Academia.eduAcademia.edu

Figure 8 – uploaded by James Britton

See full PDFdownloadDownload figure
Fig. 8. Distribution of the times of the greatest groundwater changes (top) and of the start time of the groundwater changes (bottom) with event magnitude. The greatest groundwater level changes and start times are associated with the largest earthquakes. Piecewise linear curves representing the possible extremal values of the data sets are also shown.

Figure 8 Distribution of the times of the greatest groundwater changes (top) and of the start time of the groundwater changes (bottom) with event magnitude. The greatest groundwater level changes and start times are associated with the largest earthquakes. Piecewise linear curves representing the possible extremal values of the data sets are also shown.

Related Figures (19)

Contents
Contents
Table 1
Table 1
Table 2
Table 2
Table 2 (continued)
Table 2 (continued)
Fig. 1. Distribution of reported maximum changes in radon gas concentrations in the earth (in percent relative to the background radon levels) prior to earthquakes. Most of th changes are between 20% and 200%. The vertical axis represents the number of observations for each data range. In the late 1960s and early 1970s reports primarily from Russia and China indicated that concentrations of radon gas in the earth apparently changed prior to the occurrences of nearby earthquakes (Lomnitz, 1994). This stimulated a number of experiments in other parts of the world to monitor underground radon with time and to look for radon changes associated with earthquakes. Since radon is a radioactive gas, it is easy and relatively inexpensive to monitor in- strumentally, and its short half-life (3.8 days) means that short-term changes in the radon concentrations in the earth can be monitored with very good time resolution. While other gases have also been looked at as possible earthquake precursors, the bulk of the experiments re- ported in the scientific literature have focused on radon. Fig. 3 shows the dependence of the magnitude of the reported radon anomalies on distance of the observation site to the earthquake epicenter and on the magnitude of the event. The greatest anomalies are reported closest to the epicenters of the coming earthquakes, suggesting that the
Fig. 1. Distribution of reported maximum changes in radon gas concentrations in the earth (in percent relative to the background radon levels) prior to earthquakes. Most of th changes are between 20% and 200%. The vertical axis represents the number of observations for each data range. In the late 1960s and early 1970s reports primarily from Russia and China indicated that concentrations of radon gas in the earth apparently changed prior to the occurrences of nearby earthquakes (Lomnitz, 1994). This stimulated a number of experiments in other parts of the world to monitor underground radon with time and to look for radon changes associated with earthquakes. Since radon is a radioactive gas, it is easy and relatively inexpensive to monitor in- strumentally, and its short half-life (3.8 days) means that short-term changes in the radon concentrations in the earth can be monitored with very good time resolution. While other gases have also been looked at as possible earthquake precursors, the bulk of the experiments re- ported in the scientific literature have focused on radon. Fig. 3 shows the dependence of the magnitude of the reported radon anomalies on distance of the observation site to the earthquake epicenter and on the magnitude of the event. The greatest anomalies are reported closest to the epicenters of the coming earthquakes, suggesting that the
Reported precursory groundwater level changes associated with earthquakes.
Reported precursory groundwater level changes associated with earthquakes.
Fig. 3. Distribution of reported changes in radon gas concentrations with distance to the earthquake (top) with event magnitude (bottom). The greatest anomalies are reported closest to the epicenters, but no dependence on magnitude is seen. Curves representing the possible extremal values of the data sets are also shown. On the bottom figure, two different extremal lines are shown, where the solid line ignores the one extreme data point at about 180 km epicentral distance.
Fig. 3. Distribution of reported changes in radon gas concentrations with distance to the earthquake (top) with event magnitude (bottom). The greatest anomalies are reported closest to the epicenters, but no dependence on magnitude is seen. Curves representing the possible extremal values of the data sets are also shown. On the bottom figure, two different extremal lines are shown, where the solid line ignores the one extreme data point at about 180 km epicentral distance.
Summary of equations for extremal value curves. Table 4 not surprising, because water is essential to human life and the use of wells to provide water for human settlements has been important zoing back to the beginning of human civilization. Any unusual changes in groundwater levels, particularly dug wells that either drop significantly in level or even go dry, would be noted and be a cause for concern. Unfortunately, most such reports are anecdotal rather than of a careful scientific measurement, and so they would not be reflected in the database accumulated in this study. 4.13. Groundwater level change models
Summary of equations for extremal value curves. Table 4 not surprising, because water is essential to human life and the use of wells to provide water for human settlements has been important zoing back to the beginning of human civilization. Any unusual changes in groundwater levels, particularly dug wells that either drop significantly in level or even go dry, would be noted and be a cause for concern. Unfortunately, most such reports are anecdotal rather than of a careful scientific measurement, and so they would not be reflected in the database accumulated in this study. 4.13. Groundwater level change models
Fig. 4. Distribution of the initiation times (top) and durations (bottom) of the radon anomalies with event magnitude. The greatest initiation times and anomaly durations are associated with the largest earthquakes. Curves representing the possible extremal values of the data sets are also shown. On the top figure, the solid extremal line ignores the one extreme data point at about magnitude 8, while the combination of the solid and dashed extremal lines include this data point.
Fig. 4. Distribution of the initiation times (top) and durations (bottom) of the radon anomalies with event magnitude. The greatest initiation times and anomaly durations are associated with the largest earthquakes. Curves representing the possible extremal values of the data sets are also shown. On the top figure, the solid extremal line ignores the one extreme data point at about magnitude 8, while the combination of the solid and dashed extremal lines include this data point.
Fig. 5. Distribution of reported maximum changes in groundwater level prior to earthquakes. The top plot shows all the observations, while the bottom plot shows the observations of water level changes between — 1 m and +1 m. There have been relatively few reported observations of tempera- ture changes in the earth prior to earthquakes. This is probably due to a lack of experiments to look for such an effect. The thermal
Fig. 5. Distribution of reported maximum changes in groundwater level prior to earthquakes. The top plot shows all the observations, while the bottom plot shows the observations of water level changes between — 1 m and +1 m. There have been relatively few reported observations of tempera- ture changes in the earth prior to earthquakes. This is probably due to a lack of experiments to look for such an effect. The thermal
Fig. 7. Distribution of reported changes in maximum groundwater level with distance to the earthquake (top) with event magnitude (bottom). The greatest anomalies are reported closest to the epicenters and perhaps for the largest earthquakes. Curves representing the possible extremal values of the data sets are also shown.
Fig. 7. Distribution of reported changes in maximum groundwater level with distance to the earthquake (top) with event magnitude (bottom). The greatest anomalies are reported closest to the epicenters and perhaps for the largest earthquakes. Curves representing the possible extremal values of the data sets are also shown.
'These values are approximate, as they were read off a figure. The background signal (i.e., tidal strain) levels are not available from this report. 3The exact precursor times are not provided. Reported measured precursory ground deformations associated with earthquakes. Table 6
'These values are approximate, as they were read off a figure. The background signal (i.e., tidal strain) levels are not available from this report. 3The exact precursor times are not provided. Reported measured precursory ground deformations associated with earthquakes. Table 6
Related topics:
Earth SciencesGeologyGeochemistryGeophysicsSeismic HazardEarthquake PredictionElectric and Magnetic FieldsSurface deformationsSea Surface Temperaturessurface deformation
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved