Preliminary evidence for localized lithospheric deformation in the western Basin and Range and Walker Lane from Ps receiver function analysis

Heather A. Ford

Published August 15, 2018, SCEC Contribution #8817, 2018 SCEC Annual Meeting Poster #283

Cenozoic-aged extension within portions of the Basin and Range has been estimated to be as large as 250 km, however others put estimates lower. A question that remains today is how strain is accommodated within the lithosphere beneath the Basin and Range. Vertically uniform deformation within the crust would produce large lateral variations in Moho topography, which is not observed. This is cited as evidence of viscous flow in the lower crust. Others have hypothesized that the lower crust is strong and that extension currently occurs along a mega-detachment at the base of the crust. Anisotropic receiver function analysis from six long-running stations within the greater Basin and Range province (Schnorr and Ford, 2016) found evidence for well-defined, layered anisotropy within the lowermost crust and uppermost mantle at stations located along the western margin of the Basin and Range (WVOR, TPNV, and MNV) but not in other locations (BMN, ELK and NEE). Such variability suggests that either strain or mineralogy differ locally.

In this study, additional anisotropic receiver function analysis has been performed on 16 stations located within the western Basin and Range and Walker Lane regions. 10 stations operated for ~1.5-2 years as part of Earthscope’s Transportable Array. The remainder are long-running stations from the CI network and are confined to a geographic region including Owens Valley, Death Valley and the immediate surrounding areas. Preliminary results show a positive phase at most stations, interpreted to be the Moho, at approximately 3.5-4.5 seconds, although significantly more complicated behavior is observed at some stations (e.g., MLAC, GRA, N07B). Importantly, preliminary results indicate the presence of anisotropic structure within the lower crust and upper mantle (~30-60 km). While strong evidence for anisotropy exists, it exhibits significant complexity at individual stations with multiple layers possible at some locations (e.g., SLA, TIN, FUR). Additionally, there is little coherence among stations across the region, suggesting that lower crustal mineralogy may play an important role in the observed seismic anisotropy (i.e., Brownlee, 2017; Erdmann, 2013). Further work is still needed to better constrain the geometry of the anisotropic structure at individual stations, and to determine how the structure might be related to deformation within the western Basin and Range and Walker Lane regions.

Citation
Ford, H. A. (2018, 08). Preliminary evidence for localized lithospheric deformation in the western Basin and Range and Walker Lane from Ps receiver function analysis. Poster Presentation at 2018 SCEC Annual Meeting.

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Seismology