Hoodoos – it’s a strange name for a strange-looking rock. These ethereal formations are common features of desert landscapes, but their very fragility may, according to a new study, lead to improvements in our understanding of past earthquakes and, as a consequence, our ability to help assess seismic hazard in areas where they occurs.
Research Findings: The Red Rock Canyon Hoodoos
The study team, led by geophysicist Rasool Anooshehpoor, PhD, used the fragility of two undamaged hoodoos from the Red Rock Canyon close to California’s Garlock Fault to provide constraints on ground motions from a potentially recent earthquake along that fault. The Garlock Fault is an active strike-slip fault marking the northern boundary of the Mojave Block.
The idea was to gain some indication of past levels of slip along the fault by estimating the maximum ground motion that could occur without fracturing the shafts of the hoodoos. Previous studies have tended to focus on similar desert formations known as precariously balanced rocks (PBRs), which differ from hoodoos in that the balancing rock is not attached to its pedestal.
The Garlock Fault is a currently active section of the boundary between the North American and Pacific plates, characterised by lateral (strike-slip) movement, and has undergone well-documented earthquakes in recent centuries, although the nature of the slip is not always clear.
The calculated strength of the hoodoos, however, allows some limit to be placed upon the intensity of ground-motion that occurred within the period of their existence, given that they have remained unbroken – suggesting that slip along the area could not have occurred in a single event within that time.
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