Earthquake Fault Lines: New study pinpoints Wasatch Fault zones

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SALT LAKE CITY (ABC4 News) – It can’t stop earthquakes, but it can help show where the most damage could be. Using a high tech tool called LIDAR, the Utah Geological Survey released four year study that for the first time shows a detailed mapping of faults along the Wasatch Front that could cause surface rupture during an earthquake.

Damaged building from Magna earthquake.

LIDAR which stands for Light detection and ranging uses laser pulses in conjunction with data from other components in an airborne system. Combined it creates a 3D presentation of the part of the earth it was used to map.

RELATED: Aftershocks from Magna Earthquake

In the case of UGS, it is the Wasatch Fault Zone, with the goal of showing where an earthquake here can cause a surface rupture. Giving state officials new information that can be used for decisions like where to build in the valleys.

Surface rupture is scary. If it happens when an earthquake hits, the fault can cause the land to break, rise up, or sink down. Either way, it can cause significant damage to homes, schools, buildings, businesses, and other infrastructure along the Wasatch Front.

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To see the new fault line data along the Wasatch Front look at the slide show below. What you will see is a representation of what’s happened up to 2,600,000 years ago plus the new information from the current survey.

The press release from the USGC says researchers recently acquired high-resolution elevation surveys (LIDAR) derived from laser sensors mounted on aircraft. These surveys were literally fault mapping and allowed for a new delineation of surrounding special study zones. Now it becomes a critical tool letting us know where the fault zones are and making it easier for decisions to be made when it comes to earthquakes, safety and development.

Take a look at the UGS interactive map

One of the benefits of the new survey is how it lets geologists look at faults and scarps.

What is a fault? A fault forms the boundaries between the Earth’s tectonic plates. In active faults like we have here in Utah, pieces of the earth’s crust move over time.  When it moves we call it an earthquake.

What is a scarp? Technically it’s a fault scarp, and when one side of a fault moves in relation to the other side.  They can be very hazardous to buildings when you realize they can move up to 20 feet and 40 miles long here in the Wasatch front.

Construction workers looks at the rubble from a building after an earthquake Wednesday, March 18, 2020, in Salt Lake City. A 5.7-magnitude earthquake has shaken the city and many of its suburbs. The quake sent panicked residents running to the streets, knocked out power to tens of thousands of homes and closed the city’s airport and its light rail system.  (AP Photo/Rick Bowmer)

As terrifying as that sounds, remember earthquakes in our area are modeled out not to top out at about 7.6 that’s 700 times more powerful that the quake we just had.

According to the press release from the UGS, while the increased accuracy helps to pin down fault locations, it is not precise enough to safely locate specific buildings on individual lots. Furthermore, ground cracking, tilting, and minor faulting usually accompanies surface fault rupture, This zone of deformation occurs adjacent to the main fault scarp and can extend hundreds of feet, mostly on the downthrown (valley side of the main scarp).

“While we recommend additional site-specific investigation prior to building, it’s up to local agencies to regulate development within our delineated special study zones,” said UGS Hazards Geologist Greg McDonald. 

The study was a collaborative effort between the UGS, and the U.S. Geological survey. Along with the new lidar imagery, mappers utilized previous geologic mapping and studies of ancient earthquakes., historical aerial photography, and field investigations. In addition to the increased detail, from previously mapped faults, the study identified new fault traces and what could be sites for future field investigations of Wasatch Front faults.

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