Seismic quiescence patterns as possible precursors of great earthquakes in Mexico

A catalog of shallow Mexican earthquakes (depth < 60 Km) is presented for a region bounded by 14°-21° north latitude and 94°=-106° west longitude, covering the period from January, 1806 to December, 2010, which is incomplete in this period for a wide range of magnitudes, but is complete for different ranges of magnitude in short intervals of time. The catalog is probably complete for M_w ≥ 7.0 since 1860 and for M_w ≥ 7.7 since 1846, but for earthquakes of magnitude greater than or equal to 4.3 the catalog is complete since 1969. Using the data of this master catalog, we show that there is evidence that the last earthquakes of magnitude M_w ≥ 7.6 that occurred in Mexico from 1975 to 2009 were preceded by an unusual seismic quiescence. We use the method of space-time plots and cumulative seismicity plots.