principles and applications of microearthquake networks

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a,No ak) ak) ak) TABLE I Seismic System Response Parameters for USGS Central California Microearthquake Network" Unit Standard C-factor amplitude factors Response A, specified by fo (Hz) P n I c, Ck element USGS Seismometer and L-pad I .0 0.8 2 3 I 1 iw 3/( (L) - nj)( o - ak) 1.0 V cm-' sec Seismic amplifier and voltage- 0.095 1 .o 2 2 1 1 3/(0 ~ aJ(w ~ 83 I8 x (amplifier) controlled oscillator (VCO) 44.0 I .o 2 0 WO WO - I/(w - Cxj)(W - (Yk) 37.04 Hz/V (VCO) Discriminator 60.0 1 .0 2 0 00 0 0 -I/(w - Cyj)(W - Uk) 0.0160 V/Hz 130.0 0.7 2 0 WO WO -I/(W - aj)(W ~ 16-mm film recorder and film viewer 0.53 b 1 1 I h W/(W - a,) 4 cm/V 1s.s 0.7 2 0 WO 00 - I/(w ~ ~ a Stewart and O'Neill (1980). * The response element is a single pole and is defined only by fa.
2.2. C'errtrcil C'alifornicr Microecit-thqmke Netirwk 37 rately for each unit (Table I). These units are (1) the seismometer and L-pad, (2) the seismic amplifier and voltage-controlled oscillator, (3) the discriminator at the central recording site, and (4) the 16-mm film recorder and film viewer. For the seismometer and L-pad, the constants I = 3 , = ~ 2, and Ci = Cj = 1 are determined by comparing Eq. (2.8) with the Fourier transform of the response of an electromagnetic seismometer to a delta function (Healy and O'Neill, 1977) (2.13) V(O) = G~w~/(w - aj)(w - C Y ~ ) where V(w) is the Fourier transform of the output voltage u(t), G is the effective motor constant of the seismometer and L-pad combination, and w, aj, and cxk have the same meaning as in Eq. (2.8). The constants cq and ak are computed from Eq. (2.9) using the USGS standard values& = 1.0 Hz, and /3 = 0.8. The constant A, = G = 1.0 V cm-' sec is the USGS standard value for the effective motor constant (Fig. 7). These values are all given in the first line of Table I. For the remaining three units, the amplitude factors Aj are standard values specified by the USGS (Table I), and other response parameters are determined by calibration in the laboratory. For each of the three units the measured frequency response curves were compared to sets of master response curves calculated for certain values of I, n, Cj and, where appropriate, @. A visual fit of the laboratory calibration curves to the master curves provided the values offo and /3 for each instrumental unit. From these values aj and ak were determined from Eq. (2.9). Table I contains all the data required by Eq. (2.8) to calculate the system amplitude response. If complex arithmetic is used to calculate F(w), then the system amplitude response is the absolute value of the complex expression Eq. (2.8). The amplitude response for the system specified by Table I is shown in Fig. 14. Bakun and Dratler (1976) summarized the relative merits of the Fourier transform and least-squares techniques. They pointed out that these two approaches are complementary, and each has its applications in calibrating microearthquake networks. The Fourier transform technique may be used routinely to verify that the system is operating within specifications with no unexpected sources of noise. It may also be used to correct seismic data for system response at lower frequencies, as required by some seismological studies. The least-squares approach may be used in studies that require an analytical expression for the response function. It may also be used to extend the system response to higher frequencies than those computed from the Fourier transform technique.
Page 1 and 2: PRINCIPLES AND APPLICATIONS OF MICR
Page 3 and 4: PRINCIPLES AND APPLICATIONS OF MICR
Page 5 and 6: Contents FOREWORD PREFACE vii ix 1.
Page 7: Foreword Earthquakes occur over a c
Page 10 and 11: X PI-
Page 13: PRINCIPLES AND APPLICATIONS OF MICR
Page 16 and 17: 2 1 . It1 trodir ctivn of the earth
Page 18 and 19: frequency of occurrence N by (I .2)
Page 20 and 21: 6 1. Introduction the initial P-ons
Page 22 and 23: 8 1. Ititrodiictioti that changes i
Page 24 and 25: 10 1. Introduction Fig. la. Schemat
Page 26 and 27: 12 Fig. b. Map showing seismographi
Page 28 and 29: 14 1. Introduction indicated the la
Page 30 and 31: ~ 16 2. Ins trumeri tic t ion Syste
Page 32 and 33: 18 2. Itistrirmeritation Systems In
Page 34 and 35: 20 2. Ins trumeti ta tim S ys tems
Page 36 and 37: 22 2. Ins tru inen ta t ion Systems
Page 38 and 39: 24 2. Iris trumentrt tion Systems F
Page 40 and 41: 26 2. Itistrutnetztntioti System 5H
Page 42 and 43: 28 2. Instrumentntior? Systems Fig.
