Earthquake Prediction Methods

Earthquake predictions  Because earthquakes do not happen on regular intervals it is difficult to predict when the next one will occur.  Methods for predicting earthquakes on these faults vary; none of them being 100% accurate.  Predictions are given for a time frame instead of an exact date.

Why is it important?  ess05.sci.ess.earthsys.japan/ ess05.sci.ess.earthsys.japan/ ess05.sci.ess.earthsys.japan/  Early prediction theories were based on patterns, and timing between earthquakes

Are Earthquakes Getting More Frequent?

Earthquake Fatalities Since 1800

Statistical Methods  Must collect data on location and magnitude of earthquakes  okay for smaller earthquakes but not for larger earthquakes.  This data is used in several statistical predictions

Statistical Methods  Recurrence Frequency  Looks for relationship between the magnitude and repetition of earthquakes.  Assumes that the same set of conditions leading to an earthquake occur each time.  Dependent on large amounts of historical data.

Statistical Methods  Seismic Gap Theory A seismic gap is an area along a fault where there has not been any earthquake activity for a long period of time.  Focuses on patterns in seismicity..  If a change in the pattern occurs, there is a chance for an earthquake.

Physical measurements  Events that occur before an earthquake can include:  Increase in the rate of seismic creep  Gradual tilting of the land near the fault zone  Drop or rise in the water level of a well  Decrease in the number of foreshocks  Dramatic changes in animal behavior

Physical measurements  Fault Creep Measurements  Measures the slow rate of movement at the fault.  Lots of fault creep means a small chance of a big earthquake.  Low amounts of fault creep means a high chance of a big earthquake.

Physical measurements  Drop or rise in the water level of a well  Large surface waves force particles of rock near to the surface which changes water levels in a well.  Water levels can be affected by any fault creeps, crust tilts, or other seismic activity.  We can drill wells in certain locations to measure dramatic changes in water levels.

Physical and Geophysical measurements and observations  Animal behavior  unusual animal behavior can be a way to predict earthquakes  The Chinese started recording unusual animal behavior and successfully predicted an earthquake in months before it struck.

Physical and Geophysical measurements and observations  Unusual animal behavior includes:  Hibernating animals leaving their underground nests  Animals refusing to go into pens  Animals seeking higher ground  Birds vacating the area  Deep water fish come closer to the surface

Physical measurements  This type of prediction requires a lot of data collection and review to find patterns.  Problem with this method is that some of characteristics are geographically specific so they cannot be applied to different areas.

Conclusion  Predicting earthquakes is not yet possible  The more data we review and the more patterns we find the better the predictions