Late last night, southern Mexico was hit by an earthquake that occurred offshore near the border with Guatemala. According to the USGS, the earthquake was within the Cocos Plate and was at a depth of ~70 km. In this region, the Cocos Plate is subducting beneath the North American Plate. This was an unusual earthquake for this tectonic setting given its depth and the way the earth ruptured. Typically, earthquakes in subduction zones are caused by compression of two plates colliding and they usually occur at shallow depths. The seismic waves from this earthquake show that the earth was extending during the earthquake and that this earthquake happened at a relatively deep depth. This earthquake will keep seismologists busy for a while.

I've attached a couple of seismograms recording the North Korea nuclear test this past weekend. The top was recorded at the seismic station WUAZ, located just outside of Flagstaff, AZ. The bottom is a figure made by Andy Frassetto overlaying the 2016 and 2017 tests. Earthquake seismology plays an important role in understanding these tests and assessing the yield of the explosions. Further, these images demonstrate the sensitivity of seismic instruments in detecting these types of tests. The station in Flagstaff is ~6000 miles from North Korea. More information on the test and Andy's original figure are available here: ds.iris.edu/ds/nodes/dmc/specialevents/2017/09/03/2017-north-korean-nuclear-test/