More than 230 earthquakes of magnitude 3 or above have occurred in a state since 2014, compared with an average of one a year before 2008. Frequent seismic activity has raised questions and some researchers have found that since 2014, in order to prevent toxic waste water from drilling and hydraulic fracturing in oil production from polluting surface water, start injecting this waste water into the impervious layers of underground rocks, which is likely to be the key cause of the earthquake.
 The state had fewer but larger earthquakes before 2008 and there have been many earthquakes since 2014, but the magnitude is small can best support the above conjecture.