A GIS-Based Assessment of Earthquake Property Damage and Casualty Risk: Salt Lake County, Utah

This paper offers a probabilistic assessment of expected property damage and casualty risk due to the earthquake ground shaking hazard affecting Salt Lake County, Utah (population = 725,600). Salt Lake County is bisected by a segment of the Wasatch Fault. It is also at risk from twenty-one other nearby fault segments. Findings are based on (1) a microzonation of the earthquake ground shaking hazard, (2) an inventory of buildings by value, structural frame type and use, (3) earthquake damage functions defining the performance of buildings as a function of ground shaking intensity, (4) data on the density of residential and employee populations, and (5) earthquake casualty functions defining casualty risk as a function of building damage. The analysis is supported by the algebraic combination of digital map layers within a vector-based geographic information system. Triangular irregular network models show the expected distributions of casualties. Hazard mitigation policy implications are also considered.

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Ground-shaking map for a magnitude 7.0 earthquake on the Wasatch Fault Salt Lake City, Utah, metropolitan area

10.34191/pi-76 ◽

2002 ◽

Keyword(s):

Metropolitan Area ◽

Salt Lake ◽

Salt Lake City ◽

Ground Shaking ◽

Lake City ◽

Wasatch Fault

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Paleoseismic investigation on the Salt Lake City segment of the Wasatch fault zone at the South Fork Dry Creek and Dry Gulch sites, Salt Lake County, Utah

10.34191/ss-92 ◽

1996 ◽

Keyword(s):

Fault Zone ◽

Salt Lake ◽

Salt Lake City ◽

South Fork ◽

The South ◽

Lake County ◽

Lake City ◽

Wasatch Fault

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The Benefits of a Seismic Retrofit Program for Commercial Unreinforced Masonry Structures: Salt Lake County, Utah

Earthquake Spectra ◽

10.1193/1.1585702 ◽

1993 ◽

Vol 9 (1) ◽

pp. 1-10

Author(s):

Philip C. Emmi ◽

Carl A. Horton

Keyword(s):

Salt Lake ◽

Exposure Period ◽

Seismic Retrofit ◽

Unreinforced Masonry ◽

Masonry Structures ◽

Damage Functions ◽

Lake County ◽

Evaluation Time ◽

Comparative Risk ◽

Uniform Code

This paper assesses the benefits of a seismic retrofit program for commercial unreinforced masonry structures (CURMs) in Salt Lake County, Utah. A comparative risk assessment embedded in a geographic information systems is the method used. A policy evaluation time horizon of twenty years is set. Future rates of demolition and rehabilitation, with and without a retrofit policy, are assumed. Damage functions for ordinary and retrofitted URMs are used to assess losses having a 10 percent chance of being exceeded over a 50-year exposure period. With a retrofit program, expected losses are reduced by 57 percent or more than a quarter billion dollars when compared to the no-policy scenario. Expected injuries and fatalities are reduced by more than 80 percent. These are minimal benefits expected from enforcement of the seismic provisions of the Uniform Code of Building Conservation.

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The 18 March 2020 M 5.7 Magna, Utah, Earthquake: Strong-Motion Data and Implications for Seismic Hazard in the Salt Lake Valley

Seismological Research Letters ◽

10.1785/0220200323 ◽

2021 ◽

Author(s):

Ivan Wong ◽

Qimin Wu ◽

James C. Pechmann

Keyword(s):

Seismic Hazard ◽

Fault Zone ◽

Salt Lake ◽

Salt Lake City ◽

Strong Motion ◽

Ground Shaking ◽

Fault Segment ◽

Salt Lake Valley ◽

Lake City ◽

Wasatch Fault

Abstract The 2020 oblique normal-faulting M 5.7 Magna mainshock has provided the best dataset of recorded strong ground motions for an earthquake within the Wasatch Front region, Utah, and the larger Basin and Range Province. We performed a preliminary evaluation of the strong motion and broadband data from this earthquake and compared the data with the Next Generation Attenuation - West2 Project (NGA-West2) ground-motion models (GMMs). The highest horizontal peak ground acceleration (PGA) recorded was 0.43g (geometric mean of the two horizontal components) at a station located above the rupture plane at a rupture distance of 8 km. Eleven stations recorded PGAs >0.20g. Most of these stations are located on the deep sedimentary deposits within the Salt Lake Valley, and all are at rupture distances <20 km. The data compare favorably with the NGA-West2 GMMs, although the expected variability was observed. PGAs exceed the GMM predictions at the closest distances for the source model that we used. The area of the strongest ground shaking encompassed the town of Magna, where some of the heaviest damage occurred. A significant implication of the 2020 Magna earthquake for seismic hazards in the Salt Lake Valley arises from the possibility that this earthquake occurred on the Salt Lake City segment of the Wasatch fault. If so, then the dip of this fault segment must decrease with depth to ≤30°–35°, as proposed by Pang et al. (2020)—at least along the northern part of the segment where the earthquake occurred. Because of the lack of information about the subsurface geometry of the Wasatch fault zone, modeling of this fault zone in seismic hazard analyses has assumed a moderate dip of 50°±15°. Assuming a more shallowly dipping fault results in higher estimates of ground shaking in future large earthquakes on this fault. Alternative interpretations of the Magna earthquake are that it occurred (1) on an auxiliary fault within the Wasatch fault zone or (2) on a listric section of the northern Salt Lake City segment that is not representative of the geometry of the whole fault segment.

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Earthquake Damage and Loss Estimation Methodology and Data for Salt Lake County, Utah (ATC-36)

Earthquake Spectra ◽

10.1193/1.1585972 ◽

1997 ◽

Vol 13 (4) ◽

pp. 623-642 ◽

Cited By ~ 8

Author(s):

Christopher Rojahn ◽

Stephanie A. King ◽

Roger E. Scholl ◽

Anne S. Kiremidjian ◽

Lawrence D. Reaveley ◽

...

Keyword(s):

Salt Lake ◽

Earthquake Damage ◽

Database Management System ◽

Lake County ◽

Ground Shaking ◽

Ground Failure ◽

Software Application ◽

Fire Following Earthquake ◽

Lifeline Systems ◽

Gis Software

As a follow on to the Applied Technology Council (ATC) project to develop earthquake damage evaluation data for California (ATC-13 project), ATC has conducted a project to update and translate the ATC-13 data and methodology for use in Salt Lake County, Utah (ATC-36 project). Methodology has been developed and/or updated for: (1) estimation of damage due to ground shaking, (2) estimation of damage due to collateral loss causes such as fault rupture, ground failure, inundation, and fire following earthquake, (3) estimation of time to restore damaged facilities to pre-earthquake usability, and (4) estimation of deaths and injuries. In addition, an electronic inventory of approximately 200,000 structures (buildings and lifeline systems) within Salt Lake County has been developed. The data and methodology have been developed for implementation in a geographic information system (GIS) application, or in a non-GIS software application, such as a relational database management system or spreadsheet.

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