We had a small flurry of earthquake activity in Chile today, along the subduction zone there. Today’s activity is in the the region of the 2010 earthquake sequence. The largest magnitude earthquake in today’s sequence is a M = 6.2. Here is the USGS page for that earthquake.
Here is a map showing the seismicity for the past month or so. Below I list the USGS web pages for each of the earthquakes plotted on this map. I placed the location of the surface trace of the subduction zone fault in purple. This is based on the USGS location, which is approximate as it is based on the coarse resolution global topography data set. I have also placed the historic earthquake rupture limits in green. Note how the 3/9 M 5.1 earthquake plots west of the SZ fault, so it must be in the down going plate. This earthquake has an extensional moment tensor, consistent with either bending moment stresses, or slab pull extension stresses. Without more analyses, it would be difficult to distinguish between the two.
Here are the USGS web pages for the earthquakes plotted in the above map.
- 2/17 M 5.4
- 3/2 M 5.3
- 3/5 M 5.0
- 3/9 M 5.1
- 3/14 M 5.1
- 3/18 M 6.2
Here is the map that I put together for some earthquakes in the seismic gap that I placed with an orange line in the above map. Here is my previous post about this series of M~5 earthquakes.
Here is a primer for the different types of earthquake faults and moment tensor/focal mechanisms. This comes from the USGS. This explains focal mechanisms. Moment tensors (which I use on my figures above) are determined differently, but their graphical solution/representation is the same as for focal mechanisms (for all practical purposes). Here is the USGS page on moment tensors if you want to learn more about them.