@mountaineer, if you're really interested in that question, here's a link to some articles about a state-funded study to examine that very question: http://www.beg.utexas.edu/files/content/beg/ext-aff/16-01/Program%20gets%20underway%20to%20examine%20Texas%20earthquake%20increase%20_%20The%20Star-Telegram.pdf.
And, it does download as a pdf.
Interesting. The USGS map shows one earthquake in Texas the last 30 days of magnitude 2.6 or higher.
North Dakota, Eastern Montana, Eastern Wyoming, Pennsylvania, Ohio, West Virginia, Virginia, Tennessee, Louisiana, Have none. There is a cluster inOklahoma and Kansas, which may be related to disposal wells. Note, the states listed above have both oil production, fracked wells, and disposal wells, too.
While there is oil and gas activity in the same area as the earthquakes,
Proterozoic basement Humboldt Fault (red) and Midcontinent Rift (green) in Kansas and Nebraska
The Nemaha uplift is a deep fault zone which runs diagonally across east Kansas and extends from just south of Omaha, Nebraska to Oklahoma City. This fault zone directly overlies a granite "high" in the Precambrian basement and is structurally active as the Humboldt Fault. Some fifty miles to the west the southernmost extension of the Proterozoic Midcontinent Rift System extends into northeastern Kansas.[23]
This (Humboldt) fault zone pretty much coincides with the troubled area.
Source:
https://en.wikipedia.org/wiki/Geology_of_KansasI would not exclude the possibility that the existing fault(s) in the area are being lubricated by fluids disposed of in disposal wells, and consider that to be worthy of investigation, if it has not been done.
The absence of widespread earthquake activity in other areas where tens of thousands of horizontal wells have been hydraulically fractured tends to indicate that alone is not the culprit. The presence of faults may indicate seismicity which would occur, regardless.
Fraccing is a process where a short term increase in in fluid pressure in the rock around a wellbore is caused for a limited period of time, with the aim to crack that rock and to pump sand or ceramic beads into the newly formed cracks to prop them open. This causes the formation of new pathways for oil and gas to flow out of the lower permeability rock and significantly enhances production. That pressure is reduced as the frac fluids are produced along with oil and/or gas from the rock layer along with whatever salt water is in that porosity layer as well.
Those produced fluids (other than oil, gas, and condensate) are commonly disposed of by putting them in a disposal well, where the weight of the water column exerts enough pressure to push the water at the bottom of the well into the target rock layer (called a "formation" by geologists) where there is enough porosity and permeability to accept the water. As wastewater feeds into the formation, more water is added to the column in the well, keeping the process going. This generally does not involve high pressure pumps like a frac, just gravity. Casing in the well prevents water from going into any but the target formation.
