Mainshock Timing Module
Mainshock Yearly Timing Module
Purpose and Methodology
The Mainshock Yearly Timing Module is designed to estimate the likely timing of a mainshock earthquake. It achieves this by analysing variations in the time intervals between the largest earthquakes recorded each year. This approach provides an evidence-based estimate for when the next mainshock could occur, illustrated in Figure 10 near the bottom of the page for Djibouti & “Afar Triangle”.
Analytical Process
The module plots the time in days between the largest earthquakes in consecutive years, expressing this as the fraction of a year (to six decimal places) since the previous year’s largest event. These values are mapped against the ending year of each couplet on the X-axis. Each plotted point indicates, as an exact proportion, whether the interval is less than or more than a full year since the preceding largest event.
This analytical method results in curves oscillating around the mean interval of one year between earthquakes. As shown in Figure 10, the mean interval is 0.99 years, with critical values strongly indicating the correct timing for the Djibouti region’s mainshock, which occurred on 20/08/1989.