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A High‐Frequency Distance Metric in Ground‐Motion Prediction Equations Based on Seismic Array Backprojections
Author(s) -
Feng Tian,
Meng Lingsen
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl078930
Subject(s) - metric (unit) , ground motion , distance decay , geodesy , measure (data warehouse) , seismology , point (geometry) , geology , energy (signal processing) , motion (physics) , plane (geometry) , physics , acoustics , computer science , mathematics , geometry , statistics , data mining , engineering , classical mechanics , operations management , quantum mechanics
Typical ground‐motion prediction equations (GMPEs) measure source‐to‐site distances relative to the closest point on the rupture plane ( R rup ). However, for megathrust earthquakes ( M w > 8), the oversimplification of the earthquake source characteristics in distance metrics results in significant bias. Recent studies suggest that the high‐frequency (HF) and low‐frequency (LF) energy tend to emanate from different portions of the megathrusts. This phenomenon motivates an alternative distance metric based on the array backprojection imaging technique that effectively captures regions releasing HF energy. Herein, we define an HF distance metric ( R hf ) as the distance from the site to the high‐frequency radiation zone. We study five M w > 7.2 megathrust earthquakes in Japan and Chile and find that R hf outperforms R rup in predicting the ground shaking intensity between 0.5 and 4 Hz. We consider R hf as a complementary measure to conventional GMPE distance metrics and a more accurate ground‐motion predictor in many cases.