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Utah Geological Survey Releases New Interactive Fault Map

geology.utah.gov

The Utah Geological Survey (UGS) has made the Utah Quaternary Fault and Fold Database available through a new interactive web application on the UGS website. This database contains information on faults and fault-related folds considered to be potential earthquake sources. The faults and folds in the database are considered to have been sources of large earthquakes (about magnitude 6.5 or greater) during the Quaternary geologic time period (past 2.6 million years); these geologic structures are the most likely sources of large earthquakes in the future. The Utah Quaternary Fault and Fold Database is the primary source of Utah data for the Quaternary Fault and Fold Database of the United States maintained by the U.S. Geological Survey (USGS).

The interactive map’s user interface was built using ESRI’s JavaScript API. Several search options allow the user to locate a fault of interest, or specify a location to see if any Quaternary faults are nearby. Pop-up windows provide a brief summary of important information associated with the faults, as well as a link to detailed reports available through the USGS national database. Users can select from a variety of basemaps including topographic, shaded relief, and satellite imagery. A glossary explains terms used in the pop-up windows as well as terms used in the detailed reports that may be unfamiliar to non-geologists.

In addition to the UGS interactive map, the Utah Quaternary Fault and Fold Database exists as a fully attributed GIS feature class in the State Geographic Information Database, and can be downloaded from the AGRC at http://gis.utah.gov/data/geoscience/quaternary-faults.

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New technology uncovers hidden geological hazards

A couple of our geologists, Gregg Beukelman and Adam McKean, talk about new knowledge of fault lines west of Salt Lake International Airport thanks to advances in technology. Read more about it!

ksl.com

Geologist Adam McKean said experts knew there were some faults in the earth west of the Salt Lake International Airport.

READ MORE

Joint Evening Meeting “Geologic Remapping of the Warm Springs Fault”

Tuesday, October 7, 2014, 6:00 PM 
Utah Department of Natural Resources Auditorium,
1594 West North Temple (enter on south side)

 

 

 

 

 

 

 

 

 

Joint Evening Meeting with Association of Environmental Geologists (AEG), Utah Geological Association (UGA), Utah Geological Survey (UGS)
“Geologic Remapping of the Warm Springs Fault”
presented by Adam McKean, Mapping Geologist with the UGS

The Warm Springs fault of the Wasatch fault zone is a down-to-the-west normal fault, bounding the western portion of the Salt Lake salient. Recent geologic remapping of the Salt Lake City North 7.5-minute quadrangle has provided us an opportunity to revisit the Warm Springs fault and its place within Salt Lake and Davis Counties. A draft map of the quadrangle and evidences for the Warm Springs fault location will be presented at the meeting with opportunities for open discussion, questions, and feedback. We invite the geologic and geologic engineering community and interested parties to attend the event and take part in this public comment period.

Evaluating Surface Faulting Chronologies of Graben-Bounding Faults in Salt Lake Valley, Utah- New Paleoseismic Data from the Salt Lake City Segment of the Wasatch Fault Zone and the West Valley Fault Zone

By: Christopher B. DuRoss and Michael D. Hylland

The Salt Lake City segment (SLCS) of the Wasatch fault zone and the West Valley fault zone (WVFZ) are Holocene-active faults that have evidence of large-magnitude (M ~6-7) surface-faulting earthquakes. Paleoseismic research trenches at the Penrose Drive site on the SLCS and Baileys Lake site on the WVFZ provided data that shed light on the faulting behavior and interaction of these graben-forming fault systems. Numerical age control (22 radiocarbon samples 23 optically stimulated luminescence samples) and OxCal modeling of six or seven surface-faulting earthquakes on the SLCS and four earthquakes on the WVFZ helped refine the earthquake chronologies for these faults and allowed a comparison of the chronologies to evaluate fault interaction. The chronologies, as well as vertical displacements, support a model of coseismic fault movement.

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Utah Faults

Utah Faults

Utah has experienced many earthquakes, large and small, because of its abundance of faults and fault zones. Some of the most active faults in Utah include the Wasatch fault along the Wasatch Front, the Hurricane fault in Southern Utah, and the Needles fault zone in Canyonlands National Park.




What is a fault and why is it a concern?


