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.

中文翻译：

---

美国中部和西部山间地壳地震衰减

美国西部 (WUS) 的地震衰减一般大于美国中部和东部 (CEUS)，但这种过渡的性质或边界位置的约束很差。我们使用跨越 0.5-16 Hz 的五个频段的 544 个台站记录的 106 次地震的总共 115,870 次振幅测量值，对从 CEUS 穿过落基山脉延伸到盆地和山脉的区域进行地壳地震 (Lg) 衰减断层扫描。与之前的研究类似，我们发现 WUS ( Q ₀  ∼ 190) 的衰减比名义上的 CEUS ( Q ₀  ∼ 250) 更高，而墨西哥湾沿岸 ( Q ₀ ∼ 250) 的衰减相对较高 ∼ 175)。然而，我们的模型无视简单的东西方区域化。落基山脉地区的非均质性——科罗拉多高原内部和怀俄明克拉通的低衰减 ( Q ₀  ∼ 230) 与落基山脉南部的高衰减 ( Q ₀  ∼ 110) 相比——超过了 CEUS 和美国西部之间的总体差异。这些省尺度模式很容易根据内在衰减进行解释。科罗拉多高原与盆地和山脉之间的边界拥有研究区域内成像的最高衰减 ( Q ₀  ∼ 90)，与对比地壳结构的局部散射一致。落基山脉南部的集中高衰减可能代表了代表的影响原地部分地壳熔融。在 CEUS 内，衰减相对较高的二阶带与元古代 Yavapai-Mazatzal 缝合带和中大陆裂谷对齐。这种复杂的衰减结构无视广泛的区域化，并表明需要在这些边界附近建立特定于路径的模型和关键基础设施。