Constraints on residual topography and crustal properties in the western US from virtual deep seismic sounding

Chunquan Yu, Wang-Ping Chen, & Rob van der Hilst

Submitted August 12, 2016, SCEC Contribution #6670, 2016 SCEC Annual Meeting Poster #204

We use virtual deep seismic sounding (VDSS) and data from ~1,000 broadband seismic stations to provide high-resolution estimates of crustal structure in the western Cordillera of the United States (US). The most robust result is the geographic distribution of residual topography (that is, the difference between observed elevation and that expected from crustal buoyancy alone) and, by implication, thermal or petrologic anomalies in the mantle. Overall, residual topography of the western US Cordillera varies considerably; with contrasts of up to about 3 km across distances of 200 km or less. High residual topography, indicating large mantle effects, is evident along the periphery of the Colorado Plateau and the surroundings of the Great Basin. In contrast, the central Colorado Plateau and the Wyoming Basin show low residual topography, close to what is expected of a geologically stable lithosphere. Overall, in regions to the east of the Wasatch hinge line (the eastern limit of significant extension in the North American cratonic basement) patterns of high residual topography and anomalies of low seismic wave-speeds in the upper mantle are similar, suggestive of a common, thermal origin. In contrast, such a similarity is absent in regions to the west of the hinge line, suggesting substantial effects of petrological heterogeneities in the mantle. Finally, joint analyses of VDSS and conventional receiver functions reveal a wide range of crustal P-wave speeds, locally as high as 6.7 km/s, perhaps indicating magmatic modification of the crust.

Key Words
Residual topography, isostasy, western US, crustal properties, USArray, EarthScope

Yu, C., Chen, W., & van der Hilst, R. (2016, 08). Constraints on residual topography and crustal properties in the western US from virtual deep seismic sounding. Poster Presentation at 2016 SCEC Annual Meeting.

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