Aftershocks typically begin very soon after the main earthquake—often within minutes to hours. The largest aftershock usually occurs within the first three days following an inland earthquake. Aftershocks can continue for days, weeks, months, or even years after the main event, but their frequency and magnitude generally decrease over time. The first 24 hours see the most frequent aftershocks, and larger mainshocks tend to produce aftershocks that last longer. Most aftershocks are smaller than the mainshock, often about one magnitude less, and the number of aftershocks decreases roughly tenfold over the first 10 days and continues declining thereafter.