Hi All. Quakes in Montana aren’t really anything new to the area. They have had more then their fair share of them.

Although earthquakes are common in Montana, the early history of felt shocks is incomplete. Only four felt earthquakes that occurred before 1900 are on record. The first was a shock on May 22, 1869, that reached intensity VI at Helena. In 1872 Helena was shaken again, this time by two earthquakes, one on December 10 and the other on December 11, both intensity VI. The fourth pre-1900 earthquake was an intensity VI shock that struck Dillon November 4, 1897.

The first significant 20th century Montana earthquake occurred on June 27, 1925, when a magnitude 6.7 shock caused violent shaking over a 1,600 square kilometer area in southwestern Montana. The earthquake was felt over a 803,000 square kilometer area extending from the North Dakota line to Washington and from the Canadian border to central Wyoming.

A series of severe earthquakes in the Helena area during October and November 1935 caused four deaths, several injuries, and property damage exceed $4 million. The first shock of the series came on the evening of October 3 in the form of a hard vertical jolt (intensity V). On October 12, a stronger shock occurred that caused some damage in Helena and Fort Harrison (intensity VII) and had a total felt area of 181,000 square kilometers.

The largest earthquake in Montana's history was the magnitude 7.1 Hebgen Lake earthquake of August 17, 1959. At 11:37 p.m., Mountain Standard Time, the earth beneath Hebgen Lake suddenly warped and rotated, generating a seiche that continued for about 11 1/2 hours. The first few waves were over 1 meter in height, large enough to flow over Hebgen Dam, a concrete core earth fill structure that was completed in 1914. Although the dam's concrete core wall cracked in 16 places, only a minor amount of seepage occurred. The surface of the lake, which contained 324,000 acre-feet at the time of the earthquake, dropped more than 3 meters because of the violent geologic changes.

I did a check on quakes for the immediate area of the M=5.6 quake and found that there had been a swarm of quakes that started in Jan. 2005 and ended in Feb. 2005. The swarm is located about 17 miles NE of the M=5.6 quake. Was that swarm a precursor to today’s quake? I would like to say yes, but the best I can do is, maybe. Take Care…Don in creepy town

