principles and applications of microearthquake networks

Appendix: Glossary of
Abbreviations and Unusual Terms
This glossary defines abbreviations and some unusual terms used in this volume. By
“unusual terms” we mean those terms whose definitions may be difficult to find elsewhere,
or whose meaning has enough variation that we felt it necessary to define them specifically as
used in this book. This glossary is by no means complete. We have chosen not to define many
words, particularly if their meaning is rather well known, or if they are adequately defined in
the following standard references:
Aki, K., and Richards, P. (1980). “Methods of Quantitative Seismology.“ Freeman, San
Francisco, California.
Bates, R. L., and Jackson, J. A., editors (1980). “Glossary of Geology,” 2nd ed. American
Geological Institute, Falls Church, Virginia.
James, R. C., and James, G. (1976). “Mathematics Dictionary,” 4th ed. Van Nostrand
Reinhold, New York.
Lapedes, D. N., editor (1978). “Dictionary of Scientific and Technical Terms.” 2nd ed.
McGraw-Hill, New York.
Richter, C. F. (1958). “Elementary Seismology.” Freeman, San Francisco, California.
Glosscir?
AGC: Automatic gain control. System that automatically changes the gain of an amplifier
or other piece of equipment so that the desired output signal remains essentially constant
despite variations in input strength. See Section 2.2.3.
BPI: Bits per inch. Commonly used to measure the density of information recorded on a
digital magnetic tape. For example, a nine-track 800 BPI tape contains information at a
density of 800 bitsiinchltrack. Because a byte is usually coded as 9 bits across a magnetic
tape, the effective information density in this example is 800 bytedinch.
Cholesky method: An efficient method of solving a set of linear equations Ax = b if the
matrix A is symmetric and positive definite. Matrix A is said to be positive definite if
xTAx > 0 for all x # 0. The method is based on the Cholesky decomposition ofA into LLT,
where L is a lower triangular matrix. It is commonly used to solve a set of normal
equations.
Coda magnitude: Type of earthquake magnitude. It is based on either the duration of coda
waves or some of their characteristics. Some authors have used this term interchangeably
with duration magnitude; this practice is technically incorrect. See Duration magnitude.
For a definition of coda waves, see Aki and Richards (1980, p. 526).
Compensation signals: Signals that are recorded on an analog magnetic tape along with the
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