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.

Although the Wasatch fault is currently known to have a high-seismic hazard from motion along range-bounding faults, new seismic data reveal faulted and folded 13,000–30,000-yr-old Lake Bonneville strata beneath Salt Lake City (SLC). Coupled with previous excavation trench, borehole, and other geologic and geophysical observations, we conclude that a zone of latest Pleistocene and/or Holocene faulting and folding kinematically links the East Bench and Warm Springs faults through a 3 km wide relay structure and transfer zone. We characterize faults beneath downtown SLC as active, and these faults may displace or deform the ground surface during an earthquake. Through offset but linked faults, our observations support throughgoing ruptures across faults of the Wasatch fault zone (WFZ) and an elevated risk of earthquake-induced building damage.

A 775-m 200-MHz GPR traverse was surveyed in July 2009 over a portion of the Zwillingsgletscher branch of the Gornergletscher System, Valais, Switzerland. The survey line was approximately parallel to the glacial flow direction and situated in an area of prominent wave ogive formation. The traverse shows a well-developed pattern of scattering that is strongly folded into apparent troughs and ridges with the ridges commencing at 10-20 m depth. This pattern mimics the expected ogive structure. The origin of the scattering has not yet been confirmed, but is possibly related to an onset of warmer ice or to variations in rock or sediment content.

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