I'll get resident geologist @Smokin Joe to chime in, but saying Oklahoma is as earthquake active as California is akin to saying the traffic in Oklahoma is as bad as California. Yes, they both have traffic but there is really no comparison whatsoever due to scale.
Any earthquakes recorded in Oklahoma are minor compared to California. The largest ever recorded in OK was 5.8 on Richter scale vs a 7.9 in California.
For you and guys in Rio Linda, that is over a hundred times as strong.
And are you suggesting that NW of DFW has similar earthquakes as to California? Most earthquakes recorded in Texas occur near El Paso. Do you have a record of these Texas earthquakes recorded near DFW as I cannot find them?
I believe you are simply parroting some decidedly anti-industry talking points and throwing them against the wall to see what sticks.
There have been earthquakes associated with disposal wells, from Rocky Flats (CO) to the Midwest, and in other areas. Increasing the pore pressure in formations under stress has been shown to increase the likelihood of seismic events in SOME geological settings. Deferring to the USGS and for good basic information on the topic, I recommend seeing this:
https://earthquake.usgs.gov/research/induced/myths.phpKeep in mind that without stresses already present, the amount of rock movement will be small or nonexistent. In North Dakota, the nation's second largest oil producer, there are virtually no earthquakes, despite injecting unprecedented amounts of production and used frac water in recent years.
As for groundwater contamination, there should not be any, if the well is properly constructed and operated with spill containment and prevention measures observed. A properly constructed injection well looks like this in schematic:

Anyone who is really interested in this topic can get scads of info here:
http://www.statesfirstinitiative.org/induced-seismicity-work-group There is a webinar on the site, and links to other information as well, including a primer on induced seismicity.