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The Case of the Missing Frequencies: Reduction of Artificial Spectral Deficiency in Semistochastic Broadband Simulation

Description: 

Semistochastic broadband simulation is a common method used to efficiently generate realistic full spectrum waveforms. For such methods, deterministic low frequency (e.g., < 1 Hz) waveforms are combined with stochastic high frequency (e.g., > 1 Hz) waveforms using a matched filter, which involves lowpass filtering the low frequency data, highpass filtering the high frequency data, and summing the filtered time-series. Oftentimes, a common filter corner frequency (f_cc) of 1 Hz is used for both the lowpass and highpass filters. However, this induces an artificial deficiency in the broadband spectra, which can have considerable effects on the resulting ground motion and seismic hazard assessments, especially in the field of earthquake engineering where the frequencies of ground motion hold significance. We investigate this phenomenon for Japan, Chile, and the Cascadia subduction zones, and explore various approaches to minimize the spectral deficiency, including varying the f_cc, varying the filter order, and using a two-corner frequency approach. We find that each approach, to some extent, reduces the deficiency and influences the ground motion (PGD, PGA, PGV, and SA). However, no single approach universally improves all ground motion intensity measures for events of varying magnitude. We suggest addressing this matter on a case-by-case basis.

Session: Physics-Based Ground Motion Modeling [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Tara

Student Presenter: Yes

Invited Presentation: 

Authors