Changing Probabilities: The M7.7 Canada- M7.5 Alaska Earthquakes

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The figure below shows the time-dependent changes in spatial forecast contours associated with the M7.7 Prince Rupert, Canada (10/27/2012) - M7.5 Craig, Alaska (1/5/2013) earthquake sequence.  The Prince Rupert earthquake was an oblique-thrust (compressional) event, whereas the Craig earthquake was a right lateral strike (horizontal) slip event. Of concern, the forecast contours representing chance of an earthquake correspond to a higher probability down towards the southeast, nearer to Vancouver and Seattle. Those areas are the locations where the seismic phenomenon of Episodic Tremor and Slip (ETS) was first observed [1].

The latest forecast contours do not as yet include the influence of the Craig, Alaska earthquake and its aftershocks.  The reason is that the real-time feed from the USGS is not incorporated into the ANSS catalog (from which we compute the forecast contours) until a day or two later.  So while we presently compute near real-time forecast changes, true real-time forecasts are not currently displayed.  We are currently working on a method to incorporate the real-time feed into the forecasts so that real-time forecasts will be displayed as the events occur.





Earthquake Forecasting, Earthquakes, Faults, Plate Tectonics


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