determine if a significant anisotropic contribution affected their paths through the lower mantle. Then, by plotting the location of a discrepant pairs, we were able to determine regions that exhibit evidence of anisotropy. Data and Methods The Alaska network is a permanent broadband regional network maintained by the Alaska Earthquake Information Center based in Fairbanks, Alaska. The network extends from the Aleutian Islands into mainland Alaska. The majority of stations used to gather seismic data for this study are clustered in the central Denali region of mainland Alaska; however, several additional stations from the surrounding islands were also included in this study (Figure 1). The Alaskan network of seismic stations was established in 1998 as part of a broader national effort to expand understanding of the seismic landscape (Eberhart-Phillips et al. 2006). For this study, all active stations with continuous seismic records of greater than 6 months were included in our initial data gathering efforts. Seismic records from a total of 36 stations were used to create splitting measurements of seismic data. Figure 1 shows a map of all stations included in this research. Figure 1: Display of the distribution of seismic stations included in this study. Green triangles indicate the locations of individual seismic stations. At each station, the seismic record was pulled for specific time intervals corresponding to the record of earthquakes with magnitudes greater than 5, and with epicentral distances between 108 and 120 degrees from the station. We examined just over 3000 unique station-earthquake SKS-SKKS pairs in order to produce 49 well-constrained pairs of splitting measurements (both null and from 31 individual earthquakes. Each station had logged approximately 100 events that met the necessary criteria, indicating that seismic waves from the events both passed through the desired region of the lower mantle and were substantial
determine if a significant anisotropic contribution affected their paths through the lower mantle. Then, by plotting the location of a discrepant pairs, we were able to determine regions that exhibit evidence of anisotropy. Data and Methods The Alaska network is a permanent broadband regional network maintained by the Alaska Earthquake Information Center based in Fairbanks, Alaska. The network extends from the Aleutian Islands into mainland Alaska. The majority of stations used to gather seismic data for this study are clustered in the central Denali region of mainland Alaska; however, several additional stations from the surrounding islands were also included in this study (Figure 1). The Alaskan network of seismic stations was established in 1998 as part of a broader national effort to expand understanding of the seismic landscape (Eberhart-Phillips et al. 2006). For this study, all active stations with continuous seismic records of greater than 6 months were included in our initial data gathering efforts. Seismic records from a total of 36 stations were used to create splitting measurements of seismic data. Figure 1 shows a map of all stations included in this research. Figure 1: Display of the distribution of seismic stations included in this study. Green triangles indicate the locations of individual seismic stations. At each station, the seismic record was pulled for specific time intervals corresponding to the record of earthquakes with magnitudes greater than 5, and with epicentral distances between 108 and 120 degrees from the station. We examined just over 3000 unique station-earthquake SKS-SKKS pairs in order to produce 49 well-constrained pairs of splitting measurements (both null and from 31 individual earthquakes. Each station had logged approximately 100 events that met the necessary criteria, indicating that seismic waves from the events both passed through the desired region of the lower mantle and were substantial
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