Just As I Thought

Anatomy of an Earthquake

The 4.1 Milpitas earthquake that hit here on Thursday was a small affair — like all quakes, when it first starts you kind of freeze in place and wait to see what happens next. How big will it get? Is there a huge shock coming in a second? How long will it last?

The 4.1 Milpitas earthquake that hit here on Thursday was a small affair — like all quakes, when it first starts you kind of freeze in place and wait to see what happens next. How big will it get? Is there a huge shock coming in a second? How long will it last? Thursday’s was a reminder of earthquake reality but not all that exciting. Still, any earthquake is interesting to me and sets me off surfing the USGS website.
About 24 hours later, we had a second quake, a slightly smaller aftershock. It literally hit while I was on the USGS site, looking at aftershock information. I was amazed to see how many aftershocks there had been — and how many foreshocks there had been the days before.
As of this morning, here is a list of the earthquakes that have occurred in the same general spot:

MAG DATE LOCAL-TIME LAT LON DEPTH LOCATION

y/m/d h:m:s deg deg km

2.5 2010/01/09 04:41:11 37.475N 121.793W 7.9 10 km ( 6 mi) ENE of Milpitas, CA

1.0 2010/01/09 03:42:41 37.479N 121.803W 7.9 10 km ( 6 mi) ENE of Milpitas, CA

1.3 2010/01/09 03:34:59 37.476N 121.792W 7.4 10 km ( 6 mi) ENE of Milpitas, CA

2.5 2010/01/09 03:24:41 37.476N 121.793W 7.8 10 km ( 6 mi) ENE of Milpitas, CA

2.3 2010/01/09 01:11:54 37.473N 121.802W 7.6 9 km ( 6 mi) ENE of Milpitas, CA

1.0 2010/01/08 23:10:44 37.476N 121.793W 8.6 10 km ( 6 mi) ENE of Milpitas, CA

1.5 2010/01/08 19:30:54 37.477N 121.792W 7.1 10 km ( 6 mi) ENE of Milpitas, CA

1.2 2010/01/08 17:31:16 37.481N 121.798W 7.3 10 km ( 6 mi) ENE of Milpitas, CA

1.5 2010/01/08 16:36:09 37.474N 121.794W 8.4 10 km ( 6 mi) ENE of Milpitas, CA

0.9 2010/01/08 15:36:41 37.483N 121.791W 7.5 11 km ( 7 mi) ENE of Milpitas, CA

1.3 2010/01/08 15:17:06 37.482N 121.798W 7.2 10 km ( 6 mi) ENE of Milpitas, CA

1.6 2010/01/08 14:31:52 37.480N 121.797W 7.0 10 km ( 6 mi) ENE of Milpitas, CA

2.1 2010/01/08 13:58:48 37.477N 121.798W 6.8 10 km ( 6 mi) ENE of Milpitas, CA

1.4 2010/01/08 13:55:55 37.480N 121.790W 7.4 11 km ( 7 mi) ENE of Milpitas, CA

3.7 2010/01/08 11:48:50 37.482N 121.793W 9.6 10 km ( 6 mi) ENE of Milpitas, CA

1.2 2010/01/08 11:12:28 37.476N 121.792W 8.1 10 km ( 6 mi) ENE of Milpitas, CA

0.7 2010/01/08 08:05:59 37.474N 121.802W 7.9 9 km ( 6 mi) ENE of Milpitas, CA

1.5 2010/01/08 06:07:03 37.474N 121.800W 7.6 9 km ( 6 mi) ENE of Milpitas, CA

1.2 2010/01/08 03:52:25 37.476N 121.796W 6.9 10 km ( 6 mi) ENE of Milpitas, CA

1.9 2010/01/08 03:29:30 37.471N 121.800W 8.0 9 km ( 6 mi) ENE of Milpitas, CA

