Electronic Theses and Dissertations

Identifier

417

Date

2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Engineering

Concentration

Civil Engineering

Committee Chair

Shahram Pezeshk

Committee Member

Roger W Meier

Committee Member

Stephanie S Ivey

Committee Member

Chris Harold Cramer

Abstract

First, a new path model, including the geometrical spreading and the quality factor functions, is developed for the New Madrid seismic zone (NMSZ) using recorded small and moderate earthquakes. The database consists of 500 broadband seismograms from 63 events of magnitude Mw 2.5 to 5.2. All the broadband stations are located within the Mississippi embayment. The vertical components of the records are processed and used to define the path effect term in the frequency range of 0.2 to 30 Hz. At distances less than 70 km, the spectral amplitudes decay as R-1; between 70 and 140 km, spectral amplitudes increase with distance and the geometric spreading is defined as R+0.25; beyond 140 km, the attenuation is described by R-0.5. The quality factor function is expressed as Q=614f0.32for frequencies greater than 1 Hz.Second, the horizontal-to-vertical component (H/V) spectral ratio is used as an estimation of the site response in the NMSZ. The observed average H/V ratios suggest site amplification between 2 and 4 in the low-frequency range (f<5 Hz) for stations located on the lower shear-wave velocity deposits (Lowlands). The higher shear-wave velocity deposits (Uplands) indicate low-frequency amplification between 1.5 and 3 Hz. Comparison of the observed H/V ratios with the theoretical amplification factors suggest that the H/V ratios can be a first estimate of the site amplifications. Afterward, the variability of the H/V ratios with distance is examined and no discernible trends are found; therefore, the path effect model developed for the vertical ground motions in NMSZ using the database of this study is also applicable for the horizontal ground motions.Finally, a hybrid empirical method is used to develop a new ground-motion prediction equation (GMPE), for eastern North America (ENA), using five new GMPEs developed for western North America (WNA). A new GMPE is derived for a magnitude range of 5 to 8 and closest distances to the fault rupture up to 1000 km for hard-rock sites in ENA. The new GMPE is compared with two GMPEs used in the 2008 national seismic hazard maps as well as with available observed data for ENA.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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