Northwest-trending basement fracture zones in the eastern United States and their role in controlling neotectonic movement and earthquakes

Abstract

A few northwest-trending fault zones have long been known in the United States east of the Rocky Mountains, and numerous ones have been revealed by geomorphic, geophysical, LANDSAT, side-looking-radar, and detailed geologic data during the past 15 years. Many are grouped to form long fracture zones which appear to form major zones with smaller zones between them. Enough major zones are now known to suggest that they form a basic crustal framework. Their ages range from Precambrian to post-Cretaceous. Movement along fracture zones is known to have affected Paleozoic sedimentation in places, and both these zones and offshore transform fracture zones have controlled northwest-trending late Cretaceous and Tertiary basins, referred to as embayments, in the coastal plain deposits. Much of the present-day movement, as shown by earthquakes, is occurring locally along the fracture zones, especially where they cross northeast-trending belts undergoing vertical movement. The activity at New Madrid, Missouri, (the greatest earthquakes in USA) is located where a northwest-trending fracture zone crosses a northeast-trending basement graben. -from Author