Lithospheric Mantle Earthquakes in the Wind River Range, Wyoming

Session: Earthquake Source Parameters: Theory, Observations and Interpretations [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Earthquakes occurring in the continental lithospheric mantle are unusual and their causes are not well understood. On 21 September 2013, two earthquakes of magnitudes 4.8 and 3.0 occurred at a depth of about 75km in West-Central Wyoming beneath the foothills of the eastern flank of the Wind River Range. The crustal thickness in this area is less than 50km, thus these events occurred in the upper mantle. These unusual earthquakes were the subject of several papers (Frohlich et al., 2015; Craig et al., 2015; Wang et al., 2016; Prieto et al., 2017) because they were well recorded and precisely located, allowing a rare opportunity to study the dynamics and mechanics of the lithospheric mantle. These studies verify that the events occurred in the mantle, and discuss the possible rheologic conditions that could host these events. Craig et al. argue that these events are most likely tectonically driven, rather than of fluid or magmatic origin. Prieto et al. discuss the possibility of earthquake nucleation in a ductile, rather than brittle regime due to weakening mechanisms. Wang et al. argue that these earthquakes occur either in a remnant of the subducted Farallon slab or due to the removing of a dense mantle lithospheric root. Another analysis (O’Rourke et al., 2016), identified another lithospheric mantle earthquake in this region (depth 63km, magnitude 1.5) using data from the Bighorn Arch Seismic Experiment.

Subspace detection is a method of detecting similar seismic signals from a repetitive source, by projecting a data stream onto a vector signal subspace which spans a collection of signals which the source might generate (Harris, 2004). By creating templates from these three known deep events, we applied subspace detection to about 9 years (2009-2018) of seismic data from the Pinedale Array, which is located of the western flank of the Wind River Range. This allowed us to search for other deep events that are similar to these known earthquakes. We present two events whose waveforms are very similar to those of the template events.

Presenting Author: Emma G. Devin

Authors