Effect of source rupture directivity on the ground shaking from strike-slip earthquakes and its implication for directivity models

Junju Xie, Paolo Zimmaro, Xiaojun Li, & Zengping Wen

Published August 7, 2018, SCEC Contribution #8327, 2018 SCEC Annual Meeting Poster #002

We investigate spatial variability of observed ground motions, apparent period-dependence, and azimuthal variation, as well as narrow-banded effects on various intensity measures. We develop a simplified ground motion model that includes both geometric and anelastic attenuation terms. We also perform a log-linear regression of the residuals, using a new directivity predictor. Our results show that rupture directivity produces significant amplifications in the rupture forward direction, while strong deamplification effects are observed in the rupture backward region, which has generally been omitted in directivity models of NGA-West2 project. Directivity effects are particularly relevant for PGV and long-period spectral acceleration (i.e. SA at periods ≥ 2.0 s). Such effects do not have systematic influence on PGA and short period ground motions (i.e. SA at periods < 1.0 s). Rupture directivity during larger earthquakes tend to affect ground motion in the longer periods. We anticipate that results from this study will be useful for future ground motion models development.

Key Words
rupture directivity, narrow-banded, ground motion models

Citation
Xie, J., Zimmaro, P., Li, X., & Wen, Z. (2018, 08). Effect of source rupture directivity on the ground shaking from strike-slip earthquakes and its implication for directivity models. Poster Presentation at 2018 SCEC Annual Meeting.

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