Hoodoos: Desert Formations Help Understand Seismic Hazard

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Earthquake Research: Seismological Implications

The Garlock Fault, California. Image credit: USGS

The Garlock Fault, California. Image credit: USGS

While earthquake prediction remains very much a distant dream for seismologists, earthquake specialists have concentrated instead upon preparing assessments of seismic hazard so that civil authorities can be prepared for the moment when a major earthquake occurs.

This process involves producing a probabilistic map of seismic activity for any given location.

Such maps have been produced by the United States Geological Survey for over 50 years and incorporate the findings of a wide range of research – “historical seismicity, paleoseismology, strong motion seismology, and site response” according to the USGS.

Although there are many uncertainties associated with using hoodoos or PBRs in any such analysis – most notably, the age of the structures and the fact that they erode so rapidly, which effectively restricts their usefulness to the past thousand years or so – Dr. Anooshehpoor says that the growing view among seismologists is that it is essential to regard hazard maps as the calculated output of hazard models that should be tested, and that the FGFs provide the only data to validate the predictions of these models at low probabilities.

In the absence of long-term instrumental data FGFs provide the only data to validate the predictions of these models at low probabilities,” he told Decoded Science. “In this respect, hoodoos could play an important role where there has been a recent large earthquake in their vicinity.

Fragile Formations: Hoodoos and Quake Prediction

Hoodoos, then, for all their frailty, may provide yet another piece in the jigsaw of human understanding of where and how often earthquakes occur, as well as the nature of the movement. Reassuringly, the study concluded that the survival of one of the hoodoos following a major earthquake event in the past 550 years, is broadly consistent with existing seismic mapping.

Sources

Anooshehpoor, A., Brune, J.N., Daemen, J. and Purvance, M.D. Constraints on Ground Accelerations Inferred from Unfractured Hoodoos near the Garlock Fault, California. (2013). Bulletin of the Seismological Association of America. February 4, 2013.

USGS. The National Seismic Hazard Mapping Center. (2013). Accessed 4 February 2013

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