The Southern California earthquake record-breaking drought
Posted by Lowell on April 28, 2002 at 00:18:55:

Moving onto other matters. The long dry spell in southern California
is continuing as I write this. But I thought it would be interesting
to see how unusual this period without a Ml>=3 in southern California
really is. I did a search of all the various catalogs containing
earthquakes in the southern California region and found the times
between consequetive event of Ml>=3.
When the catalog contains the region of southern California excluding
the Calexico region (36N-32.5N, 125W - 114W), the longest interevent
times (in days) - last day is identified by Month, day, year
are:

Days M D YR
37.976250 2 21 1958
31.510162 6 24 1960
30.191979 10 5 1960
29.399317 12 20 1966
29.046458 8 13 1979
27.585949 4 11 1965
26.994120 5 15 1966
24.868923 10 1 1958
24.245220 5 11 1980
23.947245 1 15 1962
23.375544 10 9 1990
22.522014 4 2 1970
22.037407 12 10 1949
21.976481 7 19 1989
20.738090 7 15 1964
20.625290 6 11 1977
20.416262 12 21 1967
20.337500 1 29 1959
20.261111 7 14 1936
20.253449 12 11 1998
20.252234 12 2 1989
20.090486 6 18 1932
20.007280 11 7 1956

The longest time between earthquakes of Ml>=3 in the region in the past 20
Years was the 23.37 day drought which ended on October 9, 1990 followed by
A 21.97 day period between Ml>=3 earthquakes ending on July 19, 1989 and
A 20.25 period ending on Dec 11, 1998 and on Dec 2, 1989.

The longest dry spell for the area INCLUDING the Calexico region (32 - 36N
125W-114W) was 19.34 days ending on Oct 5, 1990 followed by a 17.99 day spell
ending on Jan 8, 1991 and 17.17 days ending on Dec 5, 1983.

Earthquakes which ended these droughts were:

Oct 9, 1990 - South of Simi Valley Ml 3.2
July 19, 1989 - Joshua Tree Ml 3.0
Dec 2, 1989 - Anza area Ml 4.1
Dec 11, 1998 - Lake Isabella Ml 3.6
And Off coast of So. California Ml 3.6

And

Oct 5, 1990 - Calexico region Ml 3.1
Jan 8, 1991 - Anza area Ml 3.4
Dec 5, 1983 - Calexico region Ml 3.8
And Lake Isabella Ml 3.1


The current drought (not including Calexico) started on April 5, 2002
At 08:02 UT. This spell without a Ml>=3 has now lasted about 23 days
Making it the second longest drought in the past 20 years. Another
Quarter of a day (if we don't have an event my morning) it will be the
Longest in the past 20 years.

Including Calexico, the period without a Ml>=3 has now continued since
April 11 at 13:43 UT, a period of 16.5 days. The 7th longest on record.
But another day or two and we will be seeing record-breaking dry spell
For this area as well.

It would appear that the region is overdue for that Ml>=3 earthquake,
If past history is any guide, it should happen any hour now.


Follow Ups:
     ● Re: The Southern California earthquake record-breaking drought - chris in suburbia  09:28:00 - 4/28/2002  (15296)  (1)
        ● Re: The Southern California earthquake record-breaking drought - Lowell  10:31:19 - 4/28/2002  (15297)  (1)
           ● Re: The Southern California earthquake record-breaking drought - Canie  12:30:11 - 4/28/2002  (15301)  (0)