Did high magnitude (mag 6+) earthquakes indeed disappear for a 30 year period (1975 - 2005) ?

The graph is false. I experienced 3 quakes in Northern California in a 24 hr period in April of 2002 (Petrolia events) that damaged my house and caused the water source (a spring) for my home to "dry up" for an 8 month period following, causing me to buy and store water in 1000 gallon increments until the spring began producing again. These three quakes were respectively - 7.2, 6.6, and 6.7 richter. I certainly felt personally those >6.5 quakes, and as other persons have noted the amount of >6.5 events have been relatively stable in those years noted.

This image cleared it up for me. There is a large anomaly here and it has sparked my curiosity. Go to Wolfram Alpha and play with the numbers a bit it is actually very odd.

A little paranoia is good thing.



P.S. This is my first post and I would like to say I am happy to have found this place in space.

reply to post by Chadwickus


I got a different number Chad ..... 5249

FILE CREATED: Fri Jun 24 22:54:33 2011 Global Search Earthquakes= 5249 Catalog Used: PDE Magnitude Range: 6.0 - 10.0 Data Selection: Historical & Preliminary Data

What was going on in space at this time? What does data about the sun show for this same time frame? Number and size of sunspots and solar flares? CME data? It would be interesting to see if there is anything there?

reply to post by Chadwickus


And 21 quakes over 8.0

Source

Map of the quakes in the list

FILE CREATED: Sat Jun 25 00:02:34 2011
Global Search Earthquakes= 21
Catalog Used: PDE
Date Range: 1975/01/01 to 2005/12/30
Magnitude Range: 8.0 - 10.0
Data Selection: Historical & Preliminary Data


CAT YEAR MO DA ORIG TIME LAT LONG DEP MAGNITUDE IEM DTSVNWG DIST
NFO km
TF

PDE 1975 05 26 091151.50 36.00 -17.65 33 8.1 UKPAS 6D. .T.....
PDE 1976 01 14 164733.50 -28.43 -177.66 33 8.2 UKBRK .D. .T.....
PDE 1977 04 21 042409.60 -9.97 160.73 33 8.1 UKPAS 7C. .T.....
PDE 1977 08 19 060855.20 -11.09 118.46 33 8.0 UKPAS .C. .T.....
PDE 1980 07 17 194223.20 -12.52 165.92 33 8.0 UKBRK .F. .T.....
PDE 1985 09 19 131747.35 18.19 -102.53 27 8.0 MwHRV 9CM .TS...M
PDE 1986 05 07 224710.87 51.52 -174.78 33 8.0 MwHRV 6DM .T.....
PDE 1986 10 20 064609.98 -28.12 -176.37 29 8.3 MSBRK .FM .T.....
PDE 1989 05 23 105446.32 -52.34 160.57 10 8.2 MsGS 5FM .T.....
PDE 1994 06 09 003316.23 -13.84 -67.55 631 8.2 MwGS .CM ......S
PDE 1994 10 04 132255.84 43.77 147.32 14 8.3 MwHRV 9CM .T....S
PDE 1995 07 30 051123.63 -23.34 -70.29 45 8.0 MwGS 7CM .T....S
PDE 1995 10 09 153553.91 19.06 -104.21 33 8.0 MwHRV .CM ST....S
PDE 1996 02 17 055930.55 -0.89 136.95 33 8.2 MwHRV .CM .T.....
PDE 1998 03 25 031225.07 -62.88 149.53 10 8.1 MwHRV ..M .......
PDE 2000 11 16 045456.74 -3.98 152.17 33 8.0 MwHRV .CM STS...S
PDE 2001 06 23 203314.13 -16.26 -73.64 33 8.4 MwHRV 8CM .T....S
PDE 2003 09 25 195006.36 41.81 143.91 27 8.3 MwHRV 8CM .T....S
PDE 2004 12 23 145904.41 -49.31 161.35 10 8.1 MwHRV .FM .T.....
PDE 2004 12 26 005853.45 3.30 95.98 30 9.1 Mw01100 9CM STS...M
PDE 2005 03 28 160936.53 2.09 97.11 30 8.6 MwHRV 8CM 3TS....

Originally posted by davidgrouchy




Additionally if one looks at the whole trend
over a larger period of years, one finds that the
earthquakes are increasing in magnitude and frequency.


[atsimg]http://files.abovetopsecret.com/images/member/96699ee40d98.png[/atsimg]

Are you sure earthquakes are 'increasing' based on that graph, or that records going back to "AD" might be a bit shoddy?

An excellent thread, good catch!

I believe this site has good info to offer on this subject.
www.earth.webecs.co.uk...

Originally posted by Chadwickus
reply to post by tauristercus

 

Not sure, the further back we go, of course the reliability of reports reduces...

What may be interesting is that the 70's is when the Richter scale was phased out and changed to what we know as magnitude to measure earthquake intensity.

May be a coincidence, I dunno?

No it was phased out because the man Richter who devised it used the geography of California as his basis which is not compatable for measuring earthquakes accurately in other parts of the world. The waves that travel through the rock types in Califorina travel differently in other places in the world so a new system was devised albeit similar to the Richter scale.