The Department of Geology and Mineral Industries of Oregon had warned residents of the state and neighbor Nevada to prepare in case a big earthquake hits the area after a rise in both number and intensity of tremors that rocked Nevada.

Since July, about 750 temblors with magnitudes ranging from 2.0 to 3.0 have shaken the Sheldon National Wildlife Refuge, a part of the Nevada desert near Oregon's boundary, USA Today cites several reports. The area actually has a very low population with two towns that are 40 miles apart having about 2,500 residents each.

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The theory of scientists is that groundwater is slowly boiling along the area's faults and further increasing pressure. This explains why while majority of Nevadans hardly feel the tremors when they walk, the quakes have grown in strength. On Tuesday, there were three temblors that had magnitudes between 4.0 and 4.6.

"There is a slightly elevated risk of a larger earthquake while the swarm is active," CNN quotes Ian Madin, a seismologist from Oregon's geology department. According to the Nevada Seismological Laboratory, the current swarm is very similar to two previous swarms that resulted in stronger earthquakes.

Graham Kent, director of the laboratory, explained, "We've been watching the magnitudes climb during the various bursts throughout the last four or five months. We were wondering if it was going to get to this level of intensity, and it shot up there. It's really cooking right now."

Past swarms, or quake groupings, in the two states caused moderate damage in 1968 when three tremors of magnitude 5 rocked Adel in Oregon and in 2008 when another magnitude 5 quake hit Reno, Nevada.

John Vidale, director of the Pacific Northwest Seismic Network at the University of Washington, clarified, "It doesn't necessarily mean anything big is coming, but it does raise the risk there will be a bigger quake in the future. He added, "Ninety-nine percent of the time nothing too dramatic happens, but every now and then there is a good pop and everyone asks why we didn't predict it," quoted LA Times.

TagsNevada, Oregon, earthquake