Campion Park: The Hangman Fault Line and Its Relations

Within the Pacific Northwest when fault lines are discussed what typically comes to mind is areas along the coast. Simply due to the proximity to where the Juan De Fuca plate experiences subduction under the North America plate and faults often appear near tectonic plate boundaries. Most would not expect an inland location such as Spokane to have a fault line, let alone multiple. But that seems to potentially be the case.

The Spokane fault line has been proposed to exist (Wicks et al., 2013), and evidence suggest that others exist within relation to it. Specifically the Latah fault and the Hangman fault (Daley et al., 2014; Derkey and Hamilton, 2001). The focus henceforth will be on the Hangman fault, which is proposed to exist along Hangman Creek. The existence of this fault is indicated due to evidence in the natural geology of the area being exposed. A cut bank from river erosion has created a display of natural folding of the local geology. Although there is speculation that points to the folding along Hangman Creek to potentially only be present due to a landslide rather than a fold along a fault line, evidence appears to point to the contrary. The Hangman Creek folding most likely occurred due to a drag fold along the fault, creating the folded visual in the area as previously deposited sediment is dragged and uplifted accordingly. This sediment would have most likely have been deposited during glacial lake outburst flooding, meaning the sediment would be soft and ductile, lending credence to the folding of the geology occurring due to fault movements.

Evidence suggests that while both the Latah and Hangman faults are within a similar region, they are most likely not related to one another (Daley et al., 2014; Derkey and Hamilton, 2001). It is far more likely that the Hangman fault is related to the Spokane fault line as they have similar dip orientations and both appear to be compressional, while the Latah fault is shown to have growth fault movement. If these faults do indeed exist, then the existence of these fault lines potentially points to a future where earthquakes within the Spokane area become very likely, rather than a slight possibility. As, the stress from the movements of the fault lines are incredibly likely to trigger an earthquake. The question becomes when, rather than if it will happen at all. Considering that the city is not built with earthquakes in mind, as opposed to high danger areas like Japan; if a strong enough earthquake were to occur the results could be incredibly high damages.