If you’re curious how the CSZ earthquake probabilities are calculated, this page should help.

Step 1: Write down the Mean & Standard Deviation from the calculations below – provided by OSU researchers working in the Active Tectonics Lab.

SD & Mean Calculations 221.jpg

Step 2: Click on the Download Excel spreadsheet for calculations link on Seth Stein’s website below and enter the Inputs (red).

You should get the following:


According to Professor Goldfinger, the Log-Normal model fits the data pretty well, but the Gaussian model (think bell curve) is better at predicting over time.

Want to see what the risk of an earthquake is over the next 20 years, rather than 50? Change the ‘End Year’ value to 2039! Don’t you love getting to play with the numbers?!