Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / Microfiche copy available in Archives and Science. / Bibliography : leaves 199-214. / by Anthony Frank Shakal. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1979. / Microfiche copy available in Archives and Science. / Bibliography: leaves 118-124. / by Herman William Cooper. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1982. / Microfiche copy available in Archives and Science / Vita. / Bibliography: leaves 312-321. / by Anne Martine Tréhu. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1979. / Microfiche copy available in Archives and Science. / Vita. / Includes bibliographies. / by Wang-Ping Chen. / Ph.D.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Science. / Microfiche copy available in Archives and Science. / Bibliography: leaves 279-290. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1979. / Bibliography: leaves 146-150. / by James Francis Scheimer. / Ph.D.

The understanding of the impact of site effects on ground motions is crucial for improving the assessment of seismic hazards. Site response analyses (SRA) can numerically accommodate the mechanics behind the wave propagation phenomena near the surface as well as the variability associated with the input motion and soil properties. As a result, SRA constitute a key component of the assessment of site-specific seismic hazards within the probabilistic seismic hazard analysis framework. This work focuses on limitations in SRA, namely, the definition of the elastic half-space (EHS) boundary condition, the selection of input ground motions so that they are compatible with the assumed EHS properties, and the proper consideration of near-surface attenuation effects. Input motions are commonly selected based on similarities between the shear wave velocity (Vs) at the recording station and the materials below the reference depth at the study site (among other aspects such as the intensity of the expected ground motion, distance to rupture, type of source, etc.). This traditional approach disregards the influence of the attenuation in the shallow crust and the degree to which it can alter the estimates of site response. A Vs-κ correction framework for input motions is proposed to render them compatible with the properties of the assumed EHS at the site. An ideal EHS must satisfy the conditions of linearity and homogeneity. It is usually defined at a horizon where no strong impedance contrast will be found below that depth (typically the top of bedrock). However, engineers face challenges when dealing with sites where this strong impedance contrast takes place far beyond the depth of typical Vs measurements. Case studies are presented to illustrate potential issues associated with the selection of the EHS boundary in SRA. Additionally, the relationship between damping values as considered in geotechnical laboratory-based models, and as implied by seismological attenuation parameters measured using ground motions recorded in the field is investigated to propose alternative damping models that can match more closely the attenuation of seismic waves in the field. / Ph. D.

The usefulness of Coulomb (friction) damping in earthquake-resistant design of structures is examined by studying the seismic response characteristics of structures with various arrangements of sliding interfaces. First, three basic arrangements are studied for their effectiveness in reducing lateral displacements of the supporting frame, accelerations of the floor slab and the resulting secondary floor spectra. These are: (1) slab sliding system which has the sliding interface between the floor slab and the supporting frame, (2) double sliding system which consists of sliding interfaces at both top and bottom interfaces (a combination of slab sliding and base sliding), and (3) spring-assisted slab sliding system which is a slab sliding system aided by lateral springs attached to the columns to resist excessive sliding displacement of the slab. The responses are obtained for structures with different frequencies and are presented in response spectrum form. The isolation characteristics of one slab sliding system are compared with those of the base sliding and hysteretic systems. Non-dimensional design parameters defined in terms of the corresponding elastic design spectra are introduced for design purposes and for a consistent presentation of the results. Methods for predicting the important response quantities using the non-dimensional parameters are discussed and their applicability is evaluated. Next, the response of a simple slab sliding arrangement to simultaneous horizontal and vertical ground motion input is studied to see the effects of the vertical excitation on the isolation efficiency of that arrangement. Finally the suitability of adopting such sliding arrangements in multi-story structures is also examined. The seismic responses of multi-story structures with floor slabs sliding at different story levels are obtained and compared with the response of non-sliding structure and base sliding to examine the effectiveness of such sliding arrangement. / Ph. D.

Approximately 37 km of predominantly 24-fold P-wave Vibroseis data and 16 km of 24-fold SH-wave Vibroseis data were acquired in the southern portion of the folded Appalachians near the Bane Dome in Giles County, Virginia. Data processing techniques included the application of newly developed methods for crossdip removal as well as the determination of statics solutions in the case of time variant shifts within the data traces. Minimum-phase filter deconvolution was also applied for the removal of reverberating energy and multiples recorded on the SH—wave lines. V_p/V_s ratios were used to aid in the determination of lithologies in the absence of bore-hole data. Interpreted thickening of the Lower Cambrian to Upper Precambrian sequence beneath the Bane Dome appears to represent Eocambrian rifting. Faults generated at that time may now be reactivated by the present stress regime, causing earthquake activity in this area. Interpretation of the seismic data supports a duplex structure proposed for the Paleozoic rocks of the Bane Dome Complex within the Narrows thrust sheet of southwestern Virginia. / Ph. D.

A method to estimate blast-induced damage in rock considering both stress waves and gas expansion phases is presented. The method was developed by assuming a strong correlation between blast-induced damage and stress wave amplitudes, and also by adapting a 2D numerical method to estimate damage in a 3D real case. The numerical method is used to determine stress wave damage and provides an indication of zones prone to suffer greater damage by gas expansion. The specific steps carried out in this study are: i) extensive blast monitoring in hard rock at surface and underground test sites; ii) analysis of seismic waveforms in terms of amplitude and frequency and their azimuthal distribution with respect to borehole axis, iii) measurement of blast-induced damage from single-hole blasts; iv) assessment and implementation of method to utilize 2D numerical model to predict blast damage in 3D situation; v) use of experimental and numerical results to estimate relative contribution of stress waves and gas penetration to damage, and vi) monitoring and modeling of full-scale production blasts to apply developed method to estimate blast-induced damage from stress waves. The main findings in this study are: i) both P and S-waves are generated and show comparable amplitudes by blasting in boreholes; ii) amplitude and frequency of seismic waves are strongly dependent on initiation mode and direction of propagation of explosive reaction in borehole; iii) in-situ measurements indicate strongly non-symmetrical damage dependent on confinement conditions and initiation mode, and existing rock structure, and iv) gas penetration seems to be mainly responsible for damage (significant damage extension 2-4 borehole diameters from stress waves; > 22 from gas expansion). The method has the potential for application in regular production blasts for control of over-breaks and dilution in operating mines. The main areas proposed for future work are: i) verification of seismic velocity changes in rock by blast-induced damage from controlled experiments; ii) incorporation of gas expansion phase into numerical models; iii) use of 3D numerical model and verification of crack distribution prediction; iv) further studies on strain rate dependency of material strength parameters, and v) accurate measurements of in-hole pressure function considering various confinement conditions.