The Caleta cluster is named after the town of Caleta de Campos on the
coast of Michoacan, Mexico. It is unusally rich in large events,
including the 8.0 Mw earthquake on September 19, 1985. In addition there
are two other events with magnitude greater than 7.0 and six with
magnitude between 6.0 and 6.9. All the larger earthquakes are associated
with the subduction of the northernmost portion of the Cocos plate
(perhaps involving the Rivera plate as well) beneath the North American
plate. The cluster includes events down to ~100 km in the subduction
zone and a patch of generally very shallow earthquakes further inland
near the town of Los Reyes, an area that is considered somewhat
susceptible to volcanic activity. Many of these events want to locate at
zero depth, although the topography is 1.2-1.5 km in this area. All
events in the cluster have depth control, either from near-source and
local distance readings, or from teleseismic depth phases (sometimes
both). The location calibration is very robust, due to the dense local
network installed in the last several decades. Many smaller events that
were recorded only to near regional distances (minimum 3.0° epicentral
distance) were retained to improve the statistics of the relocation.
