38 Plate Boundary Evolution and Lithospheric Dynamics of Western North America (Posters)
We invite presentations on Cenozoic tectonics, volcanism, sedimentation, and geohazards offshore and along the margin of western North America. Example topics include crustal structure, mantle processes, triple-junction migration, paleomagnetism, active faulting, marine stratigraphy, and seismicity.
Friday, 24 April 2026
8:00 AM - 5:30 PM
LMH, 5th Floor Chapel
Evaluating Seismic Hazard in Baja California Using Geological and Geophysical Constraints
Paper number: 38-6
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM
Authors
Abstract
Southern California and Baja California experience significant seismic hazard due to their proximity to major fault zones that produce earthquakes. Despite this overlapping source of earthquakes, ground shaking may vary significantly across the region due to changes in local geology. A site located on a sedimentary basin is susceptible to amplified and prolonged ground shaking compared to a site on bedrock. The three-dimensional subsurface structure beneath a site may further modify shaking by trapping or focusing seismic waves. The thickness of underlying sedimentary layers governs the resonance of shaking, which must be quantified to ensure resilient engineering practices. The mitigation of seismic risk therefore requires improved constraints on the subsurface geology modifying earthquake ground motions. Horizontal-to-Vertical Spectral Ratio (HVSR) measurements constrain frequency-dependent ground motion amplification, which is largely controlled by the geologic architecture beneath a site. Here, I complete HVSR measurements using microtremor recordings at permanent broadband seismometers in Southern California and Baja California and find that site resonance is spatially correlated with the thickness of known sedimentary deposits. While observations in Southern California are significantly denser than observations in Baja California, my findings highlight the continuity of the geologic and tectonic processes controlling seismic hazard across the Mexico–U.S. border. Given the exposure of major population centers such as Tijuana and Mexicali to amplified ground shaking, I motivate the need for targeted field campaigns in northern Baja California to improve estimates of seismic hazard.
Geological Society of America Abstracts with Programs. Vol. 58, No. 3
doi: 10.1130/abs/2026CD-410898
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