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| Ground motion directionality in the 2018 Taiwan Hualien Mw 6.4 earthquake |
1.Institute of Geophysics, China Earthquake Administration, Beijing 100081，China；
2.Institute of Engineering Mechanics, China Earthquake Administration, Harbin 150080, China |
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Abstract The directionality of the near-fault ground motion, and its relationship with the focal mechanism, fault distances and spatial locations in 2018 Hualien earthquake were investigated.The applicability of the NGA-West2 model for ground motion directionality to the Hualien earthquake was considered.And the fault distance range which needs to consider the influence of the ground motion directionality was given.The results show that: The near-fault strong motions show significant variation with orientation.In various directions, the maximum acceleration response can reach 6.4 times the minimum response.The directionality of ground motions increases with the period, especially with the long period of T>1.0 s.The real ratio of the maximum/median of intensity is in conformity with that obtained by the NGA-West2 model for ground motion directionality.The ground motions exhibit strong directionality within about 30 km from the fault, especially within 5 km, the predominant orientation of ground motions is closest to the perpendicular direction of the fault strike.In the shorter period T=0.2 s, 0.5 s and 1.0 s, the predominant orientation of ground motions is relatively random.In the longer period T=3.0 s, 5.0 s and 7.5 s, the predominant orientation of ground motions is highly consistent with the relative movement direction of the fault.It is suggested that within about 30 km from the fault, the influence of the ground motion directionality should be considered.Especially, within about 10 km from the fault, it should be ensured that the weak position of the engineering structure should avoid the predominant orientation of ground motions as far as possible.
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Received: 09 January 2020
Published: 28 May 2021
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