Since summer, Nevada has seen hundreds of earthquakes, some coming in bunched groups called swarms, which appear to have intensified recently. Since July, hundreds of small quakes have hit an area in the Northwest portion of the state near the Sheldon National Wildlife refuge, and they have become even stronger since October 30. Since the end of October there have been three with a magnitude of 4.0 or above. There was a similar swarm in September in Southern California, where 500 events were registered within two days. The United States Geological Survey (USGS) says that these swarms are not uncommon, and that while there is a slightly increased risk of more serious seismic events occurring during a swarm, it is not necessarily an indication that a major quake is imminent.
The belief is that increased groundwater along the faults has facilitated tectonic movement and made this swarm more likely to happen. The majority of them have been small enough that they were barely felt on the surface, if at all. Even so, the increase in seismic activity in Nevada and California lately has revived worries in some that the much-anticipated “big one” that allegedly will change the landscape of the West Coast is on its way. According to the USGS and other agencies, the swarms are not indicators of anything like that. A mass exodus does not appear to be called for. The region of Nevada that is now seeing this swarm of earthquakes is not a heavily populated area, with only two small towns of less than 3,000 residents each even within range. No damage or injuries have been reported after even hundreds of quakes. The most significant of them over the last week was a 4.6 magnitude which struck on Tuesday, but even that had no significant impact on the area.
Similar swarms have occurred in the past several decades. In 2008, a smaller swarm hit the area around Reno, Nevada which ended seeing an earthquake with a magnitude of 5.o. Prior to that, there was a swarm back in 1968 in Adel, Oregon which saw three quakes of at least a 5.0 magnitude where there was some moderate damage. None of these swarms ever precipitated a major seismic event even close to the mythical “big one” that is being whispered about. Seismologists have said that it is prudent to be prepared for something like that, but continue to express extreme doubt that it is more than a very remote possibility.
Some have expressed the opinion that it is the increased use of the practice of “fracking” in the search for Natural Gas and oil deposits. This is an ongoing argument, and while there has been an increase in earthquakes of magnitude 3.0 or better since 2001 in the region, no direct line has yet been drawn to attribute the swarm activity to these mining practices. Considerable research is being done by environmental groups attempting to make that connection, and it has been the discussion of many protests across the nation. In light of the increase in swarm activity, it is likely to continue to be a hot-button topic for many on both sides of the industry. Regardless, alarmist or not, these swarms have people across Nevada wondering and watching for the elusive “big one” to come.
By Jim Malone