M 6.7 earthquake swarm in northern Chile! 2014/03/06

There was a really cool earthquake swarm in northern Chile. This swarm of earthquakes are at depths that places them near the subduction zone fault interface.
This earthquake swarm is interesting for several reasons, the first of which is that it is in a possible seismic gap (a region along a fault system that has not slipped in recent, or not so recent, history/prehistory). Seismic gaps may exist due to a short record of earthquakes or due to some inability for earthquakes to occur in that region of the fault (i.e. aseismic slip).
Here is a map of the globe with the swarm (orange dots) in the center. There are plate boundary faults mapped, as well as subduction zone fault contours. These fault “slab” contours were constructed based on seismicity by Gavin Hayes (USGS).


Here is a regional view of the same mapping configuration.


Here is a regional map with historic epicenters plotted as rey circles. Note the absence of earthquakes in the updip portion of hte subduction zone faul tin the region of this earthquake swarm.


Here is the swarm at a local scale. The shallowest red slab contour is 20 km. The second shallowest red contour is 40 km. These earthquakes have hypocentral depths about 20 km.


This is the Mww moment tensor for the mainshock. This shows an earthquake on a northwest striking thrust or reverse fault.

Here is the USGS Did You Feel It map for the mainshock.

Here is an older map by Matt Pritchard (Cornell) that has some historic earthquakes plotted.

This is a map from Giovanni et al. (2001) that shows some possible earthquakes in this gap region.