We cannot verify this study mentioned – FC
LOS ANGELES, CA (California Network) – In Nov 1981, a study was published that rocked the scientific world, and sparked concern in FEMA circles, in which a 1,700 mile “Crack Across America” was discovered. Worse yet, this crack cuts through the New Madrid Seismic Zone, where in 1811 and 1812 three giant earthquakes devastatingly struck the center of America. Scientists have been struggling, since then, to answer the question of what risk this mega feature may pose to our heartland today. Recently, and less known, is a study from an independent geologic research set of work [2], that has identified a possible second “Crack Through America” that crosses into and through the same volatile New Madrid Seismic Zone. . . (more)
UPDATE:
Reader, Mike L. sent a link to the NASA funded Report –
Structure of the midcontinent basement. Topography, gravity, seismic, and remote sensing
SUMMARY
http://ntrs.nasa.gov/search.jsp?R=19820017795
(IE worked better than Mozilla browser)
8.4 MB PDF of the whole thing –
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19820017795.pdf
“Some 600,000 discrete Bouguer gravity estimates of the continental United States were spatially filtered to produce a continuous tone image. The filtered data were also digitally painted in color coded form onto a shaded relief map. The resultant image is a colored shaded relief map where the hue and saturation of a given image element is controlled by the value of the Bouguer anomaly. Major structural features (e.g., midcontinent gravity high) are readily discernible in these data, as are a number of subtle and previously unrecognized features. A linear gravity low that is approximately 120 to 150 km wide extends from southeastern Nebraska, at a break in the midcontinent gravity high, through the Ozark Plateau, and across the Mississippi embayment. The low is also aligned with the Lewis and Clark lineament (Montana to Washington), forming a linear feature of approximately 2800 km in length. In southeastern Missouri the gravity low has an amplitude of 30 milligals, a value that is too high to be explained by simple valley fill by sedimentary rocks.”
[CLICK IMAGE FOR FULL SIZE]
Here’s another paper from the U of Ill. -It has good maps.
The Midcontinent exposed: Precambrian basement topography, and fault-and-fold zones, within the cratonic platform of the United States
(That white blob is Lake Michigan up at the top right.)
Nature Runs Amok at Yellowstone 