Left frames: "Time slices" showing seismicity variations at different times before correcting a catalogue (study area is Guerrero, Mexico) Right frames: same time periods but after catalog has been corrected for spurious magnitude changes. As before, positive Z values stand for seismicity decreases while negative values indicate increases. These variations are mainly caused by changes in the operation of the networks. Although some may be the result of natural causes.
(Ref: Zúñiga and Wiemer, Pure and Applied Geophysics, V. 155, 1999
Spatial variability of Mc for two time stages. a) Time interval depicted is 1987.2 - 1997.11. b) Time interval depicted is 1997.11 - 2001.5. c) Mc difference between both (positive differences are set to show improvement, i.e. indicate lower Mc for the most recent period as compared to before).
The red zones show the main decreases in seismicity rate during the period. Dark blue areas outline increases in rate. They identify regions with significant variations in reporting of events.
Color scale refers to significant decreases in seismicity before the time of some events