OKLAHOMA CITY (AP) — Oklahoma and Kansas changed their drilling regulations amid a rise in the number of earthquakes last year, but only Kansas has seen a marked drop in the number of temblors.

An Associated Press analysis shows that between late 2014 and late 2015, the number of Kansas quakes fell by 60 percent. Oklahoma’s rose 10 percent over the same period.

Kansas regulated how much wastewater could be injected into the earth after its use in oil and gas drilling. Oklahoma initially put limits on how deep the water could go.

Scientists say it is too early to reach firm conclusions, but fear that Oklahoma’s trend of having more, smaller earthquakes could be setting a course for the big one. Earthquakes two weeks ago knocked out power in an Oklahoma City suburb.