Paleoseismology of Utah, Volume 27 - Geologic mapping and paleoseismic investigations of the Washington fault zone, Washington County, Utah, and Mohave County, Arizona

2016 ◽  
Keyword(s):  
Fault Zone ◽  
Washington County ◽  
Geologic Mapping ◽  
Mohave County

Geologic Setting, Ground Effects, and Proposed Structural Model for the 18 March 2020 Mw 5.7 Magna, Utah, Earthquake

2020 ◽  
Author(s):  
Emily J. Kleber ◽  
Adam P. McKean ◽  
Adam I. Hiscock ◽  
Michael D. Hylland ◽  
Christian L. Hardwick ◽  
...  
Keyword(s):  
Fault Zone ◽  
Structural Model ◽  
Salt Lake ◽  
Hanging Wall ◽  
Great Salt Lake ◽  
Salt Lake City ◽  
Geophysical Data ◽  
Geologic Mapping ◽  
Lake City ◽  
Geologic Setting

Abstract The 18 March 2020 Mw 5.7 Magna, Utah, earthquake was the largest earthquake in Utah since the 1992 ML 5.8 St. George earthquake. The geologic setting of the Magna earthquake is well documented by recent geologic mapping at 1:24,000 scale and 1:62,500 scale at and near the epicenter northeast of Magna, Utah. Subsurface fault modeling from surficial geologic mapping, structural cross sections, deep borehole data, and geophysical data reveals a complex system of faulting concentrated in the hanging wall of the Weber and Salt Lake City segments of the Wasatch fault zone including the Harkers fault, the West Valley fault zone, and the newly interpreted Saltair graben. Based on geologic and geophysical data (seismic and gravity), we interpret the mainshock of the Magna earthquake as having occurred on a relatively gently dipping part of the Salt Lake City segment, with aftershocks concentrated in the Saltair graben and West Valley fault zone. Postearthquake rapid reconnaissance of geological effects of the Magna earthquake documented liquefaction near the earthquake epicenter, along the Jordan River, and along the Great Salt Lake shoreline. Subaerial and subaqueous sand boils were identified in regions with roadway infrastructure and artificial fill, whereas collapse features were noted along the shores of the Great Salt Lake. Potential syneresis cracking and pooling in large areas indicated fluctuating groundwater likely related to earthquake ground shaking. The moderate magnitude of the Magna earthquake and minimal geological effects highlight the critical importance of earthquake research from multidisciplinary fields in the geosciences and preparedness on the Wasatch Front.

scholarly journals An Evaluation of Earthquake Hazards of the Grand Teton National Park Emphasizing the Teton Fault

1988 ◽  
Vol 12 ◽  
pp. 133-142
Author(s):  
Robert Smith ◽  
John Byrd ◽  
Ronald Bruhn
Keyword(s):  
Fault Zone ◽  
National Park ◽  
Good Evidence ◽  
Geologic Mapping ◽  
Earthquake Hazards ◽  
East Side ◽  
Fault Trace ◽  
The University ◽  
Relationship Of

Documentation of the location, age and relationship of surface trace of the Teton fault zone to other geologic features is a prerequisite to a full understanding of seismic hazards associated with the fault. The University of Utah's mapping py David Sussong during the summer of 1987 documented the central portion of the fault trace. However, the northern and southern ends of the fault zone still required detailed mapping. Determination of the character of the fault in the areas south of Phillips Canyon and north of Webb Canyon can help to evaluate how movement on the fault would effect these areas, i.e., better evaluation of the relative seismic risk. Unfortunately, the extreme fire situation (the Huck fire started at the location of mapping) and the excessive time demands of the surveying reduced the amount of field mapping that we had planned for detailed geologic mapping. John Byrd, however, was able to do reconnaissance mapping in the Steamboat Mountain and Lizard Point area. In this area there is good evidence for the existence of several faults that are most likely splays of the Teton fault, that cross Jackson Lake and extend northward on the east side of the valley. Additional mapping is planned in this area next year.

Delineating a shallow fault zone and dipping bedrock strata using multichannal analysis of surface waves with a land streamer

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. A39-A42 ◽  
Author(s):  
Julian Ivanov ◽  
Richard D. Miller ◽  
Pierre Lacombe ◽  
Carole D. Johnson ◽  
John W. Lane
Keyword(s):  
Surface Waves ◽  
Fault Zone ◽  
Large Scale ◽  
Seismic Source ◽  
Geologic Mapping ◽  
Lower Shear ◽  
Weight Drop ◽  
Secondary Fractures ◽  
Masw Method ◽  
A Site

The multichannel analysis of surface waves (MASW) seismic method was used to delineate a fault zone and gently dipping sedimentary bedrock at a site overlain by several meters of regolith. Seismic data were collected rapidly and inexpensively using a towed 30-channel land streamer and a rubberband-accelerated weight-drop seismic source. Data processed using the MASW method imaged the subsurface to a depth of about [Formula: see text] and allowed detection of the overburden, gross bedding features, and fault zone. The fault zone was characterized by a lower shear-wave velocity [Formula: see text] than the competent bedrock, consistent with a large-scale fault, secondary fractures, and in-situ weathering. The MASW 2D [Formula: see text] section was further interpreted to identify dipping beds consistent with local geologic mapping. Mapping of shallow-fault zones and dipping sedimentary rock substantially extends the applications of the MASW method.

scholarly journals Fold-to-Fault Progression of a Major Thrust Zone Revealed in Horses of the North Mountain Fault Zone, Virginia and West Virginia, USA

2012 ◽  
Vol 2012 ◽  
pp. 1-13
Author(s):  
Randall C. Orndorff
Keyword(s):  
West Virginia ◽  
Fault Zone ◽  
Hanging Wall ◽  
Regional Scale ◽  
Fault Zones ◽  
Geologic Mapping ◽  
Important Indicator ◽  
The North ◽  
Central Appalachians ◽  
Thrust Zone

The method of emplacement and sequential deformation of major thrust zones may be deciphered by detailed geologic mapping of these important structures. Thrust fault zones may have added complexity when horse blocks are contained within them. However, these horses can be an important indicator of the fault development holding information on fault-propagation folding or fold-to-fault progression. The North Mountain fault zone of the Central Appalachians, USA, was studied in order to better understand the relationships of horse blocks to hanging wall and footwall structures. The North Mountain fault zone in northwestern Virginia and eastern panhandle of West Virginia is the Late Mississippian to Permian Alleghanian structure that developed after regional-scale folding. Evidence for this deformation sequence is a consistent progression of right-side up to overturned strata in horses within the fault zone. Rocks on the southeast side (hinterland) of the zone are almost exclusively right-side up, whereas rocks on the northwest side (foreland) of the zone are almost exclusively overturned. This suggests that the fault zone developed along the overturned southeast limb of a syncline to the northwest and the adjacent upright limb of a faulted anticline to the southeast.

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