Why Does the Earth Quake in Arkansas?

Can the oil and gas companies cause the earth to quake? It appears that indeed they may. Statistical evidence points to a strong connection between underground disposal of toxic water (commonly known as fracking) and an increase in seismic activity in central Arkansas. According to the U.S. Geological Survey, earthquake activity has increased by 95% since early in 2009. The practice of fracking began in April of 2009. Certainly a correlation can be drawn. Scientists, while reluctant to point the finger per se, admit that further investigation is warranted. With 412 companies connected to Arkansas's oil and gas industry, (Liu and Kaplan) scientists will no doubt proceed with caution before drawing a definitive conclusion in light of the current economic climate.