We present a simple method for the identification of weak signals associated with gravitational wave events. Its application reveals a signal with the same time lag as the GW150914 event in the released LIGO strain data with a significance around 3.2σ. This signal starts about 10 minutes before GW150914 and lasts for about 45 minutes. Subsequent tests suggest that this signal is likely to be due to external sources.
@article{arxiv.1609.08346,
title = {Possible associated signal with GW150914 in the LIGO data},
author = {Hao Liu and Andrew D. Jackson},
journal= {arXiv preprint arXiv:1609.08346},
year = {2016}
}