An Integrated Geophysical and Geologic Study of the Tectonic Framework of the 38th Parallel Lineament in the Vicinity of Its Intersection with the Extension of the New Madrid Fault Zone. Annual Progress Report for Fiscal Year 1980

摘要

Gravity, magnetic, seismic refraction and reflection, and basement geology are being used to investigate the northeastern extension of the New Madrid Fault Zone. Parallel, linear trends of correlative gravity and magnetic anomalies, previously related to the New Madrid Fault Zone and its associated structure, extend to the northeast into Indiana to approximately 39.5 N latitude. This feature also is suggested in the historical seismicity pattern and perhaps the basement geology and the crustal seismic model. The crustal seismic model is somewhat anomalous in comparison to the 'normal' crust adjacent to the Mississippi Embayment. An additional pair of parallel trends of geophysical anomalies has been identified extending from New Madrid to St. Louis on either side of the Mississippi River. One possible origin for the basement structures is a Precambrian triple junction associated with continental rifting during break-up of the continents.