Earthquake Mechanics

and Nondestructive Testing

Overview

Our research uses the analysis of waves in order to study material behavior such as earthquakes, faulting, friction, impact, and fracture. In order to make good use of the data, we must have a good understanding of the way waves propagate, the way seismic sources can be represented, the way waves can be measured, and how to manipulate recordings of waves (signals) for enhanced understanding.

This work is made possible by sensors. A few of the sensors I have used in my research are shown below:

The sensor on the left is was developed in the Glaser Lab and is sensitive to surface normal displacements down to 1 pm in amplitude (1 x 10^-12 m) in the frequency range of ~8 kHz to ~3 MHz. The Panametrics sensor gives a somewhat more distorted account of surface displacements and has detected ground motions ranging from about 1 MHz down to less than 100 Hz. The capacitive sensor measures the distance between the sensor probe and a target in a frequency range from mHz (hours) to kHz and has resolution less than 1 micron. When glued to a sample, strain gages (far right) provide a measurement of the distortion or strain that the sample feels averaged along the gage length. Strain is a tensor quantity, so a rosette of strain gages is needed to characterize each component of the tensor.

Main research subject areas

1) Seismic sources - their characterization, classification, and physical origins

2) Digital signal processing - spectral estimation, Fourier theory, filtering, array processing

3) The physical and chemical behavior of interfaces and surfaces - friction, fault healing, dynamic fault rupture, multiscale surface roughness

4) Wave propagation in solids - the physics of attenuation, theoretical and numerical calculation of Green's functions

5) Sensor design and calibration - electro mechanical design of piezoelectric sensors, characteristics of preamps (analog filtering and amplification), artificial sources of seismic waves for sensor calibration

Past Research Projects:

The links below lead to pages that describe some of McLaskey's past work.

--- Foreshocks and earthquake nucleation

Large scale laboratory earthquake experiments.

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--- Fault healing studied with repeating earthquakes and laboratory stick-slip

We compare results from a small laboratory apparatus to natural earthquakes in California.

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--- Micromechanics of Friction

The study of friction and the nanoseismic detection of asperity rupture.

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--- Ball Impact and System Calibration Project

Ball impact is used as a calibration source for absolute system calibration. While studying this source, I was able to test the limits of Hertzian impact theory.

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--- Drying Shrinkage Cracking Project

Microcracks due to drying shrinkage were detected and located within a small concrete specimen.