The seismic source parameters of the 1991 Costa Rica aftershock sequence: evidence for a transcurrent plate boundary
The United States Geological Survey said Tuesday's initial 6.3-magnitude quake was followed by various aftershocks, and itself was part of an aftershock sequence from last September's quake.
After the main shock, most of the stresses have been released, so the aftershock sequences show a rupture process of lower stresses.
