A New Real Time Global Earthquake Forecast

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Visitors to these pages will notice that a new earthquake forecast is now being displayed.  This is the Natural Time Weibull method for earthquake forecasting [1], which takes account not only of the rate of small earthquake activity near a location, but also the time since the last major earthquake in the region.

A series of earlier forecast displays in previous blogs have shown earlier (beta) versions of the forecast.  The theory behind the method uses space-time patterns of small earthquakes to forecast large earthquakes.  The earthquake data is from the Advanced National Seismic System earthquake catalog.  A research publication describing the basics of the method was recently published in the journal Physical Review E [1].

Earlier versions of the NTW method were used in the writing of the Four Cities Forecasts in California, Japan and elsewhere.  In the automated mode, the earthquake data are downloaded onto servers every night at about midnight eastern time.  The algorithms are then employed to compute the forecast probabilities, and KML contours are drawn on the Google maps web service (KML is Keyhole Markup Language, the computer language that Google maps understands).  The contours are then used to draw the filled contours on the Google map displayed on the user's desktop. 

As a matter of interest, the visitor may notice that the California forecast is visually more detailed and finer-scale than the global forecast.  The reason is a limitation on Google maps -- the amount of data one can display on the maps is currently limited in some ways, so the resolution of the global map is intentionally degraded to a 1 degree x 1 degree grid (soon to be 0.5 degree by 0.5 degree). 

By contrast, the California data is displayed at the 0.1 degree x 0.1 degree scale.  Note that 0.1 degree is typically approx. 11 km = approx. 7 miles scale length at mid-latitudes.  Our current plans are to add several more highly active areas for higher-resolution forecasts.  These areas should be up on the web site shortly.

One can also notice that the forecast in locations like China seem somewhat more crude than the forecast in other locations, such as Japan.  That is because the distribution and number of seismic stations, and therefore the quality of the data, is worse in the interior of China than in the Japan region.  Therefore, the forecasts are of lower quality (the better the data, the better the forecast will typically be). 

As the quality of the ANSS catalog continues to improve, the quality of the real-time forecasts should improve also.

Please visit the Earthquake Viewer under the Tools tab to see the new forecast.

[1] J.B. Rundle, J.R. Holliday, W.R. Graves,  D.L. Turcotte, K.F. Tiampo and W. Klein, Probabilities for large events in driven threshold systems, Phys. Rev. E, 86, 021106 (2012)

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