Aftershock Forecasting: the ETAS Model (2D)

After a major earthquake, the question seismic agencies have to answer within minutes is not "will there be aftershocks" but "how many, how strong, and for how long." This simulator builds a real stochastic ETAS (Epidemic-Type Aftershock Sequence) tree from a mainshock of chosen magnitude: every event's children are drawn from the Omori-Utsu decay law in time and the Gutenberg-Richter distribution in magnitude, then rendered live as a magnitude-vs-time seismicity scatter — the same plot form seismologists use to read a real sequence — with the model's own aggregate Omori-decay rate curve λ(t) overlaid on a log axis. Adjustable Omori p-value and productivity K sliders show how a sequence's decay rate and density change the forecast, while live readouts track the model's own next-24-hour aftershock rate, the largest aftershock actually produced, how many aftershocks were triggered directly by the mainshock, and how the run compares to the classic Bath's-law estimate of M₀ − 1.2.