Page 44 and 45: 30 2. Instrumentation Systems The o
Page 46 and 47: 32 2. Instrumentation Systems other
Page 48 and 49: 34 2. Instrumentation Systems 1 0 7
Page 52 and 53: 38 2. Znstrumentution Systems FREQU
Page 54 and 55: 40 2. Instrumentatiori Systems mome
Page 56 and 57: 42 2. Ins tru rneti totion Sys tenz
Page 58 and 59: 44 2. Instrumentation Systems magne
Page 60 and 61: 3. Data Processing Procedures Micro
Page 62 and 63: 48 3. Datu Processirig Procedures c
Page 64 and 65: 50 3. Data Processitig Procedures c
Page 66 and 67: 52 3. Data Processirig Procedures s
Page 68 and 69: 54 3. Ihta Processing Procedures Se
Page 70 and 71: 56 3. htcr Processirig Procedures w
Page 72 and 73: 58 3. Data Processitig PrmedureLs i
Page 74 and 75: 60 3. Datu Processirig Procedures f
Page 76 and 77: 62 3. Data Processing Procedures Th
Page 78 and 79: 64 3. Dutct Processing Procedures m
Page 80 and 81: 66 3. Data Processing Procedures ch
Page 82 and 83: 68 3. Dutu Processing Procedures an
Page 84 and 85: 70 3. Data Processirig Procedures i
Page 86 and 87: 72 3. Dnta Processing Procedures co
Page 88 and 89: 74 3. Data Processing Procedures se
Page 90 and 91: 4. Seismic Ray Tracing for Minimum
Page 92 and 93: 78 4. Seismic Ray Tracing for Minim
Page 94 and 95: 80 4. Seismic Ruy Trucing for Minim
Page 96 and 97: 82 4. Seismic Ray Tracing for Minim
Page 98 and 99: (1 84 4. Seismic Ray Tracing for Mi
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86 4. Seismic Ray Tracing for Minim
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88 4. Seismic Ray Tracirig for Mini
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90 4. Seismic Ray Trucing .for Mini
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92 4. Seismic Ruy Tracing for Minim
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% 4. Seismic Ray Tracing for Minimu
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100 4. Seismic Ray Tracing for Mini
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106 5. Inversion and Optimization u
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108 5. Inversion and Optimization G
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110 5. Inversion and Optimization t
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112 5. Inversion and Optimization n
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114 5. Inversion and Optimization n
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116 5. Inversion and Optimization B
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118 5. In versiori nnd Optimization
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120 5. Iwersioti arid Optirnizntior
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122 5. Inversion and Optimization m
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124 5. Inversion and Optimization i
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126 5. Inversion criid Optimization
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128 5. Inversiori niid Optimization
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130 6. Methods of Data Analysk 6.1.
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132 6. Methods of Data Analysis We
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134 6. Methods of Data Analysis x*
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136 6. Methods oj Data Analysis It
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138 6. Methotls of Data Analysis te
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140 6. Methods of Data Analysis pur
Page 156 and 157:
142 6. Methods of Data Analysis (a)
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144 6. Methods qf Dcrtcr Analysis N
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146 6. Methods of Dutcr Analysk imp
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148 6. Methods of Data Analysis sho
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150 6. Methods of Data Aizalysis tr
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152 6. Methods of Data Analysis (6.
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154 6. Methods of Data Analysis qua
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156 6. Methods of Datu Analysls mag
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158 6. Methods of Data Analysis 6.5
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160 6. Methods of Data Analysis (6.
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162 6. Methods of Data Analysis fro
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7. General Applications Data from m
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166 7. General Applications in ampl
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168 7. General Applications Rangely
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170 7. General Applications The inv
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8.1. Seistnicit~ Pritterns 199 made
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8.1. Seismicity Patterns 201 only p
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8.1. Seismicit! Plitterrzs 203 betw
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Keilis-Borok et al. (1980b) suggest
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8.1. Srismic.itJ Ptrtterns 207 of t
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8.2. Temporal V'iricrtions of Seism
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8.3. Temporiil Vuriiitiotis qf Otli
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8.3. TemporuI Variations of Other S
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8.3. Temporal Vcrridoris of‘ Othe
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8.3. Totnportrl Vtrritrtiotis of' O
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9. Discussion Microearthquake studi
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Automation usually does not reduce
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Glossar? of' A bbreiqiations 227 da
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Glossary of AbbrciTintions 229 said
Page 245 and 246:
References Acton, F. S. (1970). "Nu
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References 23 3 Asada, T. ( 1957).
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Rtjfcrcric-es 235 travel-time chang
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Refererices 237 Cleary, J. R., Wrig
Page 253 and 254:
References Eaton, J. P. (1976). Tes
Page 255 and 256:
References 24 1 Francis, T. J. G.,
Page 257 and 258:
243 Hagiwarii. T., and Iwata. T. (1
Page 259 and 260:
R efereiices 245 Horner, R. B., Ste
Page 261 and 262:
References 247 Kagan, Y. Y., and Kn
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Referetices 249 Kodama, K. P., and
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25 1 Lin, M. T., Tsai, Y. B., and F
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References 253 Mikumo, T., Otsuka,
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R eferetices 255 Nordquist, J. M. (
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Re feret ices 257 F'rothero, W. A.
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259 Sauber. J., and Talwani, P. (19
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References 26 1 Stephens, C. D., La
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Keferetices 263 Tsujiura, M. (1978)
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R ef ere1 ices croearthquake observ
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