This matlab program simulates aftershocks, in time and space, of earthquakes in a specified catalog. It can also simulate background earthquakes
and aftershocks of the background earthquakes. All secondary aftershock sequences are propagated through, following
the ETAS aftershock model (e.g. Ogata (1988)). Mainshocks may be specified as planar or point sources. This is a stochastic program that simulates aftershocks from the empirical statistical laws of aftershock behavior (Omori's Law, Gutenberg-Richter magnitude-frequency relationship, and the power law decay of aftershock density with distance, from Felzer and Brodsky, (2006)).
From these laws, discrete aftershocks are generated using non-stationary Poissoinan functions and Monte Carlo sampling technique. See Felzer et al. (2002) for further details on the method. Each generated aftershock sequence and catalog will be different because of the Poissonian randomness, and the positive feedback effects of the secondary aftershock sequences.
The user is encouraged to run the program multiple times to observe the full range of seismicity rates and patterns that might occur.
The tar file for download below contains four files: The main program file: AftSimulator.m, a sample data input file for California: SampleInput.mat, a program that reads in the sample data, sets parameters, and runs the matlab code: RunAftSimulator.m, and a C code that may be compiled and used to replace part of the matlab code and make the program run a bit faster: ParentInfo.c.
Full documentation, parameter, input, and output data explanation, and references to cite if you use this code for your publications are given as comments within the AftSimulator.m and RunAftSimulator.m files.
A matlab license and installation are necessary to run this code.
Please email Karen Felzer (link to email below) if there are any questions or problems. Karen is expecting to be on leave in the near future, however, so please allow ~ 1 week for a response. Thank you!
Aftershock simulator .tar file