The Tecomán, Mexico, earthquake (21 January 2003, 20:06) shows directivity in the area in which it spread (the Colima graben). The presence of soft soils and the location of 8 out of 10 major urban zones in the area are important factors concerning the acceleration, peak ground acceleration (PGA), and Modified Mercalli Intensity (MMI) caused by this earthquake. Data are not available due to the lack of instrumentation in the area. In this paper we simulate acceleration time histories whose main contribution is to reflect a model that considers the source, the path, and the site effects. In order to reach this objective, we used the source model generated by Ramírez-Gaytán and Aguirre (2008) for the Tecomán earthquake. The PGA and MMI were estimated from the waveforms in 25 points within the state of Colima and eight more outside. Thus, the maximum accelerations obtained are compared with four different ground-motion prediction equations (GMPEs). Our results show an expected and reasonable behavior in agreement with the considerations of each one of the statistical methods compared. In the end, we generated an isoseismal map for the region. This map is overlaid by the isoseismal map for this earthquake generated by other authors (who used traditional methods to determine MMI). First, we conclude that the empirical Green’s function method can be successfully applied to simulate the acceleration waveforms in sites without instrumentation during the mainshock. Second, the simulated records can be successfully used in seismic risk studies.