In Nature News Richard Monastersky has an informative article (open access) on the New Madrid fault zone and the differing views between the USGS and other scientists on the risk of another big earthquake in that area. The New Madrid area in Missouri has been something of an enigma. Its lies far away from the present day plate boundaries and yet has suffered large earthquakes in the past couple of hundred years. Some scientists have suggested that faults which originated tens to hundreds of millions of years ago - when the New Madrid area was geologically more active - may have strain stored in them.
These faults have been reactivated after the last ice age when the Mississippi river started eroding bedrock and removing large amounts of sediment. The sudden removal of weight from above the faults may have altered stresses on faults on the verge of failing, resulting in the big earthquakes in the recent past.
The article focuses on the work of Northwestern University geophysicist Seth Stein who argues that on faults which have released strain in the recent past the risk of a big earthquake is quite low, a conclusion derived from GPS measurements which show that the crust is that area is not being warped at a rate that could be dangerous. On the other hand he suggests that the earthquake activity could shift to an adjacent system of faults. According to him its best to view the entire region as one with interactive systems of faults with earthquake activity hopping from one zone to another over a time scale of hundreds to thousands of years.
This is a still a hypothesis but one for which Dr. Stein hopes to find evidence by expanding GPS measurements over larger regions around New Madrid. The USGS disagrees with his risk assessment and the article brings together the different points of view.
These faults have been reactivated after the last ice age when the Mississippi river started eroding bedrock and removing large amounts of sediment. The sudden removal of weight from above the faults may have altered stresses on faults on the verge of failing, resulting in the big earthquakes in the recent past.
The article focuses on the work of Northwestern University geophysicist Seth Stein who argues that on faults which have released strain in the recent past the risk of a big earthquake is quite low, a conclusion derived from GPS measurements which show that the crust is that area is not being warped at a rate that could be dangerous. On the other hand he suggests that the earthquake activity could shift to an adjacent system of faults. According to him its best to view the entire region as one with interactive systems of faults with earthquake activity hopping from one zone to another over a time scale of hundreds to thousands of years.
This is a still a hypothesis but one for which Dr. Stein hopes to find evidence by expanding GPS measurements over larger regions around New Madrid. The USGS disagrees with his risk assessment and the article brings together the different points of view.
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