Summary of Holocene surface faulting and fault segmentation, Wasatch fault zone, Utah

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5126731

Lund, W R ^[1]

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1. Utah Geological Survey, Salt Lake City, UT (United States)

The Wasatch fault zone (WFZ) extends for 383 km from southern Idaho to north-central Utah. It is the longest normal-slip fault in the western US, and is the easternmost expression of basin-and-range extension in the Great Basin. No historical surface-rupturing earthquakes have occurred on the WFZ, but there is ample evidence in the geologic record of numerous large, prehistoric, surface-rupturing events. For much of its length in Utah, the WFZ traverses the heavily populated Wasatch Front. More than 50 trenches and five natural exposures at 19 sites on the WFZ provide information on the size and timing of past surface-rupturing earthquakes and on fault segmentation. The composite recurrence interval (WFZ as a whole) for the 15 events is 395 [+-] 60 years. The average recurrence interval between large events on individual segments is 1,980 [+-] 310 years. Net vertical tectonic displacements (NVTD) produced by the Holocene paleoearthquakes are large, generally ranging between 1.5 and 3 m. Based on segment (rupture) length, NVTD, and the magnitude of historical surface-rupturing earthquakes elsewhere in the northern part of the intermountain seismic belt, estimated magnitudes for paleoearthquakes on individual WFZ segments are as large as 7.5. Late Pleistocene and Holocene (post Lake Bonneville) slip rates (0.5--1.5 mm/yr) may be as much as five times greater than average slip rates (0.1--0.3 mm/yr) for the WFZ recorded in deposits older than the Bonneville Lake cycle. A relation between the change in slip rate and the transgression and regression of Lake Bonneville is suspected.

• OSTI ID: 5126731
• Report Number(s): CONF-9305259--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CENOZOIC ERA
DEVELOPED COUNTRIES
DISPLACEMENT RATES
EARTHQUAKE MAGNITUDE
EARTHQUAKES
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
NORTH AMERICA
QUATERNARY PERIOD
RISK ASSESSMENT
SEISMIC EVENTS
SEISMICITY
SEISMOLOGY
STRATA MOVEMENT
USA
UTAH