Publication Date

1975

Document Type

Dissertation/Thesis

First Advisor

McGinnis, Lyle D. (Lyle David), 1931-2017

Degree Name

M.S. (Master of Science)

Department

Department of Geology

LCSH

Gravity--United States||Seismology--United States||Earth--Crust

Abstract

Qualitative interpretation of recently completed maps of seismic flux and the free-air gravity field of the midcontinent suggests a correlation between seismicity and heterogeneous crustal structure. The maps compiled for this study suggest that the regional, horizontal compressive stresses associated with movement of the North American plate are strongly modified in the presence of zones of weakness or discontinuities and mass concentrations. The available data suggest that predominantly vertical stresses acting within the lower crust or upper mantle are transmitted by creep to the upper crust, where the stress concentrates at weaknesses or discontinuities, and is subsequently relieved by unstable creep or brittle failure. The model of seismicity consists of a system of blocks within the upper crust, capable of independent movement, undergoing local, isostatic adjustment in response to regional, isostatic or isobaric adjustment.

Comments

Includes bibliographical references (pages [93]-101)

Extent

157 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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