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Chi-Yu King

Publications and source records attributed to Chi-Yu King.

8 recordsLinked to original sources
USGS2012

Anomalous chemical changes in well waters and possible relation to earthquakes

Water level, temperature, salinity, electric conductivity, and pH have been measured periodically for several years at three water wells located along a 17-km segment of the San Andreas fault between San Juan Bautista and Cienega Winery in central California. Water samples were collected at the same time for subsequent chemical analyses in the laboratory. Some sudden large changes in salinity and conductivity were recorded in early March 1980 at the two wells near San Juan Bautista. These changes coincided approximately with the beginning of an episode of increased local seismicity, including a magnitude 4.8 earthquake on April 13. Analyses of water samples revealed corresponding changes in ion concentrations, especially of Na + , Ca ++ , Mg ++ , SO 4 −− , HCO 3 − , F − , and Cl − . The observed changes may be the result of mixing of waters from different aquifers through cracks developed in the water barriers by a possible crustal strain episode that may have occurred in the study area.

Geophysical Research Letters↗
USGS2012

Variations in stable- isotope ratios of ground waters in seismically active regions of California

Measurements of D and 18 O concentrations of ground waters in seismically active regions are potentially useful in earthquake prediction and in elucidating mechanisms operative during earthquakes. Principles of this method are discussed and some preliminary data regarding a magnitude 5.7 earthquake at the Oroville Dam in 1975 and a series of events near San Juan Bautista in 1980 are presented to support the utility of such measurements. After earthquakes, the D content of nearby ground waters increased by several permil while the 18 O content remained constant. This increase implies that H 2 O may have either decomposed or reacted to form molecular H 2 at depth. It is emphasized that many areas must be investigated for these effects in order to find a sufficient number of "sensitive" water wells and springs to permit a truly effective program of earthquake research.

Geophysical Research Letters↗
USGS2012

Multicycle slip distribution along a laboratory fault

Slip distribution along a laboratory fault, which consists of eight spring-connected blocks that are elastically driven to slide on a frictional surface, has been examined for a “long” sequence of slip events to test the applicability of some conceptual models proposed recently in the literature. The distributions of large slip events are found to be quite variable and do not fit the uniform slip or characteristic earthquake models. The rupture initiation points are usually not near the corresponding maximum slip points, in contrast to observations by Thatcher (1990) and by Fukao and Kikuchi (1987) that earthquake hypocenters are commonly near corresponding regions of maximum slip in the fault planes. This contrast may suggest that either the present observations or theirs are not representative or the teleseismically determined hypocenters may not always be true rupture initiation points as usually assumed. Large slip events are also found to be a stress-roughening process. They are triggered by some small events after the stresses have been adjusted by some earlier small-to-moderate events to be near the critical levels at most locations along the fault. This suggests that earthquake prediction monitoring efforts should not be limited to a small region near an asperity but should be spread out to cover the entire fault segment in a seismic gap in order to detect the condition of simultaneous strain buildup.

Journal of Geophysical Research↗
USGS2006

Comment on “222Rn Premonitory signals for earthquakes?”

Radon and other terrestrial gases in groundwater and soil air have been studied in recent years in seismically active areas, especially in China, Japan, the former Soviet Union, and the United States, in search of changes that may be useful for earthquake prediction. Concentrations of radon, helim, hydrogen, mercury vapor, carbon dioxide, and several other gases have been found to be high along active faults. Faults may thus be paths of least resistance along which terrestrial gases generated or stored in the Earth can escape into the atmosphere. Gas-concentration changes with durations of hours to months have been observed before and after earthquakes at relatively few favorably situated sites, and their patterns have not always been repeated. Some of these sites are located as far as several hundred kilometers away from earthquake epicenters. These “sensitive” sites are generally situated along active faults, whether the seismogenic ones or not, especially at their intersections or bends, or at other structurally weak zones, possibly because of concentration of tectonic strain and abundance of pore fluids at such places (see review papers by King , 1986, 1990). Due to this selectivity and for two other important reasons, studies of terrestrial gases for earthquake prediction have not been viewed favorably by most geophysicists, especially those in the United States.

Eos Science News↗
USGS1979

On radon emanation as a possible indicator of crustal deformation

Radon emanation has been monitored in shallow capped holes by a Tracketch method along several active faults and in the vicinity of some volcanoes and underground nuclear explosions. The measured emanation shows large temporal variations that appear to be partly related to crustal strain changes. This paper proposes a model that may explain the observed tectonic variations in radon emanation, and explores the possibility of using radon emanation as an indicator of crustal deformation. In this model the emanation variation is assumed to be due to the perturbation of near-surface profile of radon concentration in the soil gas caused by a change in the vertical flow rate of the soil gas which, in turn, is caused by the crustal deformation. It is shown that, for a typical soil, a small change in the flow rate (3 · 10 −4 cm sec −1 ) can effect a significant change (a factor of 2) in radon emanation detected at a fixed shallow depth (0.7 m). The radon concentration profile has been monitored at several depths at a selected site to test the model. The results appear to be in satisfactory agreement.

Tectonophysics↗