We are accustomed to seeing earthquakes in California, but this is a particularly broad coverage for the state last week. There were multiple unusual earthquakes in Nevada alongside the California quakes. All were minor- below 5.0 magnitude, and they were accompanied by several earthquakes at river passages in the other sectors of the U.S.
One in the northeast, one in the southeast, and one near Yellowstone in the northwest of the U.S.
The anigif shows the rivers in periodic display repeats. The smaller earthquakes in the singular locations at the various sectors of the U.S. were along the river passages. The week was one of several recently that were heavy in rainfall across broad portions of the U.S. The water runoff weight and regional added ballast may be the reason for the local singular quakes at river interaction points.
It is unusual for any earthquakes across the U.S. other than California, Alabama, or Oklahoma. There are minor earthquakes in Yellowstone at times, and this was one of those weeks. The river non-the-less does pass through the location of the quake.
The dates were April 11 to 18, 2013.
The Oklahoma earthquakes were from 4.7 to very small, and were a record number in a weeks timing, most falling one a one to two day period, the past week.
A still view of the U.S. earthquakes as seen in the anigif, without the rivers displayed. Two JPG's.
A view of the same period with the rivers displayed. This record is much easier to understand with an animated GIF sequence if you can view them. You should view all my images in the 'enlarged' size either by clicking the image to enlarge it, or, downloading it to your machines. The icon for enlarging is in the upper right of the image using a mouse cursor to activate the 'switch'. Downloading is possible by mouse right clicking or by software choices.
A view of the earthquakes for the western hemisphere from April 18 to 23, 2013.
The very active linear assembly across the U.S. continent was unusual.
There is a trending low gravity field structure across the U.S. below this line of quakes, and it is fairly stable as a structure with a slight northwest to southeast diagonal trend, with few earthquakes between the line of quakes in the mid U.S., and the entire Gulf of Mexico circular structure at the bottom of the U.S. continent.
The Gulf is noticeably quiet with almost no seismic activity recorded. Some of that is caused apparently by the fluidity of the salt structures and layered, water adjusted built-up assemblies within the basin. There may be other reasoning for the circular process of the Gulf of Mexico, as the smaller rare earthquakes at times form a near perfect circular structure around the northern section of the land shoreline of the Gulf waters. It is curious that the shape is so circular. This weeks activity did not occur along that circle, but was a near straight line across the U.S. continent.
Below the Gulf, there were stronger earthquakes in a near east to west line, across the more active Central American zone, extending to the very common quakes of Haiti.
Below that line was a routine series of moderate earthquakes in the South American activity zone.
The dates for this image is April 16 to 23, 2013. The dates for these series of images are overlapping in dates.
I found the river occurrences worth mentioning as they appear to be related to local weather across the U.S and water river runoff there, except for the Oklahoma earthquakes that were active for other undetermined reasons. Many suggest 'fracking' injection of chemistry or water as the reasons for local Oklahoma smaller earthquakes, with local oil pumping of reserves causing huge loss of fill volume in the oil chambers underground, but it is not settled as a cause as yet.Local water is pumped from chambers below ground without replenishment as well, in huge volume, and that is another understood possible cause of small earthquakes. Other actions, such as the California to Oklahoma to Haiti activity cycle of a 24 hour timing sequence does exist, and was present during the past two weeks, so, no particular cause is yet obvious separated from any other cause. Unknown causes are also possible.
Seeing the several linear activity zones of the images shows possibly the mid-U.S. continent could have a activity zone only periodically visible, for non-local reasons.
We have only watched earthquake patterns accurately for a few dozen years.
We have only the past couple of years had access to detailed recording of the Earth's gravity field.
It might take a few decades or a full century to know the actual story of patterned activity.
Water runoff and river passage earthquakes may be as erosion active as the surface effects of the fluid on the rocks and soil.
Water table processes such as permafrost forcing and mineral alterations may be as effective as the surface effects. This may be, or may have been, even more true on Mars.
The images were not taken from the 'Eyes On The Earth' website display. These were from the Earthquake 3D program available free of charge on the Internet at Wolton.net. This program works well in combination with the satellite website display, as both show global recording of earth science recent processes.
Hopefully both programs can provide a base of knowledge to allow Mars geology to be interpreted with more accuracy.