Crustal Structure of Southern California from Velocity and Attenuation Tomography
Thomas H. JordanPublished October 31, 2024, SCEC Contribution #13671
Recent studies of Southern California have employed velocity and attenuation tomography to gain new knowledge about two types of crustal structure. Low-frequency velocity tomography reveals large-scale structures that can be represented by a discrete set of tectonic regions, each characterized by an isostatically balanced lithospheric column reflecting the composition and tectonic history of the region. The boundaries between tectonic regions are typically high-angle structures expressed at the surface by major faults, topographic fronts, and geochemical transitions. High-frequency attenuation tomography indicates that the decay of P and S waves propagating through the upper and middle crust is dominated by elastic scattering from small-scale heterogeneities of high fractal dimension, rather than by anelastic dissipation. The amplitude of the scattering varies systematically among the tectonic regions and correlates with the degree of faulting and deformation within a tectonic region. These results motivate speculation that small-scale crustal heterogeneities responsible for high-frequency attenuation are generated within the seismogenic zone through a dynamic interplay of between distributed deformation and localized fracturing.
Citation
Jordan, T. H. (2024). Crustal Structure of Southern California from Velocity and Attenuation Tomography. Annals of Geophysics, 67. doi: 10.4401/ag-9149.