catalog=ANSS
start_time=2004/01/01,00:00:00
end_time=2005/07/26,05:53:29
minimum_magnitude=0.1
maximum_magnitude=10
event_type=E
delta=0 km to 32 km from (45.398,-112.550)
Date Time Lat Lon Depth Mag Magt Nst Gap Clo RMS SRC Event ID
----------------------------------------------------------------------------------------------
2004/01/05 05:56:46.00 45.1690 -112.4540 18.10 0.70 Mc 6 142 33 0.20 MB
2004/02/21 03:26:55.70 45.3910 -112.3770 16.50 0.60 Mc 7 127 32 0.12 MB
2004/04/20 18:47:50.80 45.2420 -112.5390 21.40 1.40 Mc 12 124 39 0.18 MB
2004/04/27 17:54:42.70 45.2390 -112.4860 10.60 2.40 Mc 35 111 35 0.19 MB
2004/05/17 04:00:57.00 45.2370 -112.4880 12.30 2.30 Mc 36 108 35 0.19 MB
2004/07/05 06:47:30.00 45.2690 -112.5270 9.20 1.20 Mc 8 147 38 0.09 MB
2004/08/16 09:33:47.60 45.2370 -112.4520 9.60 1.00 Mc 6 134 32 0.01 MB
2004/08/26 05:06:02.10 45.2220 -112.5060 17.20 0.90 Mc 7 141 37 0.06 MB
2004/09/26 12:47:59.10 45.4700 -112.3770 8.40 1.50 Mc 19 126 37 0.19 MB
2004/09/27 17:09:13.90 45.2640 -112.8170 9.80 1.20 Mc 11 136 48 0.05 MB
2004/10/03 15:50:09.20 45.3300 -112.3510 13.40 1.50 Mc 15 122 27 0.16 MB
2004/10/13 01:07:07.80 45.3630 -112.8820 7.60 1.50 Mc 17 122 52 0.15 MB
2004/10/15 01:27:49.40 45.2140 -112.6560 12.20 1.20 Mc 9 164 46 0.16 MB
2004/11/05 12:55:00.60 45.4660 -112.3710 12.40 2.90 Mc 51 74 37 0.18 MB
2004/11/06 05:45:04.90 45.4550 -112.3340 6.40 1.60 Mc 18 120 34 0.13 MB
2004/11/08 20:15:21.30 45.1110 -112.5410 21.70 1.10 Mc 10 138 40 0.05 MB
2004/11/10 06:04:57.60 45.4680 -112.3750 6.90 1.10 Mc 13 115 37 0.09 MB
2004/11/11 04:12:20.10 45.4690 -112.3740 9.50 1.80 Mc 31 105 37 0.15 MB
2004/11/11 09:46:25.70 45.4730 -112.3690 14.80 1.10 Mc 7 131 39 0.04 MB
2004/11/15 19:14:35.80 45.6090 -112.7650 11.80 2.10 Mc 25 116 24 0.19 MB
2004/11/23 18:02:01.90 45.4650 -112.3770 10.60 2.10 Mc 26 115 37 0.17 MB
2004/12/10 06:46:38.40 45.4680 -112.3690 7.30 0.80 Mc 9 125 37 0.12 MB
2004/12/12 13:37:26.80 45.1670 -112.6160 3.50 1.40 Mc 11 154 42 0.12 MB
2004/12/13 15:23:26.30 45.5350 -112.3470 20.60 1.00 Mc 8 124 33 0.10 MB
2005/01/09 21:27:21.90 45.4950 -112.9180 8.30 0.90 Mc 8 200 52 0.24 MB
2005/01/11 07:43:47.50 45.6290 -112.4210 1.00 0.90 Mc 10 121 22 0.08 MB
2005/01/11 10:06:02.30 45.6280 -112.4450 6.30 1.90 Mc 21 101 22 0.12 MB
2005/01/11 10:09:57.50 45.6400 -112.4330 6.20 1.00 Mc 9 227 20 0.09 MB
2005/01/11 13:07:43.20 45.6530 -112.4450 13.70 0.60 Mc 8 225 19 0.08 MB
2005/01/11 15:20:48.30 45.6260 -112.4230 2.60 1.00 Mc 9 229 22 0.06 MB
2005/01/11 16:42:15.80 45.6370 -112.4430 7.20 1.40 Mc 13 105 21 0.14 MB
2005/01/11 17:44:49.00 45.6350 -112.4370 6.20 0.70 Mc 7 229 21 0.05 MB
2005/01/11 20:46:20.60 45.6290 -112.4390 6.30 0.90 Mc 10 180 22 0.09 MB
2005/01/12 00:27:58.50 45.6310 -112.4510 9.90 1.30 Mc 14 127 21 0.09 MB
2005/01/12 02:51:58.30 45.6380 -112.4370 7.90 0.30 Mc 6 228 21 0.07 MB
2005/01/12 03:35:52.70 45.6510 -112.4450 12.40 0.90 Mc 12 122 19 0.08 MB
2005/01/12 04:39:34.90 45.6390 -112.4450 10.30 1.20 Mc 15 124 20 0.07 MB
2005/01/12 07:29:31.90 45.6300 -112.4520 8.20 2.00 Mc 15 105 21 0.12 MB
2005/01/12 08:33:57.10 45.6540 -112.4400 13.40 0.40 Mc 8 224 19 0.05 MB
2005/01/12 14:27:35.90 45.6610 -112.4300 14.10 0.90 Mc 8 220 18 0.12 MB
2005/01/12 15:35:41.80 45.6460 -112.4450 11.40 1.00 Mc 12 123 20 0.08 MB
2005/01/12 16:08:31.00 45.6290 -112.4400 6.60 1.30 Mc 17 104 22 0.11 MB
2005/01/12 20:01:24.70 45.6200 -112.4440 5.10 2.10 Mc 22 90 22 0.16 MB
2005/01/12 20:31:56.70 45.6340 -112.4520 11.60 1.90 Mc 17 120 21 0.09 MB
2005/01/13 05:35:24.00 45.6340 -112.4520 10.90 1.60 Mc 14 126 21 0.10 MB
2005/01/13 12:00:18.20 45.6280 -112.4310 3.50 0.50 Mc 9 230 22 0.04 MB
2005/01/14 01:41:49.80 45.6320 -112.4510 10.60 1.50 Mc 16 127 21 0.10 MB
2005/01/14 04:25:52.00 45.6320 -112.4400 5.50 0.70 Mc 9 230 21 0.04 MB
2005/01/14 17:52:27.80 45.2300 -112.5260 7.60 0.50 Mc 8 145 38 0.24 MB
2005/01/15 01:30:57.30 45.6380 -112.4370 6.80 0.90 Mc 8 228 20 0.07 MB
2005/01/15 01:39:43.30 45.6410 -112.4440 10.00 0.50 Mc 6 229 20 0.13 MB
2005/01/15 13:17:35.70 45.6760 -112.4510 18.30 0.50 Mc 6 219 16 0.06 MB
2005/01/15 13:19:29.30 45.6750 -112.4440 17.40 0.60 Mc 8 117 16 0.08 MB
2005/01/16 21:13:10.60 45.6320 -112.4380 6.90 1.10 Mc 14 124 21 0.11 MB
2005/01/18 05:47:55.40 45.6460 -112.4410 11.00 0.70 Mc 10 122 20 0.10 MB
2005/01/21 14:28:29.90 45.4780 -112.8730 7.20 0.90 Mc 8 212 41 0.23 MB
2005/01/23 20:20:08.10 45.6330 -112.4310 4.60 0.90 Mc 11 106 21 0.09 MB
2005/01/28 04:38:21.80 45.6440 -112.4420 9.10 0.40 Mc 6 227 20 0.02 MB
2005/01/30 15:48:47.90 45.6380 -112.4380 6.50 1.70 Mc 22 96 20 0.15 MB
2005/01/31 13:54:49.90 45.6470 -112.4320 8.70 0.90 Mc 10 118 20 0.07 MB
2005/02/01 13:58:48.10 45.6350 -112.4390 7.60 0.60 Mc 6 229 21 0.10 MB
2005/02/01 21:22:00.90 45.6380 -112.4260 4.70 1.30 Mc 13 103 21 0.13 MB
2005/02/02 01:36:52.90 45.6360 -112.4390 7.00 1.30 Mc 13 104 21 0.13 MB
2005/02/02 10:11:29.30 45.6460 -112.4300 9.30 0.80 Mc 7 225 20 0.09 MB
2005/02/03 00:04:39.20 45.6340 -112.4480 10.90 1.60 Mc 14 120 21 0.10 MB
2005/02/03 01:25:47.30 45.3750 -112.2670 13.50 2.50 Mc 39 88 24 0.22 MB
2005/02/17 02:43:40.20 45.6720 -112.4270 15.80 0.50 Mc 6 154 17 0.09 MB
2005/02/24 19:10:31.00 45.1990 -112.5030 17.50 1.20 Mc 9 139 36 0.09 MB

• Montana Earthquake History