1.8 2010/01/08 03:25:27 37.471N 121.798W 7.1 9 km ( 6 mi) ENE of Milpitas, CA

0.8 2010/01/08 02:21:15 37.477N 121.793W 8.1 10 km ( 6 mi) ENE of Milpitas, CA

1.0 2010/01/07 23:20:25 37.469N 121.777W 5.5 11 km ( 7 mi) ENE of Milpitas, CA

1.1 2010/01/07 21:09:36 37.476N 121.798W 7.6 10 km ( 6 mi) ENE of Milpitas, CA

1.2 2010/01/07 19:53:16 37.475N 121.801W 7.9 9 km ( 6 mi) ENE of Milpitas, CA

2.2 2010/01/07 17:22:12 37.476N 121.791W 7.9 10 km ( 6 mi) ENE of Milpitas, CA

0.8 2010/01/07 16:41:56 37.476N 121.802W 8.5 9 km ( 6 mi) ENE of Milpitas, CA

1.4 2010/01/07 16:21:08 37.475N 121.802W 8.2 9 km ( 6 mi) ENE of Milpitas, CA

0.7 2010/01/07 16:00:45 37.476N 121.794W 8.4 10 km ( 6 mi) ENE of Milpitas, CA

2.1 2010/01/07 15:52:06 37.476N 121.804W 8.7 9 km ( 6 mi) ENE of Milpitas, CA

0.8 2010/01/07 15:37:59 37.474N 121.801W 7.9 9 km ( 6 mi) ENE of Milpitas, CA

0.8 2010/01/07 15:02:03 37.475N 121.793W 8.6 10 km ( 6 mi) ENE of Milpitas, CA

0.9 2010/01/07 14:31:00 37.477N 121.794W 7.8 10 km ( 6 mi) ENE of Milpitas, CA

0.9 2010/01/07 14:17:40 37.475N 121.795W 8.3 10 km ( 6 mi) ENE of Milpitas, CA

1.5 2010/01/07 13:56:52 37.478N 121.793W 8.3 10 km ( 6 mi) ENE of Milpitas, CA

0.8 2010/01/07 13:46:40 37.475N 121.797W 7.9 10 km ( 6 mi) ENE of Milpitas, CA

0.9 2010/01/07 12:34:55 37.476N 121.797W 8.4 10 km ( 6 mi) ENE of Milpitas, CA

0.6 2010/01/07 12:33:37 37.477N 121.795W 8.1 10 km ( 6 mi) ENE of Milpitas, CA

1.7 2010/01/07 12:21:04 37.474N 121.790W 8.4 10 km ( 6 mi) ENE of Milpitas, CA

0.7 2010/01/07 12:16:10 37.475N 121.794W 8.6 10 km ( 6 mi) ENE of Milpitas, CA

1.0 2010/01/07 12:09:07 37.474N 121.801W 7.9 9 km ( 6 mi) ENE of Milpitas, CA

0.8 2010/01/07 11:39:21 37.477N 121.801W 8.0 10 km ( 6 mi) ENE of Milpitas, CA

1.3 2010/01/07 11:36:38 37.478N 121.800W 8.4 10 km ( 6 mi) ENE of Milpitas, CA

1.3 2010/01/07 11:34:06 37.474N 121.800W 8.0 9 km ( 6 mi) ENE of Milpitas, CA

0.9 2010/01/07 11:05:13 37.475N 121.794W 8.9 10 km ( 6 mi) ENE of Milpitas, CA

2.2 2010/01/07 10:54:42 37.476N 121.795W 8.2 10 km ( 6 mi) ENE of Milpitas, CA

2.2 2010/01/07 10:36:46 37.475N 121.799W 8.0 10 km ( 6 mi) ENE of Milpitas, CA

1.4 2010/01/07 10:34:48 37.478N 121.798W 7.9 10 km ( 6 mi) ENE of Milpitas, CA

1.5 2010/01/07 10:24:10 37.475N 121.803W 8.2 9 km ( 6 mi) ENE of Milpitas, CA

1.5 2010/01/07 10:22:49 37.473N 121.800W 8.4 9 km ( 6 mi) ENE of Milpitas, CA

1.5 2010/01/07 10:19:26 37.476N 121.794W 7.9 10 km ( 6 mi) ENE of Milpitas, CA

4.1 2010/01/07 10:09:35 37.481N 121.799W 11.0 10 km ( 6 mi) ENE of Milpitas, CA

0.9 2010/01/06 04:55:45 37.476N 121.798W 8.3 10 km ( 6 mi) ENE of Milpitas, CA

1.3 2010/01/06 04:45:31 37.474N 121.798W 8.2 10 km ( 6 mi) ENE of Milpitas, CA

1.2 2010/01/05 20:01:19 37.462N 121.819W 7.3 7 km ( 5 mi) ENE of Milpitas, CA

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