Surface faulting of the 1954 Fairview Peak (MS7.2) and Dixie Valley (MS6.8) earthquakes, central Nevada

Abstract

AbstractThe 1954 Fairview Peak earthquake was followed 4 min and 20 sec later by the Dixie Valley earthquake. Surface ruptures were distributed among six different faults that define a complex north-trending zone 100-km long and over 15-km wide. The rupture sequence progressed from south to north. The initial event produced a 32 km rupture of right-oblique slip along the east-dipping Fairview fault where the components of right-lateral offset and vertical separation reached 2.9 and 3.8 m, respectively. The northernmost ruptures occurred during the subsequent event along a 46-km portion of the east-dipping Dixie Valley fault where the sense of slip was normal and reached a maximum vertical separation of 2.8 m. Average surface offset for both events is about 1.2 m. The west-dipping West Gate, Louderback Mountains, and Gold King faults also ruptured during the earthquake sequence. These faults form a complex structural linkage within a 15-km left-step that separates the surface traces of the Fairview and Dixie Valley faults. The west-dipping faults likely played an important role in the redistribution of static stress from the Fairview Peak earthquake and subsequent triggering of the Dixie Valley earthquake. Right-lateral offsets of more than a meter occurred along both the West Gate and Louder-back Mountains faults. Slip was limited to normal motion of 1 m or less along the Gold King fault. The change from right-oblique motion along the Fairview fault to pure normal motion on the Dixie Valley fault may reflect the transition from principally northwest extension in the south to more westerly extension in the north. Alternatively, slip at the latitude of the Dixie Valley fault may be partitioned between pure normal slip along the Dixie Valley fault and strike-slip motion on faults immediately to the west. Observations of fault dip provide insight to the complex three-dimensional geometry of the rupture sequence. Of particular note, a significant section of the Dixie Valley fault appears to be characterized by dip angles as low as 25° at the surface. Slip variation or earthquake endpoints do not generally appear to have been influenced by changes in bedrock type. We do not observe systematic relations between slip variation and aspects of fault-trace geometry, such as salients and reentrants. Yet, the relative competence of footwall bedrock appears to have influenced the long-term development of large salients and reentrants along both the Dixie Valley and the Fairview faults, as well as the style of rupture along the southern portion of the Dixie Valley fault.