The Pg-Pn method of determining depth of focus with applications to Nevada earthquakes

1965 ◽  
Vol 55 (2) ◽  
pp. 391-403
Author(s):  
Roger W. Greensfelder
Keyword(s):  
Error Analysis ◽  
Shear Zone ◽  
Surface Expression ◽  
Crustal Thickness ◽  
Depth Of Focus ◽  
Lateral Shear ◽  
Walker Lake ◽  
Walker Lane ◽  
Crustal Model

Abstract The Pg-Pn method is theoretically developed, including a complete error analysis, and then applied to some Nevada earthquakes. It is found that, as expected, the method is very sensitive to the crustal model used, and the appearance of large errors in depths of focus calculated for some earthquakes leads to the conclusion of a major discontinuity in crustal thickness (ca. 10 km) north and east of Walker Lake, Nevada. This discontinuity may have its surface expression in the Walker Lane, a major right-lateral shear zone which has been defined on both physiographic and geologic grounds.

scholarly journals Distributed extensional deformation in a zone of right-lateral shear: Implications for geodetic versus geologic rates of deformation in the eastern California shear zone-Walker Lane

Tectonics ◽  
2012 ◽  
Vol 31 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
T. Andrew Foy ◽  
Kurt L. Frankel ◽  
Zachery M. Lifton ◽  
Christopher W. Johnson ◽  
Marc W. Caffee
Keyword(s):  
Shear Zone ◽  
Lateral Shear ◽  
Extensional Deformation ◽  
Walker Lane ◽  
Eastern California Shear Zone

scholarly journals Flow of Rutford Ice Stream and Comparison with Carlson Inlet, Antarctica

1989 ◽  
Vol 12 ◽  
pp. 51-56 ◽  
Author(s):  
R.M. Frolich ◽  
D.G. Vaughan ◽  
C.S.M. Doake
Keyword(s):  
Surface Expression ◽  
Ice Thickness ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Ice Stream ◽  
Grounding Line ◽  
Subglacial Topography ◽  
Characteristic Features ◽  
Basal Shear ◽  
Thickness Measurements

Results from movement surveys on Rutford Ice Stream are presented with complementary surface-elevation and ice-thickness measurements. Surface velocities of 300 m a−1 occur at least 130 km up-stream of the grounding line and contrast strongly with the neighbouring Carlson Inlet, where a velocity of 7 m a−1 has been measured. This contrast in velocity is not topographically controlled but appears to be due instead to differences in basal conditions, with Carlson Inlet probably being frozen to its bed. Concentration of lateral shear close to the margins and surface expression of subglacial topography both support a view of significant basal shear stresses in the central part of Rutford Ice Stream. The pattern of principal strain-rate trajectories shows a small number of characteristic features which can be compared with results from future modelling of the glacier's flow.

The Denholm landslide, Saskatchewan. Part I: Geology

1983 ◽  
Vol 20 (2) ◽  
pp. 197-207 ◽  
Author(s):  
E. A. Christiansen
Keyword(s):  
Shear Zone ◽  
Radiocarbon Dating ◽  
Upper Cretaceous ◽  
Average Rate ◽  
Surface Expression ◽  
Recent Time ◽  
Displacement Rate ◽  
The North ◽  
Colorado Group ◽  
Judith River Formation

The Denholm landslide, whose surface is composed of scarps, ridges, and elongated depressions, is 160 m high, 2000 m wide, and up to 100 m thick. The shear zone is in silty, montomorillonitic clay of the upper part of the Lea Park Formation and Upper Colorado Group unit. The Upper Cretaceous Judith River Formation and the Quaternary Empress, Sutherland, and Saskatoon groups were affected by the landslide. Although these sediments were fractured and gravity faulted by tension when the landslide moved, they can be readily traced through the landslide, particularly the upper part. The scarps (gravity faults), ridges (horsts), and elongated depressions (grabens) are the surface expression of tension resulting from the stretching of beds during the landslide.The movement of the landslide is thought to have started when the North Saskatchewan spillway eroded to the level of the present shear zone about 11 000 years ago (established by radiocarbon dating) and is believed to have stopped in recent time. During this time, it moved about 390 m across the North Saskatchewan River alluvium at an average rate of 35 mm per year. As the landslide moved across the valley, it encountered deposition of alluvium at an average rate of about 2.4 mm per year which resulted in the curved shear zone on the alluvium. Keywords: retrogressive landslide, shale-alluvium, displacement, rate, age.

scholarly journals Extension-driven right-lateral shear in the Centennial shear zone adjacent to the eastern Snake River Plain, Idaho

Lithosphere ◽  
2013 ◽  
Vol 5 (4) ◽  
pp. 407-419 ◽  
Author(s):  
S. J. Payne ◽  
R. McCaffrey ◽  
S. A. Kattenhorn
Keyword(s):  
Shear Zone ◽  
Snake River Plain ◽  
Snake River ◽  
Lateral Shear ◽  
River Plain
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