Award Date

5-15-2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

First Committee Member

Wanda J. Taylor

Second Committee Member

Rodney Metcalf

Third Committee Member

Gabriel Judkins

Fourth Committee Member

Barbara Luke

Number of Pages

83

Abstract

The left-lateral Pahranagat shear zone (PSZ) and Caliente-Enterprise zone (CEZ) exist at the boundary between two sub-provinces, the Northern (NBR) and Central Basin and Range (CBR). The PSZ contains three major ENE striking sinistral faults, including the Maynard Lake fault (MLF), which is the longest fault and marks the southern boundary of the zone. The PSZ has been suggested to be a transfer zone, but little is known about the structures along these major faults that are involved in strain transfer. These left-lateral systems exist within the Central Nevada seismic belt which has experienced significant earthquakes in recent history. Possible earthquake nucleation sites may exist along active portions of the MLF. Structures along the fault zone such as step-overs can influence the magnitude of an earthquake that could pose a risk to populated areas proximal to these faults. This Thesis focuses on the PSZ’s role at the subprovince boundary, and in particular MLF to determine what structures exist along the zone, how they are involved in strain transfer and potential for earthquakes.

Map and field data suggest that the central MLF is active; it offsets Quaternary units and may pose an earthquake hazard. A resurgent fan cut by the MLF formed within the last ~10,000 years as recorded by radiocarbon sediment analysis. Map data and cross-sections reveal a transpressional zone between left-lateral, right-stepping overlapping fault strands. This transpressional step-over structure could arrest an earthquake should nucleation occur along either fault strand, which may reduce total rupture length. Moment magnitude calculations using fault length, fault segment length and an assumption of a 10 km earthquake depth suggest possible moment magnitudes between M5.7 and M6.9.

The MLF is the longest fault within the PSZ and forms the southern boundary of the PSZ. The map and kinematic data suggest that the MLF is a transfer fault that transfers strain from surrounding N-striking normal fault systems. The other major PSZ faults are also transfer faults. Thus, the PSZ is a transfer zone that accommodates differences in regional strain to the north and south of the NBR and CBR subprovince boundary. Along the boundary to the NE, hard linkage between the PSZ and CEZ cannot be confirmed, but soft linkage is possible between these distinct zones along the subprovince boundary.

Keywords

faults; folds; pahranagat; quaternary; shear zone; transfer zone

Disciplines

Geology | Tectonics and Structure

Language

English

Plate_1.pdf (14209 kB)
Plate_2.pdf (1736 kB)


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