Variability in the Period of Velocity Pulse Based on Nucleation Position on the Fault

Karthik Reddy, K S K and Somala, S N (2021) Variability in the Period of Velocity Pulse Based on Nucleation Position on the Fault. In: 7th International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, ICRAGEE 2020, 13 July 2020 through 16 July 2020, Bangalore; India.

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Abstract

Spatial variability is observed in ground motions depending on various factors like path, site, and source. Based on board classification concerning the path characteristics, the ground motions can be classified as near field and far field depending on the distance of the station from the source. The elementary difference between the near-field and far-field ground motions lies in the reflection of pulse in the velocity field of a near field which is not apparent in far-field ground motions. Less emphasis is placed on variation in pulse period of these ground motions with the change in source kinematics. In order to explore the content to a deeper extent, one can rely on dynamic simulation. The objective is to run dynamic rupture simulations using an open-source code SPECFEM3D to study the variability of pulse period by modifying the source parameters like the positioning of the nucleation region to explore the variation in the amplitude and time period content of pulse exhibited in near-field stations. The alignment of stations is equidistant with a similar rupture distance from the fault. Two scenarios were considered by placing the nucleation region at the center of the fault in scenario-1 and away from the center from the axis of fault symmetry in scenario-2. Baker’s method was employed to quantify pulse period for chosen race track configuration of stations. The results depict that change of nucleation center transforms the non-pulse-type ground motions to pulse-like ground motions for similar (Mw = 6.5) magnitude earthquake, and for stations in front and behind the fault, there is considerable difference of 6% in pulse period for scenario-2.

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