 A large number of these small quakes were felt from the latter part of 2010 to the first months of 2011.A number of communities including Villa Emiliano Zapata, San Juanico, El Alamo and Peñamiller have reported smelling sulfur and other foul odors and seeing vapor in connection with the quakes.As of January 2011, over fifty small quakes have been reported in Peñamiller alone, but the cause of the quakes is not known.