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Author(s): Luo, Yang; Hanasoge, Shravan; Tromp, Jeroen; Pretorius, Frans

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Abstract: Galaxies observed today are likely to have evolved from density perturbations in the early universe. Perturbations that exceeded some critical threshold are conjectured to have undergone gravitational collapse to form primordial black holes (PBHs) at a range of masses. Such PBHs serve as candidates for cold dark matter, and their detection would shed light on conditions in the early universe. Here, we propose a mechanism to search for transits of PBHs through/nearby Earth by studying the associated seismic waves. Using a spectral-element method, we simulate and visualize this seismic wave field in Earth’s interior. We predict the emergence of two unique signatures, namely, a wave that would arrive almost simultaneously everywhere on Earth’s free surface and the excitation of unusual spheroidal modes with a characteristic frequency spacing in free oscillation spectra. These qualitative characteristics are unaffected by the speed or proximity of the PBH trajectory. The seismic energy deposited by a proximal M-PBH = 10(15) g PBH is comparable to a magnitude M-w = 4 earthquake. The non-seismic collateral damage due to the actual impact of such small PBHs with Earth would be negligible. Unfortunately, the expected collision rate is very low even if PBHs constituted all of dark matter, at similar to 10(-7) yr(-1), and since the rate scales as 1/M-PBH, fortunately encounters with larger, Earth-threatening PBHs are exceedingly unlikely. However, the rate at which non-colliding close encounters of PBHs could be detected by seismic activity alone is roughly two orders of magnitude larger-that is once every hundred thousand years-than the direct collision rate.
Publication Date: 20-May-2012
Electronic Publication Date: 30-Apr-2012
Citation: Luo, Yang, Hanasoge, Shravan, Tromp, Jeroen, Pretorius, Frans. (2012). DETECTABLE SEISMIC CONSEQUENCES OF THE INTERACTION OF A PRIMORDIAL BLACK HOLE WITH EARTH. ASTROPHYSICAL JOURNAL, 751 (10.1088/0004-637X/751/1/16
DOI: doi:10.1088/0004-637X/751/1/16
ISSN: 0004-637X
EISSN: 1538-4357
Type of Material: Journal Article
Journal/Proceeding Title: ASTROPHYSICAL JOURNAL
Version: Final published version. This is an open access article.

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