Hi All. Just out of curiosity I thought I would take a look at the quake activity prior to the two M=5.2 quakes that struck Santa Rosa in 1969. Keep in mind that most likely the seismomter density didn’t exist then as it does today so a lot of the smaller quakes (if there were any) weren’t recorded. It isn’t until August of 1970 that the first quake in the M=1.0+ was recorded.

What I found interesting was the swarm of quakes that occurred in April of 1956. There were two smaller swarms prior to the swarm in 1956. The first was in 1949 and the second in 1951. After 1956 it appears the activity decreased, but there really isn’t anyway of knowing if this was only for this period, or if there were other periods in which there were active periods and then quiet periods.

Note that there were two M=4.0+ in 1956 and there weren’t any M=4.0+ quakes after the M=4.5 aftershock until the Bennett Valley M=4.2 quake in 1999 and the 2003 M=4.3 in Santa Rosa which is centered between the two 1969 quakes. I wonder what’s next??? Take Care…Don in creepy town

catalog=ANSS
start_time=1898/01/01,00:00:00
end_time=1969/12/01,00:00:00
minimum_magnitude=0.1
maximum_magnitude=10
event_type=E
delta=0 km to 16 km from (38.4963,-122.6638)
Date Time Lat Lon Depth Mag Magt Nst Gap Clo RMS SRC Event ID
----------------------------------------------------------------------------------------------
1945/11/21 22:56:10.00 38.4200 -122.7800 3.50 ML BK
1949/08/09 00:39:27.00 38.5800 -122.6700 3.60 ML BK
1949/08/14 08:19:58.00 38.5800 -122.6700 2.50 ML BK
1949/08/15 23:52:54.00 38.5000 -122.5000 2.20 ML BK
1949/11/08 12:41:16.00 38.5000 -122.7000 2.50 ML BK
1951/02/20 06:52:47.00 38.4200 -122.6500 2.20 ML BK
1951/08/11 14:15:59.00 38.5000 -122.5000 2.80 ML BK
1951/11/26 07:21:53.00 38.5200 -122.7500 3.40 ML BK
1951/11/26 08:53:30.00 38.5300 -122.7700 3.20 ML BK
1951/11/26 13:21:26.00 38.5200 -122.7500 2.10 ML BK
1952/07/09 22:04:48.00 38.5300 -122.6200 2.50 ML BK
1952/09/26 04:35:43.00 38.4200 -122.5800 3.20 ML BK
1952/11/21 23:27:25.00 38.4000 -122.6700 2.40 ML BK
1954/01/29 07:36:56.00 38.5000 -122.6500 2.80 ML BK
1955/02/25 00:50:05.00 38.4000 -122.6000 2.80 ML BK
1956/02/14 17:26:28.00 38.5500 -122.5500 2.30 ML BK
1956/04/05 04:29:13.00 38.5300 -122.5200 4.40 ML BK
1956/04/05 04:29:32.00 38.5300 -122.5200 4.20 ML BK
1956/04/05 04:32:29.00 38.5300 -122.5200 2.50 ML BK
1956/04/05 04:33:28.00 38.5300 -122.5200 2.30 ML BK
1956/04/05 04:33:52.00 38.5300 -122.5200 2.70 ML BK
1956/04/05 06:17:49.00 38.5300 -122.5200 2.50 ML BK
1956/05/03 03:30:30.00 38.4300 -122.5300 3.00 ML BK
1960/08/05 06:15:53.00 38.4000 -122.6000 2.00 ML BK
1962/02/28 13:40:32.60 38.5700 -122.7300 3.10 ML 14 BK
1962/12/06 01:41:06.10 38.5200 -122.5800 2.60 ML 11 BK
1963/12/07 12:04:11.60 38.5000 -122.7000 2.70 ML 9 BK
1964/09/23 16:30:12.90 38.5800 -122.7200 3.00 ML 7 BK
1965/07/15 02:57:08.00 38.5000 -122.8000 2.80 ML 8 BK
1965/10/18 23:19:00.00 38.6000 -122.7000 3.00 ML 9 BK
1969/10/02 04:56:45.33 38.4963 -122.6638 0.07 5.27 Md 39 104 52 0.20 NC -1003132
1969/10/02 05:14:22.65 38.4473 -122.6690 4.34 3.40 Md 18 136 47 0.16 NC -1003133
1969/10/02 06:19:56.33 38.4515 -122.7522 4.16 5.22 Md 52 170 58 0.20 NC -1003135
1969/10/02 07:10:11.34 38.5018 -122.7755 22.58 3.93 Md 16 318 51 0.21 NC -1003136
1969/10/02 12:27:04.65 38.5085 -122.6872 0.02 4.52 Md 52 106 53 0.23 NC -1003137
1969/10/06 14:28:06.96 38.4753 -122.6987 4.50 4.28 Md 18 53 1 0.02 NC -1003160
1970/08/28 20:08:21.58 38.4225 -122.6155 0.03 1.78 Md 5 159 7 0.07 NC -1005560

catalog=ANSS
start_time=1898/01/01,00:00:00
end_time=2005/12/01,00:00:00
minimum_magnitude=4.0
maximum_magnitude=10
event_type=E
delta=0 km to 16 km from (38.4963,-122.6638)
Date Time Lat Lon Depth Mag Magt Nst Gap Clo RMS SRC Event ID
----------------------------------------------------------------------------------------------
1956/04/05 04:29:13.00 38.5300 -122.5200 4.40 ML BK
1956/04/05 04:29:32.00 38.5300 -122.5200 4.20 ML BK
1969/10/02 04:56:45.33 38.4963 -122.6638 0.07 5.27 Md 39 104 52 0.20 NC -1003132
1969/10/02 06:19:56.33 38.4515 -122.7522 4.16 5.22 Md 52 170 58 0.20 NC -1003135
1969/10/02 12:27:04.65 38.5085 -122.6872 0.02 4.52 Md 52 106 53 0.23 NC -1003137
1969/10/06 14:28:06.96 38.4753 -122.6987 4.50 4.28 Md 18 53 1 0.02 NC -1003160
1999/09/22 22:27:13.11 38.3950 -122.6342 9.79 4.20 ML 61 47 14 0.12 NC 21054737
2003/05/25 07:09:33.67 38.4578 -122.6980 5.06 4.32 ML 68 52 2 0.17 NC 30225889