Hi All. The two quakes in Nevada are well within the Walker Lane Belt. The term Walker Lane, Walker line, Walker belt, and Walker Lane belt are names applied to a generally north-northwest-trending linear zone of ranges lying between the Sierra Nevada on the west and northeast trending basin and ranges of the Basin and Range physiographic province on the east and lies within the Eastern California Shear Zone. Some descriptions of this belt note strike-slip faulting (mostly right-lateral) as a tectonic element. The original description of the belt by Giannella and Callagahn (1934) defined it as a narrow zone of northwest- striking right-lateral rupture typified by the faults that caused the Cedar Mountain earthquake of 1932. This broad zone is about 700 kilometers long and 80 to 240 kilometers wide. Stewart (1988) divided this belt into nine tectonic blocks, each with distinctive tectonic style.

A somewhat more restrictive Walker Lane belt is that of Carr (1984), whose southwestern boundary is the northwest striking Death Valley-Furnace Creek-Fish Lake Valley fault zone, but his northeastern boundary is poorly defined as passing southeast across the Nevada Test Site with no physiographic or geologic definition. In southern Nevada, including the Nevada Test Site, the eastern boundary of the Walker Lane is difficult to mark because there are no northwest striking structural or topographic features-- the topography is dominated by nonlinear Miocene volcanic features, in particular, resurgent collapsed calderas and widespread ash-flow sheets. The Walker Lane can be expanded eastward to include these calderas and eruptive rocks in the Black Mountain, Timber Mountain, and Pahute Mesa region or it can be restricted to the northwest striking belt running west of the calderas (west of the Nevada Test Site).

If it is expanded eastward, the Las Vegas Valley shear zone merges into it from the southeast. If it is restricted, there is no obvious connection between the Las Vegas Valley shear zone and the Walker Lane. In his analysis of the Walker Lane belt, Stewart (1988) divided the Walker Lane into a number of structural blocks each with distinctive geologic features, tectonic styles, and structural trends. One block, called the Spotted Range-Mine Mountain block, is separated from the Spring Mountain block to the south, along Rock Valley. Making Rock Valley a domain boundary between major blocks in the Walker Lane belt suggests that it is a crustal structure of regional significance.

The stratigraphy and structure of the Paleozoic rocks north and south of Rock Valley indicate, however, that left-lateral offset on the Rock Valley fault is only 1.4 to 3.2 kilometers (O'Leary, 1998). Other southwest-striking, left-lateral, strike-slip faults north of Rock Valley near Cane Springs and in the Spotted Range augment the amount of cumulative left-lateral displacement in the region.

It should be noted that both quakes occurred after the P.N.G. 8.0Ms and the 7.7Ms quakes. This is not to say that both quakes were triggered by the P.N.G. quakes, but there does seem to be a connection between them.

Every earthquake generates 4 types of waves. Type I is the P-Wave, also known as a pressure wave, primary, push-pull wave, longitudinal wave, or compression-rarefaction wave. It travels in a straight line. Type II is the S-Wave, also known as a shear wave, secondary wave, shake wave, or transverse wave. It causes molecules to travel in a zigzag pattern, like the motion of a tuning fork. Surface waves similar to P-waves, but having backwards rotational orbits, are called Rayleigh Waves. Surface waves similar to S-waves are called Love Waves. As to which wave triggered the quakes it would largely depended on the amount of accumulated stress at the location of the quake and how the waves passed through that area. If the waves passed through the fault from the side then more of the fault would be affected at the same thereby increasing the chance that they would trigger a quake. If the waves moved up or down the fault only a small portion of the fault would be affected at any one time thereby lessening the probability of trigger a quake. At least that is how I view it. Take Care…Don in creepy town.