Improving Seismic Microzonation of the Taipei Basin Using Response Spectra and Geology Informed Interpolation

The seismic response of the Taipei Basin is heavily influenced by its basin geometry and thick sedimentary deposits. These conditions focus seismic energy and govern surface shaking, resulting in prolonged durations and enhanced long-period content that pose significant risks to high-rise buildings and critical infrastructure. In structural design, the corner period (T₀) of the response spectrum is a concise measure of frequency content that integrates source, path, and site effects. With the basin's dense strong-motion network, this study directly derives T₀ from observations to refine seismic microzonation and design evaluations.

This study compiled a comprehensive dataset of moderate-to-large earthquakes (M_W ≥ 5 or local PGA ≥ 10 gal) recorded in Taiwan from 1992 to 2024. Records underwent a unified processing workflow of baseline correction, filtering, and 5%-damped response spectra generation, after which events were categorized into crustal, subduction-interface, and intraslab types. For each category, the T₀ was determined using the mean plus one standard deviation spectrum as the target. Results indicate pronounced spatial variations in T₀ for crustal and subduction-interface earthquakes. Values are longest in the northwestern to north-northeastern regions (exceeding 1.5 sec) and shortest along the southeastern region. In contrast, intraslab events exhibit minimal spatial variation. Correlation analysis confirms that T₀ distribution is strongly controlled by geological conditions, specifically bedrock depth and sediment thickness. By incorporating these geological parameters into spatial interpolation, this study enhances the resolution and physical interpretability of the microzonation, providing a more robust and detailed reference for seismic design in the Taipei Basin.