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Session: Metamaterials, Resonances and Seismic Wave Mitigation, an Emerging Trend in Seismology [Poster]

Type: Poster

Date: 4/25/2019

Time: 06:00 PM

Room: Grand Ballroom

[Withdrawn] Towards a Seismic Cloak for Ground-Based Gravitational-Wave Detectors

The first direct detection of gravitational waves has been possible by constructing a pair of highly sensitive detectors called Laser Interferometer Gravitational-wave Observatory (LIGO) which involve the most accurate measurement of displacements up to the order of 10^-20 m. Since it is a ground-based interferometer, various noise sources limit its sensitivity. Ground vibrations in the range 0.01-10 Hz, generated through both anthropogenic as well as natural sources become an issue. These displacements, in turn, cause a fluctuation in the local gravitational field due to density perturbations of the surrounding geology introducing Newtonian Noise. The seismic isolation systems can suppress the displacements by several orders of magnitude, however, cannot reduce Newtonian noise. To further shield the detector building and also the walls of the vacuum chambers from such noise, we consider the idea of seismic metamaterials in this study.

Lately, using the concepts in metamaterial physics it has been demonstrated that judicious arrangement of either resonators or soil inclusions can largely affect the seismic wave field on the geophysical scale. In this study, the feasibility of using two different seismic metamaterials is explored; one with steel poles over the surface acting as vertical resonators and another with a periodic arrangement of vertical concrete inclusions in the soil medium. We consider the ground model at the site chosen for the upcoming LIGO-India project at Hingoli in India. To shield the ends of the interferometer, we seek to achieve band gaps below 10 Hz. We develop models for realistic cloak designs and perform time-domain simulations in SPECFEM3D, an open-source code which solves the elastodynamic equations using finite difference in time and the spectral-element method (O>4) in space. This interesting approach to shield the LIGO detectors can potentially improve its sensitivity in the low-frequency range and the results from this study can have an impact on the existing and future ground-based detectors.

Presenting Author: Shoaib Ayjaz Mohammed

Additional Authors