The beautiful mountains of Utah, the abundant streams of Idaho, the wide-open expanses of Nevada, the little hamlets of eastern California, and the urban centers next to steep mountain ranges – all part of the Intermountain West (IMW) region of the U.S. The IMW encompasses a large area of the middle western part of the country from the Rocky Mountains to the Sierra Nevada and Cascade Ranges and is approximately bound on the north by the Canadian border and on the south by the Mexican border (shown on map to left inside yellow border). The IMW is a broad zone of east-west extension, meaning the crust is being stretched, so there are predominantly normal faults within the region – except for the western edge, which is a zone of strike-slip faults parallel to the San Andreas fault called the Walker Lane. This broad region of the western U.S. typically has a fair number of small earthquakes each year, but in 2020 there was an unusual amount of seismic activity – four moderate-sized earthquakes (shown as red stars on the map) and their prolific aftershocks occurred in various locations.

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