Abstract

The Omori-law aftershock parameters for 13 earthquakes in stable continental regions (SCRs) globally are found to distribute in the same way as those for California aftershock sequences. Of 19 SCR mainshocks with M ≥ 6.0 since 1968, eight had their largest aftershock within five days of the mainshock and 11 within 30 days of the mainshock. The mean magnitude difference between the mainshock and the largest aftershock of these 19 SCR events is 1.4 ± .7 magnitude units, with a range from 0.3 to 3.6 magnitude units. From 1968 to 2003 the rate at which SCR earthquakes of M ≥ 4.5 worldwide were followed by a comparable or larger earthquake within the next 30 days is 5%. These statistics can be used to produce aftershock forecasts for strong SCR earthquakes and to estimate the chances that an SCR earthquake of M ≥ 4.5 will be followed by a larger seismic event within the next month.

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