A fault is a break in the earth’s crust along which movement can take place causing an earthquake. In Utah, movement along faults is mostly vertical; mountain blocks (for example, the Wasatch Range) move up relative to the downward movement of valley blocks (for example, the Salt Lake Valley).

Faults with evidence of Holocene (about 10,000 years ago to present) movement are the main concern because they are most likely to generate future earthquakes. If the earthquake is large enough, surface fault rupture can occur.


What is a surface fault rupture?

With a large earthquake (about magnitude 6.5 and greater), the fault rupture can reach and displace the ground surface, forming a fault scarp (steep break in slope). The resulting fault scarp may be several inches to 20 feet in height, and up to about 40 miles in length, depending on the size of the earthquake.

What are the effects of surface fault rupture?

An area hundreds of feet wide can be affected, called the zone of deformation, which occurs chiefly on the downthrown side of the main fault and encompasses multiple minor faults, cracks, local tilting, and grabens (downdropped blocks between faults). Buildings in the zone of deformation would be damaged, particularly those straddling the main fault.

Also, anything crossing the fault, such as transportation corridors, utilities, and other lifelines, both underground and above ground, can be damaged or broken. The ground can be dropped below the water table on the downdropped side, resulting in localized flooding.

Surface fault rupture can also cause tectonic subsidence, which is the broad, permanent tilting of the valley floor down toward the fault scarp. Tilting can cause flooding along lake and reservoir shorelines nearest the fault; along altered stream courses; and along canals, sewer lines, or other gravity-flow systems where slope gradients are lessened or reversed.

Where and when is surface fault rupture likely to occur?

On the Holocene fault on which a magnitude 6.5 (approximate) or larger earthquake occurs. On average, these earthquakes may occur once every 120 years on various faults in the Wasatch Front region; once every 350 years somewhere along the central part of the Wasatch fault (between Brigham City and Nephi); once every 2,000 years at any specific locality along the central Wasatch fault; and once every 5,000 to 20,000 years or more on other Holocene faults in the state.

What can be done to protect homes?

Faults can be avoided by setting homes back a safe distance. Special-study areas have been delineated along faults where geologic studies are recommended to assess the hazard, locate faults, and recommend setbacks. However, the use of special-study areas in land-use ordinances varies by county and city, as does the level of enforcement.

Therefore, buyers, particularly of older homes (pre-1985), should personally check available fault maps to see if the home is near a fault (within a few hundred feet) and, if so, may want a geological site investigation performed. For newer homes, buyers should check with the county or city to determine whether geologic studies were performed for the site or subdivision and, if so, look at a copy of the geologic report.



Survey Notes: Glad You Asked - Earthquake Early Warning System

Wasatch Front Earthquake Early Warning System

Earthquake early warning (EEW) systems work on the principle that an alert signal can be transmitted almost instantaneously, whereas seismic waves take longer to travel through the Earth’s crust. Earthquake early warning (EEW) systems work on the principle that an alert signal can be transmitted almost instantaneously, whereas seismic waves take longer to travel through the Earth’s crust. Sensors detect the first-arriving P wave and trigger the sending of an alert signal, which can give people and automated systems some time to take action before the arrival of stronger S waves and surface waves. This diagram illustrates a conceptual EEW system in the Wasatch Front urban corridor.





Exposing the Wasatch Fault

Past large earthquakes on the central, most active segments of the fault and how geologists interpret evidence of large, prehistoric earthquakes, with footage from the North Creek trench investigation.


North Creek Trench on Wasatch Fault

Time-lapse video of the excavation and investigation of the North Creek trench on the Nephi segment of the Wasatch fault zone.


Wasatch Fault Flyby

The Salt Lake City segment of the Wasatch fault and related geologic features.

What Causes an Earthquake? Faults Explained

news.nationalgeographic.com

We all have our faults, and that includes planet Earth. Earthquakes rattle the globe every day, big and small, most recently making news this week with temblors in Puerto Rico and southern California.

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IRON COUNTY POSTPONES VOTE ON GEOLOGIC ORDINANCE

sltrib.com

The Iron County Commission was poised to vote Monday on a geologic hazard ordinance that has been in the making for about six months when Commissioner Lois Bulloch threw a wrench in the works.

Bulloch recommended that an independent group review the proposed ordinance and make recommendations.

“I’ve heard a lot of consternation over this issue and had input in letters and calls and am just not comfortable moving forward,” said Bulloch. “Sorry to drop this bomb.”

