Ph.D. Thesis - John Clinton, Caltech, 2004
Modern Digital Seismology - Instrumentation,
and Small Amplitude Studies for the Engineering world
(defended, April 27 2004)
(submitted, May 24 2004)
Caltech
ETD version
Abstract:
The recording of ground motions is a fundamental part of both
seismology and earthquake engineering. The current state-of-the-art
24-bit continuously recording seismic station is described, with
particular attention to the frequency range and dynamic range of the
seismic sensors typically installed. An alternative method of
recording the strong-motions would be to deploy a velocity sensor
rather than an accelerometer. This instrument has the required ability
to measure the strongest earth motions, with enhanced long period
sensitivity.
An existing strong motion velocity sensor from Japan was tested for
potential use in US seismic networks. It was found to be incapable of
recording strong motions typically observed in the near field of even
moderate earthquakes. The instrument was widely deployed near the M8.3
Sept 2003 Tokachi-Oki earthquake. The dataset corroborated our
laboratory observations of low velocity saturations. The dataset also
served to show all inertial sensors are equally sensitive to tilting,
which is widespread in large earthquakes. High rate GPS data is also
recorded during the event. Co-locating high-rate GPS with strong
motion sensors is suggested to be currently the optimal method by
which the complete and unambiguous deformation field at a station can
be recorded.
A new application of the modern seismic station is to locate them
inside structures. A test station on the 9th floor of Millikan
Library is analysed. The continuous data-stream facilitates analysis
of the building response to ambient weather, forced vibration tests,
and small earthquakes that have occurred during its lifetime. The
structure's natural frequencies are shown to be sensitive not only to
earthquake excitation, but rainfall, temperature and wind. This has
important implications on structural health monitoring, which assumes
the natural frequencies of a structure do not vary significantly
unless there is structural damage.
Moderate to small earthquakes are now regularly recorded by dense,
high dynamic range networks. This enhanced recording of the earthquake
and its aftershock sequences makes possible the development of a
Green's Function deconvolution approach for determining rupture
parameters.
---all the following files in pdf format--- (as submitted 24 May 2004)
Abstract; Table of Contents; List of Figures/Tables
170KB
Chapter 1: Introduction
1210KB
Chapter 2: A Strong Motion Velocity Sensor in a Modern Seismic Network?
1.27MB
Chapter 3: Examination of a Strong Motion Velocity Instrument - The VSE-355G2
4.61MB
Chapter 4: Strong Motion Velocity Performance in 2003 Tokachi-Oki Earthquake
12.73MB
Chapter 5: Modifications ot the VSE-355G2 - The VSE-355G3
2.36MB
Chapter 6: Small Amplitude Studies in Structures
9.82MB
Chapter 7: Source-Time Functions
3.95MB
Bibliography
75KB
Appendixes: A- VSE-355g2/3 Testing Regime;
B- Previous Studies of Millikan Library;
C- Millikan Library Dynamic Response to Forced Vibration
2.19MB
John Clinton
Last modified: Tue Jun 15 11:28:19 PDT 2004