Shumagin Earthquakes (IMAGE) Penn State Caption Earthquakes in Shumagin Gap region. Earthquakes shown in blue are the July 21 subduction event and its aftershocks, and the earthquakes shown in orange are the October strike-slip earthquake and its aftershocks. The July event occurred on the edge of the Shumagin Gap changing stress conditions in the gap, favoring the occurrence of the unexpected October earthquake (clearly within the gap), in a region not expected to host large earthquakes. Credit Kevin Furlong, Penn State Usage Restrictions none License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.