Monday, May 16, 2011

I found this interesting paper today written by John K. Costain of Virginia Tech, about links between US seismic zones and surface and ground-water. With today’s flooding and storms, it may be an interesting read.

The conclusion of the paper states:

A conventional groundwater model with meteorological forcing (rainfall) on the atmosphere-water-table interface producing diffusion of pore-fluid pressure at depth appears to be a useful one for understanding the origin of intraplate seismicity in stable and even in some unstable tectonic regions. Fluctuations in the elevation of the water table accompanied by changes in river flow transmit pore-fluid pressure transients to hypocentral depths where they trigger earthquakes in a crust already stressed close to failure. This was the original concept of the “hydroseismicity” model. New results in Virginia, West Virginia, and the NMSZ seismic zone show a clear correlation between the supply of water at the Earth’s surface and the distribution of earthquake epicenters. Seismicity in each of these areas is coincident with a relatively large and abrupt supply of water available to the shallow and deep crust. The timing of three large earthquakes in Virginia and West Virginia with respect to hurricanes Camille and Agnes, together with the known or inferred values of crustal hydraulic diffusivity, suggests a causal relationship between the hurricanes and the earthquakes. The eastern and central United States seem to be especially favorable for further investigations into the links between meteorological forcing functions and triggered earthquakes. The two regions are relatively stable tectonically and yet the number of earthquakes per year in each of several well-identified seismogenic zones varies by several orders of magnitude, suggesting opportunities for investigations within different magnitude ranges. The many correlations between meteorological parameters (rainfall, streamflow) and seismicity that are now being reported in the literature suggest the need for more local and regional earthquake monitoring networks as well as additional stream gaging stations. In the future it should be possible to discover and quantify causal relationships between earthquakes and meteorological parameters when better focal depths and more stream gaging stations become available. Groundwater hydrology and earthquake monitoring and forecasting might eventually complement each other, providing additional controls on focal depths or crustal hydraulic diffusivity, respectively, and this suggestion is offered as a principal conclusion of this paper.

To see the full paper, click here


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