Bulloch suggested that a committee with representatives of the county’s six municipalities, a city attorney and engineers look at the ordinance line by line and make specific changes.

“This way we won’t be accused of not listening,” said Bulloch.

Bill Lund, a geologist with the Utah Geological Survey, told commissioners a review by new eyes is a good idea and recommended including an official of a city or county in Utah that has already dealt with a similar ordinance.

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Utah Geological Survey Releases New Interactive Fault Map

geology.utah.gov

The Utah Geological Survey (UGS) has made the Utah Quaternary Fault and Fold Database available through a new interactive web application on the UGS website. This database contains information on faults and fault-related folds considered to be potential earthquake sources. The faults and folds in the database are considered to have been sources of large earthquakes (about magnitude 6.5 or greater) during the Quaternary geologic time period (past 2.6 million years); these geologic structures are the most likely sources of large earthquakes in the future. The Utah Quaternary Fault and Fold Database is the primary source of Utah data for the Quaternary Fault and Fold Database of the United States maintained by the U.S. Geological Survey (USGS).

The interactive map’s user interface was built using ESRI’s JavaScript API. Several search options allow the user to locate a fault of interest, or specify a location to see if any Quaternary faults are nearby. Pop-up windows provide a brief summary of important information associated with the faults, as well as a link to detailed reports available through the USGS national database. Users can select from a variety of basemaps including topographic, shaded relief, and satellite imagery. A glossary explains terms used in the pop-up windows as well as terms used in the detailed reports that may be unfamiliar to non-geologists.

In addition to the UGS interactive map, the Utah Quaternary Fault and Fold Database exists as a fully attributed GIS feature class in the State Geographic Information Database, and can be downloaded from the AGRC at http://gis.utah.gov/data/geoscience/quaternary-faults.

READ MORE

New technology uncovers hidden geological hazards

A couple of our geologists, Gregg Beukelman and Adam McKean, talk about new knowledge of fault lines west of Salt Lake International Airport thanks to advances in technology. Read more about it!

ksl.com

Geologist Adam McKean said experts knew there were some faults in the earth west of the Salt Lake International Airport.

READ MORE

Joint Evening Meeting “Geologic Remapping of the Warm Springs Fault”

Tuesday, October 7, 2014, 6:00 PM 
Utah Department of Natural Resources Auditorium,
1594 West North Temple (enter on south side)

 

 

 

 

 

 

 

 

 

Joint Evening Meeting with Association of Environmental Geologists (AEG), Utah Geological Association (UGA), Utah Geological Survey (UGS)
“Geologic Remapping of the Warm Springs Fault”
presented by Adam McKean, Mapping Geologist with the UGS

The Warm Springs fault of the Wasatch fault zone is a down-to-the-west normal fault, bounding the western portion of the Salt Lake salient. Recent geologic remapping of the Salt Lake City North 7.5-minute quadrangle has provided us an opportunity to revisit the Warm Springs fault and its place within Salt Lake and Davis Counties. A draft map of the quadrangle and evidences for the Warm Springs fault location will be presented at the meeting with opportunities for open discussion, questions, and feedback. We invite the geologic and geologic engineering community and interested parties to attend the event and take part in this public comment period.

Evaluating Surface Faulting Chronologies of Graben-Bounding Faults in Salt Lake Valley, Utah- New Paleoseismic Data from the Salt Lake City Segment of the Wasatch Fault Zone and the West Valley Fault Zone

By: Christopher B. DuRoss and Michael D. Hylland

The Salt Lake City segment (SLCS) of the Wasatch fault zone and the West Valley fault zone (WVFZ) are Holocene-active faults that have evidence of large-magnitude (M ~6-7) surface-faulting earthquakes. Paleoseismic research trenches at the Penrose Drive site on the SLCS and Baileys Lake site on the WVFZ provided data that shed light on the faulting behavior and interaction of these graben-forming fault systems. Numerical age control (22 radiocarbon samples 23 optically stimulated luminescence samples) and OxCal modeling of six or seven surface-faulting earthquakes on the SLCS and four earthquakes on the WVFZ helped refine the earthquake chronologies for these faults and allowed a comparison of the chronologies to evaluate fault interaction. The chronologies, as well as vertical displacements, support a model of coseismic fault movement.

GET IT HERE