An Integrated Geophysical and Geological 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

摘要

An integrated gravity, magnetic, crustal seismic refraction, and basement geology study is being conducted of the northeastern extension of the New Madrid Fault Zone in the vicinity of the 38th Parallel Lineament. Gravity and magnetic anomaly maps prepared of this area plus regional seismicity suggest that the basement structural feature associated with the New Madrid seismicity extends northeasterly into southern Indiana to at least 39 degrees N latitude. Gravity and subsurface data indicate that the Rough Creek Fault Zone, a major element of the 38th Parallel Lineament, is the northern boundary of a complex graben which formed in late Precambrian-early Paleozoic time and since has been reactivated. Surface wave studies indicate that the crustal thickness of the northern Mississippi Embayment is probably in the range of 50-55 km and the structure of the crust obtained from these studies is highly suggestive of a failed rift.