Abstract
New inversions of existing magnetic and gravity data lead to insights on upper crustal structures in the central Illinois basin. The results of 2D and 3D inversion techniques suggest that the source of the Commerce geophysical lineament follows the southeast boundary of a dense and magnetic, northeast-Trending igneous center, named the Vincennes igneous center. Thus the Commerce geophysical lineament, defining the 5-To 10-km-wide Commerce deformation zone, appears to have influenced the structural development of the Vincennes igneous center. Overlying this igneous center is the Centralia seismic-reflection sequence, expressed as highly coherent reflectors (McBride and Kolata, 1999). We suggest that the buried Vincennes igneous center is the source of inferred volcanic units of the Centralia sequence and is related to a rifted margin or a Proterozoic plate boundary. A comparison of gravity and magnetic fields over the Vincennes igneous center and the St. Francois Mountains igneous center in southeastern Missouri suggests that the associated sources in these regions are similar in composition and perhaps origin. Such a conclusion, although speculative, suggests that -1.47 Ga-year-old volcanic fields of high-silica rocks, with more abundant mafic components at depth, characterize basement in the regions of the Vincennes igneous center and the St. Francois Mountains. Further, we conclude that the Commerce deformation zone evolved in the Mesoproterozoic (1.1 to 1.5 Ga) as a major cratonic rheological boundary and was the focus of episodic reactivation related to varying stress regimes throughout its history. Spatial relations of the Commerce deformation zone with large Pleistocene and Holocene earthquakes suggest that the zone represents a major rheological boundary intimately related to both surface and deep structures and to the seismic hazard of the Illinois basin region. Assuming recent right-lateral slip along the Commerce deformation zone, we propose that a jog or left step in the Vincennes area leads to thrusting or a restraining bend, where associated stress accumulations may have resulted in nearby large prehistoric earthquakes and may also be the nucleation sites of future large earthquakes.
| Original language | English |
|---|---|
| Pages (from-to) | 640-659 |
| Number of pages | 20 |
| Journal | Seismological Research Letters |
| Volume | 73 |
| Issue number | 5 |
| DOIs | |
| State | Published - Sep 2002 |
Bibliographical note
Funding Information:Thoughtful reviews by Glen Bear, Pat Bickford, Ed Lidiak, Jeff Phillips, and Rus Wheeler greatly improved the manuscript. The views and conclusions contained in this document are solely those of the authors. It should be noted that Jack Odum first pointed out the possibility that the Commerce geophysical lineament had exceptional length and correlated with surface topography. Randy Keller, University of Texas at El Paso, kindly furnished about 16,000 gravity stations. Research supported by the U. S. Geological Survey (USGS), Department of the Interior, partly under USGS award numbers 1434-HQ97GR-03194 and 1434-HQ97GR-03065 (University of Illinois). This work was also supported, in part, by the Earthquake Engineering Research Centers Program of the National Science Foundation under Award Number EEC-9701785. The publication of this report is authorized by the Chief, Illinois State Geological Survey.
ASJC Scopus subject areas
- Geophysics