Back to back surface earthquakes occurred in Nevada — a hundred miles apart — both at dormant volcanic locations.
First, a 3.0M struck near the Lunar Craters volcanic complex. Occurring at 0km , recorded as a surface earthquake.
2014-04-17 23:04:29 UTC
2014-04-17 16:04:29 UTC-07:00 at epicenter
2014-04-17 18:04:29 UTC-05:00 system time
38.684°N 115.709°W depth=0.0km (0.0mi)
This surface event literally means a shallow rupture in the crust has occurred, the earthquake happening actually at, or near the surface.
In this case, the surface is already prone for movement at the Lunar Craters of Nevada — a natural weak spot in the crust.
Lunar Craters volcanic field 2255 m / 7,398 ft
Nevada, USA , 38.25°N / -116.05°W
Last Eruption: approximately 15,000 years ago
The Lunar Crater volcanic field is a zone of vulcanism covering over 300 km2 at the southern end of the Pancake Range in the Great Basin Desert, Nevada. It contains numerous cinder cones and lava flows, fissures, and, most visibly, the 150 m deep Lunar Crater, a 1050 m wide and nearly circular maar (explosion crater) believed to have formed about 15,000 years ago.
Lunar Crater is one of Nevada’s 6 National Natural Landmarks.
From Wood and Kienle, 1990, Volcanoes of North America: United States and Canada: Cambridge University Press, 354p., p.256-262, Contribution by John C. Dohrenwend (cited on CVO / USGS website):
The Lunar Crater volcanic field, an apparent middle to late Pliocene and Pleistocene continuation of the Reveille Range volcanic field immediately to the southwest, is superposed across the 25-million-year-old Lunar Lake caldera, a crudely circular topographic basin on the crest of the Pancake Range. The field contains approximately 95 late Pliocene and Pleistocene vents and at least 35 associated lava flows contained within a northeast-trending zone, up to 10 kilometers wide and approximately 40 kilometers long, that extends obliquely across the flanks and crest of the range. Vents include cinder cones, elongate fissures, and at least two maars. Lunar Crater, a nearly circular maar, approximately 130 meters deep and 1,050 meters wide, is the most distinctive feature of the field. A second maar, approximately 550 meters wide and 65 meters deep, occurs at the south end of a northeast-trending chain of coalesced cinder cones. Several other northeast-trending alignments of closely spaced and coalesced cinder cones characterize the field. Lava flows range up to 1.9 kilometers wide and 6.1 kilometers long with thicknesses from less than 3 meters to as much as 25 meters. Progressive degradation of the cones and flows is very similar to that displayed by other basaltic volcanic fields in the southwest Basin and Range (including the Cima, Crater Flat, and Coso fields). Many of the flows in the northeast and central parts of the field are veneered with varying thicknesses of air-fall tephra. In other areas, all but the youngest flows are mantled with extensive deposits of aeolian silt and fine sand.
The Lunar Crater volcanic field is in the central Great Basin, approximately 105 kilometers east-northeast of Tonopah, Nevada, and 140 kilometers southwest of Ely, Nevada. U.S. Highway 6 runs through the center of the Lunar Crater field.
The 2nd earthquake which occurred in Nevada was ALSO a surface event.
Occurring at 0km depth, again near dormant volcanoes, however these volcanoes are being MINED FOR GOLD. The actual earthquake occurring several miles away from the strip mines in this screenshot:
2014-04-17 17:07:21 UTC
2014-04-17 10:07:21 UTC-07:00 at epicenter
2014-04-17 12:07:21 UTC-05:00 system time
40.834°N 116.344°W depth=0.0km (0.0mi)
Overall, this is a further sign of the obvious unrest occurring along the Western portion of the craton.
See my most recent earthquake overview for an idea of what is going on, why this is occurring: