows in the worldwide search (chosen at random).
1984, 12, 28, 103753.76, 56.194, 163.46, 7, 33,PDE

Shows in the centennial catalog with the following magnitude determinations:
6.7 Mw HRV
6.7 Mw GS
6.7 Mw P&S
7.0 Ms P&S
7.1 Ms ISC
6.4 Ms PAS
6.7 Ms BRK
6.2 mb ISC

It should be interesting correlating this catalog with the others. But think about what those variations in magnitudes means and note that Mw is sometimes higher and sometimes lower than Ms. Please read and understand the description of how the catalog was compiled.
earthquake.usgs.gov...
earthquake.usgs.gov...

reply to post by Phage

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Thanks for that link
I think I can use that, just a quick glance at a random year 1951 it has 13 quakes and I just had 11.
They seem to have the same parameters as I started out with, if it has the number 7 in it then it goes in the lists, rgardless if its Mw , mb or Ms etc.

I'm about to refresh the 1940's next, so I'll run those numbers along with the stuff I already have and see whats up.

reply to post by muzzy

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Not quite, it's quite a bit more complex than that.
As I said you should read and understand the PDF before you start working on any analysis. It pays to know your data source.

reply to post by Phage

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OK I read the whole thing, what was I looking for

I already know its complex, and from what they say there they don't even understand it themselves

We'll see how it goes, perhaps they have already done what I am trying to do i.e. bring all sources together into one database listing, I'm trying to make it easier to get an overall view using maps, and breaking it down into 12 month periods, the text lists are just to show the sources.
If I use any of their data I'll put the original source on the popup balloons instead of "usgs" eg, G&R for Gutenburg and Richter, PAS for CIT Pasadena , Ustu for Utsu (instead of iisee) etc

Prior to 1900 all I have to work with is Utsu's work,
The Catalogue of Destructive Earthquakes AD7 - AD 1899 by John Milne,
Historic Costa Rica quakes by Cole &Yee,
Study of Historical Earthquakes in Japan by Usami,
Historical earthquakes of Syria 1365BC to 1900AD by Sbeinati, Darawcheh and Mounty
and a few other bits and pieces like the
NZ Earthquake Catalogue which goes back to 1830,
Catalogue of Tsunamis in the Samoa Islands by Parara-Carayannis & Dong

reply to post by muzzy

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I was referring to this:

They seem to have the same parameters as I started out with, if it has the number 7 in it then it goes in the lists, rgardless if its Mw , mb or Ms etc.

You will find earthquakes which do not meet that criterion.

reply to post by Phage

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Oh OK. I seen that as I went down the list.

Man I wish I had seen this page/list/work before I started on my little project.
I just crosschecked 1949 with what I had and all those were there, .... plus 17 more

I'll have to redo the whole thing again.

Do you think this is the list that USGS have used to formulate their statement that quakes are not increasing?
If 1949 is any indication and the other years are similar then yes you are right, the current numbers appear normal.

I wonder how long it took them?

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