Crustal Seismic Attenuation of the Central United States and Intermountain West

Seismic attenuation is generally greater in the western United States (WUS) than the central and eastern United States (CEUS), but the nature of this transition or location of this boundary is poorly constrained. We conduct crustal seismic (Lg) attenuation tomography across a region that stretches from the CEUS across the Rocky Mountains to the Basin and Range using a total of 115,870 amplitude measurements from 106 earthquakes recorded on 544 stations across five frequency bands spanning 0.5–16 Hz. Similar to previous studies, we find higher attenuation in the WUS (Q0 ∼ 190) than the nominally CEUS (Q0 ∼ 250) and comparatively high attenuation on the Gulf Coast (Q0 ∼ 175). Our models defy simple east versus west regionalization, however. Heterogeneity within the Rocky Mountain region—low attenuation in the Colorado Plateau interior and Wyoming Craton (Q0 ∼ 230) compared to high attenuation in the southern Rockies (Q0 ∼ 110)—exceeds the gross differences between the CEUS and western United States. These province‐scale patterns are readily interpreted in terms of intrinsic attenuation. The boundary between the Colorado Plateau and Basin and Range hosts the highest attenuation imaged in the study area (Q0 ∼ 90), consistent with localized scattering across contrasting crustal structure. Focused high attenuation in the southern Rockies may represent the effects of represent in situ partial crustal melt. Within the CEUS, second‐order bands of comparatively high attenuation align with the Proterozoic Yavapai‐Mazatzal suture zone and Midcontinent Rift. This complex attenuation structure defies broad regionalization and suggests a need for path‐specific models near these boundaries and for critical infrastructure. Plain Language Summary Shaking dies away, or attenuates, with distance from an earthquake. Attenuation is slower in the eastern United States than the West, which greatly increases the area over which shaking is felt and damage can occur. Low seismicity rates in central North America have made it challenging to determine and understand the boundary between East and West, however. Recent manmade earthquakes in parts of Oklahoma and Colorado provide new data to map attenuation across the nation, and we find that there is not simple dichotomy between East and West after all. Instead, ancient tectonic events and modern processes combine to create a complex tapestry of attenuation. Understanding this complexity, however, will make it easier to forecast and pr