Dynamic earthquake triggering above the Socorro magma body, New Mexico

Abstract

When earthquakes occur they release energy in the form of waves that cause ground movements. For high magnitude earthquakes, these waves can travel around the world and interact with other faults at great distances from where the earthquake originally occurred. This interaction through ground displacements can alter the stress state on these remote faults, reduce the friction on the faults, and cause them to fail, or trigger another earthquake. This dynamic triggering process can occur in a variety of tectonic settings but particularly occurs in areas characterized by the presence of hot fluids and/or magma. Therefore we hypothesize that triggering should be common within the region above the Socorro Magma Body (SMB) within the Rio Grande Rift. To test this, I examined data from 319 large earthquakes from around the world with magnitudes > 6.0 between January 15, 2008 and November 30, 2009 and analyzed the seismograms recorded on seismometers stationed around Socorro, NM to see if local earthquakes corresponded with the passage of waves from the large earthquake. 93 local events were found corresponding to 66 of the large earthquakes. I have been looking at background rates of seismicity in the area to determine if the amount of local earthquakes increases with the passage of large earthquake waves, indicating that some events are a result of “delayed triggering” rather than being independent of the large earthquake. The majority of local events occur above the Socorro Magma Body, showing that it is more conducive to triggering in New Mexico, but the events can be spread throughout the rift as well. We hypothesized that large earthquake locations would show a region that preferentially triggers events in New Mexico, however the only clustering of possibly triggering large earthquakes is a reflection of areas naturally more seismically active. I am also looking into triggering and triggering delay dependence on the large earthquake’s location and wave amplitude.