Predicting Earthquakes A Scientific and Technical Evaluation, With Implications for Society (1976) / Chapter Skim
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Appendix A: Earthquake-Prediction Research in the United States
Appendix A: Earthquake-Prediction Research in the United States
Pages 37-50
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From page 37... ...
The major shortcoming of the statistical approach has been that it provides neither exact locations nor reliable recurrence intervals for the larger earthquakes(2)
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From page 39... ...
Most notable among these have been the changes in seismic compressional and shear-wave velocities and of their ratio (Vp/Vs) , and changes in electrical conductivity, water pressure, ground tilt direction, and surface elevations in and around the earthquake source.
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These are discussed in greater detail in Appendix B Precursory Velocity Changes Field tests of the feasibility of earthquake prediction have been carried out in the United States primarily using precursory changes in seismic velocity.
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From page 41... ...
• U1LDUPOF ELASTIC STRAIN UNSTABLE DE FORMATION IN FAULT ZONE AND PARTIAL RELAXATION OF STRESS IN SURROUNDING REGION SUDDEN DROP IN STRESS FOLLOWED IV AFTERSHOCKS OILATANCV DEVELOPMENT OF CRACKS BUILDUP OF ELASTIC STRAIN RADON EMISSION ELECTRICAL RESISTIVITY NUMBER OF SEISMIC EVENTS Fig.
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From page 42... ...
3a. Velocity ratio Vp/Vs as a function of time for two events in the Blue Mountain Lake, N.Y., earthquake swarm of l97l.
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From page 43... ...
Analysis of travel-time data from earthquakes and quarry blasts in California did not show precursory velocity anomalies over large areas preceding some strike-slip-type earthquakes in the Bear Valley section of the San Andreas Fault(l9, 20) or for the Borrego Mountain Earthquake in l958(2l)
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From page 44... ...
for the August 3, l973, Blue Mountain Lake earthquake predicted by Aggarwal et al.(l3)
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The laboratory studies still provide very valuable data necessary for developing a physical model and better understanding of earthquake processes. Changes in Direction of Ground Tilt The most consistent precursory phenomenon for San Andreas earthquakes has been change in the tilt direction(27)
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From page 46... ...
, electrical conductivity, magnetic anomalies, and groundwater pressure, among others. Most of these measurements were begun relatively recently and do not span sufficiently long time periods for clear-cut evaluation of their potential usefulness in earthquake prediction.
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From page 47... ...
, earthquake activity increased. When pressure dropped as a result of water withdrawal, the seismic activity decreased.
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From page 48... ...
. Temporal and spatial analysis of premonitory velocity anomalies for the August 3, l973, Blue Mountain Lake earthquake.
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From page 49... ...
. Earthquake predictions based on station residuals.
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From page 50... ...
. Accelerated fault creep along the central San Andreas Fault after moderate earthquakes during l97l-l973.
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