SAN FRANCISCO (AP) - New research is linking oil and gas activity in California to earthquakes for the first time. Researchers at the University of California at Santa Cruz, the University of Southern California and two French universities published the study Thursday with the American Geophysical Union. Researchers say a surge of 2005 quakes in Kern County that topped out at magnitude 4.6 were almost certainly linked to a spike in oilfield injection in the immediate area. Oklahoma and some other Midwestern states have experienced hundreds of quakes in recent years that geologists link to oilfield activity. Many of the quakes are in areas where oil companies dump large amounts of salty oilfield wastewater deep underground. Lead author Thomas Goebel says he wouldn't expect a similar scale of increase in quakes in California.