Seismic wave attenuation in sedimentary basins results from a mix of material behavior, basin geometry, and wave–structure interactions that together control how earthquake energy is absorbed, scattered, and trapped. Intrinsic absorption converts seismic energy to heat in the rock and sediment, while scattering redistributes energy among directions and frequencies. These processes determine shaking amplitude, duration, and frequency content at the surface and thus shape earthquake hazard.
Physical controls: material properties and fluids
The mineralogy, grain size, porosity, and degree of consolidation of basin fill strongly influence intrinsic attenuation. Unconsolidated, high-porosity sediments exhibit higher energy loss than lithified rocks because grain contacts and pore-scale friction dissipate energy more efficiently. Fluid saturation and the type of fluids present change attenuation through squirt-flow and Biot mechanisms that move fluid relative to the solid frame, so water- or hydrocarbon-saturated layers can raise attenuation at specific frequencies. Temperature and burial diagenesis reduce porosity and typically lower attenuation with depth. Peter M. Shearer, University of California San Diego, summarizes these controls and the frequency dependence of seismic Q in his textbook treatments of seismic wave propagation.
Structural controls: geometry, heterogeneity, and resonance
Basin geometry and lateral velocity contrasts create waveguiding and edge-reflection effects that can amplify and lengthen shaking. Thick sedimentary packages produce low-velocity zones that trap surface and guided waves, producing long-duration, low-frequency motion through constructive interference and resonance. Heterogeneities at many scales scatter energy, shifting it from coherent body waves into coda and surface-wave energy. Measurements and modeling by United States Geological Survey scientists document how basin-edge focusing and trapped waves produced dramatic amplification during historical earthquakes, notably the 1985 Mexico City event where basin effects exacerbated urban damage.
Consequences for society and environment include prolonged shaking that increases structural damage, greater hazard concentration in basin-hosted cities, and challenges for seismic design and emergency planning. Local cultural and territorial factors—historic settlement on river plains or nearby tectonic basins—mean that attenuation behavior directly connects geology to public safety. Understanding attenuation requires integrated field measurements, laboratory rock physics, and numerical modeling to resolve intrinsic versus scattering contributions and to improve ground-motion predictions for communities built atop sedimentary basins.