Are earthquakes increasing in strength or frequency?
Just found myself in a debate where the opposition claims earthquakes is on the rise (judgement day, wrath of god, etc..), being a skeptic I of course needed evidence, and where better to get it than to analyse it for myself from raw data?
How many earthquakes are there?
I went to the United States Geological Survey for the raw data, they have a pretty big list of “selected earthquakes of general historic interest” (6.0+) earthquakes recorded (ordered by magnitude, strongest quake first)
http://earthquake.usgs.gov/earthquakes/world/historical_mag_big.php
I then made a little computer program to parse the text, and output it in csv format:
java program: Test.java
data text file: quakes.txt (program input)
csv result file: quakes.csv (program output)
The output from the data was opened in a spreadsheet for further analysis. There are 722 quakes in the input data file. I used the data from the period 1900 to 2010 in the statistics below (660 of the 722 total data entries).
The data in table form
| 6+ | 7+ | 8+ | |
| 1900 | 9 | 5 | 1 |
| 1905 | 14 | 12 | 5 |
| 1910 | 14 | 9 | 1 |
| 1915 | 9 | 6 | 0 |
| 1920 | 10 | 8 | 3 |
| 1925 | 15 | 10 | 0 |
| 1930 | 20 | 13 | 4 |
| 1935 | 12 | 7 | 2 |
| 1940 | 16 | 15 | 4 |
| 1945 | 21 | 18 | 5 |
| 1950 | 21 | 11 | 3 |
| 1955 | 20 | 18 | 3 |
| 1960 | 12 | 10 | 3 |
| 1965 | 34 | 18 | 3 |
| 1970 | 21 | 13 | 2 |
| 1975 | 18 | 12 | 0 |
| 1980 | 15 | 4 | 0 |
| 1985 | 17 | 6 | 1 |
| 1990 | 17 | 11 | 1 |
| 1995 | 31 | 21 | 1 |
| 2000 | 110 | 50 | 5 |
| 2005 | 194 | 67 | 8 |
The first column is the date of the quakes, the next 3 are number of earthquakes with a magnitude of at least 6, 7 and 8 respectively.
Data is grouped into 5 years.. so the first row with year 1900, is data from 1900 to 1904, followed by 1905 to 1909, etc..
Graph
Click for larger version
Conclusion
This graph makes it look like earthquakes are running rampant, and you might have seen a very similar graph on the Internet (YouTube and other places), used by conspiracy cranks as an argument that earthquakes are increasing. But fortunately this graph is very misleading.
The data used to make it is complete rubbish, to quote the page they are collected from: “selected earthquakes of general historic interest”.. These quakes have been hand picked as the most interesting ones, and the data has a HUGE bias towards newer earthquakes, so you can’t make any meaningful statistics out of it (except if you are making statistics of which years the guy who compiled the data finds “interesting”).
Maybe we should try and remake the graphs using some good solid data..
== Real Data ==
A scientist at the USGS was kind enough to send me a datafile with all the 7.0+ earthquakes from 1900 to 2010 (all the registered quakes, not filtered in any way).
Making some graphs from those data yields results consistent with what the experts on earthquakes are saying.. They are totally random and unpredictable, and there has been no increase of earthquakes since we started recording them:
Frequency of earthquakes from 1900 to 2010. Click for bigger version:
Distribution of earthquakes by month:
Distribution of earthquakes by day of month, (day 31 omitted for obvious reasons):
